Showing papers in "Journal of Animal Ecology in 2010"

An ecologist's guide to the animal model

Abstract: 1. Efforts to understand the links between evolutionary and ecological dynamics hinge on our ability to measure and understand how genes influence phenotypes, fitness and population dynamics. Quantitative genetics provides a range of theoretical and empirical tools with which to achieve this when the relatedness between individuals within a population is known. 2. A number of recent studies have used a type of mixed-effects model, known as the animal model, to estimate the genetic component of phenotypic variation using data collected in the field. Here, we provide a practical guide for ecologists interested in exploring the potential to apply this quantitative genetic method in their research. 3. We begin by outlining, in simple terms, key concepts in quantitative genetics and how an animal model estimates relevant quantitative genetic parameters, such as heritabilities or genetic correlations. 4. We then provide three detailed example tutorials, for implementation in a variety of software packages, for some basic applications of the animal model. We discuss several important statistical issues relating to best practice when fitting different kinds of mixed models. 5. We conclude by briefly summarizing more complex applications of the animal model, and by highlighting key pitfalls and dangers for the researcher wanting to begin using quantitative genetic tools to address ecological and evolutionary questions.

Dendritic network structure constrains metacommunity properties in riverine ecosystems.

Abstract: 1. Increasingly, ecologists conceptualize local communities as connected to a regional species pool rather than as isolated entities. By this paradigm, community structure is determined through the relative strengths of dispersal-driven regional effects and local environmental factors. However, despite explicit incorporation of dispersal, metacommunity models and frameworks often fail to capture the realities of natural systems by not accounting for the configuration of space within which organisms disperse. This shortcoming may be of particular consequence in riverine networks which consist of linearly -arranged, hierarchical, branching habitat elements. Our goal was to understand how constraints of network connectivity in riverine systems change the relative importance of local vs. regional factors in structuring communities. 2. We hypothesized that communities in more isolated headwaters of riverine networks would be structured by local forces, while mainstem sections would be structured by both local and regional processes. We examined these hypotheses using a spatially explicit regional analysis of riverine macroinvertebrate communities, focusing on change in community similarity with distance between local communities [i.e., distance-decay relationships; (DDRs)], and the change in environmental similarity with distance. Strong DDRs frequently indicate dispersal-driven dynamics. 3. There was no evidence of a DDR in headwater communities, supporting our hypothesis that dispersal is a weak structuring force. Furthermore, a positive relationship between community similarity and environmental similarity supported dynamics driven by local environmental factors (i.e., species sorting). In mainstem habitats, significant DDRs and community x environment similarity relationships suggested both dispersal-driven and environmental constraints on local community structure (i.e., mass effects). 4. We used species traits to compare communities characterized by low vs. high dispersal taxa. In headwaters, neither strength nor mode (in-network vs. out of network) of dispersal changed our results. However, outcomes in mainstems changed substantially with both dispersal mode and strength, further supporting the hypothesis that regional forces drive community dynamics in mainstems. 5. Our findings demonstrate that the balance of local and regional effects changes depending on location within riverine network with local (environmental) factors dictating community structure in headwaters, and regional (dispersal driven) forces dominating in mainstems.

Nestedness versus modularity in ecological networks: two sides of the same coin?

Abstract: 1. Understanding the structure of ecological networks is a crucial task for interpreting community and ecosystem responses to global change. 2. Despite the recent interest in this subject, almost all studies have focused exclusively on one specific network property. The question remains as to what extent different network properties are related and how understanding this relationship can advance our comprehension of the mechanisms behind these patterns. 3. Here, we analysed the relationship between nestedness and modularity, two frequently studied network properties, for a large data set of 95 ecological communities including both plant-animal mutualistic and host-parasite networks. 4. We found that the correlation between nestedness and modularity for a population of random matrices generated from the real communities decreases significantly in magnitude and sign with increasing connectance independent of the network type. At low connectivities, networks that are highly nested also tend to be highly modular; the reverse happens at high connectivities. 5. The above result is qualitatively robust when different null models are used to infer network structure, but, at a finer scale, quantitative differences exist. We observed an important interaction between the network structure pattern and the null model used to detect it. 6. A better understanding of the relationship between nestedness and modularity is important given their potential implications on the dynamics and stability of ecological communities.

Maximal heat dissipation capacity and hyperthermia risk: neglected key factors in the ecology of endotherms

Abstract: Summary 1. The role of energy in ecological processes has hitherto been considered primarily from the standpoint that energy supply is limited. That is, traditional resource-based ecological and evolutionary theories and the recent ‘metabolic theory of ecology’ (MTE) all assume that energetic constraints operate on the supply side of the energy balance equation. 2. For endothermic animals, we provide evidence suggesting that an upper boundary on total energy expenditure is imposed by the maximal capacity to dissipate body heat and therefore avoid the detrimental consequences of hyperthermia – the heat dissipation limit (HDL) theory. We contend that the HDL is a major constraint operating on the expenditure side of the energy balance equation, and that processes that generate heat compete and trade-off within a total boundary defined by heat dissipation capacity, rather than competing for limited energy supply. 3. The HDL theory predicts that daily energy expenditure should scale in relation to body mass (Mb) with an exponent of about 0AE63. This contrasts the prediction of the MTE of an exponent of 0AE75. 4. We compiled empirical data on field metabolic rate (FMR) measured by the doubly-labelled water method, and found that they scale to Mb with exponents of 0AE647 in mammals and 0AE658 in birds, not significantly different from the HDL prediction (P >0 AE05) but lower than predicted by the MTE (P <0 AE001). The same statistical result was obtained using phylogenetically independent contrasts analysis. Quantitative predictions of the model matched the empirical data for both mammals and birds. There was no indication of curvature in the relationship between Loge FMR and Loge Mb. 5. Together, these data provide strong support for the HDL theory and allow us to reject the MTE, at least when applied to endothermic animals. 6. The HDL theory provides a novel conceptual framework that demands a reframing of our views of the interplay between energy and the environment in endothermic animals, and provides many new interpretations of ecological and evolutionary phenomena.

