Microgeographical breeding structure of the tsetse fly, Glossina pallidipes in south‐western Kenya

Abstract

The origins of extant G. pallidipes Austen (Diptera: Glossinidae) populations in the ecologically well studied Lambwe and Nguruman valleys in Kenya are controversial because populations have recovered after seemingly effective attempts to achieve high levels of control. We investigated microgeographic breeding structure of the tsetse fly, Glossina pallidipes (Diptera: Glossinidae) by analyzing spatial and temporal variation at eight microsatellite loci to test hypotheses about endemism and immigration. Samples were obtained at seasonal intervals from trap sites separated by 200 m to 14 km and arranged into blocks. G. pallidipes populations nearest to Lambwe and Nguruman also were sampled. Spatial analysis indicated genetic differentiation by genetic drift was much less among trapping sites within Lambwe and Nguruman (F ST ≤ 0.049) than between them (F ST = 0.232). F ST between Serengeti and Nguruman was 0.16 and F ST between Kodera Forest and Lambwe was 0.15. The genetic variance in G. pallidipes explained by dry and wet seasons (0.33%) was about one-fifth the variance among collection dates (1.6%) thereby indicating reasonable temporal stability of genetic variation. Gene frequencies in Kodera and Serengeti differed greatly from Lambwe and Nguruman thereby falsifying the hypothesis that Lambwe and Nguruman were repopulated by immigrants. Harmonic mean effective (= breeding) population sizes were 180 in Lambwe and 551 in Nguruman. The genetic data suggest G. pallidipes in Lambwe and Nguruman have been endemic for long intervals.

Tsetse flies: Genetics, evolution, and role as vectors

“…They are codominant and highly polymorphic. SSRs have been developed for the Morsitans group (Baker and Krafsur, 2001; Ouma et al, 2003, 2006). Some primers for Morsitans group tsetse also amplify orthologous loci in the Fusca and Palpalis groups.…”

“…Better resolution of population structure may be afforded by survey of diploid loci. Nine putative microsatellite loci were identified (Baker and Krafsur, 2003; Ouma et al, 2006), but no survey of diversity has yet been carried out.…”

“…Microsatellite and mitochondrial variation was examined in detail at macrogeographic (Krafsur and Wohlford, 1999; Ouma et al, 2005) and microgeographic scales (Ouma et al, 2006). Single strand conformational polymorphisms (SSCPs) were used to characterize mitochondrial variation (later, direct sequencing was adopted to obtain better resolution).…”

“…At the microgeographic level, G. pallidipes subpopulations were sampled at scales of 200 m to 14 km (Ouma et al, 2006). The chief locations were Lambwe in the Ruma National Park in western Kenya, and Nguruman, in southwestern Kenya, adjacent to Tanzania.…”

“…At the geographically larger Nguruman site, estimates varied from c . 250 to 1000 (Ouma et al, 2006). Estimates of N e varied from 18 to 66 in G. swynnertoni (Marquez et al, 2006).…”