Showing papers by "Luis Mauricio Bini published in 2009"

Partitioning and mapping uncertainties in ensembles of forecasts of species turnover under climate change

Abstract: Forecasts of species range shifts under climate change are fraught with uncertainties and ensemble forecasting may provide a framework to deal with such uncertainties. Here, a novel approach to partition the variance among modeled attributes, such as richness or turnover, and map sources of uncertainty in ensembles of forecasts is presented. We model the distributions of 3837 New World birds and project them into 2080. We then quantify and map the relative contribution of different sources of uncertainty from alternative methods for niche modeling, general circulation models (AOGCM), and emission scenarios. The greatest source of uncertainty in forecasts of species range shifts arises from using alternative methods for niche modeling, followed by AOGCM, and their interaction. Our results concur with previous studies that discovered that projections from alternative models can be extremely varied, but we provide a new analytical framework to examine uncertainties in models by quantifying their importance and mapping their patterns.

No evidence for environmental and spatial processes in structuring phytoplankton communities

Abstract: The relative importance of local and regional processes in shaping natural communities within a metacommunity context has been a focus of intense debate in recent years. Floodplain lakes provide a good system for testing this theoretical approach, as they undergo seasonal variations in physical, chemical and biological factors, as well as in their degree of connectivity. Here, we investigated how local phytoplankton communities in lakes of a tropical river-floodplain system (Araguaia River floodplain – Central Brazil) were affected by environmental and spatial (dispersal) predictors in two rainy and two dry seasons (two consecutive years). Partial redundancy analysis indicated that during the periods analyzed the effects of neither predictor were significant. Although we cannot exclude the possibility that these tropical phytoplankton communities could be regulated by stochastic events, we suggested that further studies will have greater explanatory power if they include other variables related to biotic interactions (e.g., abundance of grazers) and fine-scale environmental variation.

Climate history, human impacts and global body size of Carnivora (Mammalia: Eutheria) at multiple evolutionary scales

Abstract: Aim One of the longest recognized patterns in macroecology, Bergmann’s rule, describes the tendency for homeothermic animals to have larger body sizes in cooler climates than their phylogenetic relatives in warmer climates. Here we provide an integrative process-based explanation for Bergmann’s rule at the global scale for the mammal order Carnivora. Location Global. Methods Our database comprises the body sizes of 209 species of extant terrestrial Carnivora, which were analysed using phylogenetic autocorrelation and phylogenetic eigenvector regression. The interspecific variation in body size was partitioned into phylogenetic (P) and specific (S) components, and mean P- and S-components across species were correlated with environmental variables and human occupation both globally and for regions glaciated or not during the last Ice Age. Results Three-quarters of the variation in body size can be explained by phylogenetic relationships among species, and the geographical pattern of mean values of the P-component is the opposite of the pattern predicted by Bergmann’s rule. Partial regression revealed that at least 43% of global variation in the mean phylogenetic component is explained by current environmental factors. In contrast, the mean S-component of body size shows large positive deviations from ancestors across the Holarctic, and negative deviations in southern South America, the Sahara Desert, and tropical Asia. There is a moderately strong relationship between the human footprint and body size in glaciated regions, explaining 19% of the variance of the mean P-component. The relationship with the human footprint and the P-component is much weaker in the rest of the world, and there is no relationship between human footprint and S-component in any region. Main conclusions Bergmannian clines are stronger at higher latitudes in the Northern Hemisphere because of the continuous alternation of glacial– interglacial cycles throughout the late Pliocene and Pleistocene, which generated increased species turnover, differential colonization and more intense adaptive processes soon after glaciated areas became exposed. Our analyses provide a unified explanation for an adaptive Bergmann’s rule within species and for an interspecific trend towards larger body sizes in assemblages resulting from historical changes in climate and contemporary human impacts.

