Where to Live? How Morphology and Evolutionary History Predict Microhabitat Choice by Tropical Tadpoles

Abstract

Tadpoles have diverse morphologies and occupy diverse habitats. The morphological differences between tadpoles can be represented by linear and geometric measurements and used to explain the organization of tadpole assemblages. However, the effects of evolutionary history must be isolated from the morphological differences before we can determine which patterns result from the use and sharing of common ecological resources. Here, we aimed to determine how morphological similarities and phylogenetic distances affect microhabitat choice by tadpoles. We analyzed the tadpoles of 101 anuran species and classified them according to ecomorphological guild, habitat use, position in the water column, and floor substrate. We used geometric and traditional morphometric approaches to describe the morphological variation among tadpoles and calculated the patristic distance for each species. Afterwards, we used morphometric and phylogenetic matrices as predictors of the variance in the ecological matrix, using a partial redundancy analysis. When we used traditional morphometric data, phylogeny explained a large amount of the ecological variation. By contrast, when we used geometric morphometric data, morphology and phylogeny explained similar amounts of the ecological variation, showing that the technique used to extract morphological variation affects the results. We provide evidence that both morphology, as a surrogate for contemporary factors, and evolutionary inertia are important in determining the behavior of tadpoles. Thus, niche conservatism can be important in modeling the behavior of tadpoles, but does not explain all the preferences of tadpoles.

Ecomorphological diversity of Australian tadpoles

“…shapes, but we found substantial within-guild variation and overlap among the categories and the mean guild body shapes were not significantly different after accounting for phylogeny. A similarly large-scale study (Marques & Nomura, 2015) of morphological diversity across guilds for 101 species of anurans from Central and South America revealed comparable results to ours: that there is great morphological diversity within guilds, and substantial overlap of guilds in morphospace. Their results revealed significant differences in tadpole body shape among guilds, but they did not take into account phylogenetic relatedness in their model.…”

“…Microhabitat use in tadpoles is known to be plastic and can differ substantially among tadpoles of closely-related species (Eterovick et al, 2010). Therefore, the observed morphological diversity in our study and that of Marques and Nomura (2015) is likely an indication that morphological-specificity is not strictly necessary for many microhabitats and tadpoles are potentially more generalist and adaptable than we expect.…”

“…Tadpole external morphology, usually examined in the lateral view, is thus considered to confer ecomorphological guilds. However, since this framework was proposed, the extent to which guilds comprise distinct morphologies resulting from convergent evolution, the degree of morphological variability within each guild, and the degree of continuity in shape between guilds has not been examined in a phylogenetically informed statistical framework (but see Marques & Nomura, ).…”

Influence of substrate orientation on tadpoles feeding efficiency

“…Body shape commonly reflects tadpoles' preferred microhabitat (Marques and Nomura, 2015; Queiroz et al, 2015), but this may not correlate closely with the substrate orientations upon which tadpoles feed most efficiently. Tadpoles of S. fuscovarius are usually found close to leaves and aquatic plants in midwater (Schulze et al, 2015).…”

“…We tested our hypotheses using tadpoles of five anuran species: Physalaemus cuvieri Fitzinger, 1826, Leptodactylus fuscus (Schneider, 1799), Scinax fuscovarius (Lutz, 1925), Dendropsophus minutus (Peters, 1872) and Trachycephalus typhonius (Linnaeus, 1758). These species are usually classified in two guilds – benthic ( P. cuvieri and L. fuscus ) and nektonic ( S. fuscovarius , D. minutus and T. typhonius ) (Rossa-Feres and Nomura, 2006; Marques and Nomura, 2015). This classification is based primarily on the position where tadpoles are found in the water body (benthic, bottom; nektonic, midwater) and on their external morphology.…”