Sexual size dimorphism and microhabitat use of the orange-tail skink (Gongylomorphus spp.) on Flat Island, Mauritius: conservation implications
TL;DR: Microhabitat use was found to be non-random with lizards occurring in areas with high humidity, high numbers of natural refugia, increased leaf litter coverage and plant species diversity, and low grass cover.
Abstract: The Gongylomorphus skinks are an endemic genus of Mauritius and comprise two described species. Following the recent discovery of a third putative species, endemic to Flat Island, 11 km off the coast of Mauritius, this study was conducted to examine morphometrics and the pattern of microhabitat use by the species in an effort to provide effective conservation recommendations. There was a clear sexual size dimorphism with males significantly larger than females in terms of; snout-vent length, head length, head width, snout-mouth length, snout-ear length, upper and lower fore- and hind-limb lengths and fourth toe length. There was no sexual dimorphism in other measures including pelvic width, width at the base of the tail, head depth or body weight. Microhabitat use was found to be non-random with lizards occurring in areas with high humidity, high numbers of natural refugia, increased leaf litter coverage and plant species diversity, and low grass cover. We found no evidence that microhabitat use varied in relation to sex or age of lizards. The implications of these results for the conservation management of Flat Island for the orange-tail skink are discussed.
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TL;DR: In a sample of 81 field-collected adult Blue Mountains water skinks (Eulamprus leuraensis), males and females averaged similar overall body sizes, and reproductive success increased with SVL at similar rates in both sexes.
Abstract: Sex-based divergences in body sizes and/or shapes within a species imply that selective forces act differently on morphological features in males versus females. That prediction can be tested with data on the relationship between morphology and reproductive output in females, and between morphology and realized paternity (based on genetic assignment tests) in males. In a sample of 81 field-collected adult Blue Mountains water skinks (Eulamprus leuraensis), males and females averaged similar overall body sizes (snout-vent lengths (SVLs)). Reproductive success (based on 105 progeny produced by the females) increased with SVL at similar rates in both sexes (as expected from the lack of sexual size dimorphism). Multiple paternity was common. Males had larger heads than females of the same body size, and (as predicted) reproductive success increased with relative head size in males but not in females. Males also had relatively longer limbs and shorter trunks than females, but we did not detect significant sex differences in selection on those traits. Reproductive success in both sexes was increased by relatively longer hind limbs. Our data clarify mating systems in this endangered species, and suggest that mating systems are diverse within the genus Eulamprus.
25 citations
Dissertation•
01 Aug 2019
TL;DR: It is found that morphological differences between populations were associated with ancestral origins and infer a greater invasion potential for animals of Italian origin over French, and clear indication that charismatic non-native species such as P. muralis may have use as model species with which to raise awareness and minimise the subjectivity shaping perceptions of invasive species in general.
Abstract: The potentially damaging outcomes of species introductions to areas outside of their natural range are well known, and invasive non-native species are regarded as one of the most significant threats to biodiversity worldwide. Social perceptions of non-native species are open to subjective influence, and in a rapidly changing world the implications of species introductions are becoming less defined. Understanding the ecology of invasions and the human perceptions of them, is therefore fundamentally important for managing all stages of species introductions, relying on a multidisciplinary approach to understanding the invasion process. Invasions can also provide opportunities to study adaptive responses of organisms to novel or changing environments, which in turn can provide insight into mechanistic workings of the invasion process and range expansion. In this study I investigate the ecology of introduced populations of the Common Wall lizard (Podarcis muralis). Using a multidisciplinary approach including population ecology, functional ecology, predictive modelling, social science, and behavioural experiments, I focus on the species’ invasion potential, adaptive responses, and implications for ecological impacts on native lizards in the UK and on Vancouver Island, British Columbia. I found that morphological differences between populations were associated with ancestral origins and infer a greater invasion potential for animals of Italian origin over French. Comparison of physical and performance traits, and a broad dietary niche of P. muralis, indicate considerable overlap between P. muralis and native lizards, suggesting high potential for competitive interaction. However, the varied behavioural responses observed towards scent cues in P. muralis and native lizards suggests an interplay between naivety and threat sensitivity may influence interspecific interaction. Models of predicted range expansion suggest P. muralis populations are likely to remain localised, but that potential for secondary translocation is likely to increase with increasing population size, particularly in urban habitats. I also found clear indication that charismatic non-native species such as P. muralis, may have use as model species with which to raise awareness and minimise the subjectivity shaping perceptions of invasive species in general.
4 citations
Cites background from "Sexual size dimorphism and microhab..."
...Within factors, correlations of variables with loading values > 0.4 were considered significant (Pernetta et al., 2005; Ross et al., 2008)....
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TL;DR: It is shown that woodland mosaics lacking shrubs and temporary grasslands next to forest edges are important for the species, and it is important to reconsider habitat management activities, which should not be limited to shrub control.
