Nesomyinae (Rodentia,Mammalia) protocoles for skull form evolution study

Here we aim to define how skull morphology of an endemic and monophyletic clade of rodents (sub-family Nesomyinae), that show considerable morphological variation, has evolved and how its disparity is characterized in this particular geographical and ecological context. We performed a two-dimensional geometric morphometric analysis on 371 dorsal and 400 ventral skull images of 19 species (comprising all nine extant endemic genera) from various Museums voucher specimens (FMNH,MNHN,UADBA, NHM) and tested the influence of three ecological parameters (climate, locomotor habitat and nychthemeral cycle) in a phylogenetic context on size and shape.
We addressed the following question:
What shaped the morphological diversity observed in extant Nesomyinae rodents in the particular context of Madagascar? To what extent does the skull shape of Nesomyinae reflect their phylogenetic history? 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 methods. Then, we assessed the significance of phylogenetic signal and tested the influence of ecology on the skull shape and size. We expect that the skulls of different nesomyines, and especially size, to display adaptations to local environments, as insular context is known to favor rapid character displacement towards local optima, but, Madagascar being a particular case with several geographical and ecological continental characteristics more at a continental level, typical insular evolutionary trends might not be observed. In addition, skull morphology can also show low evolutionary lability because of the strong phylogenetic signal in teeth, that are morphologically conserved. In this case, because of the strength of phylogenetic signal, we would expect Nesomyinae skull to be less influenced by ecological variability.
As main results of our study: Skull shape appears to importantly reflect phylogeny, whereas skull size does not carry a significant phylogenetic signal. Skull shape also revealed to be significantly influenced by climate while, conversely to what is expected in insular context, skull size is not impacted by any of the ecological factors tested.

本研究旨在阐明一种特有且单系群鼠类（亚科Nesomyinae）的头骨形态如何演化，以及在该特定地理和生态背景下，其形态差异如何被表征。我们对来自不同博物馆的371个背侧和400个腹侧头骨图像（包括所有九个现存特有属的19个物种）进行了二维几何形态计量分析，并测试了三个生态参数（气候、运动栖息地和昼夜节律）在系统发育背景中对头骨大小和形状的影响。我们针对以下问题进行了探讨：在马达加斯加的特定背景下，是什么塑造了现存Nesomyinae鼠类的形态多样性？Nesomyinae的头骨形态在多大程度上反映了其系统发育历史？环境参数是否显著影响了头骨形状，如果是，其影响程度如何？为了回答这些问题，我们利用几何形态计量方法对Nesomyinae头骨的背侧和腹侧视图进行了形态分析，并评估了系统发育信号的重要性，以及生态对头骨形状和大小的影响。我们预期不同nesomyines的头骨，尤其是其大小，将表现出对当地环境的适应性，因为岛屿环境众所周知会促进快速的特征位移，趋向于局部最优。然而，马达加斯加作为一个具有多个地理和生态大陆特征的独特案例，典型的岛屿进化趋势可能无法观察到。此外，由于牙齿在形态上保守且具有强烈的系统发育信号，头骨形态也可能表现出较低的进化可塑性。在这种情况下，由于系统发育信号的强烈性，我们预计Nesomyinae头骨将较少受到生态变异的影响。我们的主要研究结果如下：头骨形状似乎重要地反映了系统发育关系，而头骨大小则没有携带显著的系统发育信号。头骨形状还揭示了其受到气候的显著影响，而与岛屿环境预期相反，头骨大小并未受到所测试的任何生态因素的影响。