Rattus rattus

Rattus rattus (Linnaeus, 1758). Syst. Nat., 10th ed., 1:61.

TYPE LOCALITY: Sweden, Uppsala County, Uppsala.

DISTRIBUTION: Native to Indian Peninsula, and introduced worldwide in the tropics and temperate zone (Becker, 1978a; de Roguin, 1991; Dieterlen, 1979; Duplantier et al., 19916; Johnson, 1962a, b; Niethammer, 1975; Taylor and Horner, 1973; Taylor et al., 1982; Twigg, 1992; Yosida, 1980; Yosida et al., 1985).

SYNONYMS: aethiops, albiventer, albus, alexandrino-rattus, alexandrinus, arboreus, arboricola, asiaticus, ater, atratus, atridorsum, auratus, beccarii, brookei, brunneusculus, caeruleus, ceylonus, chionogaster, coquimbensis, crassipes, cyaneus, doboensis, domesticus, doriae, erythronotus, flavescens, flaviventris, frugivorus, fuliginosus, fulvaster, fuscus, gangutrianus, girensis, griseocaeruleus, indicus (Desmarest, 1822, not Bechstein, 1800), infralineatus (nomen nudum), intermedius, jujensis, jurassicus, kandianus, kandiyanus, kelaarti, kijabius, latipes, leucogaster, muansae, narbadae, nemoralis, nericola, osorninus, picteti, rattiformis, rattoides, rufescens, ruthenus, saltuum, samharensis, satarae, siculae, subcaeruleus, subrufus, sueirensis, sylvestris, tectorum, tetragonurus, tettensis, tompsoni, variabilis, varius (see Allen, 1939; Ellerman and Morrison-Scott, 1951; Mahoney and Richardson, 1988; Osgood, 1943; Schütter and Thonglongya, 1971; Taylor et al., 1982).

COMMENTS: Numerous cytogenetic studies focusing on the R. rattus complex, summarized by Baverstock et al. (1983c), Bekasova and Mezhova (1983), Niethammer (1975), and Yosida (1980), have revealed the complex to consist of two basic groups of populations. The Oceanian or European type has 2N=38 (40 in some), the Asian type is characterized by 2N=42; the two are also distinguished by biochemical features (Baverstock et al., 1983c) as well as morphological traits (Schwabe, 1979). Where the Asian type is indigenous, the Oceanian form is restricted to ports or on ships in harbor. Both chromosomal kinds apparently occur together without evidence of interbreeding on the Polynesian island of Fiji (Yosida et al., 1985), but do hybridize in the laboratory (usually producing sterile offspring) and on the South Pacific islands of Chichijima and Eniwetok (with apparent introgression). The biological status of the two kinds were best summarized by Baverstock et al. (1983c:978), who noted that if "the chromosomal, electrophoretic and laboratory hybridization data are considered together, it seems that the 2n=38 and 2n=42 forms are best considered as incipient species. Where they meet, they may introgress, become sympatric without interbreeding or one may replace the other depending upon the prevailing biological conditions," a view earlier espoused by Capanna (1974). Rattus rattus is the name for the 2N=38 /40 group, and we list it as a species separate from the 2N=42 form, for which the oldest name is R. tanezumi (see that account).