Abstract: Although Ablepharus kitaibelii and its subspecies are wide-spread, being distributed from the Carpathian Basin through the Balkans to Iraq, their habitat and environmental niche is poorly known. Ablepharus kitaibelii fitzingeri is almost entirely limited to the Carpathian Basin, and is amongst the most strictly protected and least known reptiles of Central and Eastern Europe. The main aim of our study was to determine habitat use preferences of different age groups of A. kitaibelii fitzingeri and Lacerta viridis . The occurrence of green lizard was determined by the abundance of refugia rather than by the naturalness of grasslands. The snake-eyed skink prefers semi-natural grasslands with abundant tussock-forming grass or sedge species, avoiding densely shrubby places. For the first time, we show that woodland mosaics lacking shrubs and temporary grasslands next to forest edges are important for the species. Microhabitat use by snake-eyed skink varies with age group; adults preferring shady edge zones rich in leaf litter and shadier grassland spots provided by woodland mosaics, whereas juveniles were found in natural, more open grasslands far from forest edges and in woodland mosaics with dense shrubby understory. Our results contribute to a better understanding of the ecological needs of A. kitaibelii fitzingeri . Our methodology could be adapted to other species and subspecies of Ablepharus . Based on our results, it is important to reconsider habitat management activities, which should not be limited to shrub control: the main goal should be the development of a diverse habitat structure.
3 citations
TL;DR: It is found that measures of body condition suggest the non-native gecko is less able to exploit such habitats and that its ability to thrive on Barbados is due to utilisation of a broader niche as befitting a habitat “generalist”, rather than competitive displacement of the native gecko from cliff side habitat.
Abstract: Island endemic reptiles face many threats that potentially have a negative effect on their conservation status, such as habitat loss, interactions with introduced predators and competitors, and sto...
3 citations
Dissertation•
11 Apr 2011
Abstract: In Canada, the prairie skink (Plestiodon septentrionalis, formerly Eumeces septentrionalis) exists only in southwestern Manitoba and is listed as Endangered under the Species at Risk Act. One of the main goals of the proposed recovery strategy for this species is to protect and restore prairie skink habitat in order to maintain self-sufficient populations. Habitat loss is the most significant threat faced by the prairie skink in Canada. Factors contributing to habitat loss include, native prairie cultivation, aspen (Populus tremuloides) encroachment, leafy spurge (Euphorbia esula) invasion, urbanization and road construction. The objective of this study was to determine microhabitat preferences of prairie skinks in southwestern Manitoba. Classification and regression tree analysis was used to compare microhabitats used by prairie skinks to randomly located sites within the individual’s estimated home range. Artificial cover was the most important microhabitat element for prairie skinks in southwestern Manitoba during the active season. Prairie skinks did not select microhabitat based on thermal characteristics, number of leafy spurge stems or percent cover of vegetation, exposed soil, gravel, juniper or leaf litter. The presence of artificial cover plays an important role in prairie skink conservation in Manitoba. Land owners and managers should use artificial cover as an interim solution in areas that are under pressure from habitat loss until landscape management goals can be achieved. This would create suitable microhabitat, provide refuge from predators, increase prey abundance, provide suitable nesting sites, and provide a substrate for thermoregulation.
2 citations
References
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TL;DR: A ‘silver bullet’ strategy on the part of conservation planners, focusing on ‘biodiversity hotspots’ where exceptional concentrations of endemic species are undergoing exceptional loss of habitat, is proposed.
Abstract: Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.
24,867 citations
"Sexual size dimorphism and microhab..." refers background in this paper
...Islands, whilst typically species poor, contain some of the highest levels of global endemicity (Cronk, 1997; Whittaker, 1998; Myers et al., 2000; Drake et al., 2002)....
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...Olesen and Valido (2003) have proposed that lizards may be important island seed dispersers....
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TL;DR: If ecological causation for dimorphism can be demonstrated in so many cases, despite the inadequacies of the available criteria, the degree of sexual sizeDimorphism in many other animal species may well also have been influenced by ecological factors, and it may be premature of dismiss this hypothesis.
Abstract: Can sexual dimorphism evolve because of ecological differences between the sexes? Although several examples of this phenomenon are well known from studies on birds, the idea has often been dismissed as lacking general applicability. This dismissal does not stem from contradictory data so much as from the difficulties inherent in testing the hypothesis, and its apparent lack of parsimony, in comparison to the alternative explanation of sexual selection. The only unequivocal evidence for the evolution of sexual dimorphism through intersexual niche partitioning would be disproportionate dimorphism in trophic structures (e.g., mouthparts). This criterion offers a minimum estimate of the importance of ecological causes for dimorphism, because it may fail to identify most cases. A review of published literature reveals examples of sexually dimorphic trophic structures in most animal phyla. Many of these examples seem to be attributable to sexual selection, but others reflect adaptations for niche divergence between the sexes. For example, dwarf non-feeding males without functional mouthparts have evolved independently in many taxa. In other cases, males and females differ in trophic structures apparently because of differences in diets. Such divergence may often reflect specific nutritional requirements for reproduction in females, or extreme (sexually selected?) differences between males and females in habitats or body sizes. Ecological competition between the sexes may be responsible for intersexual niche divergence in some cases, but the independent evolution of foraging specializations by each sex may be of more general importance. If ecological causation for dimorphism can be demonstrated in so many cases, despite the inadequacies of the available criteria, the degree of sexual size dimorphism in many other animal species may well also have been influenced by ecological factors. Hence, it may be premature to dismiss this hypothesis, despite the difficulty of testing it.
