Reproductive Failure Among the Hybridizing Anolis Lizards of Trinidad

Gorman, George; Light, Paul; Dessauer, Herbert; Boos, Julius

Gorman, G. C. (Mus. Vert. Zool., U. Calif., Berkeley, 94720), Licht P. (Dept. Zool., U. Calif., Berkeley, 94720), Dessauer, H. C. (Dept. Biochem., L.S.U. Med. Ctr., New Orleans, La. 70112) and Boos, ]. 0. (Amoco Trinidad Oil Co., Port of Spain, Trinidad). Reproductive failure among the hybridizing Anolis lizards of Trinidad. Syst. Zool., 20:1-18.The lizards Anolis trinitatis and Anolis aeneus probably were introduced onto Trinidad. They tend to be found in pure species enclaves, but populations do overlap. Where they overlap they hybridize. Hybrid males are normal in size, but hybrid females are "giants," exceeding the parental females in length and weight. Hybrids have greatly reduced reproductive fitness, and are presumed to be largely sterile. Intersex hybrids have been found. Spermatogenesis occurs in hybrid males but few sperm are produced because of impaired meiosis; spermatogenic failure is not due to hormonal deficiencies. Androgen production appears normal in hybrid males. Few eggs are produced among the hybrid females. Electrophoresis of blood proteins serves to describe the structure of the hybridizing population. Species specific albumins, hemoglobins, and transferrins were useful for recognition of hybrids. The distribution of protein variants throughout the population showed that backcrosses were rare if they occurred at all. There are no distinct behavioral or ecological isolating mechanisms between the two species and little character displacement has occurred. It is not obvious if either species has a competitive advantage. However, large adult aeneus males are slightly more robust than male trinitatis. This may confer an advantage on the aeneus in territorial interactions. Casual observations suggest that aeneus is replacing trinitatis. The pure enclaves may result from the "advantage of numbers": the less abundant species will fail to find conspecific mates, will produce sterile hybrids, and therefore will not become established.

Reproductive Failure Among the Hybridizing Anolis Lizards of Trinidad

Series