Niche modelling and landscape genetics of Caryocar brasiliense ("Pequi" tree: Caryocaraceae) in Brazilian Cerrado: an integrative approach for evaluating central-peripheral population patterns

Abstract: Complex and integrative approaches may be necessary to understand the abundant-centre model and the patterns in genetic diversity that may be explained by this model. Here we developed an integrated framework to study spatial patterns in genetic diversity within local populations, coupling genetic data, niche modelling and landscape genetics, and applied this framework to evaluate population structure of Caryocar brasiliense, an endemic tree from the Brazilian Cerrado. We showed different geographical patterns for genetic diversity, allelic richness and inbreeding levels, estimated using microsatellite data for ten local populations. Ecological suitability was estimating by combining five niche modelling techniques. Genetic diversity tend to follow a central-periphery model and is associated with ecological variables. On the other hand, inbreeding levels may be alternatively explained by isolation processes and habitat fragmentation more related to intense recent human occupation in the southern border of the biome, or by deeper historical patterns in the origin of the populations. Although still suffering from some of the problems of central-periphery analysis (small number of local populations), our analyses show how these patterns can be better investigated and offering a better understanding of the processes structuring genetic diversity within species’ geographic ranges.

The role of niche measures in explaining the abundance–distribution relationship in tropical lotic chironomids

Abstract: The positive relationship between species regional distribution and local abundance is one of the most ubiquitous patterns in ecology. Among the hypotheses proposed to explain the relationship, the niche breadth and the niche position (or habitat availability) hypothesis are the most investigated. An unappreciated issue, but that is likely to be important for the understanding the relationship is the nature of variables used to estimate niche measures. Here, we analyzed the form of this relationship in lotic chironomid genera and tested whether niche measures estimated from local and landscape variables explain the observed pattern. Analyses were based in 47 forested streams within Southeastern Brazil. From our data set, we randomly partitioned the data in two non-overlapping sets to estimate taxa distribution and abundance (Distribution Data; n = 23 sites) and to generate niche measures (Niche Data; n = 24). We repeated that process 1,000 times, and for each one, we generated niche breadth and position measures using in-stream and landscape variables and estimated abundance and distribution for each taxa. With these, we estimated the relationship between both abundance and distribution and niche measures using ordinary least-squares regressions. We found no relationship between niche position estimated from local variables and local abundance nor regional distribution. There was a negative relationship between niche position estimated from landscape and local abundance, and regional distribution. We found a positive relationship between niche breadth (local and landscape) and both local abundance and regional distribution. When the relationship was significant, both niche position and niche breadth explained less than a half of total variation in abundance and distribution. This suggests that not only niche-based processes, but also other mechanisms may be responsible for the abundance–distribution relationship in lotic chironomids. A novel finding of this study was that although there was much unexplained variability around the relationships, niche breadth was a better predictor of abundance and distribution than niche position. We suggest that future studies should investigate if spatial processes, like dispersal, together with environmental processes affect interspecific abundance–distribution relationships.

Agriculture, habitat loss and spatial patterns of human occupation in a biodiversity hotspot

Abstract: The Cerrado biome, the second largest biome in Neotropical region, consists of a mosaic of different habitat types, ranging from open grasslands to dense woodlands and dry forests. An intensive recent occupation process has transformed it into the most important region for cattle ranching and intensive commodity crops in Brazil. In this study, a macroecological approach was used to evaluate broad-scale spatial patterns of habitat loss in the Brazilian Cerrado, applying a series of spatial autocorrelation and partial regression analyses to understand how the proportion of remaining natural habitats is correlated with socio-economic variables, expressing different dimensions of human occupation and climatic variation. On average, 59% of the area is occupied by natural remnants at the spatial scale analyzed, although patterns of habitat loss are strongly spatially structured, with a Moran's I spatial autocorrelation coefficient equal to 0.825 ± 0.055 (p < 0.001). The partial regression analysis explains 89% of variation in percentage of natural remnants. The highest proportion of variance is explained by the multiple overlap between human occupation, climatic variation and geographic structure (67%), as well as by the climatically structured component of human occupation (8%). Based on the space-time interactive process of human occupation in the biome, future scenarios should be rather pessimistic. If the wave of human occupation continues towards the northern parts of the biome, as expected, we can predict that percentages will decline rapidly including even stronger losses of habitat at the biome scale.