1,312 citations
"Sexual size dimorphism and microhab..." refers background in this paper
...ual size dimorphism (Shine, 1989; Olsson et al., 2002), whilst considering habitat and microhab-...
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...aration between sexes in reptiles (Shine, 1989)....
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Book•
18 Feb 1999
TL;DR: The natural laboratory paradigm is presented as a model for island evolution, followed by island theory and conservation and island remedies: the conservation of islands ecosystems.
Abstract: PART 1 - ISLANDS AS NATURAL LABORATORIES 1. The natural laboratory paradigm 2. Island environments 3. The biogeography of island life: biodiversity hotspots in context PART 2- ISLAND ECOLOGY 4. Species number games: the macroecology of island biotas 5. Community assembly and dynamics 6. Scale and island ecological theory: towards a new synthesis PART 3- ISLAND EVOLUTION 7. Arrival and change 8. Speciation and the island condition 9. Emergent models of island evolution PART 4- ISLANDS AND CONSERVATION 10. Island theory and conservation 11. Anthropogenic losses and threats to island ecosystems 12. Island remedies: the conservation of islands ecosystems
1,301 citations
"Sexual size dimorphism and microhab..." refers background in this paper
...Islands, whilst typically species poor, contain some of the highest levels of global endemicity (Cronk, 1997; Whittaker, 1998; Myers et al., 2000; Drake et al., 2002)....
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TL;DR: The model allows us to compare the relative contribution of different types of habitats to a species' growth rate and population size and predict how the loss of habitat of a particular type may affect a population.
Abstract: In the model described, we attempt to link breeding-site selection to population dynamics for situations in which there is more than one distinct type of habitat. The distribution of individuals between habitat types depends on the selective abilities of the species. This distribution, in turn, influences the population dynamics of the species as a whole. We show that the consequences of habitat selection on population dynamics for an ideal free distribution of individuals across habitats is predictably different from what would be predicted if habitat selection were preemptive, that is, if individuals, upon selecting a site, prevented others from sharing the site. If preemptive selection is ideal, average reproductive success declines with increasing density because each individual selects the best site available from those sites not yet occupied. The model allows us to compare the relative contribution of different types of habitats to a species' growth rate and population size. Furthermore, we can also...
1,197 citations
TL;DR: Analyses of the physiological consequences of habitat selection are exemplified in several case studies, the importance of considering food and other factors in the analyses is stressed, and an extension to endotherms is briefly discussed.
Abstract: By determining the microclimates that an animal experiences, habitats influence an animal's physiological capacities and ultimately its demographic and ecological performance. As a result, the ecology of organisms-especially of ectotherms-can be profoundly affected by the physiological consequences of habitat selection. Early ecologists such as Shelford and Chapman appreciated these issues, but most later ones tended to ignore physiology and instead focused on biotic interactions (e.g., competition). Recent technical and conceptual developments are now fostering a reintroduction of physiology into ecology. For issues relevant to thermal physiology, three steps are involved. First, the microclimates available in a habitat must be mapped. For ectotherms, this involves determining the operative environmental temperatures (Te)-that is, the potential body temperatures available in a habitat. Biophysical techniques can now generate Te maps with considerable accuracy. Second, the physiological effects of body temperature must be quantified. This requires laboratory studies of the effect of temperature on key performance traits. Third, the physiological suitability of habitats can be predicted by integrating the above environmental and physiological data. Analyses of the physiological conse- quences of habitat selection are exemplified in several case studies, and the importance of considering food and other factors in the analyses is stressed. An extension to endotherms is briefly discussed. The study of how and why organisms select particular habitats has long been central to ecology. In fact, the early literature of ecology was often dominated by discussions of habitat associations. Of special interest in the early days of ecology was the concept of limiting factors: which physical factors (e.g., tempera- ture, pH, salinity) limit the occurrence of organisms to particular habitats. Not surprisingly, early discussions often focused on interactions between physiology and the physical environment. Indeed, for many early ecologists, ecology and physiology were more or less synonomous concepts. Shelford, for example, de- fined ecology as "that branch of general physiology which deals with the organism as a whole . . and which also considers the organism with particular reference to its usual environment" (1913, p. 1). Similarly, Chapman argued: "The inter- relations of organisms in nature may be considered under the subject matter of ecology which is closely related to physiology, and in the minds of some biologists should be a subdivision of it" (1931, p. 3). Clearly, physiology was central to ecology at this time. In fact, physiological issues dominated nearly the first half of Chapman's (1931) book (Animal Ecology). Beginning with Elton (1927), however, ecological studies began to shift their focus from analyses of physiologically mediated interactions between organisms and their physical environments to analyses of interactions between individuals or between species, in other words, to analyses of population and community
829 citations
"Sexual size dimorphism and microhab..." refers background in this paper
...species’ physiological processes (Huey, 1991), population dynamics (Holt, 1987; Pulliam and...
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