Abstract
Body mass is rarely recorded in amphibians, and other body measurements (e.g. snout to vent length, SVL) are generally collected instead. However, length measurements, when used as proxies of body mass in comparative analyses, are problematic if different taxa and morphotypes are included. We developed allometric relationships to derive body mass from SVL measurements. We fitted phylogenetic generalized least square models for frogs (Anura) and salamanders (Caudata) and for several families separately. We tested whether allometric relationships differed between species with different habitat preferences and between morphs in salamanders. Models were fitted with SVL-mass measurements for 88 frog and 42 salamander species. We assessed the predictive performance of the models by cross-validation. Overall, the models showed high explained variance and low forecasting errors. Models differed among semi-aquatic, terrestrial and arboreal frogs, and between paedomorphic and non-paedomorphic salamanders. Body mass estimates derived from our models allow for comparability of studies on multiple taxa and can be used for testing theories built upon evolutionary and ecological processes which are directly related to body mass.
Highlights
Body mass is a fundamental parameter in ecology, as it is related to several key ecological features, such as species metabolic rates and energy intake (Gillooly et al 2001; Brown et al 2004), population abundance (Peters & Wassenberg 1983), dispersal distance (Jenkins et al 2007; Hillman et al 2014) and reproductive output (Blueweiss et al, 1978)
We found body mass data on 190 frog species and 88 salamander species, but for 111 and 49 species only paired snout to vent length (SVL) measurements calculated on the same individuals were available
Because not all species in our datasets were included in the phylogeny, we excluded from the analyses 23 species of frogs and 3 species of salamanders
Summary
Body mass is a fundamental parameter in ecology, as it is related to several key ecological features, such as species metabolic rates and energy intake (Gillooly et al.2001; Brown et al 2004), population abundance (Peters & Wassenberg 1983), dispersal distance (Jenkins et al 2007; Hillman et al 2014) and reproductive output (Blueweiss et al, 1978). Body mass is highly variable within the same species, but can vary in the same individual over short time frames. Body mass in amphibians depends on the level of hydration of the animal, the physiological state, the content of the bladder and the cloaca, as well as the reproductive state in females (Dodd 2010). Amphibians’ body masses are rarely reported in ecological or taxonomic literature as compared to other morphometric measurements. Snout to vent length (SVL) is the most common measure of body size in amphibians (Dodd 2010; Vitt & Caldwell 2013). While SVL is available for many species, body mass data are sparse in the literature and only available for a minority of species
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