Morphometric analysis of seven species of pocket gophers (Geomys)

Interspecific morphometric variation was assessed in seven species of pocket gophers (Geomys). One hundred and seven characters, representing cranial and post-cranial characters were examined in 131 individuals. A basic premise of this study was that previously under-represented appendicular, skeletal, and mandibular structures may provide informative data for species discrimination. Principal components analysis established that ca. 50% of among-group variation in males and females was attributable to size as determined by the magnitude, sign, and distribution of character loadings on the first principal component. Sexual dimorphism in these species primarily is a function of size, and shape differences are less important in the discrimination of gender. A phenogram of all species, constructed from the Mahalanobis distances, indicated that G. texensis and G. bursarius were most similar and G. breviceps and G. personatus were distinct compared with other species of Geomys. Other taxa were not discriminated completely in multivariate space. The low level of morphological evolution does not reflect the level of genetic differentiation reported by other investigators, suggesting that many species of Geomys may represent cryptic species.