Rapid range expansion is not restricted by inbreeding in a sexually cannibalistic spider.

Stefanie M Zimmer,Jutta M Schneider,Henrik Krehenwinkel,Claude Wicker-Thomas

doi:10.1371/journal.pone.0095963

Stefanie M Zimmer, Jutta M Schneider + Show 2 more

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https://doi.org/10.1371/journal.pone.0095963

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Abstract

Few studies investigated whether rapid range expansion is associated with an individual's short-term fitness costs due to an increased risk of inbred mating at the front of expansion. In mating systems with low male mating rates both sexes share potential inbreeding costs and general mechanisms to avoid or reduce these costs are expected. The spider Argiope bruennichi expanded its range recently and we asked whether rapid settlement of new sites exposes individuals to a risk of inbreeding. We sampled four geographically separated subpopulations, genotyped individuals, arranged matings and monitored hatching success. Hatching success was lowest in egg-sacs derived from sibling pairs and highest in egg-sacs derived from among-population crosses, while within-population crosses were intermediate. This indicates that inbreeding might affect hatching success in the wild. Unlike expected, differential hatching success of within- and among-population crosses did not correlate with genetic distance of mating pairs. In contrast, we found high genetic diversity based on 16 microsatellite markers and a fragment of the mitochondrial COI gene in all populations. Our results suggest that even a very recent settlement secures the presence of genetically different mating partners. This leads to costs of inbreeding since the population is not inbred.

Highlights

Inbreeding, defined as the mating between two related individuals, increases the occurrence of homozygous deleterious alleles
The average hatching rate was lowest for sibling matings (28.18%66.9; median = 3.95, N = 21), followed by within-population matings (40.63%65.27; median = 46.84, N = 31) and was highest when the pair originated from different populations (57.0%64.46; median = 67.15, N = 43; KruskalWallis test: x2 = 13.12, p = 0.0014; Figure 1 and Table 1)
We found the lowest hatching success in egg-sacs from pairs derived from the same brood and the highest hatching success when members of a pair came from different populations, while hatching success was intermediate for pairs of the same population

Summary

Introduction

Inbreeding, defined as the mating between two related individuals, increases the occurrence of homozygous deleterious alleles. Inbreeding depression has been reported for most taxa and has led to a variety of inbreeding-avoidance mechanisms [3] e.g. by sex differences in dispersal [4,5,6], in life-history [7,8], or by mate choice [9]. The latter requires a kin-recognition mechanism (but see [10]) and can occur before and after mating [11,12]. Avoidance or reduction of inbreeding costs through post-copulatory mate choice have been identified as a major benefit of female multiple mating in several taxa, such as house mice [15], birds [16], field crickets [17,18,19], and spiders [20]

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