Evolutionary history of the genus Sus inferred from cytochrome b sequences

Abstract

The systematic status of species belonging to the genus Sus has been a matter of debate for decades (Groves, 1981). According to a recent review of its taxonomy, there are a total of 7 living species (Sus scrofa, Sus salvanius, Sus barbatus, Sus verrucosus, Sus celebensis, Sus philippensis, Sus cebifrons) and approximately 22 subspecies (Groves and Grubb, 1993), to which one recently recognized species, Sus bucculentus (Groves et al., 1997) and many new subspecies (Groves, 1997) should be added. South-East Asia (SEA) may be considered the homeland of the genus, as 6 out of the 8 species are endemic to the area, the only exception being the pygmy hog (S. salvanius), nowadays present only in the north of India, and S. scrofa, which is distributed worldwide (and not limited to SEA). In particular, the relationship between SEA species was investigated, but the evidence presented until now is still not conclusive. Morphological analyses point toward the identification of two main lineages, one leading to scrofa/celebensis/philippensis and the other to barbatus/verrucosus (Groves, 1997), but molecular evidence does not support the same grouping, but merges scrofa, barbatus and verrucosus (Lucchini et al., 2005). Recent findings have further complicated this issue rather than solving it, highlighting a substantial level of polyphyly among some of these species (see Larson et al., 2005).