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Influential Interactions: Group Dynamics of the Maritime Earwig, Anisolabis maritima
Abstract
Dispersion patterns of individuals within a group can reveal important aspects about
social interactions and the mating system of the species. Our study examined the
distribution patterns of the maritime earwig, Anisolabis maritima, to determine the
influence of sexual selection on the mating system. Male and female Anisolabis maritima
both possess weaponry – however, females are very aggressive whereas males are
tolerant of cohabitation, which led us to hypothesize that leks might be forming, or that
aggressive females would maintain territories that would control the group environment.
We examined single-sex and mixed-sex groups of 18 earwigs in a large enclosure
throughout their active period to determine whether they were distributing themselves
randomly, uniformly, or in clumps. We found that, in single-sex groups, males form
clumps and females form uniform territories. Mixed-sex groups are uniform at first and
become clumped, where females controlled uniformity and males changed their behavior
in response to females. We also conducted a series of trials between three individuals,
either single-sex groups or mixed-sex groups with two different-sized individuals of one
sex and one individual of the other, to examine sexual selection and cohabitation
preferences. Among single-sex groups, we found that females were unwilling to
cohabitate, and small females were more likely to be excluded from shelters than large
females – in single-sex male groups, however, males were willing to cohabitate, with
small and medium-sized males equally likely to be excluded. Among mixed-sex groups
we found a preference for smaller opposite sex partners, but the patterns suggest
assortative mating.