What determines a species’ geographical range? Thermal biology and latitudinal range size relationships in European diving beetles (Coleoptera: Dytiscidae)

Abstract: 1. The geographical range sizes of individual species vary considerably in extent, although the factors underlying this variation remain poorly understood, and could include a number of ecological and evolutionary processes. A favoured explanation for range size variation is that this result from differences in fundamental niche breadths, suggesting a key role for physiology in determining range size, although to date empirical tests of these ideas remain limited. 2. Here we explore relationships between thermal physiology and biogeography, whilst controlling for possible differences in dispersal ability and phylogenetic relatedness, across 14 ecologically similar congeners which differ in geographical range extent; European diving beetles of the genus Deronectes Sharp (Coleoptera, Dytiscidae). Absolute upper and lower temperature tolerance and acclimatory abilities are determined for populations of each species, following acclimation in the laboratory. 3. Absolute thermal tolerance range is the best predictor of both species' latitudinal range extent and position, differences in dispersal ability (based on wing size) apparently being less important in this group. In addition, species' northern and southern range limits are related to their tolerance of low and high temperatures respectively. In all cases, absolute temperature tolerances, rather than acclimatory abilities are the best predictors of range parameters, whilst the use of independent contrasts suggested that species' thermal acclimation abilities may also relate to biogeography, although increased acclimatory ability does not appear to be associated with increased range size. 4. Our study is the first to provide empirical support for a relationship between thermal physiology and range size variation in widespread and restricted species, conducted using the same experimental design, within a phylogenetically and ecologically controlled framework.

Guild-specific patterns of species richness and host specialization in plant–herbivore food webs from a tropical forest

Abstract: 1.The extent to which plant-herbivore feeding interactions are specialized is key to understand the processes maintaining the diversity of both tropical forest plants and their insect herbivores. However, studies documenting the full complexity of tropical plant-herbivore food webs are lacking. 2. We describe a complex, species-rich plant-herbivore food web for lowland rain forest in Papua New Guinea, resolving 6818 feeding links between 224 plant species and 1490 herbivore species drawn from 11 distinct feeding guilds. By standardizing sampling intensity and the phylogenetic diversity of focal plants, we are able to make the first rigorous and unbiased comparisons of specificity patterns across feeding guilds. 3.Specificity was highly variable among guilds, spanning almost the full range of theoretically possible values from extreme trophic generalization to monophagy. 4.We identify guilds of herbivores that are most likely to influence the composition of tropical forest vegetation through density-dependent herbivory or apparent competition. 5.We calculate that 251 herbivore species (48 of them unique) are associated with each rain forest tree species in our study site so that the 200 tree species coexisting in the lowland rain forest community are involved in 50 000 trophic interactions with 9600 herbivore species of insects. This is the first estimate of total herbivore and interaction number in a rain forest plant?herbivore food web. 6. A comprehensive classification of insect herbivores into 24 guilds is proposed, providing a framework for comparative analyses across ecosystems and geographical regions.

How do landscape composition and configuration, organic farming and fallow strips affect the diversity of bees, wasps and their parasitoids?

Abstract: 1. Habitat destruction and increasing land use intensity result in habitat loss, fragmentation and degradation, and subsequently in the loss of species diversity. The fact that these factors are often highly confounded makes disentangling their effects extremely difficult, if not impossible, and their relative impact on species loss is mostly speculative. 2. In a two-year study, we analysed the relative importance of changed landscape composition (increased areas of cropped habitats), reduced habitat connectivity and reduced habitat quality on nest colonization of cavity-nesting bees, wasps and their parasitoids. We selected 23 pairs of conventional and organic wheat fields in the centre of landscape circles (500 m radius) differing in edge densities (landscape configuration) and % non-crop habitats (landscape composition). Standardized trap nests were established in the field centres and in neighbouring permanent fallow strips (making a total of 92 nesting sites). 3. Factors at all three scales affected nest colonization. While bees were enhanced by high proportions of non-crop habitat in the landscape, wasps profited from high edge densities, supporting our hypothesis that wasps are enhanced by connecting corridors. Colonization of herbivore-predating wasps was lower in field centres than in fallow strips for conventional sites, but not for organic sites, indicating a fallow-like connectivity value of organic fields. The relative importance of habitat type and farming system varied among functional groups suggesting that their perception of crop-non-crop boundaries or the availability of their food resources differed. 4. Local and landscape effects on parasitoids were mainly mediated by their hosts. Parasitism rates were marginally affected by local factors. A specialist parasitoid was more sensitive to high land use intensity than its host, whereas generalist parasitoids were less sensitive. 5. We conclude that the conversion of cropland into non-crop habitat may not be a sufficiently successful strategy to enhance wasps or other species that suffer more from isolation than from habitat loss. Interestingly, habitat connectivity appeared to be enhanced by both higher edge densities and by organic field management. Thus, we conclude that high proportions of conventionally managed and large crop fields threaten pollination and biological control services at a landscape scale.

Personality, space use and tick load in an introduced population of Siberian chipmunks Tamias sibiricus.

Abstract: 1. Although behaviours can contribute to the heterogeneity in parasite load among hosts, links between consistent individual differences in behaviour and parasitic infection have received little attention. We investigated the role of host activity and exploration on hard tick infestations of marked individuals in a population of Siberian chipmunks Tamias sibiricus introduced in a suburban French forest over 3 years. 2. Individual activity-exploration profiles were assessed from 106 hole-board tests on 73 individuals, and chipmunks' trappability and trap diversity were used respectively as indices of their activity-exploration and space use on a sub-sample of 60 individuals. At each capture, we counted the total number of ticks per head of chipmunk. 3. We found significant and consistent individual differences in activity-exploration, trappability, trap diversity and tick load, and could estimate individual indices for these four variables, corrected for confounding effects of year, season, body mass and sex. 4. Using a path analysis, we found an indirect effect of activity-exploration on tick load: tick load increased with space use, which in turn was positively affected by trappability in the field. Trappability was itself positively related to activity-exploration in the hole board. Habitat type affected tick load, independently of behavioural traits. A second path model revealed a lack of either direct or indirect influence of tick loads on chipmunks' personality and trappability. 5. Our results show that host personality-related patterns in space use can lead to a non-random parasite distribution among hosts.

