Premium
Coexistence of ecologically similar colonising species. II. Population differentiation in Drosophila aldrichi and D. Buzzatii for competitive effects and responses at different temperatures and allozyme variation in D. aldrichi
Author(s) -
Krebs Robert A.,
Barker J. S. F.
Publication year - 1993
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1046/j.1420-9101.1993.6020281.x
Subject(s) - biology , sympatric speciation , cactus , population , ecology , drosophila (subgenus) , genetic divergence , divergence (linguistics) , natural selection , zoology , genetic diversity , demography , genetics , linguistics , philosophy , sociology , gene
Drosophila aldrichiandD. buzzatiiare cactophilic species that colonised Australia about 55–60 years ago. They are sympatric only in Australia. Thus they may be in the process of adapting to new environments and to each other, and diversifying among local, possibly isolated, populations. Larval competitive effects for three populations of each species (Roma, Planet Downs, and Binjour) were measured on semi‐natural cactus rots at three temperatures, with preadult viability, developmental time and adult body weight scored for each sex and species. Populations of both species varied in their responses to the other species as competitor, and oneD. buzzatiipopulation (Roma) reduced larval performance ofD. aldrichisignificantly more than did otherD. buzzatiipopulations. Geographic divergence for the three traits was similar in both species, with a relative performance index derived from these traits highest for Roma, second for Binjour, and least for the Planet Downs population of each species. The RomaD. aldrichipopulation was the most different from the other populations for the performance index and in terms of genetic distances derived from allozyme frequencies. Additionally, comparisons of climatic variables among the population localities showed that the Roma environment was most different from the others. Differential natural selection in different areas of the cactus distribution may be a major cause of population divergence in both species.Drosophila aldrichiis superior for some fitness components at the highest temperature. Thus temperature variation throughout the cactus distribution may contribute to the different ranges of these two species, with competitive exclusion ofD. aldrichi in the southern, cooler region of the cactus distribution, but coexistence in the northern, warmer region.