LOCOMOTION IN TRIADOBATRACHUS


photographs were taken digitally with ScreenCaliper, Version 4.0 (Iconico, New York), whereas those from dry specimens were taken with a manual digital caliper (0.01mm error). Prior to statistical analyses we corrected


morphometric data for global size differences by dividing each value by the geometric mean of the five linear measurements of each specimen. This transformation, which is derived from the nth root of the product of n measurements and the ratio of any particular measurement to the overall geometric mean (Mosimann and James 1979), is robust in recovering similarities in shape or proportions if isometric size differences are disregarded (Jungers et al. 1995). Locomotor Modes.—All species were assigned


a primary locomotor mode. Locomotor modes for extant species were obtained from the literature (e.g., Emerson 1978, 1979, 1988; Taigen et al. 1982; Jorgensen and Reilly 2013), Webresources (AmphibiaWeb 2015) or personal observations (see Appendix S1). As was done in most previous studies, we considered jumping performance of paramount importance in characterizing terrestrial locomotion of anurans. Species were scored as hoppers or jumpers based on the definition of Emerson (1979) that regards jumpers (J) as those frogs that jump more than eight to nine body lengths in a single leap. Frogs that hop usually also walk (Emerson 1979), and hence were accordingly classified as hoppers/walkers (HW). This category also encompasses frogs that walk but typically do not hop, such as species of Pseudophryne. Even though burrowing has been typically considered a locomotor mode of many anurans (Emerson 1978, 1979, 1988; Taigen et al. 1982; Jorgensen andReilly 2013),we consider this behavior as an activity pattern related to substrate use rather than a locomotor mode (a distinction that has previously been made for xenarthran mammals; Toledo et al. 2012). Similarly, although “arboreal” and “terrestrial” have previously been used as categories in ecomorphological studies of anuran locomotion (e.g., Emerson 1978, 1979, 1988; Zug 1978; Gomes et al. 2009; Jorgensen and Reilly 2013), we did not include those in our categorization, because we focused on


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locomotor modes and not on substrate preference or habitat. Swimming ability is almost ubiquitous among frogs, with most species making use of aquatic environments in the mating season and/or to escape from predators. Thus, we only classified as swimmers (Sw) those species that are almost totally aquatic (e.g., pipids, Pseudis spp., and some species of Telmatobius). It is noteworthy that in spite of their ecological diversity, salamanders exhibit the same overall pattern of limb kinematics whether in an aquatic, semiaquatic, or terrestrial environment (Ashley-Ross et al. 2009). Thus, we classified the “lateral undulatory” (LU) locomotion exhibited by salamanders and lizards as a single category. Statistical Analyses.—To evaluate the


relationship between limb proportions and locomotor modes previously reported for anurans (e.g., Emerson 1988; Jorgensen and


Reilly 2013; Enriquez-Urzelai et al. 2015), we first conducted a multivariate analysis of variance (MANOVA) to test whether the morphometric variables differ among


locomotor groups in our sample. We used all five size-corrected linear measurements as the dependent variables and locomotor modes as the independent variable (four levels: J, Sw, HW, LU). We performed UnequalNHSD post hoc tests (p=0.05) to assess differences in group means. Assumptions of the model were checked before the analysis. To properly test trait correlations indepen-


dently of phylogenetic history, we conducted a phylogenetic generalized least-squares (PGLS) analysis (Grafen 1989; Martins and Hansen 1997) as implemented inNTSYS pc v. 2.11j (Rohlf 2004), which has been recognized as a robust comparative phylogenetic method (Rohlf 2001; Barr and Scott 2014; Symonds and Blomberg 2014). An advantage of comparative methods over others also used in ecomorphological approaches, such as a discriminant analysis, is that lack of significance inthe resultswouldmean that trait correlation might be due to common ancestry alone (Barr and Scott 2014). The PGLS analysis was performed on the size-corrected limb variables with respect to the locomotor categories, which were scored as dummy variables, with a phylogenetic covariance matrix


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