Considering ecological dynamics in resource selection functions

Abstract: Summary 1. Describing distribution and abundance is requisite to exploring interactions between organisms and their environment. Recently, the resource selection function (RSF) has emerged to replace many of the statistical procedures used to quantify resource selection by animals. 2. A RSF is defined by characteristics measured on resource units such that its value for a unit is proportional to the probability of that unit being used by an organism. It is solved using a variety of techniques, particularly the binomial generalized linear model. 3. Observing dynamics in a RSF – obtaining substantially different functions at different times or places for the same species – alerts us to the varying ecological processes that underlie resource selection. 4. We believe that there is a need for us to reacquaint ourselves with ecological theory when interpreting RSF models. We outline a suite of factors likely to govern ecologically based variation in a RSF. In particular, we draw attention to competition and density-dependent habitat selection, the role of predation, longitudinal changes in resource availability and functional responses in resource use. 5. How best to incorporate governing factors in a RSF is currently in a state of development; however, we see promise in the inclusion of random as well as fixed effects in resource selection models, and matched case–control logistic regression. 6. Investigating the basis of ecological dynamics in a RSF will allow us to develop more robust models when applied to forecasting the spatial distribution of animals. It may also further our understanding of the relative importance of ecological interactions on the distribution and abundance of species.

Paternally derived immune priming for offspring in the red flour beetle, Tribolium castaneum

Abstract: Summary 1. Parasitized females in mammals, fish and birds can enhance the immune defence of their offspring by transferring specific antibodies for the embryo. Likewise, social insect mothers transfer immunity despite the fact that invertebrates lack antibodies. 2. Female trans-generational immune priming is consistent with parental investment theory, because mothers invest more into rearing their offspring than fathers. However, when immune priming is not directly linked to parental care, as is often the case in insects that abandon their eggs after oviposition, both sexes might benefit from protecting their offspring. 3. Using the red flour beetle, Tribolium castaneum, we show that after parental exposure to heat-killed bacteria, trans-generational immune priming occurs through fathers as well as mothers. 4. This novel finding challenges the traditional view that males provide only genes to their offspring in species without paternal care, and raises the possibility of a division of tasks with respect to immune protection between parents.

Survival and breeding of polar bears in the southern Beaufort Sea in relation to sea ice

Abstract: 1. Observed and predicted declines in Arctic sea ice have raised concerns about marine mammals. In May 2008, the US Fish and Wildlife Service listed polar bears (Ursus maritimus) - one of the most ice-dependent marine mammals - as threatened under the US Endangered Species Act. 2. We evaluated the effects of sea ice conditions on vital rates (survival and breeding probabilities) for polar bears in the southern Beaufort Sea. Although sea ice declines in this and other regions of the polar basin have been among the greatest in the Arctic, to date population-level effects of sea ice loss on polar bears have only been identified in western Hudson Bay, near the southern limit of the species' range. 3. We estimated vital rates using multistate capture-recapture models that classified individuals by sex, age and reproductive category. We used multimodel inference to evaluate a range of statistical models, all of which were structurally based on the polar bear life cycle. We estimated parameters by model averaging, and developed a parametric bootstrap procedure to quantify parameter uncertainty. 4. In the most supported models, polar bear survival declined with an increasing number of days per year that waters over the continental shelf were ice free. In 2001-2003, the ice-free period was relatively short (mean 101 days) and adult female survival was high (0.96-0.99, depending on reproductive state). In 2004 and 2005, the ice-free period was longer (mean 135 days) and adult female survival was low (0.73-0.79, depending on reproductive state). Breeding rates and cub litter survival also declined with increasing duration of the ice-free period. Confidence intervals on vital rate estimates were wide. 5. The effects of sea ice loss on polar bears in the southern Beaufort Sea may apply to polar bear populations in other portions of the polar basin that have similar sea ice dynamics and have experienced similar, or more severe, sea ice declines. Our findings therefore are relevant to the extinction risk facing approximately one-third of the world's polar bears.

The phenology mismatch hypothesis: are declines of migrant birds linked to uneven global climate change?

Abstract: 1. Migrant bird populations are declining and have been linked to anthropogenic climate change. The phenology mismatch hypothesis predicts that migrant birds, which experience a greater rate of warming in their breeding grounds compared to their wintering grounds, are more likely to be in decline, because their migration will occur later and they may then miss the early stages of the breeding season. Population trends will also be negatively correlated with distance, because the chances of phenology mismatch increase with number of staging sites. 2. Population trends from the Palaearctic (1990-2000) and Nearctic (1980-2006) were collated for 193 spatially separate migrant bird populations, along with temperature trends for the wintering and breeding areas. An index of phenology mismatch was calculated as the difference between wintering and breeding temperature trends. 3. In the Nearctic, phenology mismatch was correlated with population declines as predicted, but in the Palaearctic, distance was more important. This suggests that differential global climate change may be responsible for contributing to some migrant species' declines, but its effects may be more important in the Nearctic. 4. Differences in geography and so average migration distance, migrant species composition and history of anthropogenic change in the two areas may account for the differences in the strength of the importance of phenology mismatch on migrant declines in the Nearctic and Palaearctic.

Influence of climate and reproductive timing on demography of little brown myotis Myotis lucifugus.

