Incipient sexual isolation in thenasuta-albomicans complex ofDrosophila: mating preference in male-, female- and multiple-choice mating experiments

Abstract

Interracial divergence is an important facet of speciation. The nasuta-albomicans complex of Drosophila with sixteen morphologically identical, karyotypically different but cross-fertile races is an excellent system to study a few dimensions of raciation. Drosophila nasuta nasuta, Drosophila nasuta albomicans, Cytorace 1, Cytorace 2, Cytorace 3 and Cytorace 4 of this subgroup have been subjected to male-, female- and multiple-choice mating experiments. Out of 8456 crosses conducted, 7185 had successful matings. The overall impression is that mating is far from random amongst these six closely related races of the nasuta-albomicans complex. The males of D. n. albomicans, Cytorace 1 and Cytorace 4 in male-choice, the females of Cytorace 1 and Cytorace 2 in female-choice, and the males and females of D. n. nasuta, D. n. albomicans, Cytorace 1 and Cytorace 4 against the males and females of Cytorace 2 in multiple-choice experiments, had significantly more homogamic matings than expected. Thus in this study of evolutionary experimentation on raciation under laboratory conditions, we have documented the initiation of preference for conspecific matings among closely related and independently evolving members of the nasuta-albomicans complex of Drosophila.

Assortative Mating in Drosophila Adapted to a Microsite Ecological Gradient

“…Theoretically, male choice could also exist and be revealed in the case of equal female receptivity, but it was not the case in flies derived from EC collections. The importance of male choice has already been shown (Marin, 1997;Tanuja et al, 2001). It is possible to estimate thoroughly the degree of females' receptivity, discrimination, or males' activity in no-choice experiments (Iliadi et al, 2001).…”

Evidence for no sexual isolation between Drosophila albomicans and D. nasuta

“…; Ramachandra and Ranganath ; Tanuja et al. ,b; Chang and Tai ), but the conclusions differed among these studies. Using male‐choice tests, Kitagawa et al.…”

“…Using no‐, female‐, male‐ and multiple‐choice tests, Ramachandra and his colleagues showed a significant departure from random mating between these two species (Ramachandra and Ranganath ; Tanuja et al. ,b). Chang and Tai () reported asymmetric sexual isolation between the two species with more homogamic matings occurring in D. albomicans than in D. nasuta .…”

Genomic introgression in laboratory evolved hybrid races, Cytorace 1 and Fissioncytorace-1 ofNasuta-albomicanscomplex (NAC) ofDrosophila(Insecta, Diptera) as revealed by RAPD and ISSR markers

“…The nasuta-albomicans complex (NAC) of Drosophila is an artificial hybrid zone with "allo-sympatric" populations, showing variation in their cytogenetic differentiation, mating preference, body size and fitness (Ramachandra & Ranganath 1996;Tanuja et al 2001;Harini & Ramachandra 2003). This is an assemblage comprising of Drosophila nasuta nasuta (♂ 2n = 8: 2 n 2 n 3 n 3 n X n Y n 4 n 4 n , ♀ 2n = 8: 2 n 2 n 3 n 3 n X n X n 4 n 4 n ), Drosophila nasuta albomicans (♂ 2n = 6: 2 a 2 a X3 a Y3 a 4 a 4 a , ♀ 2n = 6: 2 a 2 a X3 a X3 a 4 a 4 a ) and 16 Cytoraces, which are the evolutionary product of a long range hybridization experiment.…”