The interplay of past diversification and evolutionary isolation with present imperilment across the amphibian tree of life

Jetz, Walter; Pyron, R. Alexander

doi:10.1038/s41559-018-0515-5

Cited by 433 publications

(568 citation statements)

References 69 publications

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“…We gathered an exhaustive global‐scale dataset on caecilians spanning body size data for > 99% (207 out of 208; Supplementary material Appendix 1 Table A1) of the world's known species. We followed the taxonomy in Frost (). To investigate the above set of hypotheses, we used the largest recorded total body length (from snout to tail tip) as the proxy for body size, as this is the most commonly reported measure of size for caecilians (Wells , Pough et al 2015).…”

Section: Methodsmentioning

confidence: 99%

“…We used AIC and Akaike model weights to reduce the whole set of models employing a dredging approach that retains a confidence subset of models that lay within six AIC units of the most informative model. This method removes models that have spurious parameter estimates due to poor model fit above the chosen AIC threshold (Richards , Harrison et al ). The importance of each explanatory variable was judged according to AIC‐weighted mean effect sizes averaged across the subset of regression models, and are presented as AIC‐weighted slope estimates ±95% confidence intervals to estimate the significance of the effect of each predictor on body size (Table 1).…”

Section: Methodsmentioning

confidence: 99%

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Global patterns of body size evolution are driven by precipitation in legless amphibians

et al. 2019

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Body size shapes ecological interactions across and within species, ultimately influencing the evolution of large‐scale biodiversity patterns. Therefore, macroecological studies of body size provide a link between spatial variation in selection regimes and the evolution of animal assemblages through space. Multiple hypotheses have been formulated to explain the evolution of spatial gradients of animal body size, predominantly driven by thermal (Bergmann's rule), humidity (‘water conservation hypothesis’) and resource constraints (‘resource rule’, ‘seasonality rule’) on physiological homeostasis. However, while integrative tests of all four hypotheses combined are needed, the focus of such empirical efforts needs to move beyond the traditional endotherm–ectotherm dichotomy, to instead interrogate the role that variation in lifestyles within major lineages (e.g. classes) play in creating neglected scenarios of selection via analyses of largely overlooked environment–body size interactions. Here, we test all four rules above using a global database spanning 99% of modern species of an entire Order of legless, predominantly underground‐dwelling amphibians (Gymnophiona, or caecilians). We found a consistent effect of increasing precipitation (and resource abundance) on body size reductions (supporting the water conservation hypothesis), while Bergmann's, the seasonality and resource rules are rejected. We argue that subterranean lifestyles minimize the effects of aboveground selection agents, making humidity a dominant selection pressure – aridity promotes larger body sizes that reduce risk of evaporative dehydration, while smaller sizes occur in wetter environments where dehydration constraints are relaxed. We discuss the links between these principles with the physiological constraints that may have influenced the tropically‐restricted global radiation of caecilians.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Global patterns of body size evolution are driven by precipitation in legless amphibians

et al. 2019

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“…). At the broader‐scale of global threat status, previous work indicates that rapidly diversifying amphibian genera have a high proportion of range‐restricted, threatened species (Greenberg & Mooers ), though at the species‐level evolutionary distinctiveness is not a strong predictor of threat status (Jetz & Pyron ). If rapid diversification is associated with range‐restriction and affiliation to wet and forested biomes, then we may expect that not only should evolutionarily distinct amphibian species not be disadvantaged, but possibly even have an advantage in human‐modified ecosystems.…”

Section: Introductionmentioning

confidence: 99%

Evolutionarily distinct amphibians are disproportionately lost from human‐modified ecosystems

et al. 2018

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Humans continue to alter terrestrial ecosystems, but our understanding of how biodiversity responds is still limited. Anthropogenic habitat conversion has been associated with the loss of evolutionarily distinct bird species at local scales, but whether this evolutionary pattern holds across other clades is unknown. We collate a global dataset on amphibian assemblages in intact forests and nearby human-modified sites to assess whether evolutionary history influences susceptibility to land conversion. We found that evolutionarily distinct amphibian species are disproportionately lost when forested habitats are converted to alternative land-uses. We tested the hypothesis that grassland-associated amphibian lineages have both higher diversification and are pre-adapted to human landscapes, but found only weak evidence supporting this. The loss of evolutionarily distinct amphibians with land conversion suggests that preserving remnant forests will be vital if we aim to preserve the amphibian tree of life in the face of mounting anthropogenic pressures.

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“…; Fouquet et al. ; Jetz and Pyron ; Sabbag et al. ), the intensity of male‐male competition has been well characterized.…”

Section: Discussionmentioning

confidence: 99%

“…; Fouquet et al. ; Jetz and Pyron ; Sabbag et al. ), we selected as out‐groups Thoropa lutzi and Thoropa taophora (from the sister genus of the Cycloramphus ‐ Zachaenus clade) and one species each from the genera Crossodactylus , Hylodes , and Megaelosia (family Hylodidae).…”

Section: Methodsmentioning

confidence: 99%

Male‐male competition and repeated evolution of terrestrial breeding in Atlantic Coastal Forest frogs*

et al. 2019

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Terrestrial breeding is a derived condition in frogs, with multiple transitions from an aquatic ancestor. Shifts in reproductive mode often involve changes in habitat use, and these are typically associated with diversification in body plans, with repeated transitions imposing similar selective pressures. We examine the diversification of reproductive modes, male and female body sizes, and sexual size dimorphism (SSD) in the Neotropical frog genera Cycloramphus and Zachaenus, both endemic to the Atlantic rainforest of Brazil. Species in this clade either breed in rocky streams (saxicolous) or in terrestrial environments, allowing us to investigate reproductive habitat shifts. We constructed a multilocus molecular phylogeny and inferred evolutionary histories of reproductive habitats, body sizes, and SSD. The common ancestor was small, saxicolous, and had low SSD. Terrestrial breeding evolved independently three times and we found a significant association between reproductive habitat and SSD, with shifts to terrestrial breeding evolving in correlation with decreases in male body size, but not female body size. Terrestrial breeding increases the availability of breeding sites and results in concealment of amplexus, egg‐laying, and parental care, therefore reducing male‐male competition at all stages of reproduction. We conclude that correlated evolution of terrestrial reproduction and small males is due to release from intense male‐male competition that is typical of exposed saxicolous breeding.

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The interplay of past diversification and evolutionary isolation with present imperilment across the amphibian tree of life

Cited by 433 publications

References 69 publications

Global patterns of body size evolution are driven by precipitation in legless amphibians

Global patterns of body size evolution are driven by precipitation in legless amphibians

Evolutionarily distinct amphibians are disproportionately lost from human‐modified ecosystems

Male‐male competition and repeated evolution of terrestrial breeding in Atlantic Coastal Forest frogs*

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