Population Gennetical, Behavioural and Evolutionary Studies in the Drosophila Bipectinata Species Complex

Abstract

Comparison of population dynamics with regard to chromosomal arrangements, protein and nucleotide polymorphism among closely related species can provide invaluable glimpses into the intricacies of speciation. In addition, recently diverged closely related species may also exhibit behavioural differences especially sexual behaviour which can be compared across the species and eventually may aid in understanding the process of speciation. To get the finer details of the so called 'speciation genes', evolutionary studies pertaining to hybrid incompatibilities are required. This involves detailed mapping of the speciation genes through introgression of a candidate gene from one species into the genetic background of another species. Evolutionary studies also include studies on the degree and pattern of sexual isolation among closely related species.The Drosophila bipectinata species complex comprises four species namely, D. bipectinata, D. parabipectinata, D. malerkotliana and D. pseudoananassae. In three members of this complex i.e. D. bipectinata, D. malerkotliana and D. pseudoananassae, subspecies have been identified. This complex with its species and their subspecies is a good model for speciation studies and has been extensively utilized for the purpose. This review attempts to compile all the important population genetical, behavioural and evolutionary studies that have been done in this complex so far. Eventually, we have also discussed what is still left to be done and the prospects of this complex being used in future to get answers relating to speciation. Keywords: Drosophila bipectinata IntroductionStudies on the intricacies of speciation involve varied approaches dealing mostly with population genetics, behaviour and evolution.Population genetics constitutes studies on changes in the genetic composition of a population, spanning investigations on polymorphism at the level of chromosomes (chromosomal arrangements), proteins and nucleotides. Comparing polymorphism levels across different populations of a species throws light on the pattern of polymorphism exhibited by the species. Further, comparing the pattern across different closely related species can definitely indicate the degree of their divergence and phylogenetic relationship.During the process of speciation, behavioural differentiation is expected as divergence in traits related to male courtship and female preference is necessary for reproductive isolation. Adaptations to their respective niches may also cause differences in certain behavioural aspects in different species. Also, alterations in the behavioural echelon may be a pleiotropic sequel of divergence at a certain locus/ loci not having any direct behavioural implication or simply a by-product of the divergence (although not often the case with behaviour). Therefore, studies on behavioural divergence amongst closely related species aids in unfolding the knots of the complex process of speciation. Behavioural studies mostly involve analysis of the courtship rituals of males and preferen...

The Drosophila bipectinata species complex: phylogenetic relationship among different members based on chromosomal variations

“…Given such small nucleotide divergence, morphological differences (among the males of three species) are far from being just barely evident, they are in fact very prominent). In addition to this, there are behavioural differences and strong reproductive isolation among these species (see review by Singh and Banerjee 2016). Therefore, more than divergence at the level of single nucleotides, rearrangement of gross chromosomal blocks must have played a greater role and have influenced regulation of gene expression in a big way causing speciation.…”

Reproductive Isolating Mechanisms and Speciation

“…However, these three species are distantly related to D. pseudoananassae. Based on asymmetrical mating pattern, it has been suggested that D.parabipectinata is derived from D. bipectinata (Singh & Banerjee, 2016). Thus as far as speciation is concerned, both isolating mechanisms are important: sexual isolation (premating) and hybrid sterility (post mating) in this complex.…”

Impact of environmental stress on biochemical profile and fitness traits in Drosophila malerkotliana

“…The present work has been done on Drosophila malerkotliana, a species thatbelongs to D. bipectinataspecies complex (Banerjee & Singh, 2017;Singh et al 2015;Singh & Banerjee, 2016;Singh & Singh, 2001). Among the Drosophila species that occur most commonly in the Indian subcontinent, this species is highly prevalent.…”