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Ortíz-Gamino D, Cunha L, Martínez-Romero E, Flores-Estévez N, Ortíz-Ceballos ÁI.2017. Genetic diversity and population structure in an invasive pantropical earthworm along an altitudinal gradient. PeerJ Preprints5:e3024v1https://doi.org/10.7287/peerj.preprints.3024v1
Population genetic analyses of the invasive pantropical earthworm P. corethrurus populations will contribute significantly to better understand the ecology and especially the reproductive system of this species. Using 34 polymorphic ISSR markers the genetic diversity and population structure was assessed for four populations of P. corethrurus along an altitudinal gradient, ranging from sea level up to ~1667 meters. Nuclear markers were able to distinguish two genetic clusters, probably corresponding to two distinct genetic lineages, herein defined as A and B. Clones were detected in one population (Actopan at 480 masl) and its number was lower than expected for a parthenogenetic species. Nevertheless, low levels of genetic diversity and a high number of intermediary genotypes were detected among the studied P. corethrurus populations with no apparent population structure related to the distinct geographic regions, which may indicate that human-mediated transference is prevalent, in particular, for the lower altitude regions. Hybridisation between the two genetic clusters was tested and pointed to 11 MLGs as being later-generation hybrids (B1 introgression) mainly associated with the three lower altitude regions. Still, most of the individuals seem to belong to lineage A and only five individuals seem to belong exclusively to the lineage B. Interestingly, these parental individuals were only found present at the highest altitude site, Naolinco (1566-1667 masl), which also showed the highest values of genotypic richness. During the biological invasion, multiple introduction of different genetic lineages can provide opportunities for admixture among genetically distinct clusters. The signatures of admixture among P. corethrurus populations along the altitudinal gradient in Mexico may have allowed the invasion success by directly increasing fitness. ISSR markers revealed to be useful for the study of genetic variation in the invasive pantropical earthworm, P. corethrurus.
I tried to involve the Ecology and Molecular Biology with the same species. I need to publish like a Preprints because I need more comments to do this version a little more substantial.
Supplementary Figure 1: Linkage disequilibrium
Linkage disequilibrium test using r̄d as implemented in R package Poppr (Kamvar et al., 2014). Visualizations of tests for linkage disequilibrium, where observed values (blue dashed lines) of r̄d are compared to histograms showing results of 999 permutations.