Do outbreaks affect genetic population structure? A worldwide survey inLocusta migratoria, a pest plagued by microsatellite null alleles

Abstract

An understanding of the role of factors intrinsic to a species' life history in structuring contemporary genetic variation is a fundamental, but understudied, aspect of evolutionary biology. Here, we assessed the influence of the propensity to outbreak in shaping worldwide genetic variation in Locusta migratoria, a cosmopolitan pest well known for its expression of density-dependent phase polyphenism. We scored 14 microsatellites in nine subspecies from 25 populations distributed over most of the species' range in regions that vary in the historical frequency and extent of their outbreaks. We rejected the hypothesis that L. migratoria consists of two genetically distinct clusters adapted to habitats either rarely (nonoutbreaking) or cyclically (outbreaking) favourable to increases in population density. We also invalidated the current subspecific taxonomic classification based on morphometrics. Bayesian inferences indicated evidence of a homogenizing effect of outbreaks on L. migratoria population structure. Geographical and ecological barriers to gene flow in conjunction with historical events can also explain the observed patterns. By systematically assessing the effects of null alleles using computer simulations, we also provide a template for the analysis of microsatellite data sets characterized by a high prevalence of null alleles.

Molecular characterization of Spanish Prunus avium plus trees

“…2.2.3 (Van Oosterhout et al, 2004). Loci with estimated null allele frequencies higher than 0.19 were excluded from further analysis because from this threshold, the underestimation of the expected heterozygosity due to null alleles is signif icant (Chapuis et al, 2008).Several standard measures were calculated with GENCLONE v2.0 (Arnaud-Haond and Belkhir, 2007) in order to detect the presence of potential clones in the defined populations: the number of samples (N), the number of multilocus genotypes (MLGs), the number of repeated MLGs (MLG r ), the number of unique MLGs within each population (MLG l ) (Ellstrand and Roose, 1987), the number of multilocus lineages (MLLs), and the modified index of genotypic richness (R) (Dorken and Eckert, 2001). The probability that two individuals with the same MLG were originated from different sexual reproductive events, Psex, was also calculated.…”

Connectivity rescues genetic diversity after a demographic bottleneck in a butterfly population network

“…Allelic richness also allows for robust comparisons of genetic diversity despite very unequal sample sizes (37). Because null allele frequency was consistent between sampling periods (mean of 10.8% in 2008 and 7.9% in 2013, with overlapping CIs ; Table S1), the presence of null alleles should not affect temporal changes in allelic richness, which are estimated using the visible alleles (38). For comparisons between 2008 and 2013, we focused our analyses to the nine populations in which a minimum of five individuals were sampled in each year (Table S1), thus allowing us to estimate A R with rarefaction to ten gene copies.…”

Fauna crime: elucidating the potential source and introduction history of European smelt (Osmerus eperlanus L.) into Lake Storsjøen, Norway

“…The software MICRO-CHECKER 2.2.3 (Van Oosterhout et al 2004) was used to check for genotyping errors, followed by the program FREENA (Chapuis and Estoup 2007;Chapuis et al 2008) that corrects for allele-frequency bias. There was no systematic occurrence of homozygote excess within loci across populations, and no significant differentiation in F st when comparing uncorrected and corrected loci.…”