The climate envelope may not be empty

Abstract: A recent paper (1) purported to document negligible climatic determination among European bird species, with implications for forecasting range shifts in changing climates. However, only 12 of 100 species analyzed were endemic—thus, for the remaining 88% of test species, key limits with likely climatic determination were excluded, particularly eastward and southward (2). Second, the authors developed null distributions conserving the same prevalence and semivariogram as real species' distributions and showed that real distributions were not modeled better than “null” distributions. However, most variation in null and real distributions at broad geographic scales is explained by spatially structured climate variation that is difficult to disentangle. The authors' manipulation fails to eliminate climate as a correlate of null ranges exactly because their occurrences were spatially clumped: as climate is autocorrelated, null distributions have climate signatures just like real distributions. Producing null models removing effects of climate but keeping the spatial cohesion of the distribution is unlikely, as in recent debates regarding mid-domain effects as appropriate null models for diversity (3). Null distributions will show climate signatures similar to those of real species that are not eliminated in their randomization algorithm, so the authors cannot reject the hypothesis of a climate association in European birds. Nonetheless, we agree that, because distributions can be modeled by using current spatially structured climatic predictors without necessity of direct causal linkages (4), more studies oriented at testing the robustness of correlative methods in predicting species' distributions under future climate scenarios are needed (5).

Macroecologia, biogeografia e áreas prioritárias para conservação no cerrado

Abstract: revista vol 13 no 3.indd Normal 0 21 false false false PT-BR X-NONE X-NONE MicrosoftInternetExplorer4 Ha consenso entre os cientistas de que a ha atualmente uma “crise da biodiversidade”, resultado da constante e intensa perda de habitat natural causada pela expansao da ocupacao. Como a biologia da conservacao tem sido muitas vezes reconhecida como uma ciencia da crise, ela deve fornecer informacoes capazes de mediar, de forma mais cientifica possivel, as tomadas de decisao que sao necessarias. Dentre estas, uma das mais importantes e indicar regioes prioritarias para a conservacao, ja que por motivos obvios nao e possivel preservar todos os ecossistemas por inteiro. Nesse contexto, recentemente sugeriu-se que a aplicacao de principios, teorias e analises provenientes da biogeografia e da macroecologia seriam importantes na Biologia da Conservacao, formalizando uma abordagem que tem sido denominada “Biogeografia da Conservacao”. Assim, o objetivo deste artigo e discutir e revisar esses componentes da biogeografia da conservacao, utilizando uma abordagem macroecologica para desenvolver e aplicar metodos de planejamento sistematico em conservacao, utilizando o bioma Cerrado como um modelo de estudo. Foram discutidos inicialmente os padroes de riqueza e diversidade beta e, em um segundo momento, como esses padroes podem ser correlacionados a ocupacao humana do Bioma. Essa relacao e fundamental para subsidiar a aplicacao de modelos de planejamento sistematico de conservacao em escala regional (analises de insubstituibilidade, complementaridade e de lacunas). E preciso considerar tambem que ha serias falhas de conhecimento sobre os padroes de biodiversidade na regiao e que a escolha de grupos indicadores pode ser importante para minimizar problemas gerados pela falta de conhecimento. Assim, essa abordagem e interessante em um cenario de grandes incertezas (ausencia de dados detalhados) e de rapida transformacao da paisagem, possibilitando a otimizacao de estudos em grandes escalas e depois transferir os resultados para escalas espaciais mais locais e realmente relevantes para a conservacao. Nessas regioes, podem ser realizados, em um segundo momento, estudos mais detalhados a fim de avaliar padroes de viabilidade populacional, fragmentacao de habitat e regioes potenciais de manutencao da diversidade genetica.