Abstract: Summary 1. Estimating variation in demographic rates, such as survival and fecundity, is important for testing life-history theory and identifying conservation and management goals. 2. We used 16 years (1993–2008) of mark–recapture data to estimate age-specific survival and breeding probabilities of the little brown myotis Myotis lucifugus LeConte in southern New Hampshire, USA. Using Kendall & Nichols’ (1995) full-likelihood approach of the robust design to account for temporary emigration, we tested whether survival and breeding propensity is influenced by regional weather patterns and timing of reproduction. 3. Our results demonstrate that adult female survival of M. lucifugus ranged from 0AE63 (95% CL = 0AE56, 0AE68) to 0AE90 (95% CL = 0AE77, 0AE94), and was highest in wet years with high cumulative summer precipitation. First-year survival [range: 0AE23 (95% CL = 0AE14, 0AE35) to 0AE46 (95% CL = 0AE34, 0AE57)] was considerably lower than adult survival and depended on pup date of birth, such that young born earlier in the summer (c. late May) had a significantly higher probability of surviving their first year than young born later in the summer (c. mid-July). Similarly, the probability of young females returning to the maternity colony to breed in the summer following their birth year was higher for individuals born earlier in the summer [range: 0AE23 (95% CL = 0AE08, 0AE50) to 0AE53 (95% CL = 0AE30, 0AE75)]. 4. The positive influence of early parturition on 1st-year survival and breeding propensity demonstrates significant fitness benefits to reproductive timing in this temperate insectivorous bat. 5. Climatic factors can have important consequences for population dynamics of temperate bats, which may be negatively affected by summer drying patterns associated with global climate change. 6. Understanding long-term demographic trends will be important in the face of a novel disease phenomenon (White-Nose Syndrome) that is associated with massive mortalities in hibernating bat species, including M. lucifugus, in the northeastern United States.

Allometric functional response model: body masses constrain interaction strengths.

Abstract: 1. Functional responses quantify the per capita consumption rates of predators depending on prey density. The parameters of these nonlinear interaction strength models were recently used as successful proxies for predicting population dynamics, food-web topology and stability. 2. This study addressed systematic effects of predator and prey body masses on the functional response parameters handling time, instantaneous search coefficient (attack coefficient) and a scaling exponent converting type II into type III functional responses. To fully explore the possible combinations of predator and prey body masses, we studied the functional responses of 13 predator species (ground beetles and wolf spiders) on one small and one large prey resulting in 26 functional responses. 3. We found (i) a power-law decrease of handling time with predator mass with an exponent of -0.94; (ii) an increase of handling time with prey mass (power-law with an exponent of 0.83, but only three prey sizes were included); (iii) a hump-shaped relationship between instantaneous search coefficients and predator-prey body-mass ratios; and (iv) low scaling exponents for low predator-prey body mass ratios in contrast to high scaling exponents for high predator-prey body-mass ratios. 4. These scaling relationships suggest that nonlinear interaction strengths can be predicted by knowledge of predator and prey body masses. Our results imply that predators of intermediate size impose stronger per capita top-down interaction strengths on a prey than smaller or larger predators. Moreover, the stability of population and food-web dynamics should increase with increasing body-mass ratios in consequence of increases in the scaling exponents. 5. Integrating these scaling relationships into population models will allow predicting energy fluxes, food-web structures and the distribution of interaction strengths across food web links based on knowledge of the species' body masses.

Mechanisms driving change: altered species interactions and ecosystem function through global warming.

Abstract: Summary 1. We review the mechanisms behind ecosystem functions, the processes that facilitate energy transfer along food webs, and the major processes that allow the cycling of carbon, oxygen and nitrogen, and use case studies to show how these have already been, and will continue to be, altered by global warming. 2. Increased temperatures will affect the interactions between heterotrophs and autotrophs (e.g. pollination and seed dispersal), and between heterotrophs (e.g. predators-prey, parasites ⁄ pathogens-hosts), with generally negative ramifications for important ecosystem services (functions that provide direct benefit to human society such as pollination) and potential for heightened species co-extinction rates. 3. Mitigation of likely impacts of warming will require, in particular, the maintenance of species diversity as insurance for the provision of basic ecosystem services. Key to this will be long-term monitoring and focused research that seek to maintain ecosystem resilience in the face of global warming. 4. We provide guidelines for pursuing research that quantifies the nexus between ecosystem function and global warming. These include documentation of key functional species groups within systems, and understanding the principal outcomes arising from direct and indirect effects of a rapidly warming environment. Localized and targeted research and monitoring, complemented with laboratory work, will determine outcomes for resilience and guide adaptive conservation responses and long-term planning.

Carbon isotope fractionation of amino acids in fish muscle reflects biosynthesis and isotopic routing from dietary protein

Abstract: 1. Analysis of stable carbon isotopes is a valuable tool for studies of diet, habitat use and migration. However, significant variability in the degree of trophic fractionation (Delta(13)C(C-D)) between consumer (C) and diet (D) has highlighted our lack of understanding of the biochemical and physiological underpinnings of stable isotope ratios in tissues. 2. An opportunity now exists to increase the specificity of dietary studies by analyzing the delta(13)C values of amino acids (AAs). Common mummichogs (Fundulus heteroclitus, Linnaeus 1766) were reared on four isotopically distinct diets to examine individual AA Delta(13)C(C-D) variability in fish muscle. 3. Modest bulk tissue Delta(13)C(C-D) values reflected relatively large trophic fractionation for many non-essential AAs and little to no fractionation for all essential AAs. 4. Essential AA delta(13)C values were not significantly different between diet and consumer (Delta(13)C(C-D) = 0.0 +/- 0.4 per thousand), making them ideal tracers of carbon sources at the base of the food web. Stable isotope analysis of muscle essential AAs provides a promising tool for dietary reconstruction and identifying baseline delta(13)C values to track animal movement through isotopically distinct food webs. 5. Non-essential AA Delta(13)C(C-D) values showed evidence of both de novo biosynthesis and direct isotopic routing from dietary protein. We attributed patterns in Delta(13)C(C-D) to variability in protein content and AA composition of the diet as well as differential utilization of dietary constituents contributing to the bulk carbon pool. This variability illustrates the complicated nature of metabolism and suggests caution must be taken with the assumptions used to interpret bulk stable isotope data in dietary studies. 6. Our study is the first to investigate the expression of AA Delta(13)C(C-D) values for a marine vertebrate and should provide for significant refinements in studies of diet, habitat use and migration using stable isotopes.

