The evolution of palate shape in the Lepilemur‐Cheirogaleidae clade (Primates: Strepsirrhini)

Abstract

Objectives Phylogenies consistently group the folivorous Lepilemur species with the small‐bodied insectivorous‐frugivorous cheirogaleids. Juvenile lepilemurs and adult cheirogaleids share allometries in most aspects of skull morphology, except the palate. We investigated potential influences on palate shape in these taxa and several outgroups using geometric morphometrics. Materials and Methods Our sample included representatives of four extant strepsirrhine families, Cheirogaleidae (including Lepilemurinae), Lemuridae, Indriidae, and Galagidae, and one subfossil Megaladapis. Our dataset comprised 32 landmarks collected from 397 specimens representing 15 genera and 28 species, and was analyzed using generalized procrustes analyses and between group principal component analysis. We explored the influence of size, phylogeny, diet, and the propagation of loud vocalizations on palate shape. Results While congeneric species clustered within the morphospace, the phylomorphospace did not mirror molecular phylogenetic hypotheses of higher‐order relationships. Four palate forms were distinguished within the Cheirogaleidae. Diet, strongly linked to body size, had the single greatest influence on palate shape. The production of long‐distance advertisement calls was most often associated with positive scores on the PC1 axis. Discussion Our results suggest that the extensive variation in palate shape among Cheirogaleidae is related to dietary shifts that accompanied changes in body size during the clade's radiation. Molecular phylogenies indicate that cheirogaleid diversification involved repeated dwarfing events, which in turn drove dietary shifts from ancestral folivory‐frugivory to frugivory, gummivory, and faunivory in the descendant species. The elongated Lepilemur palate is probably related to accelerated eruption of the cheek teeth to render juveniles competent to shear leaves upon weaning.

Deciphering the mandibular shape variation in a group of Malagasy primates using Fourier outline analysis

“…Such variation within the lemurids and the high difference between folivorous and non‐folivorous species have already been reported on cranial shape (e.g., Andrews et al, 2020 work on palate shape variation) as well as on mandibular shape (Dumont, 1997; Marcé‐Nogué et al, 2017; Raveloson et al, 2005). For instance, in the work published in 2005 Raveloson et al, highlighted this difference, and separated their analysis in two sub analyses, with and without the folivorous specimens (all classified as Hapalemur in their case).…”

“…Such variation within the lemurids and the high difference between folivorous and non-folivorous species have already been reported on cranial shape (e.g., Andrews et al, 2020 work on palate shape variation) as well as on mandibular shape (Dumont, 1997;Marcé-Nogué et al, 2017;Raveloson et al, 2005) et al, 2005 conclusions of a great mandibular shape variation within the family. This high variation was also suggested by other authors, based on the morphometric analysis of the mandibular shape (Oh et al, 2019;St Clair et al, 2018;Viguier, 2004).…”

“…for Hapalemur griseus and Prolemur simus . We based this classification on data summarized in previous studies on primate dietary adaptation (e.g., Andrews et al, 2020; Coiner‐Collier et al, 2016; Eronen et al, 2017; St Clair et al, 2018; Steffens, 2020; Winchester et al, 2014; Wright & Willis, 2012, mainly from Ganzhorn, 1988; Ganzhorn et al, 2006; Mittermeier et al, 2006, 2010; Yamashita, 1996 for behavioral ecology data).…”

“…Factors threatening primates are dynamic and interact with each other at local, regional, and national scales, leading to a reduction in population sizes and, a probable extinction (Estrada et al, 2017). Previous studies have shown that morphology covaries with ecological parameters in Malagasy primates (e.g., Andrews et al, 2020;Meloro et al, 2015;Pitirri et al, 2020;Pitirri & Begun, 2019;Raveloson et al, 2005;Ravosa, 1990Ravosa, , 1991Ravosa, , 1992Ross et al, 2012) but also that the morphofunctional adaptations are difficult to discern from other sources of mandibular variation (e.g., Humphrey et al, 1999;Marcé-Nogué et al, 2017;Meloro et al, 2015;Pitirri et al, 2020;Raveloson et al, 2005;Ravosa, 1990;Ross et al, 2012;Schmittbuhl et al, 2007;Taylor & Groves, 2003). In addition, morphology clearly carries a phylogenetic signal (Fleagle et al, 2010(Fleagle et al, , 2016Masters et al, 2014;Masters & Couette, 2015;St Clair & Boyer, 2016).…”