time for Spalacidae from the muroid-cricetoid stock 40 to
45 million years ago (mya), which was in middle Eocene
times. However, DNA-DNA hybridization, based on entire
genome comparisons, suggests an evolutionary divergence
time of 19 mya (Catzeflis et al. 1989; Szalay et al. 1993).
The oldest fossil spalacid known is Heramys eviensisfrom
the lower Miocene of Greece, 25 mya (Hofmeijer and De
Bruijn 1985), now considered late Oligocene. These esti-
mates taken together suggest an Oligocene (probably late
Eocene – early Oligocene) age to the origin of the Spalacidae
(Nevo 1999).
To avoid confusion, and until a thorough taxonomic re-
vision of the Spalacidae is conducted, including chromo-
somal, molecular-genetic, and fossil data, Savic ́ and Nevo
(1990, and their table 1) used only one generic name, Spa-
lax,involving eight superspecies. Likewise, the four Israeli
species were described under Spalax(Nevo et al. 2001). Re-
cently, between fourteen and twenty new species, based on
karyotypes and allozyme evidence, have been described in
Asia Minor, almost doubling the number of extant species
in the Spalacidae to about sixty (Nevo et al. 1994, 1995,
2001). Recently, four new species were discovered in Jor-
dan, which also increased the number of species (Nevo et al.
2000).
Chromosomal Speciation
Chromosomal sibling species, or allospecies, based on Rob-
ertsonian changes (primarily fissions) and /or pericentric in-
versions, are generally widespread in the Spalacidae (Nevo
1999 and references therein). Notably, classical species of
this family involve many cryptic sibling species or allo-
species based on Robertsonian fissions (Nevo 1991, 1999;
Nevo et al. 2001). The eight classical species of mole-
rats from Russia, Ukraine, Balkans, Asia Minor, Israel, and
North Africa actually include more than sixty species (2n
38 – 62; NF 72 –124; Savic ́ and Nevo 1990 references
therein and table 2; Nevo, Simson, Heth, Redi, and Filip-
pucci 1991; Nevo et al., 1994, 1995, 2000). Some (like the
2n60) of the S. ehrenbergisuperspecies in Israel, Egypt,
and Jordan (Nevo 1991; Nevo et al. 1994, 1995) are late
Pleistocene and recent in origin. Based on multidisciplinary
studies involving natural hybridization, gene flow, pre- and
post-zygotic reproductive isolation, and even morphologi-
cal differentiation in middle ear ossicles (Burda et al. 1989)
and baculum (Simson et al. 1993) in the S. ehrenbergisu-
perspecies in Israel, most of the described karyotypes seem
to be distinct biological species.
Restricted mobility, spatial isolation, and numerous
small isolates in spalacids permitted their relatively rapid
chromosomal evolution (Wahrman et al. 1969a, 1969b,
1985) and parapatric speciation (Nevo 1989, 1991). The ini-
tiation of speciation by Robertsonian chromosomal muta-
tions and /or pericentric inversions and postmating repro-
ductive isolation was complemented gradually by premating
isolating mechanisms comprising olfaction, vocalization,
seismic communication (reviewed in Nevo 1990, 1991) and
middle ear ossicles (Burda et al. 1989), leading to the bud-
ding of new species adapted to increasing aridity, primarily
in the periphery of the distribution (Nevo et al. 1997). If
2n38 in west Turkey occurs near the origin of the Spa-
lacidae, then 2n increases in the three major gradients of in-
creasing aridity: the Balkans (up to 2n62), Russia and
the Ukraine (up to 2n62), and the Near East and North
Africa (up to 2n60, and even buds of 2n62; Nevo
1991, 1999).
Spalax ehrenbergisuperspecies in Israel represent an
evolutionary model of active speciation, studied multi- and
interdisciplinarily (reviewed in Nevo 1991, 1999; Nevo
et al. 2001). Adaptive speciation to four climatic regimes of
the four species Spalax galili, S. golani, S. carmeli, and S.
judaei(2n52, 54, 58, and 60, respectively) was demon-
strated at all organizational levels, from genetics through
morphology, physiology, and behavior (Nevo 1991, 1999).
Our recent finding of four presumable species in Jordan as-
sociated with varied climates (Ivanitskaya and Nevo 1998;
Nevo et al. 2000) needs further substantiation. The mono-
graph by Nevo et al. (2001) elaborates the speciation dy-
namics of the S. ehrenbergisuperspecies in Israel, including
natural hybridization (Nevo and Bar El 1976).Population Structure and Dynamics, Home Range,
and Territoriality in Subterranean MammalsThe optimal area hypothesis assumes that the home range
of animals — the area they know and patrol (Burt 1943)—
is large enough to yield an adequate supply of energy. The
home ranges of subterranean mammals are generally also
their exclusive and defended territories (Brown and Orians
1970), except for brief periods during the breeding season
when multiple occupancies by both sexes occur. (The so-
cial subterranean animals are the exception, where colonies
contain from several individuals to several hundreds of in-
dividuals [e.g., Sherman et al. 1991; Burda 1999; Lacey
2000; Bennett and Faulkes 2000].) This pattern is found
in pocket gophers, mole-rats, some tuco-tucos, and moles
(Nevo 1999). Territories, once established and used for one
breeding season, remain largely fixed for life (except for
minor boundary changes). Exceptions usually involve sub-
adults living in marginal habitats (Howard and Childs 1959;Evolution of Pacifism and Sociality in Blind Mole-Rats 295