Published online before print January 21, 2003, 10.1073/pnas.0234412100
Proc Natl Acad Sci U S A. 2003 February 4; 100 (3): 10781083
DOI: 10.1073/pnas.0234412100
Evolution Genetic diversity, asymmetrical aggression, and
recognition in a widespread invasive species
Neil D. Tsutsui,* Andrew V. Suarez, and Richard K. Grosberg*
*Center for Population Biology, Division of Biological
Sciences, University of California, One Shields Avenue,
Davis, CA 95616; and Department of Environmental Science,
Policy and Management, Division of Insect Biology,
University of California, 201 Wellman Hall, No. 3112,
Berkeley, CA 94720-3112 Edited by May R. Berenbaum,
University of Illinois, Urbana, IL, and approved December 4,
2002, (received for review July 24, 2002) To whom
correspondence should be addressed. E-mail:
[email hidden].
Abstract The evolution and persistence of cooperative
social units depends on the ability to distinguish group
members from nonmembers. The precision of discrimination, in
turn, relies on variation in the labels that individuals use
to recognize group members. However, this same variation can
be selected against if individuals that are rejected as
nonmembers incur a high cost. Here we provide evidence that
selection against individuals from genetically diverse
groups has contributed to the formation of the unicolonial
colony structure that characterizes introduced populations
of the invasive Argentine ant (Linepithema humile). Studies
in both the laboratory and the field showed that individuals
from less genetically diverse colonies attack individuals
from more diverse colonies and that attackers survived
agonistic encounters more than six times as often as
recipients of aggression. This selection, in concert with
reductions in genetic diversity after a founder event,
likely creates a barrier to the establishment of new,
genetically diverse introductions from the native range and
may reduce genetic diversity within established populations
in the introduced range.
Copyright © 2003, The National Academy of Sciences
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