Variation in sex-linked interchange heterozygosity in the termite Incisitermes schwarzi Banks (Insecta: Isoptera) on the island of Jamaica

Abstract

Collections of colonies of the termite Incisitermes schwarzi from mangroves around the coast of Jamaica revealed six chromosomal types, all involving variations or rearrangements of the sex chromosomes. One of the types had a heteromorphic sex bivalent in which the Y chromosome was larger than the X. The other five races had complex interchange multiples: a chain of 11, a chain of 12, a ring of 12, a ring of 14, and a ring of 18 chromosomes. The situation is similar to that described previously for Kalotermes approximatus, another member of the family Kalotermitidae, in the southeastern United States. The different chromosomal types can be arranged in an evolutionary series, each step requiring an interchange or fusion between an autosome and a previously existing sex chromosome. Such polymorphic chromosome systems, containing Y-segregating elements of different evolutionary ages, may offer an unusual opportunity for studying the sequence of changes accompanying the evolution of Y chromosomes. Key words: termite, Incisitermes, sex-linkage, translocation, interchange, Jamaica.