Natural history predicts patterns of thermal vulnerability in amphibians from the Atlantic Rainforest of Brazil

Abstract

Among vertebrates, amphibians have particular characteristics (e.g., permeable skin) that make them extremely dependent on abiotic factors such as temperature and humidity (Duellman & Trueb, 1994).Amphibians are the most endangered group of vertebrates in the world (Alroy, 2015;Ceballos et al., 2017;Stuart et al., 2004). Recent studies estimate that approximately 200 amphibian species (2.4% of all global diversity) are already extinct, and direct and indirect factors related to human activities threaten 41% (Alroy, 2015;Hoffmann et al., 2010; IUCN, 2020). Even those classified as Least Concern (LC) by the IUCN (International Union for Conservation of Nature-an

Can we improve our ability to interpret ectotherm thermal tolerance?

“…For instance, arboreal frogs may create foam nests in the canopy but the larva inhabit puddles on the forest floor (Haddad & Prado, 2005). While it would be possible to classify larval ecotypes or egg microhabitats (Carilo Filho et al, 2021), this information is not readily available at the scale of this study, and we encourage further investigation into these modulators. Doing so may reveal whether diversity in developmental traits within ecotypes masks local scale signals of environmental adaption via interactions with ecotype.…”

“…The discrete nature of complex life cycles with metamorphosis and the need to survive thermal stress at one stage until the transition to the next stage may place high importance on the interaction between traits and the environment where a thermal bottleneck is a selective disadvantage. Microhabitat preferences has been demonstrated to strongly correlate with thermal biology in reptiles (Greer, 1980; Michelangeli, Goulet, Kang, Wong, & Chapple, 2018), bees (Wilson, Murphy, Rinehart, Yocum, & Bowsher, 2020), frogs (Carilo Filho et al, 2021; Duarte et al, 2012), and ants (Bujan, Roeder, de Beurs, Weiser, & Kaspari, 2020; Leahy, Scheffers, Williams, & Andersen, 2022). We found strong phylogenetic conservatism in CT max which likely reflects how ecotypes strongly correlate within Family (Moen & Wiens, 2017).…”

“…The large overlap in thermal tolerance across ecotypes suggests developmental or genetic constraints have a greater influence on the evolution of thermal tolerances than environmental factors. Developmental or genetic constraints on climate niches or thermal traits are suggested for reptiles and amphibians (Bodensteiner et al, 2021; Carilo Filho et al, 2021; Pie, Campos, Meyer, & Duran, 2017). Several inferences support developmental or genetic constraints underlie consistent differences between larva and adult thermal tolerance.…”

“…Thermal bottlenecks can also be identified using a macrophysiological approach which has described stage-specific differences in thermal sensitivities and tolerances in marine invertebrates (Collin, Rebolledo, Smith, & Chan, 2021; Pandori & Sorte, 2019; Truebano, Fenner, Tills, Rundle, & Rezende, 2018), fish (Dahlke et al, 2020; Moyano et al, 2017), insects (Kingsolver & Buckley, 2020; Klockmann, Günter, & Fischer, 2017) and reptiles (Levy et al, 2015). Among species comparisons in frogs are often limited to a single geographic region and are often limited to either adults or larva even if both are collected from the same region (Carilo Filho et al, 2021; Cheng et al, 2022; Pintanel et al, 2022; Pintanel, Tejedo, Ron, Llorente, & Merino-Viteri, 2019; Ruthsatz et al, 2022). Thus, whether thermal bottlenecks occur and how consistent they are across Anuran species is not well understood.…”

“…Among species, frogs show strong microhabitat preferences that are associated with phenotypic syndromes encompassing behaviour, morphology and physiology and can broadly be categorised into ecological types (“ecotype”) (Moen, Cabrera-Guzman, Caviedes-Solis, Gonzalez-Bernal, & Hanna, 2022; Moen & Wiens, 2017). In turn, the animal’s ecotype may mediate the confounding interaction between life stages and their respective microenvironment (Carilo Filho et al, 2021; Pincebourde & Casas, 2015). We tested whether ecotypes are reliable proxies of environmental adaptation to resolve ontogeny by environment interaction of CT max and identify thermal bottlenecks.…”