Microsatellite evolutionary rate and pattern in Schistocerca gregaria inferred from direct observation of germline mutations

Abstract

Unravelling variation among taxonomic orders regarding the rate of evolution in microsatellites is crucial for evolutionary biology and population genetics research. The mean mutation rate of microsatellites tends to be lower in arthropods than in vertebrates, but data are scarce and mostly concern accumulation of mutations in model species. Based on parent-offspring segregations and a hierarchical Bayesian model, the mean rate of mutation in the orthopteran insect Schistocerca gregaria was estimated at 2.1e(-4) per generation per untranscribed dinucleotide locus. This is close to vertebrate estimates and one order of magnitude higher than estimates from species of other arthropod orders, such as Drosophila melanogaster and Daphnia pulex. We also found evidence of a directional bias towards expansions even for long alleles and exceptionally large ranges of allele sizes. Finally, at transcribed microsatellites, the mean rate of mutation was half the rate found at untranscribed loci and the mutational model deviated from that usually considered, with most mutations involving multistep changes that avoid disrupting the reading frame. Our direct estimates of mutation rate were discussed in the light of peculiar biological and genomic features of S. gregaria, including specificities in mismatch repair and the dependence of its activity to allele length. Shedding new light on the mutational dynamics of grasshopper microsatellites is of critical importance for a number of research fields. As an illustration, we showed how our findings improve microsatellite application in population genetics, by obtaining a more precise estimation of S. gregaria effective population size from a published data set based on the same microsatellites.

Importance of solitarious desert locust population dynamics: lessons from historical survey data in Algeria

“…They probably cover hundreds of kilometres between complementary areas for breeding (Waloff, ; Roffey & Magor, ). These solitarious populations are probably much more abundant than previously believed (Chapuis et al., , ). Their role in the invasions’ genesis is crucial (Lecoq, , ; Magor et al., ), as it was also demonstrated in other locust and grasshopper species (Lecoq, , ).…”

The population genomics of multiple tsetse fly (Glossina fuscipes fuscipes) admixture zones in Uganda

“…For this reason, priors for ABC models (Supporting Information Table ) were based on independently derived estimates wherever possible. Mutation priors were based on estimates of microsatellite mutation rates in other insects (Chapuis, Plantamp, Streiff, Blondin, & Piou, ) and results from a published ABC analysis in a closely related species, Glossina pallidipes (Ciosi et al, ). Population size and bottleneck priors were based on previous population genetics estimates (Beadell et al, ; Echodu et al, ; Hyseni et al, ; Opiro et al, ).…”

Exploring the relationship between tychoparthenogenesis and inbreeding depression in the Desert Locust, Schistocerca gregaria

“…The Belgian populations were genotyped in 2009 (Berthier et al., 2010), the French population in 2011 (Chapuis, Plantamp, Streiff, Blondin, & Piou, 2015), and the English population in 2013 for this study. A Mauritanian population sample (different from the population used in this experiment) was genotyped in the past (Chapuis et al., 2014).…”

“…Based on microsatellite genotyping, we characterized the genetic diversity (expected heterozygosity H E ) and the inbreeding coefficients (F IS ) of the studied populations. The Belgian populations were genotyped in 2009 (Berthier et al, 2010), the French population in 2011 (Chapuis, Plantamp, Streiff, Blondin, & Piou, 2015), and the English population in 2013 for this study. A Mauritanian population sample (different from the population used in this experiment) was genotyped in the past (Chapuis et al, 2014).…”