Conservation biogeography and climate change in the brazilian cerrado

Abstract: Many studies on climate changes have been developed based on experimental ap- proaches at local scales, despite the much broader geographical scales at which these changes are ex- pected to affect biodiversity patterns. Here we applied an ensemble forecasting approach to model the effects of climate change on diversity patterns found in the Brazilian Cerrado, using six different niche model techniques to evaluate potential shifts in geographic ranges of 753 species of vertebrates in the year 2050. We used the prediction of three global circulation models (GCMs) to project species distributions in 2050. Our analyses provide evidences of shifts in species geographic ranges and turnover rates in the Brazilian Cerrado, especially at location of maximum species richness. Although future conservation conflicts are difficult to predict because of the uncertainties (and actually lack of data) in spatial dynamics of future expansions of human activities throughout the biome, our analy- ses show that expansions of species' distribution may encompass regions currently used for cattle ranching activities.

Conservation biogeography of mammals in the Cerrado biome under the unified theory of macroecology.

Abstract: Understanding what limits the distribution and abundance of species is critical for adopting optimal conservation planning strategies, although it is still difficult to obtain abundance data at broad spatial scales. Here we propose conservation priorities in the Brazilian Cerrado based on density values of 108 mammal species. These values were estimated by an abundant-centre model coupled with McGill and Collin's unified theory for macroecology. We assumed that species' densities decay with a Gaussian distribution towards the range borders from a maximum density placed at the centre of each species' range. We used allometric equations to estimate maximum densities, at the Cerrado region we corrected the estimated densities by the natural vegetation remnants. Then we used a Simulated Annealing algorithm to select alternative sets of areas that met several levels of minimum viable population sizes (MVPSs) for each species. With low MVPSs, there were a small number of highly irreplaceable areas located in the northwest region of the biome, whereas with high MVPSs, highly irreplaceable areas occurred in up to 95% of the biome. By incorporating principles from the unified theory of macroecology, we were able to generate a conservation network for the Cerrado biome aiming to prioritise species' persistence and not just their presence.

Distribuição geográfica potencial de espécies americanas do caranguejo "violinista" (Uca spp.) (Crustacea, Decapoda) com base em modelagem de nicho ecológico

Abstract: Caranguejos do genero Uca Leach, 1814 (caranguejo "violinista") sao um grupo bem conhecido e caracterizado por um acentuado dimorfismo sexual e assimetria da quela do macho. Atualmente, estao descritas 97 especies no mundo. Objetivou-se estimar a distribuicao geografica potencial de 4 especies do genero Uca que ocorrem na costa do continente Americano: Uca maracoani Latreille, 1802-1803, U. uruguayensis Nobili, 1901, U. panacea Novak & Salmon, 1974 e U. monilifera Rathbun, 1914. Para modelar a distribuicao dessas especies nas Americas foram utilizados pontos de ocorrencia compilados da literatura. Para a modelagem foram utilizados os programas Maxent e GARP a partir de 10 variaveis climaticas e tres variaveis topograficas. Todas as variaveis foram convertidas para uma malha com resolucao de 0,0417 graus. Nos dois modelos (Maxent e GARP) as especies apresentaram distribuicao geografica maior do que sugerido por outros trabalhos de registro de ocorrencia, com excecao de U. monilifera. Segundo o criterio de area sob a curva (AUC), os modelos gerados pelo GARP apresentaram melhores resultados do que os modelos do Maxent. Entretanto, avaliando em conjunto os resultados dos dois modelos e possivel melhor estabelecer planos de conservacao para especies com habitat restrito (U. panaceae e U. monilifera), alem de recomendar um aumento na amostragem de U. maracoani no nordeste brasileiro e U. uruguyaensis no sudeste brasileiro, a fim de detectar possiveis aumentos na sua distribuicao geografica com base nas predicoes dos modelos de nicho.