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Alhajeri B (2017)
Craniomandibular Variation in the Taxonomically Problematic Gerbil Genus Gerbillus (Gerbillinae, Rodentia): Assessing the Influence of Climate, Geography, Phylogeny, and Size
Journal of Mammalian Evolution 1-16.
The taxonomy of Gerbillus, the most speciose gerbil genus, is highly debated. Of particular contention is the relationship of Dipodillus to Gerbillus; some consider it to be a closely related genus, while others synonymize it with Gerbillus—either with or without recognizing it as a subgenus. The main objective of this study is to test the validity of common taxonomic groupings within the Gerbillus-Dipodillus species complex, which was achieved by using geometric morphometrics to examine cranial and mandibular variation in 34 out of the 52 Gerbillus-Dipodillus species. Craniomandibular size and shape were highly correlated, indicating strong allometric patterns in shape variation. The common taxonomic groups were significantly different in craniomandibular size and shape, yet they did overlap considerably in morphospace. A notable exception was the extreme divergence of Monodia (G. mauritaniae) from all other species in the occlusal view of the mandible. Morphospace overlap is likely a consequence of both phylogenetic history and environmental adaptation. Only the ventral cranium was associated with climate, particularly in areas related to resource acquisition. Geographic distance was not significantly associated with craniomandibular morphometric distance, and the groups overlapped greatly in their geographic range. Cranial and mandibular regions differed in discrimination power—the ventral cranium had among the highest, while the dorsal cranium and the occlusal mandible had the lowest. Craniomandibular regions varied in association with climate, phylogeny, and size—previous studies suggest this difference may be a consequence of different genetic controls for shape variation
Keywords: Crania, Desert, Dipodillus, Geometric morphometrics, Skull, Systematics
Alhajeri B, Hunt O, Steppan S (2015)
Molecular systematics of gerbils and deomyines (Rodentia: Gerbillinae, Deomyinae) and a test of desert adaptation in the tympanic bulla
Journal of Zoological Systematics and Evolutionary Research.
Recent molecular studies in gerbils found multiple instances of discordance between molecular and morphological phylogenies. In this study, we analyse the largest molecular data set to date of gerbils and their sister group the deomyines to estimate their phylogenetic relationships. Maximum-likelihood and Bayesian analyses were largely concordant, and both generally had high levels of node support. For gerbils, the results were generally concordant with previous molecular phylogenies based on allozymes, chromosomes, DNA/DNA hybridization and DNA sequences, and discordant with morphological phylogenies. None of the traditional gerbil tribes and subtribes were monophyletic. In addition, paraphyly was found in the genera Gerbillus, Gerbilliscus and Meriones as well as in five subgenera within Dipodillus, Gerbillurus and Meriones. Short branches separating taxa in small clusters within Dipodillus and Meriones suggest synonymy. Within deomyines, all genera and subgenera were monophyletic; however, two species groups within Acomys appear to contain synonymous taxa. We also find support for the discordance between molecular and morphological phylogenies in gerbils being partly due to convergent adaptations to arid environments, primarily in the suite of traits associated with inflation of the tympanic bullae. Relative bullar size does appear to be a desert adaptation and is correlated with aridity independent of phylogeny. Further, it varies more strongly along bioclimatic clines than between binary habitat classifications (desert versus mesic).
Keywords: Arid environments, Muroidea, geometric morphometrics, molecular phylogenetics, skull morphology