Using evolutionary demography to link life history theory, quantitative genetics and population ecology.

Abstract: 1. There is a growing number of empirical reports of environmental change simultaneously influencing population dynamics, life history and quantitative characters. We do not have a well-developed understanding of links between the dynamics of these quantities. 2. Insight into the joint dynamics of populations, quantitative characters and life history can be gained by deriving a model that allows the calculation of fundamental quantities that underpin population ecology, evolutionary biology and life history. The parameterization and analysis of such a model for a specific system can be used to predict how a population will respond to environmental change. 3. Age-stage-structured models can be constructed from character-demography associations that describe age-specific relationships between the character and: (i) survival; (ii) fertility; (iii) ontogenetic development of the character among survivors; and (iv) the distribution of reproductive allocation. 4. These models can be used to calculate a wide range of useful biological quantities including population growth and structure; terms in the Price equation including selection differentials; estimates of biometric heritabilities; and life history descriptors including generation time. We showcase the method through parameterization of a model using data from a well-studied population of Soay sheep Ovis aries. 5. Perturbation analysis is used to investigate how the quantities listed in summary point 4 change as each parameter in each character-demography function is altered. 6. A wide range of joint dynamics of life history, quantitative characters and population growth can be generated in response to changes in different character-demography associations; we argue this explains the diversity of observations on the consequences of environmental change from studies of free-living populations. 7. The approach we describe has the potential to explain within and between species patterns in quantitative characters, life history and population dynamics.

Scaling of basal metabolic rate with body mass and temperature in mammals

Abstract: Summary 1. We present a statistical analysis of the scaling of resting (basal) metabolic rate, BMR, with body mass, Bm and body temperature, Tb, in mammals. 2. Whilst the majority of the variance in ln BMR is explained by ln Bm, the Tb term is statistically significant. The best fit model was quadratic, indicating that the scaling of ln BMR with ln Bm varies with body size; the value of any scaling exponent estimated for a sample of mammals will therefore depend on the size distribution of species in the study. This effect can account for much of the variation in scaling exponents reported in the literature for mammals. 3. In all models, inclusion of Tb reduced the strength of scaling with ln Bm. The model including Tb suggests that birds and mammals have a similar underlying thermal dependence of BMR, equivalent to a Q10 of 2·9 across the range of Tb values 32–42 °C. 4. There was significant heterogeneity in both the mass scaling exponent and mean BMR across mammalian orders, with a tendency for orders dominated by larger taxa to have steeper scaling exponents. This heterogeneity was particularly marked across orders with smaller mean Bm and the taxonomic composition of the sample will thus also affect the observed scaling exponent. After correcting for the effects of ln Bm and Tb, Soricomorpha, Didelphimorphia and Artiodactyla had the highest BMR of those orders represented by more than 10 species in the data set. 5. Inclusion of Tb in the model removed the effect of diet category evident from a model in ln Bm alone and widely reported in the literature; this was caused by a strong interaction between diet category and Tb in mammals. 6. Inclusion of mean ambient temperature, Ta, in the model indicated a significant inverse relationship between ln BMR and Ta, complicated by an interaction between Ta and Tb. All other things being equal, a polar mammal living at −10 °C has a body temperature ∼2·7 °C warmer and a BMR higher by ∼40% than a tropical mammal of similar size living at 25 °C.

Forage quantity, quality and depletion as scale-dependent mechanisms driving habitat selection of a large browsing herbivore.

Abstract: 1. Mechanisms that affect the spatial distribution of animals are typically scale-dependent and may involve forage distribution. Forage quality and quantity are often inversely correlated and a much discussed trade-off is whether or not to select for high-quality forage at the expense of forage abundance. This discussion has rarely involved scale-dependence or been applied to Northern browsing herbivores. At small spatial scales, browsers are assumed to select for the best quality forage. But, as high-quality forage resources are often scarce and may become depleted, coarse-scale habitat selection is assumed to be driven by forage availability. 2. To evaluate if moose selection for forage quantity and quality is scale-dependent we modelled summer and winter habitat selection of 32 GPS-marked female moose (Alces alces) at two spatial scales (landscape-scale vs. within-home range-scale). We used mixed-effects resource selection functions (RSFs) and landscape-scale forage availability models of six tree species of varying quality for moose. We considered silver birch (Betula pendula), downy birch (Betula pubescens.), Scots pine (Pinus sylvestris) as low quality browse species and rowan (Sorbus aucuparia), aspen (Populus tremula), willow (Salix spp.) as high-quality species. 3. As expected, the overall selection patterns for available browse biomass and quality varied across spatiotemporal scales. At the landscape-scale, moose selected for habitat with high available browse biomass of low quality species while at the within-home range-scale moose selected for sites with the highest quality browse species available. Furthermore, selection patterns during summer remained fairly stable, while during winter, selection at the within-home range-scale switched from sites with high quality to sites with lower quality browse species which suggests depletion of high-quality species. Consistent with expectations from seasonal resource depletion, site fidelity (bimonthly home range overlap) was much lower in winter than in summer. 4. Coarse-scale habitat selection by moose as a function of forage variability revealed a scale-dependent trade-off between available browse quantity and browse quality. Moreover, resource depletion changed the winter selection criteria of free-ranging moose and we demonstrate how the behavioural response to such a dynamic process can be inferred from RSFs.

