Challenges to assessing connectivity between massive populations of the Australian plague locust

Abstract

Linking demographic and genetic dispersal measures is of fundamental importance for movement ecology and evolution. However, such integration can be difficult, particularly for highly fecund species that are often the target of management decisions guided by an understanding of population movement. Here, we present an example of how the influence of large population sizes can preclude genetic approaches from assessing demographic population structuring, even at a continental scale. The Australian plague locust, Chortoicetes terminifera, is a significant pest, with populations on the eastern and western sides of Australia having been monitored and managed independently to date. We used microsatellites to assess genetic variation in 12 C. terminifera population samples separated by up to 3000 km. Traditional summary statistics indicated high levels of genetic diversity and a surprising lack of population structure across the entire range. An approximate Bayesian computation treatment indicated that levels of genetic diversity in C. terminifera corresponded to effective population sizes conservatively composed of tens of thousands to several million individuals. We used these estimates and computer simulations to estimate the minimum rate of dispersal, m, that could account for the observed range-wide genetic homogeneity. The rate of dispersal between both sides of the Australian continent could be several orders of magnitude lower than that typically considered as required for the demographic connectivity of populations. (Résumé d'auteur

Worldwide population genetic structure of the oriental fruit moth (Grapholita molesta), a globally invasive pest

“…There were significant deviations from HWE at multiple loci from all sampling locations (data not shown), and in all cases these were the result of heterozygote deficiencies (Table  3). Null allele frequencies varied from 0.05 to 0.33 among the 13 microsatellite loci (Table  2), which is typical for lepidopteran DNA loci [38], and lower than or comparable to other studies that have used microsatellite markers to determine the genetic structure of populations [39,40]. Significant linkage disequilibrium was present in 15 out of 78 pairs of loci overall, but was unlikely due to physical linkage; patterns of significant allelic associations were not consistently restricted to certain pairs of loci within the 26 populations (data not shown).…”

Patterns of range-wide genetic variation in six North American bumble bee (Apidae: Bombus) species

“…2009; Lepais et al. 2010), which in a large widespread insect population with a fairly continuous distribution may be sufficient to maintain high genetic connectivity in the absence of more substantial barriers such as mountain ranges (Chapuis et al. 2011).…”

“…Significant heterozygosity deficits detected in some populations, most notably in B. occidentalis from Alaska, and only weak IBD could point to such dynamics in some species, although disequilibrium does not appear widespread. In any event, results suggest that reductions in gene flow that might characterize declining species are not yet apparent in the genetic data, and additional research is clearly needed to better link genetic parameters with ecologically relevant dispersal patterns (Chapuis et al. 2011).…”

Population Genetics of Ceratitis capitata in South Africa: Implications for Dispersal and Pest Management

“…Third, the reported high levels of genetic diversity may be linked with exceptionally large population sizes in South Africa, among other factors (e.g. high mutation rate, see discussions in [61], [62]). This high genetic diversity may contribute to their ability to colonize novel habitats through increased evolutionary potential [63], [64].…”