TALPIDAE, G. Fischer, 1814

Barrow, Eugenie & Macleod, Norman, 2008, Shape variation in the mole dentary (Talpidae: Mammalia), Zoological Journal of the Linnean Society 153 (1), pp. 187-211 : 188-190

THE TALPIDAE

Diverse lifestyles have evolved among the Talpidae . They are distributed throughout Eurasia and North America and include species that are ambulatory (the shrew-like moles), semi-aquatic (desmans), semi-

Taxonomy at the genus level follows Hutterer (2005) and includes Nesoscaptor within Mogera ( Motokawa et al., 2001) . *Genera from which one species is represented in this study.

Numbers in parentheses indicate the number of species in each genus.

fossorial (shrew moles) and fully fossorial ( Hutchison, 1976; Yates & Moore, 1990). Talpids are largely faunivorous, but to varying degrees depending on their habitat. Aquatic forms consume small crustaceans and fish whereas terrestrial forms concentrate, to different degrees, on worms, insect larvae and other small invertebrates ( Raw, 1966; Nowak, 1999; Silcox & Teaford, 2002).

There are 17 recognized extant talpid genera and approximately 42 species ( Nowak, 1999), separated into several clades ( Table 1). The Talpinae form the largest group within the Talpidae and include both fossorial and semi-fossorial moles. Shrews and hedgehogs are thought to be the most likely talpid sister groups, and together these three groups form the clade Eulipotyphla ( Waddell, Okada & Hasegawa, 1999; Asher, Novacek & Geisler, 2003).

Recent phylogenetic studies have been based on both morphological and molecular data and concur that Uropsilus is the most basal talpid genus ( Hutchison, 1976; Whidden, 2000; Motokawa, 2004; Cabria et al., 2006; Sánchez-Villagra, Horovitz & Motokawa, 2006). However, the position of other groups within the clade is less certain. For example, there is inconsistency in the relationship between the shrew moles Urotrichus and Neurotrichus (from Japan and North America, respectively; see Moore, 1986; Whidden, 2000; Shinohara, Campbell & Suzuki, 2003) and the relationships between and within the two fully fossorial clades, Talpini and Scalopini ( Rohlf, Loy & Corti, 1996; Okamoto, 1997; Shinohara et al., 2004). The most recent comprehensive talpid cladogram is that of Sánchez-Villagra et al. (2006; Fig. 2 ). This is based on a maximum-parsimony analysis of 157 morphological characters and is an extension of Motokawa’s (2004) research on talpid phylogenetics.

The fully fossorial lifestyle most likely evolved from semi-fossorial moles, but uncertainties in their phylogenetic relationships have triggered some debate as to whether it evolved in a single evolutionary step ( Whidden, 2000) or as a result of parallel adaptations ( Motokawa, 2004). The fully fossorial clade Talpini ranges throughout Eurasia while the Scalopini is known mostly from North America (one genus, Scapanulus , appears endemic to China but only a few specimens have been found to date). Sánchez-Villagra et al. (2006) argued that the monospecific genus Scaptonyx was sister group to the Talpini clade. Nowak (1999) points out that little is known about this mole but it is thought to be semi-fossorial, indicating that the fully fossorial lifestyle evolved at least twice ( Motokawa, 2004; Sánchez-Villagra et al., 2006).

Morphological studies have identified characters of the dentary used in talpid phylogenetic studies, for example by Motokawa (2004: characters 51–55). These have also been used in species descriptions. True (1896) described the form of the coronoid and angular processes and features of the horizontal ling 14 out of the 17 extant genera recognized in the current taxonomy (see Table 1). Sample sizes for each genus varied from three to 15 individuals. Specimens used came from the mammalogy collections at The Natural History Museum, London (BMNH), and the Museum für Naturkunde, Humboldt University (MNHU), Berlin. A full list of all specimens used in this study is available from the senior author on written request.

ramus in his review of the American talpid species and subspecies. A comparative study of the mole Scalopus aquaticus and the shrew Blarina brevicauda highlighted important differences in the dentary ( Gaughran, 1954). These include the scoop-like angular process of Scalopus (monospecific) compared with the narrow, spicular angular process of Blarina brevicauda and the larger, heavier condylar process but thinner coronoid process in the Scalopus as compared with the shrew Blarina brevicauda .

Dental characters have also been used as a source of information in talpid phylogenetic and taxonomic studies. Absence of the lower canine in the East Asian mole genus Mogera distinguishes them from the Old World moles Talpa , with which they were once included ( Nowak, 1999). Ziegler (1971) examined how tooth formula differentiations, including fossil talpid taxa, related to their functional groups/lifestyles. The effect of variation in dental formula (and tooth size) is likely to contribute to aspects of the dentary form, particularly the shape of the horizontal ramus.

Figures

Figure 2. Phylogenetic relationships among the Talpidae proposed by Sánchez-Villagra et al. (2006) based on a maximum-parsimony analysis of 157 morphological characters. Clades indicated (in grey) are discussed in the text (see also Table 1).