Mixed conditional logistic regression for habitat selection studies

Abstract: 1. Resource selection functions (RSFs) are becoming a dominant tool in habitat selection studies. RSF coefficients can be estimated with unconditional (standard) and conditional logistic regressions. While the advantage of mixed-effects models is recognized for standard logistic regression, mixed conditional logistic regression remains largely overlooked in ecological studies. 2. We demonstrate the significance of mixed conditional logistic regression for habitat selection studies. First, we use spatially explicit models to illustrate how mixed-effects RSFs can be useful in the presence of inter-individual heterogeneity in selection and when the assumption of independence from irrelevant alternatives (IIA) is violated. The IIA hypothesis states that the strength of preference for habitat type A over habitat type B does not depend on the other habitat types also available. Secondly, we demonstrate the significance of mixed-effects models to evaluate habitat selection of free-ranging bison Bison bison. 3. When movement rules were homogeneous among individuals and the IIA assumption was respected, fixed-effects RSFs adequately described habitat selection by simulated animals. In situations violating the inter-individual homogeneity and IIA assumptions, however, RSFs were best estimated with mixed-effects regressions, and fixed-effects models could even provide faulty conclusions. 4. Mixed-effects models indicate that bison did not select farmlands, but exhibited strong inter-individual variations in their response to farmlands. Less than half of the bison preferred farmlands over forests. Conversely, the fixed-effect model simply suggested an overall selection for farmlands. 5. Conditional logistic regression is recognized as a powerful approach to evaluate habitat selection when resource availability changes. This regression is increasingly used in ecological studies, but almost exclusively in the context of fixed-effects models. Fitness maximization can imply differences in trade-offs among individuals, which can yield inter-individual differences in selection and lead to departure from IIA. These situations are best modelled with mixed-effects models. Mixed-effects conditional logistic regression should become a valuable tool for ecological research.

Long foraging distances impose high costs on offspring production in solitary bees

Abstract: Summary 1. Solitary bees are central place foragers returning to their nests several times a day with pollen and nectar to provision their brood cells. They are especially susceptible to landscape changes that lead to an increased spatial separation of suitable nesting sites and flower rich host plant stands. While knowledge of bee foraging ranges is currently growing, quantitative data on the costs of foraging flights are very scarce, although such data are crucial to understand bee population dynamics. 2. In this study, the impact of increased foraging distance on the duration of foraging bouts and on the number of brood cells provisioned per time unit was experimentally quantified in the two pollen specialist solitary bee species Hoplitis adunca and Chelostoma rapunculi. Females nesting at different sites foraged under the same environmental conditions on a single large and movable flowering host plant patch in an otherwise host plant free landscape. 3. The number of brood cells provisioned per time unit by H. adunca was found to decrease by 23%, 31% and 26% with an increase in the foraging distance by 150, 200 and 300 m, respectively. The number of brood cells provisioned by C. rapunculi decreased by 46% and 36% with an increase in the foraging distance by 500 and 600 m, respectively. 4. Contrary to expectation, a widely scattered arrangement of host plants did not result in longer mean duration of a foraging bout in H. adunca compared to a highly aggregated arrangement, which might be due to a reduced flight directionality combined with a high rate of revisitation of already depleted flowers in the aggregated plant arrangement or by a stronger competition and disturbance by other flower visitors. 5. The results of this study clearly indicate that a close neighbourhood of suitable nesting and foraging habitats is crucial for population persistence and thus conservation of endangered solitary bee species.

Analysis of variance with unbalanced data: an update for ecology & evolution

Abstract: 1. Factorial analysis of variance (anova) with unbalanced (non-orthogonal) data is a commonplace but controversial and poorly understood topic in applied statistics. 2. We explain that anova calculates the sum of squares for each term in the model formula sequentially (type I sums of squares) and show how anova tables of adjusted sums of squares are composite tables assembled from multiple sequential analyses. A different anova is performed for each explanatory variable or interaction so that each term is placed last in the model formula in turn and adjusted for the others. 3. The sum of squares for each term in the analysis can be calculated after adjusting only for the main effects of other explanatory variables (type II sums of squares) or, controversially, for both main effects and interactions (type III sums of squares). 4. We summarize the main recent developments and emphasize the shift away from the search for the 'right' anova table in favour of presenting one or more models that best suit the objectives of the analysis.

A phylogenetic approach to disentangling the role of competition and habitat filtering in community assembly of Neotropical forest birds

Abstract: 1. Methods that assess patterns of phylogenetic relatedness, as well as character distribution and evolution, allow one to infer the ecological processes involved in community assembly. Assuming niche conservatism, assemblages should shift from phylogenetic clustering to evenness with decreasing geographic scale because the relative importance of mechanisms that shape assemblages is hypothesized to be scale-dependent. Whereas habitat filtering is more likely to act at regional scales because of increased habitat heterogeneity that allows sorting of ecologically similar species in contrasting environments, competition is more likely to act at local scales because low habitat heterogeneity provides few opportunities for niche partitioning. 2. We used species lists to assess assemblage composition, data on ecologically-relevant traits, and a molecular phylogeny, to examine the phylogenetic structure of antbird (Thamnophilidae) assemblages at three different geographical scales: regional (ecoregions), intermediate (100-ha plots) and local (mixed-flocks). In addition, we used patterns of phylogenetic beta diversity and beta diversity to separate the factors that structure antbird assemblages at regional scales. 3. Contrary to previous findings, we found a shift from phylogenetic evenness to clustering with decreasing geographical scale. We argue that this does not reject the hypothesis that habitat filtering is the predominant force in regional community assembly, because analyses of trait evolution and structure indicated a lack of niche conservatism in antbirds. 4. In some cases, phylogenetic evenness at regional scales can be an effect of historical biogeographic processes instead of niche-based processes. However, regional patterns of beta diversity and phylogenetic beta diversity suggested that phylogenetic structure in our study cannot be explained by the history of speciation and dispersal of antbirds, further supporting the habitat-filtering hypothesis. 5. Our analyses suggested that competitive interactions might not play an important role locally, which would provide a plausible explanation for the high alpha diversity of antbirds in Amazonia. 6. Finally, we emphasize the importance of including trait information in studies of phylogenetic community structure to adequately assess the mechanisms that determine species co-existence.

