Spalacinae Gray 1821

Wilson, Don E. & Reeder, DeeAnn, 2005, Order Rodentia - Family Spalacidae, Mammal Species of the World: a Taxonomic and Geographic Reference (3 rd Edition), Volume 2, Baltimore: The Johns Hopkins University Press, pp. 907-926 : 907

Spalacinae Gray 1821

Spalacinae Gray 1821 , London Med. Repos., 15: 303.

Synonyms: Aspalacidae Gray 1825 ; Aspalacina Gray 1825 ; Aspalacina Bonaparte 1837 ; Spalasina Reichenbach 1836 ; Spalacini Giebel 1855 ; Spalacini Fejfar 1972 .

Genera: 1 genus with 13 species:

Genus Spalax Guldenstaedt 1770 (13 species)

Discussion: First comprehensive monograph by Méhely (1909), who arranged all taxa into three subgenera of Spalax . A single genus had been recognized in most influential checklists and faunal accounts ( Ellerman, 1940; Ellerman and Morrison-Scott, 1951; Ognev, 1963 a; Simpson, 1945) until Topachevskii (1969, 1976) monographed the subfamily and defended two genera, Spalax and Microspalax (= Nannospalax ; proposed by Palmer, 1903, to replace the preoccupied Microspalax ). His dual arrangement is accepted by some ( de Bruijn, 1984; Gromov and Erbajeva, 1995; Kretzoi, 1970 -71; Lyapunova et al., 1974; McKenna and Bell, 1997; Mitchell-Jones et al., 1999; Musser and Carleton, 1993; Pavlinov and Rossolimo, 1987, 1998; Pavlinov et al., 1995 a; Savič, 1982 a; Vorontsov et al., 1977 b) but not others ( Carleton and Musser, 1984; Corbet, 1978 c; Kowalski, 2001; Nevo et al., 2001; Savič and Nevo, 1990; Ünay, 1996, 1999). Topachevskii (1969) documented variation in a suite of cranial, postcranial, and dental traits that formed the basis for his taxonomy, and de Bruijn (1984) found appreciable differences in dentition to distinguish the two genera among fragmentary fossils. Species of Spalax include high diploid and fundamental numbers, no acrocentric chromosomes, smaller interspecific differences in karyotypic structure, and lack of significant interpopulation variation (Savič and Nevo, 1990). Those in Nannospalax have low diploid and fundamental numbers and exhibit significant interpopulational differences that correlate with biological and ecological distinctions that have prompted investigators to suspect that this group is composed of superspecies, each comprised of many separate biological species (Savič and Nevo, 1990). Unfortunately, no study integrates variation in morphological and dental traits, karyotypes, and biochemical data within the framework of a cladistic analyses that would test Topachevskii’s monophyletic groups. Until such results are available, we recognize only Spalax , an expedient endorsed by researchers who focus on living ( Nevo et al., 2001; Savič and Nevo, 1990) or fossil (Ünay, 1996, 1999) spalacines.

In addition to the classical monographs (Méhely, 1913; Topachevskii, 1969), taxonomy and distribution of Spalacinae are reviewed by Corbet (1978 c, 1984), and illuminating regional reviews are available for species in Europe ( Mitchell-Jones et al., 1999; Savič, 1982 a), Russia and adjacent regions ( Gromov and Erbajeva, 1995; Ognev, 1963 a), and Egypt ( Osborn and Helmy, 1980). Carleton and Musser (1984) provided a diagnosis of the subfamily based upon morphology and summarized general characters and distribution; and Ünay (1996, 1999) reiterated the diagnostic dental traits. Savič and Nevo (1990) gave an excellent synopsis of the evolutionary history, speciation, and population biology of blind mole rats, updated by Nevo et al. (2001) in a review of Israeli populations. The answer to why spalacines live underground may be found in the transition during the early Tertiary from a subtropical to generally temperate world where an "underground ecotype provided subterranean mammals with shelter from extreme climatic fluctuations, and predators" (Ünay, 1999:421).

