Ecology influences the process of speciation. The interspecific differences in mammalian skull morphology, induced by environmental factors, are important when investigating speciation. In the Qinghai–Tibetan Plateau, the genus Eospalax consists of six species of subterranean rodents, each with its unique niche, making it an ideal model for studying the relationship between biological evolution and the environment. Here, the interspecific differences in five of the six extant species (E. cansus, E. baileyi, E. rufescens, E. smithii, and E. fontanierii) were evaluated at the morphometric and ecological levels using geometric morphometrics, a powerful tool for studying morphological variation. The multivariate analysis of variance showed significant differences in skull morphology on the dorsal and ventral sides in all species. The thin‐plate splines showed that the variations in skull morphology were primarily in the infraorbital foramen, frontal bone, zygomatic arch, occipital bone, incisors, incisive foramen, and tooth row. The multivariate regression analysis showed a significant positive correlation between skull morphological variations and ecological factors; precipitation accounted for the more variations than altitude and temperature. Species inhabiting regions with the highest altitude, minimum precipitation, and temperature (E. baileyi) had the largest infraorbital foramen and zygomatic arch, shortest occipital bone and widest frontal bone, smallest angle formed by two incisors, and longest incisive foramen. Our study elucidates the relationship between skull morphological differentiation and environmental factors in Eospalax, while the biological response to the environment detected warrants further investigation. Our results can provide references for speciation at local environmental scale.
The gonadotropins, luteinizing hormone (LH) and follicle stimulating hormone (FSH), are glycoprotein hormones in the hypothalamic-pituitary-gonadal (HPG) axis and regulate mammalian reproduction. The expression of these genes in the plateau zokor (Eospalax baileyi) is poorly understood. We characterized the immunolocalization of the luteinizing hormone receptor (LHR) and follicle stimulating hormone receptor (FSHR) in the testes and evaluated the positive immunohistochemical results and the relative mRNA expression of gonadotropin genes. During the non-breeding season (September), the relative testes’ weight and the seminiferous tubule diameter were significantly reduced. All germ cell types were observed during the breeding season (May), whereas only spermatogonia were observed during the non-breeding season. LHR was present in the Leydig cells whereas FSHR was present in the Sertoli cells. The mean optical density was higher during the breeding season. The mRNA expression of LHβ and FSHβ was lower in the pituitary but LHR and FSHR genes expression were higher in the testes during the breeding season. These data elucidate the expression of gonadotropin genes in the HPG axis of the male plateau zokor and suggest that gonadotropins play a vital role in the regulation of seasonal breeding.
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