Top predators, mesopredators and their prey: interference ecosystems along bioclimatic productivity gradients

Abstract: 1. The Mesopredator Release Hypothesis (MRH) suggests that top predator suppression of mesopredators is a key ecosystem function with cascading impacts on herbivore prey, but it remains to be shown that this top-down cascade impacts the large-scale structure of ecosystems. 2. The Exploitation Ecosystems Hypothesis (EEH) predicts that regional ecosystem structures are determined by top-down exploitation and bottom-up productivity. In contrast to MRH, EEH assumes that interference among predators has a negligible impact on the structure of ecosystems with three trophic levels. 3. We use the recolonization of a top predator in a three-level boreal ecosystem as a natural experiment to test if large-scale biomass distributions and population trends support MRH. Inspired by EEH, we also test if top-down interference and bottom-up productivity impact regional ecosystem structures. 4. We use data from the Finnish Wildlife Triangle Scheme which has monitored top predator (lynx, Lynx lynx), mesopredator (red fox, Vulpes vulpes) and prey (mountain hare, Lepus timidus) abundance for 17 years in a 200 000 km(2) study area which covers a distinct productivity gradient. 5. Fox biomass was lower than expected from productivity where lynx biomass was high, whilst hare biomass was lower than expected from productivity where fox biomass was high. Hence, where interference controlled fox abundance, lynx had an indirect positive impact on hare abundance as predicted by MRH. The rates of change indicated that lynx expansion gradually suppressed fox biomass. 6. Lynx status caused shifts between ecosystem structures. In the 'interference ecosystem', lynx and hare biomass increased with productivity whilst fox biomass did not. In the 'mesopredator release ecosystem', fox biomass increased with productivity but hare biomass did not. Thus, biomass controlled top-down did not respond to changes in productivity. This fulfils a critical prediction of EEH. 7. We conclude that the cascade involving top predators, mesopredators and their prey can determine large-scale biomass distribution patterns and regional ecosystem structures. Hence, interference within trophic levels has to be taken into account to understand how terrestrial ecosystem structures are shaped.

Identifying predators clarifies predictors of nest success in a temperate passerine.

Abstract: 1. Nest predation negatively affects most avian populations. Studies of nest predation usually group all nest failures when attempting to determine temporal and parental activities, habitat or landscape predictors of success. Often these studies find few significant predictors and interpret patterns as essentially random. 2. Relatively little is known about the importance of individual predator species or groups on observed patterns of nest success, and how the ecology of these predators may influence patterns of success and failure. 3. In 2006 and 2007, time-lapse, infrared video systems were deployed at nests of Swainson's warblers (Limnothlypis swainsonii Audubon) in east-central Arkansas to identify dominant nest predators and determine whether factors predicting predation differed among these predators. 4. Analysis of pooled data yielded few predictors of predation risk, whereas separate analyses for the three major predator groups revealed clear, but often conflicting, patterns. 5. Predation by ratsnakes (Elaphe obsoleta) and raptors was more common during the nestling period, whereas predation by brown-headed cowbirds (Molothrus ater) occurred more during incubation. Additionally, the risk of predation by raptors and cowbirds decreased throughout the breeding season, whereas ratsnake predation risk increased. 6. Contrary to expectations, predation by ratsnakes and cowbirds was more common far from edges, whereas raptor predation was more common close to agricultural edges. 7. Collectively, our results suggest that associating specific predators with the nests they prey on is necessary to understand underlying mechanisms.

Explaining abundance–occupancy relationships in specialists and generalists: a case study on aquatic macroinvertebrates in standing waters

Abstract: 1. A positive interspecific abundance-occupancy relationship is one of the most robust patterns in macroecology. Yet, the mechanisms driving this pattern are poorly understood. Here, we use biological traits of freshwater macroinvertebrates to gain a mechanistic understanding and disentangle the various explanations. We ask whether mechanisms underlying the abundance-occupancy relationship differ between species, and whether information on individual species can be used to explain their contribution to the interspecific relationship. 2. We test the hypothesis that the importance of metapopulation dynamics or niche differences in explaining the relationship differs between species, varying in relation to their habitat breadth. In addition, we analyse how a species' biological traits shape its habitat breadth and its abundance and occupancy. 3. The abundance and occupancy of the 234 different aquatic macroinvertebrate species were strongly and positively related. Marked differences were found between habitat specialists and habitat generalists in the goodness-of-fit of abundance-occupancy relationships. The occupancy-frequency distribution was bimodal for habitat generalists, allowing 'satellite species' to be distinguished from 'core species'. 4. Habitat generalists appeared to be more widespread but less abundant than habitat specialists, suggesting that the jack-of-all-trades may be master-of-none. Species traits (trophic position and other life-history traits) explained a significant part of the variation around the general relationship. Among habitat specialists, more species showed synchronized life cycles, a low dispersal capacity or clustered oviposition, being better adapted to predictable habitats. Among habitat generalists, more species had long-lived adults, spreading reproductive effort in time and space, and were strong dispersers, being better adapted to unpredictable habitats. 5. Interspecific abundance-occupancy relationships can be best understood by examining the contribution of individual species. For habitat specialists, the interplay between niche differences (diet and habitat use) and the underlying spatial distribution of environmental conditions result in competitive displacement and differences in species' success. For habitat generalists, differences in colonization and extinction rates between species are more important. Therefore, both metapopulation dynamics and niche differences can operate simultaneously but apply to different species, thus constituting different endpoints of the same continuum.

