Pattern of shape variation in the eastern African gerbils of the genus Gerbilliscus (Rodentia, Muridae): Environmental correlations and implication for taxonomy and systematics

Abstract

Gerbilliscus has been in recent years the subject of new molecular and karyological investigations that shed new light on the evolutionary processes of this taxon. However, the patterns of phenotypic diversification of Gerbilliscus remain poorly understood. Furthermore, the molecular phylogenetic analyses posed new questions concerning the systematics and taxonomy of the whole genus and revealed the possible occurrence of cryptic species and hence the need to carry out a taxonomic revision. We used geometric morphometrics to investigate the adaptive value of morphological changes and to elucidate the systematic relationships and taxonomic status of the Gerbilliscus species of east Africa. Our results show concordance between morphological and genetic species boundaries. However, the observed morphological differences appear not only related to hereditary characters. In fact, the correlation with the climatic variables suggests an adaptive value of shape changes related to different trophic resources availability. Finally, discriminant analysis of the eastern Africa Gerbilliscus species highlight the distinctiveness of G. vicinus, clearly separated from G. robustus and G. nigricaudus. (C) 2009 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved

Cranial variation in geographically widespread dwarf gerbilGerbillus nanus(Gerbillinae, Rodentia) populations: Isolation by distance versus adaptation to local environments

“…Furthermore, TPS deformation grids from extreme PLS-1 environmental values showed no obvious patterns in these differences ( Figure 5), indicating that they were not concentrated in functionally important cranial regions. This result is unlike that of other similar gerbil studies, which show stronger cranial climatic adaptation patterns, in regions that include the tympanic bulla, palate, and teeth (Alhajeri, 2014(Alhajeri, , 2018Colangelo et al, 2010;Tabatabaei Yazdi, Colangelo, & Adriaens, 2014).…”

“…Intraspecific morphological variation in rodents (and gerbils in particular) is increasingly being assessed using geometric morphometrics—an approach that allows for the examination of shape and size variation independently (see Zelditch, Swiderski, Sheets, & Fink, ). For example, Colangelo, Castiglia, Franchini, and Solano () investigated the association between cranial variation with environmental variability in four species of Gerbilliscus Thomas,1897—they found that cranial shape variation was correlated with climatic variables, which they interpreted in terms of adaptation to “different trophic resources.” Tabatabaei Yazdi, Adriaens, and Darvish () examined the association between cranial variation with geography in Meriones meridianus Pallas, 1773, and found evidence that populations exhibited geographic disparity in both cranial size and shape, the latter includes differences in the morphology of the bulla, nasals, molars, and the incisive foramen. Similarly, Tabatabaei Yazdi, Adriaens, and Darvish () examined the association between cranial variation with both environmental and geographical variability in Meriones crassus Sundevall, 1842.…”

Molecular systematics of gerbils and deomyines (Rodentia: Gerbillinae, Deomyinae) and a test of desert adaptation in the tympanic bulla

“…) and their morphological variation (Colangelo et al. ). In these studies, Colangelo and colleagues recognized three major clades within Gerbilliscus that correspond to major geographic subdivisions, and supported the synonymy of the Gerbillurus and Gerbilliscus (Colangelo et al.…”

Cranial phenotypic variation in Meriones crassus and M. libycus (Rodentia, Gerbillinae), and a morphological divergence in M. crassus from the Iranian Plateau and Mesopotamia (Western Zagros Mountains)

“…The increase in tympanic bulla size can be considered to be adaptive (Lay 1972;Webster & Webster 1984;Van der Straeten & Dieterlen 1992;Webster & Plassmann 1992;Huang et al 2002), as it causes an increased amplification of sound that allows rodents to increase low-frequency hearing and detect an approaching predator more rapidly (Burda et al 1990;Mason 2001Mason , 2003Huang et al 2002;Schleich & Vasallo 2003). As such, a bulla hypertrophy may reflect a morphological adaptation for efficient vocal communication in a desert environment, where rodent population densities are low, and in an underground environment as well (Petter 1961;Harrison 1972;Lay 1972;Darvish 2009;Colangelo et al 2010). This is corroborated by Vaughan et al (2000) and our study, as smaller tympanic bullae were found in populations occurring in regions with higher levels of rainfall (and vice versa).…”