Allometric Comparison of Skulls from Two Closely Related Weasels,Mustela itatsiandM. sibirica

Abstract

We conducted an interspecific comparison of skulls from two closely related but differently sized mustelid species, Mustela itatsi and M. sibirica (Mammalia, Carnivora, Mustelidae); a sexual comparison within the latter species showed remarkable size dimorphism. We clarified several differences in skull proportion related to size using allometric analyses and qualitative comparisons. Allometric analysis revealed that the skulls of male M. itatsi (the smaller species) have a relatively long palate; a slender viscerocranium and postorbital constriction; a broad, short, and low neurocranium; small carnassials; and a short mandible with a thin body and small ramus compared to the skulls of male M. sibirica (the larger species). Similar results were obtained when male M. itatsi were compared to female M. sibirica, although the male M. itatsi had a broader viscerocranium than female M. sibirica. A sexual comparison in M. sibirica revealed a larger skull size among the males with a relatively wide viscerocranium; wide postorbital constriction; a slender, long, and high neurocranium; short and wide auditory bullae; short carnassials; and a long and high mandible compared to females. Qualitative comparisons revealed changes in a few characters depending on skull size or with respect to some cranial components in each species. The interspecific differences observed were clearly larger than the intraspecific differences for three qualitative characters. The allometric and qualitative differences detected between these species suggest that each species is not simply the dwarf and/or giant morph of the other, and complicated differences were clarified.

Do functional demands associated with locomotor habitat, diet, and activity pattern drive skull shape evolution in musteloid carnivorans?

“…Indeed, even if it was previously shown that sexual dimorphism may have an influence in skull shape (e.g. Loy et al, 2004;Christiansen & Harris, 2012), the interspecific variation is much larger than the intra-specific one (Lee & Mill, 2004;Suzuki, Abe & Motokawa, 2011). Previously studies have also demonstrate that sexual dimorphism is related to reproductive demands rather than diet, habitat, or activity pattern (Gittleman & Van Valkenburgh, 1997;Christiansen (2011) Most prominent point of the postparietal, middle 5…”

Molecular phylogeography of the Japanese weasel, Mustela itatsi (Carnivora: Mustelidae), endemic to the Japanese islands, revealed by mitochondrial DNA analysis

“…Abramov (, b) studied the morphotypic characteristics of the skull, body size, coloration and baculum, and positioned itatsi as an independent species in the phylogeny of Mustela . Recently, Suzuki, Abe & Motokawa () reported interspecific and sexual differences in the skulls between the two species. Thus, both morphological and genetic data strongly support the first description that itatsi is a distinct species.…”

Head shape evolution in monitor lizards (Varanus): interactions between extreme size disparity, phylogeny and ecology

“…Allometric scaling is generally the null hypothesis and suggests that when the size of a structure is changed, shape must be altered in a compensatory fashion to preserve function (Sweet, ; Smith, ). Allometric scaling can be established in an ontogenetic growth series, over evolutionary time, among related species, populations and sexes (Blackstone, ; Gerber et al ., ; Klingenberg, ; Wilson & Sánchez‐Villagra, ; Suzuki et al ., ). The absence of size‐required shape change is often termed ‘geometric similarity' or ‘isometry'.…”