The panoply of adaptations necessary for living underground in tubular burrows has dramatically defined the blind mole rat phenotype, which facilitates their diagnosis but obscures phylogenetic connections to other muroid rodents. Spalax has been classified in a family with all burrowing myomorphous and even some hystricomorphous species ( Alston, 1876; Murray, 1866), with Myospalax , Rhizomys , and Tachyoryctes (Weber, 1928; Tullberg, 1899), with just Myospalax (G. M. Allen, 1940; Miller and Gidley, 1918), with only Rhizomys and Tachyoryctes ( Sen, 1977; Thomas, 1896), or by itself ( de Bruijn, 1984; Ellerman, 1940; Ellerman and Morrison-Scott, 1951; Nevo et al., 2001; Pavlinov and Rossolimo, 1987, 1998; Pavlinov et al., 1995 a; Reig, 1980; Simpson, 1945; Topachevskii, 1969; Ünay, 1996, 1999). Even the fundamental muroid affinity of Spalacidae was questioned by Stehlin and Schaub (1951) and Schaub (1958), who arranged Spalax and Rhizomys together in a separate suborder Pentalophodonta that also contained Theridomyidae, Oligocene rodents with premolars and molars characterized by complex lophate occlusal patterns. Petter (1961 b) reassociated blind mole rats with muroid rodents based on their possession of only three molars with simple cricetine occlusal patterns. He homologized their pattern to that of Malagasy Brachyuromys , placed in Cricetidae at the time, and suggested that Spalax is within the range of dental variation characteristic of Cricetidae . Petter’s view was ratified by Chaline et al. (1977), who allocated Spalax to a subfamily of Cricetidae , a significant departure from previous classifications. Whether placed in its own family or subfamily, the cladistic affinity of Spalax is indisputably with other muroid rodents, a connection established not only by morphology, but also by analyses of the nuclear gene IRBP ( DeBry and Sagel, 2001), nuclear genes LCAT and vWF ( Huchon et al., 1999; Michaux and Catzeflis, 2000; Michaux et al., 2001 b; Robinson et al., 1997), and mitochondrial cytochrome b and 12S rRNA genes ( Montgelard et al., 2002). Sequencing results from alpha crystalline A chain, a lens protein of the eye, and its significance for molecular clock hypothesis and phyletic analysis in Spalax were discussed by McKenna (1992).

SE Europe, SW Russia and Ukraine around Black and Caspian Seas, Asia Minor, Caucasia, Middle East adjacent to the Mediterranean, and N Africa encompass the modern geographic distribution of spalacines (see summary map in Nevo et al., 2001), which is generally concordant with range of described fossils (Ünay, 1999). Evolutionary history, based upon those fossils, dates from about 20 million years ago in the early Miocene of Anatolian Turkey ( Debruijnia Ünay, 1996), somewhat later during the early Miocene of Greece ( Heramys Hofmeijer and de Bruijn, 1985 ), and Pleistocene of N Africa ( McKenna and Bell, 1997). Those early Miocene genera are replaced by the extinct and speciose Pliospalax , ranging from early middle Miocene to Pliocene in Turkey, and from middle Miocene to early Pleistocene in Europe ( Kowalski, 2001; see review by Ünay, 1999). Living Spalax is apparently a relict of a once extremely diverse group, especially during the Miocene, that Ünay (1999:422) speculated originated and evolved in what is now Anatolia because it is there where the oldest and most numerous fossil species have been found: from Anatolia, spalacines "probably spread into the Balkans, Russia, the Near East and Africa … at different times." Using DNA-DNA hybridization, Catzeflis et al. (1989) estimated spalacines to have diverged from the other muroids sampled (arvicolines and murines) about 19 million years ago, which is consistent with antiquity claimed for the earliest fossil spalacines, and also for the divergence time estimated from LCAT nuclear gene sequences ( Michaux and Catzeflis, 2000; Robinson et al., 1997).

Spalacines were once phylogenetically linked with the extinct Anomalomyidae ( Anomalomys , Anomalospalax , Prospalax ), ranging from early Miocene to late Pliocene mostly in Europe, because of similar molar patterns; the latter are now viewed as fossorial rodents that are dentally convergent with spalacines and have a separate evolutionary history ( de Bruijn, 1984; Fejfar, 1972; see reviews by Bolliger, 1996, 1999, and Hugueney and Mein, 1993) with possible derivation from very early Miocene Eumaryion ( de Bruijn et al., 1981). Whether the earliest spalacines, Debruijnia and Heramys , were subterranean dwellers is unknown, but fossorial adaptations characterize the Miocene and Pliocene Pliospalax (Şen, 1977), and spalacines may have evolved into a fossorial and subterranean habitus around 15-14 million years ago, much earlier than either rhizomyines or tachyoryctines ( Flynn, 1990).