Assessing genetic structure with multiple classes of molecular markers: a case study involving the introduced fire ant Solenopsis invicta

Abstract

We used 30 genetic markers of 6 different classes to describe hierarchical genetic structure in introduced populations of the fire ant Solenopsis invicta. These included four classes of presumably neutral nuclear loci (allozymes, codominant random amplified polymorphic DNAs (RAPDs), microsatellites, and dominant RAPDs), a class comprising two linked protein-coding nuclear loci under selection, and a marker of the mitochondrial DNA (mtDNA). Patterns of structure revealed by F statistics and exact tests of differentiation were highly concordant among the four classes of neutral nuclear markers, although the microsatellites were the most effective markers for detecting structure. The results from the mtDNA complemented those from the neutral nuclear markers by revealing that strong limitations to female-mediated gene flow were the cause of the local structure registered by the nuclear markers. The pattern of structure inferred from the selected nuclear loci was markedly different from the patterns derived from the other sets of markers but was predictable on the basis of the presumed mode of selection acting on these loci. In general, the results for all six classes of markers can be explained by known features of the social and reproductive biology of fire ants. Thus, the results from these diverse sets of markers, combined with detailed natural history data, provide an unusually complete picture of how the fundamental evolutionary forces of gene flow, drift, and selection govern the distribution of genetic variation within and between fire ant populations.

The genetic structure of endangered populations in the Cranberry Fritillary, Boloria aquilonaris (Lepidoptera, Nymphalidae): RAPDs vs allozymes

“…With the RAPD markers, populations of B. aquilonaris were characterized by greater genetic diversity than with allozymes. This is consistent with the majority of previous studies comparing these two population genetic markers (Table 2), though there are exceptions to this trend (Liu andFurnier, 1993, LeCorre et al, 1997;Ross et al, 1999). Mostly, this difference is explained by the inherently higher rate of detectable mutations and weaker degree of selective constraint at RAPD compared to allozyme loci since RAPDs can detect variation in both coding and noncoding regions (Szmidt et al, 1996;Aagaard et al, 1998;Waycott, 1998;Sun et al, 1999;Wu et al, 1999;Oiki et al, 2001).…”

“…Genetic diversity F st or equivalent Population structure (cluster, …) Aagard et al, 1998 Allozymes Ͻ RAPDs Allozymes Х RAPDs Apostol et al, 1996 Allozymes Ͻ RAPDs Ayres and Ryan 1999 Allozymes Ն RAPDs a Regional scale concordance Bartish et al, 2000 Allozymes Ͻ RAPDs Allozymes Ͼ RAPDs Allozymes Х RAPDs Baruffi et al, 1994 Allozymes Wolf et al, 1998 Allozymes Ͻ RAPDs General congruence Haig et al, 1994 Allozymes Х RAPDs Allozymes RAPDs but neither resulted in overall assortment of clusters geographically Isabel et al, 1995 b Allozymes Х RAPDs Allozymes Х RAPDs Jenczewski et al, 1999 Allozymes Ͼ RAPDs Similar Agreement between the global patterns of populations structure Le Corre et al, 1997 Allozymes Ͼ RAPDs Allozymes Х RAPDs Allozymes RAPDs Liu and Furnier 1993 Allozymes Յ RAPDs* Mamuris et al, 1999 Allozymes Ͻ RAPDs Allozymes Ͻ RAPDs Isolation by distance observed in RAPDs, not in allozymes Oiki et al, 2001 Allozymes Ͻ RAPDs General congruence Peakall et al, 1995 Allozymes Ͻ RAPDs Large-scale concordance Puterka et al, 1993 Allozymes Ͻ RAPDs Allozymes Х RAPDs Allozymes Х RAPDs Ross et al, 1999 Similar Similar General congruence Sun et al, 1999 Allozymes Ͻ RAPDs Clustering pattern of isozymes has poorer discrimination power than for RAPDs Szmidt et al, 1996 b Allozymes Ͻ RAPDs Allozymes Х RAPDs Waycott, 1998 Allozymes Ͻ RAPDs Wu et al, 1999 Allozymes Ͻ RAPDs Allozymes Ͻ RAPDs Allozymes Х RAPDs a Depending on the species studied. Haploid tissue was analyzed in this study.…”

A Formal Assessment of Gene Flow and Selection in the Fire Ant Solenopsis Invicta

“…Nevertheless, indirect evidence for matings between polygyne queens and monogyne males does exist. For instance, the allele frequencies at more than 25 presumably neutral nuclear makers show a high degree of similarity between neighboring monogyne and polygyne populations, thus suggesting the two social forms are linked by gene flow (Ross and Shoemaker 1993;Ross et al 1999). Also, our analyses of the distribution of queen and worker genotypes from the 1997 study of this polygyne population indicate that some gene flow (with m ϭ 0.32 Ϯ 0.22) may occur in conjunction with selection in workers.…”

Genetic diversity and differentiation in Eryngium alpinum L. (Apiaceae): comparison of AFLP and microsatellite markers

“…will always be very informative, especially if these markers exhibit various characteristics such as different mutation rates, different segregation patterns (eg nuclear vs cytoplasmic markers) or if they are influenced by distinct evolutionary forces (eg isozymes are more likely to be under selection than microsatellites). Even if such studies are still rare in the evolutionary biology literature (but see Ross et al, 1999), this kind of meta-analysis is being initiated more frequently and is at the origin of a new research area called 'population genomics' (Hedges, 2000;Black et al, 2001). Owing to recent technical and statistical advances, it is likely to represent an important step forward for population biology.…”