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.