20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
Student - oral presentation
Male-male competition and chelicera mor-
phology in New Zealand sheet-web spiders
*Leilani Walker1, Cor Vink2, Greg Holwell1
1School of Biological Sciences, University of Auckland,
Private Bag 92019, Auckland Mail Centre, Auckland
1142, New Zealand; 2Canterbury Museum, Rolleston
Avenue, Christchurch, New Zealand
Animal weaponry has long captured the imagination of
researchers, and can occur with varying degrees of exag-
geration in different taxa. Exaggerated male weaponry
are particularly common in species in which males
defend females or their resources from potential rivals.
While sexual selection is generally credited with their
exaggeration, the particular processes and drivers are far
from uniform. In particular, exaggerated jaws, horns and
teeth may evolve through selection for males who can
physically defend females or they may develop as badges
of status to warn rivals off. New Zealand sheet-web spiders
(Cambridgea foliata) are one such species in which male
chelicerae (jaws) are substantially larger than those of
female conspecifics. We used an integrative approach,
combining behavioural and morphological analyses to
pinpoint the selective pressures acting on male chelicera
and to examine how chelicera morphology varies among
males. We randomly paired males on female webs and
recorded their behaviours. Then, we compared both
internal and external chelicera morphology of males and
females of varying sizes to see how internal and external
traits covaried. In this species, male jaws are positively
allometric while female jaws are not and larger males
tend to win fights against smaller males while chelicera
size does not seem to have an effect.
Keywords: sexual selection, male-male competition,
chelicera morphology, allometry
Student - poster presentation
Fitness consequences of geographic varia-
tion in mate choice in a wolf spider
J. Colton Watts, Brigitte Tenhumberg, Eileen A. Hebets
School of Biological Sciences, University of
Nebraska-Lincoln, Lincoln, Nebraska, USA
Variation in mate choice within and among populations
can have profound effects on sexually selected traits
and ultimately on population divergence. However, our
understanding of how changes in the costs or benefits
of mate choice per se shape mate choice in and among
natural populations remains limited. We use a population
comparison approach in Schizocosa wolf spiders to deter-
mine the extent to which changes in benefits provided by
males contribute to among-population variation in mate
choice. Specifically, we test for population differences
in the male signal variants that maximize copulation
success and those that maximize female fitness, and we
then determine whether signal variants associated with
copulation and with female fitness are correlated among
populations. In addition to contributing to the limited lit-
erature on adaptive mate choice variation, our work lays
the foundation for further investigations of ecological
causes of changing benefits as well as the potential role of
variation in mate choice in driving signal divergence and
premating reproductive isolation.
Keywords: mate choice, sexual selection, communica-
tion, divergence
Student - oral presentation
Genetic consequences of rapid range expan-
sion in Argiope bruennichipopulations
Wioletta Wawer, Robert Rutkowski, Wiesław Bogdanowicz
Museum & Institute of Zoology Polish Academy of
Sciences, Wilcza 64, 00-679 Warsaw, Poland
Environmental changes, e.g., climate warming or increase
in the area of wastelands, contribute to the expansion of
many terrestrial invertebrates. In Europe, a strong north-
ward expansion of Argiope bruennichi is observed. In
Poland, by the end of the 1990s ca. 100 sites have been
identified in many regions, except north-eastern parts of
the country and mountains region in the south, where the
climate is harsh. Currently, the wasp spider is distributed
over the whole territory of Poland and it has become a
20th International Congress of Arachnology