Skull morphological evolution in Malagasy endemic Nesomyinae rodents.

Léa Terray,Voahangy Soarimalala,Steven M Goodman,Raphaël Cornette,Christiane Denys,Aude Lalis

doi:10.1371/journal.pone.0263045

Abstract

Madagascar is a large island to the south-east of Africa and in many ways continental in size and ecological complexity. Here we aim to define how skull morphology of an endemic and monophyletic clade of rodents (sub-family Nesomyinae), that show considerable morphological variation, have evolved and how their disparity is characterized in context of the geographical and ecological complexity of the island. We performed a two-dimensional geometric morphometric analysis on 370 dorsal and 399 ventral skull images of 19 species (comprising all nine extant endemic genera) and tested the influence of three ecological parameters (climate, locomotor habitat and nychthemeral cycle) in a phylogenetic context on size and shape. The results indicate that skull shape appears to importantly reflect phylogeny, whereas skull size does not carry a significant phylogenetic signal. Skull shape is significantly influenced by climate while, skull size is not impacted by any of the ecological factors tested, which is controversial to expectations in an insular context. In conclusion, Nesomyinae must have evolved under unusual types of local constraints, preventing this radiation from demonstrating strong ecological release.

Highlights

Madagascar is a large island [1] situated about 400 km off the southeastern coast of Africa
We addressed the following question: in this particular geographical and ecological context of Madagascar, what shaped the morphological diversity observed in extant Nesomyinae rodents? To better understand the patterns and processes of evolution of the Nesomyinae, we examined the two following sub-questions: 1) To what extent does the skull shape of Nesomyinae reflect their phylogenetic history? 2) Did environmental parameters significantly influenced the shape of the skull and if so, how? To answer those questions, we performed shape analysis of Nesomyinae skulls in dorsal and ventral views, using geometric morphometrics
The list of specimens used is presented in S1 Table. These are housed in the Field Museum of Natural History (FMNH), Chicago; The Natural History Museum, London; the Mention Zoologie et Biodiversite Animale, Universited’Antananarivo (UADBA), Antananarivo, Madagascar; the Museum fur Naturkunde (ZMB), Berlin; and the Museum national d’Histoire naturelle (MNHN), Paris

Summary

Introduction

Madagascar is a large island [1] (nearly 590,000 km2) situated about 400 km off the southeastern coast of Africa. Madagascar has greater ecosystem richness than any other island [2, 3] This fact is supported by the high rate of endemism observed at different taxonomic levels, resulting in this island being considered as a biodiversity hotspot [4, 5]. This diversity is illustrated by the four extant groups of endemic living Malagasy land mammals (Lemuroidea, Eupleridae, Tenrecidae and Nesomyinae), representing several hundred of species [6, 7]

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Discussion

Conclusion