Elevated genetic diversity of mitochondrial genes in asexual populations of Bark Lice (‘Psocoptera’: Echmepteryx hageni)

Abstract

Asexual reproduction is commonly thought to be associated with low genetic diversity in animals. Echmepteryx hageni (Insecta: 'Psocoptera') is one of several psocopteran species that are primarily parthenogenetic, but also exists in small, isolated sexual populations. We used mitochondrial DNA sequences to investigate the population history and genealogical relationships between the sexual and asexual forms of this species. The asexual population of E. hageni exhibits extremely high mitochondrial haplotype diversity (H=0.98), whereas the sexual forms had significantly lower haplotypic diversity (H=0.25, after correcting for sample size). This diversity in asexuals represents one the greatest genetic diversities reported for asexual animals in the literature. Nucleotide diversities were also higher in asexual compared to sexual populations (π=0.0071 vs. 0.00027). Compared to other reported estimates of π in insects, asexual nucleotide diversity is high, but not remarkably elevated. Three hypotheses might explain the elevated genetic diversity of asexual populations: (i) larger effective population size, (ii) greater mutation rate or (iii) possible recent origin of sexuals. In addition, phylogeographic analysis revealed little geographic structure among asexual E. hageni, although specimens from the upper Midwest form a single clade and are genetically differentiated. The mismatch distribution and neutrality tests indicate a historical population size increase, possibly associated with expansion from glacial refugia.

The Exact Distributions of FIS under Partial Asexuality in Small Finite Populations with Mutation

“…Globally, partial asexuality increased the probability to observe negative F IS while it decreased the probability to observe positive F IS and the probabilities of fixation. As already demonstrated in previous theoretical [39] and empirical studies [40], reproduction through asexuality increased the allelic diversity expected within populations, as reported by the F IS index, when compared to similar fully sexual populations, because asexuality sets heritability and genetic drift at a genotypic level and conserves ancestral genetic states against drift, which finally decreases allelic identities within individuals. Our study also supports the fact that the rates of asexuality (or its opposite, the rate of genetic segregation in its broad definition) should be considered as a full evolutionary force because it distinctively impacts the transmission of genetic diversity through generations.…”

Population Genetics of Two Asexually and Sexually Reproducing Psocids Species Inferred by the Analysis of Mitochondrial and Nuclear DNA Sequences

“…Among these factors, environmental heterogeneity is the most key factor [4] and asexual reproduction can also have important consequences for observed levels of sequence polymorphism [59], [60]. Indeed, the higher genetic diversity of mitochondrial genes in asexual populations of psocid, Echmepteryx hageni (bark lice) was reported when comparing to its sexual populations [24]. In this study, both psocids were sampled at the same grain facilities (e.g.…”

“…It was proposed that larger effective population size, greater mutation rate or possible recent origin of sexual might explain the high genetic diversity of asexual animal populations [24]. Perhaps the most robust explanation for the genetic diversity of L. bostrychophila is that this pest is a primarily parthenogenetic psocid occasionally undergoes sexual reproduction, which even at very low frequencies can generate substantial diversity, and that the species is panmictic [62].…”

“…Asexual reproduction is commonly thought to be associated with low genetic diversity in animals (due to lacking of recombination) and such organisms have generally been regarded as evolutionary dead ends [21], [22]. However, the apparent lower genetic diversity of asexual animals compared to closely relate sexual species has been called into question [23], [24]. Paradoxically, against the background of its parthenogenetic characteristics, L. bostrychophila also shows a considerable degree of morphological and physiological variation both between and within clones [19], [25].…”

Effects of habitat fragmentation on genetic diversity and population differentiation of Liposcelis bostrychophila badonnel (Psocoptera: Liposcelididae) as revealed by ISSR markers

“…Thus, L. bostrychophila from bedroom and library display lower genetic diversity when the habitat was fragmented. However, the genetic diversity of populations from herbstore and flourmill in our study remains at a high level (Table 3) demonstrating the effect of habitat fragmentation on genetic diversity of L. bostrychophila is can be influenced by other factors, which include large population size and possibly gene mutation (Shreve et al, 2011). L. bostrychophila populations can increase explosively in a feedstock storage environment with sufficient food and favorable conditions (Turner, 1994).…”