Evolutionary experimentation through hybridization under laboratory condition in Drosophila: Evidence for Recombinational Speciation

Abstract

BackgroundDrosophila nasuta nasuta (2n = 8) and Drosophila nasuta albomicans (2n = 6) are a pair of sibling allopatric chromosomal cross-fertile races of the nasuta subgroup of immigrans species group of Drosophila. Interracial hybridization between these two races has given rise to new karyotypic strains called Cytorace 1 and Cytorace 2 (first phase). Further hybridization between Thailand strain of D. n. albomicans and D. n. nasuta of Coorg strain has resulted in the evolution of two more Cytoraces, namely Cytorace 3 and Cytorace 4 (second phase). The third phase Cytoraces (Cytorace 5 to Cytorace 16) have evolved through interracial hybridization among first, second phase Cytoraces along with parental races. Each of these Cytoraces is composed of recombined genomes of the parental races. Here, we have made an attempt to systematically assess the impact of hybridization on karyotypes, morphometric and life history traits in all 16 Cytoraces.ResultsThe results reveal that in most cases, the newly evolved Cytoraces, with different chromosome constitutions, exhibit decreased body size, better fitness and live longer than their parents. Particularly, Cytorace 5, 6 and 8 have evolved with very much higher range values of quantitative traits than the parents and other Cytoraces, which suggests the role of transgressive segregation in the evolution of these Cytoraces.ConclusionThus, the rapid divergence recorded in the chromosomes, karyotypes, body size and fitness traits of Cytoraces exhibit the early event of recombinational raciation / speciation in the evolution of the Cytoraces under laboratory conditions.

Genetic Distance Between Species Predicts Novel Trait Expression in Their Hybrids

“…The occurrence of phenotypic novelty through interspecific hybridization is common and has been suggested to be a potentially important source of adaptive genetic variation where ecological opportunity exists (Harini and Ramachandra 2003;Lexer et al 2003b;Johnston 2004;Seehausen 2004;Albertson and Kocher 2005). We predicted, based on the previous finding that transgression in hybrids is often caused by complementary gene action or epistasis (Rieseberg et al , 2003, that the frequency of transgression should positively scale with the genetic distance between the hybridizing species.…”

Phylogeographic relationships and the evolutionary history of the Carassius auratus complex with a newly born homodiploid raw fish (2nNCRC)

“…A fundamental question in evolutionary biology is whether speciation is gradual or punctuated [ 1 ]. Hybridization is regarded as an ‘evolutionary catalyst’ that may be an important source for the origination of a new species or an increase the amount of genetic variability.…”

De novo assembly, annotation and gene expression profiles of gonads of Cytorace-3, a hybrid lineage of Drosophila nasuta nasuta and D. n. albomicans

“…1 ). The rapid divergence in C3 is extensively recorded through comparative studies for male and female reproductive fitness, wing size, genitalia size, body weight, body size, longevity [ 10 ], mating latency, and copulation duration in heterogamic crosses [ 11 ]. This empirical evidence makes C3 an attractive model to study the molecular basis of early events in racial divergence.…”