The Genetic Structure ofDrosophila ananassaePopulations From Asia, Australia and Samoa

Abstract

Information about genetic structure and historical demography of natural populations is central to understanding how natural selection changes genomes. Drosophila ananassae is a widespread species occurring in geographically isolated or partially isolated populations and provides a unique opportunity to investigate population structure and molecular variation. We assayed microsatellite repeat-length variation among 13 populations of D. ananassae to assess the level of structure among the populations and to make inferences about their ancestry and historic biogeography. High levels of genetic structure are apparent among all populations, particularly in Australasia and the South Pacific, and patterns are consistent with the hypothesis that the ancestral populations are from Southeast Asia. Analysis of population structure and use of F-statistics and Bayesian analysis suggest that the range expansion of the species into the Pacific is complex, with multiple colonization events evident in some populations represented by lineages that show no evidence of recent admixture. The demographic patterns show isolation by distance among populations and population expansion within all populations. A morphologically distinct sister species, D. pallidosa, collected in Malololelei, Samoa, appears to be more closely related to some of the D. ananassae populations than many of the D. ananassae populations are to one another. The patterns of genotypic diversity suggest that many of the individuals that we sampled may be morphologically indistinguishable nascent species.

Population Genetics of Drosophila ananassae: Evidence for Population Sub-Structuring at the Level of Inversion Polymorphism in Indian Natural Populations

“…Similar studies (Vogl et al, 2003;Das et al, 2004;Schug et al, 2007) done earlier at molecular level in D. ananassae have arrived on the similar conclusion. These studies have shown that F ST values of the order of 0.1 (much lower than our F ST estimates) could be applied to Indian populations.…”

“…ananassae displays high population sub-structure across the whole distribution range (Stephan, 1989;Stephan & Langely, 1989;Stephan & Mitchell, 1992;Stephan et al, 1998;Das, 2005;Schug et al, 2007). It exhibits more population structure than both D. melanogaster and D. simulans (Vogl et al, 2003;Das, 2005).…”

Bottlenecks, population differentiation and apparent selection at microsatellite loci in Australian Drosophila buzzatii

“…In addition to mean D 0 estimates, we use for each population the percentage of locus pairs that had significant (Po0.05) D 0 values. As 5% of pair-wise LD are expected by chance to be significant, higher percentages indicate more LD than would be expected (Schug et al, 2007).…”

A primary role of developmental instability in sexual selection

“…Furthermore, comb size in Noumea is significantly greater than at Cape Tribulation , indeed indicating the probable recent evolution of alleles conferring large ornament size in New Caledonia, which may be destabilizing trait-specific networks (Clarke & McKenzie 1987;Sangster et al 2004). This model assumes that New Caledonian D. bipectinata is derived from mainland Australia (or Southeast Asia), which is reasonable (Kopp & Barmina 2005;Schug et al 2007). …”