Studies on microsatellites and chromosome evolution in a few stabilized hybrids of the Nasuta-albomicans complex of drosophila

Abstract

In evolutionary biology, speciation being gradual or punctuated remains as a newlinefundamental question and the poor availability of evolutionary history of most plant and animal species makes the critical evaluation of this question a difficulty. Hybrid or recombinational speciation is one of the suggested pathways by which new species might arise rapidly via hybridization between chromosomally or genetically divergent parental species. Drosophila nasuta nasuta (2n=8) and D. n. albomicans (2n=6) are a pair of chromosomal cross fertile races belong to the nasuta subgroup of immigrans species group of Drosophila. Interracial hybridization between them resulted in the production of karyotypically stabilized hybrid races called cytoraces. The parents and the newly evolved 16 cytoraces are grouped under a new assemblage called, nasuta-albomicans complex (NAC) of Drosophila. This complex is an artificial hybrid zone of Drosophila with allosympatric populations exhibits racial divergences. In view of this, these members were subjected forgenetic analysis to understand the molecular basis of introgression. The findings and their implications are presented in three sections. Section I reviewed the published literature about the members of NAC of Drosophila and the molecular markers. In Section II the evolutionary genetics of Fissioncytorace-1 was dealt in 5 parts as (A) Phenomes (B) Inter-genotypic competitive ability assessment (C) Random Amplified Polymorphic DNA (RAPD) analysis (D) Microsatellite analysis and (E) Inter Simple Sequence Repeats (ISSR)analysis. Fissioncytorace-1 showed increased body size, sternopleural bristle number, ovarioles number, lifetime fecundity and lifetime fertility with reduced inter-specific competitive ability and hatching success when compared to cytorace 1. RAPD, microsatellite and ISSR analyses placed cytorace 1 and Fissioncytorace-1 in one cluster indicating that though both differ in their chromosome number, at the genomic level, they are identical.