Craniomandibular Variation in the Taxonomically Problematic Gerbil Genus Gerbillus (Gerbillinae, Rodentia): Assessing the Influence of Climate, Geography, Phylogeny, and Size

Original Paper

DOI: 10.1007/s10914-016-9377-2

Cite this article as:
Alhajeri, B.H. J Mammal Evol (2017). doi:10.1007/s10914-016-9377-2

Abstract

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 

Supplementary material

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Fig. S1

Gerbillus-Dipodillus clade extracted from the Alhajeri et al. (2015) chronogram. Bayesian posterior probabilities (PP) are indicated on the nodes, with unannotated nodes being strongly supported (PP ≥ 0.95). Node bars denote the 95% highest posterior densities. (GIF 143 kb)

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Fig. S2

Principal component analyses performed on the interspecific procrustes coordinates of the (a) combined (all views), (b) ventral cranial, (c) dorsal cranial, (d) lateral cranial, (e) lateral mandibular, and the (f) occlusal mandibular datasets with species arranged according to the taxonomic groupings of Lataste (1881, 1882). Symbols representing different groups are indicated in the second panel. The percentage of explained variance by each PC are also indicated in parentheses. (GIF 119 kb)

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High Resolution Image (EPS 1229 kb)
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Fig. S3

Principal component analyses performed on the interspecific procrustes coordinates of the (a) combined (all views), (b) ventral cranial, (c) dorsal cranial, (d) lateral cranial, (e) lateral mandibular, and the (f) occlusal mandibular datasets with species arranged according to the taxonomic groupings of Pavlinov (2001, 2008). Symbols representing different groups are indicated in the second panel. The percentage of explained variance by each PC are also indicated in parentheses. (GIF 119 kb)

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High Resolution Image (EPS 1236 kb)
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Fig. S4

Ventral cranial thin-plate spline deformation grids, depicting of the shape differences between the consensus landmark configuration of the whole sample vs. the consensus landmark configuration of (a) Lataste’s (1881, 1882) Dipodillus, (b) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Gerbillus, (c) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Hendecapleura, (d) Pavlinov’s (2001, 2008) Dipodillus, (e) Pavlinov’s (2001, 2008) Petteromys, (f) Pavlinov’s (2001, 2008) Monodia. Deformations were not magnified. (GIF 185 kb)

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Fig. S5

Dorsal cranial thin-plate spline deformation grids, depicting of the shape differences between the consensus landmark configuration of the whole sample vs. the consensus landmark configuration of (a) Lataste’s (1881, 1882) Dipodillus, (b) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Gerbillus, (c) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Hendecapleura, (d) Pavlinov’s (2001, 2008) Dipodillus, (e) Pavlinov’s (2001, 2008) Petteromys, (f) Pavlinov’s (2001, 2008) Monodia. Deformations were not magnified. (GIF 168 kb)

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High Resolution Image (EPS 2842 kb)
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Fig. S6

Lateral cranial thin-plate spline deformation grids, depicting of the shape differences between the consensus landmark configuration of the whole sample vs. the consensus landmark configuration of (a) Lataste’s (1881, 1882) Dipodillus, (b) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Gerbillus, (c) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Hendecapleura, (d) Pavlinov’s (2001, 2008) Dipodillus, (e) Pavlinov’s (2001, 2008) Petteromys, (f) Pavlinov’s (2001, 2008) Monodia. Deformations were not magnified. (GIF 174 kb)

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High Resolution Image (EPS 2936 kb)
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Fig. S7

Lateral mandibular thin-plate spline deformation grids, depicting of the shape differences between the consensus landmark configuration of the whole sample vs. the consensus landmark configuration of (a) Lataste’s (1881, 1882) Dipodillus, (b) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Gerbillus, (c) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Hendecapleura, (d) Pavlinov’s (2001, 2008) Dipodillus, (e) Pavlinov’s (2001, 2008) Petteromys, (f) Pavlinov’s (2001, 2008) Monodia. Deformations were not magnified. (GIF 179 kb)

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High Resolution Image (EPS 2970 kb)
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Fig. S8

Occlusal mandibular thin-plate spline deformation grids, depicting of the shape differences between the consensus landmark configuration of the whole sample vs. the consensus landmark configuration of (a) Lataste’s (1881, 1882) Dipodillus, (b) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Gerbillus, (c) Lataste’s (1881, 1882) and Pavlinov’s (2001, 2008) Hendecapleura, (d) Pavlinov’s (2001, 2008) Dipodillus, (e) Pavlinov’s (2001, 2008) Petteromys, (f) Pavlinov’s (2001, 2008) Monodia. Deformations were not magnified. (GIF 143 kb)

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10914_2016_9377_MOESM9_ESM.xlsx (12 kb)
Table S1List of specimens digitized in this study. Museum abbreviations are as follows: AMNH = American Museum of Natural History; FMNH = Field Museum of Natural History; MVZ = Museum of Vertebrate Zoology; USNM = United States National Museum of Natural History; UF = University of Florida Museum of Natural History. (XLSX 12 kb)
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Table S2Taxonomy of the sampled species according to the most commonly cited authorities of the Gerbillus-Dipodillus group (all cited in the paper). Here and throughout the manuscript, for the purpose of consistency, only the taxonomy of Musser and Carleton (2005) is followed when referring to the species. Several species were described much later than the published classification of Lataste (1881, 1882), and thus were assigned to subgenera in this table based on Musser and Carleton (2005). The last column indicates the three main phylogenetic clades retrieved from the phylogeny of Alhajeri et al. (2015); NA = unsampled species. (XLSX 13 kb)
10914_2016_9377_MOESM11_ESM.docx (19 kb)
Table S3Description of all landmarks used in the study. The numbers preceding the landmarks match the numbers in Fig. 1. (DOCX 19 kb)
10914_2016_9377_MOESM12_ESM.xlsx (10 kb)
Table S4List of reference and target specimens used in the missing data estimation procedure. (XLSX 10 kb)
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Table S5Average morphometric, climatic, and geographic data for all gerbil species used in this study. (XLSX 203 kb)
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Table S6Output of Tukey‘s HSD test, indicating the significance of the pairwise differences in centroid size means (based on the five individual datasets and the concatenated dataset) among the taxonomic groups of Lataste (1881, 1882). The difference in the observed means along with the P-value, adjusted for the multiple comparisons, are shown. Significant P-values are indicated in bold. (XLSX 12 kb)
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Table S7Output of Tukey‘s HSD test, indicating the significance of the pairwise differences in centroid size means (based on the five individual datasets and the concatenated dataset) among the taxonomic groups of Pavlinov (2001, 2008). The difference in the observed means along with the P-value, adjusted for the multiple comparisons, are shown. Significant P-values are indicated in bold. (XLSX 13 kb)

Copyright information

© Springer Science+Business Media New York 2017

Authors and Affiliations

  1. 1.Department of Biological SciencesKuwait UniversitySafatKuwait

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