Vertical distribution, flight behaviour and evolution of wing morphology in Morpho butterflies

Abstract: 1 Flight is a key innovation in the evolution of insects that is crucial to their dispersal, migration, territoriality, courtship and predator avoidance Male butterflies have characteristic territoriality and courtship flight behaviours, and females use a characteristic flight behaviour when searching for host plants This implies that selection acts on wing morphology to maximize flight performance for conducting important behaviours among sexes 2 Butterflies in the genus Morpho are obvious components of neotropical forests, and many observations indicate that they show two broad categories of flight behaviour and flight height Although species can be categorized as using gliding or flapping flight, and flying at either canopy or understorey height, the association of flight behaviour and flight height with wing shape evolution has never been explored 3 Two clades within Morpho differ in flight behaviour and height Males and females of one clade inhabit the forest understorey and use flapping flight, whereas in the other clade, males use gliding flight at canopy level and females use flapping flight in both canopy and understorey 4 We used independent contrasts to answer whether wing shape is associated with flight behaviour and height Given a single switch to canopy habitation and gliding flight, we compared contrasts for the node at which the switch to canopy flight occurred with the distribution of values in the two focal clades We found significant changes in wing shape at the transition to canopy flight only in males, and no change in size for either sex A second node within the canopy clade suggests that other factors may also be involved in wing shape evolution Our results reinforce the hypothesis that natural selection acts differently on male and female butterfly wing shape and indicate that the transition to canopy flight cannot explain all wing shape diversity in Morpho 5 This study provides a starting point for characterizing evolution of wing morphology in forest butterflies in the contexts of habitat selection and flight behaviour Further, these observations suggest that exploring wing shape evolution for canopy and understorey species in other insects may help understand the effects of habitat destruction on biological diversity

Phenotype-environment correlations in a putative whitefish adaptive radiation

Abstract: 1. The adaptive radiation of fishes into benthic (littoral) and pelagic (lentic) morphs in post-glacial lakes has become an important model system for speciation. Although these systems are well studied, there is little evidence of the existence of morphs that have diverged to utilize resources in the remaining principal lake habitat, the profundal zone. 2. Here, we tested phenotype-environment correlations of three whitefish (Coregonus lavaretus) morphs that have radiated into littoral, pelagic and profundal niches in northern Scandinavian lakes. We hypothesized that morphs in such trimorphic systems would have a morphology adapted to one of the principal lake habitats (littoral, pelagic or profundal niches). Most whitefish populations in the study area are formed by a single (monomorphic) whitefish morph, and we further hypothesized that these populations should display intermediate morphotypes and niche utilization. We used a combination of traditional (stomach content, habitat use, gill raker counts) and more recently developed (stable isotopes, geometric morphometrics) techniques to evaluate phenotype-environment correlations in two lakes with trimorphic and two lakes with monomorphic whitefish. 3. Distinct phenotype-environment correlations were evident for each principal niche in whitefish morphs inhabiting trimorphic lakes. Monomorphic whitefish exploited multiple habitats, had intermediate morphology, displayed increased variance in gillraker-counts, and relied significantly on zooplankton, most likely due to relaxed resource competition. 4. We suggest that the ecological processes acting in the trimorphic lakes are similar to each other, and are driving the adaptive evolution of whitefish morphs, possibly leading to the formation of new species.

Mating behaviour, life history and adaptation to insecticides determine species exclusion between whiteflies.

Abstract: Summary 1. Negative interspecific interactions, such as resource competition or reproductive interference, can lead to the displacement of species (species exclusion). 2. Here, we investigated the effect of life history, mating behaviour and adaptation to insecticides on species exclusion between cryptic whitefly species that make up the Bemisia tabaci species complex. We conducted population cage experiments independently in China, Australia, the United States and Israel to observe patterns of species exclusion between an invasive species commonly referred to as the B biotype and three other species commonly known as biotypes ZHJ1, AN and Q. 3. Although experimental conditions and species varied between regions, we were able to predict the observed patterns of exclusion in each region using a stochastic model that incorporated data on development time, mating behaviour and resistance to insecticides. 4. Between-species variation in mating behaviour was a more significant factor affecting species exclusion than variation in development time. Specifically, the ability of B to copulate more effectively than other species resulted in a faster rate of population increase for B, as well as a reduced rate of population growth for other species, leading to species exclusion. The greater ability of B to evolve resistance to insecticides also contributed to exclusion of other species in some cases. 5. Results indicate that an integrative analysis of the consequences of variation in life-history traits, mating behaviours and adaption to insecticides could provide a robust framework for predicting species exclusion following whitefly invasions.

Carry‐over effects reveal reproductive costs in a long‐distance migrant

Abstract: 1. It has been known for some time that the consequences of 'decisions' made at one point in an animal's life may not always be borne immediately. For example, numerous studies have demonstrated the trade-off between current and future breeding success across multiple taxa. 2. It is becoming increasingly clear that such processes may also operate among seasons, such that the conditions experienced at one point in the annual cycle may have significant downstream impacts, or 'carry-over effects', and this is particularly evident among migratory species. We might therefore predict that certain combinations of reproductive and migratory strategy could lead to profound carry-over effects. However, the extent to which these phenomena might generate variation in fitness within a population is unclear. 3. Here, we investigate how winter habitat selection in a long-distance migrant, with extended parental care (the Light-bellied Brent goose) is influenced by parental status and how this has a counterintuitive effect on subsequent breeding success. 4. Dominant individuals and groups generally monopolize the best quality resources. In the case of geese, families are dominant; however, our findings highlight a hidden cost to raising a family. Stable isotope analysis demonstrates that later in the non-breeding season, adults with families utilize lower quality resources than non-breeders. This is probably caused by parents being constrained in habitat choice by the lower foraging efficiency of their juveniles. Consequently, parental adults end the winter in poorer condition than non-breeders. 5. We further demonstrate that parents in one year are less likely than expected to breed again in the next year and suggest that this is caused by conditions during the non-breeding period being carried over into the breeding season. In conclusion, we demonstrate previously hidden costs to raising a family, which are likely to be important in terms of life-history evolution.