Chromosomal evolution in Malagasy lemurs: XII. Chromosomal banding study of Avahi laniger occidentalis (Syn: Lichanotus laniger occidentalis) and cytogenetic data in favour of its classification in a species apart-Avahi occidentalis.

A cytogenetical study of the western form of Avahi (Avahi laniger occidentalis) shows that its karyotype differs from that of A. laniger laniger by at least 3 chromosomal rearrangements. Meiotic chromosomal pairing of hypothetical hybrids has been constructed. Its configuration, a tetravalent with an inversion loop, is likely to strongly reduce fertility, especially in the male. This leads us to propose that the two forms correspond to two distinct species, separated by a gametic barrier: Avahi laniger and a species apart, Avahi occidentalis.