20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
phylogenetic distance in Latrodectus spiders. Among these
spiders, females release cuticular and/or silk-based sex
pheromones (chemical signals) that can be detected as air-
borne volatiles (attracting males) or as contact chemicals
(initiating courtship). We quantified 1) male responses
to conspecific and heterospecific females and their sex
pheromones using a bioassay of male searching activity
on methanol extracts of females’ silk; and 2) male court-
ship and mating success when on the webs of females. We
compared male responses in light of the phylogeny, and as
a function of estimated genetic distance between species.
Consistent with our hypothesis 1) male L. geometricus,
the most distantly related of our focal species, respond
only to silk extracts from conspecifics; whereas males
from the other species also responded to extracts from
more closely related heterospecific species, however, 2)
males of all species initiate courtship and attempt to mate
when heterospecific females are present. Thus some males
discriminate silk chemicals of more distantly related het-
erospecifics, but intact silk and/or females eliminate this
effect.
Keywords: Latrodectus species, sex pheromones, genetic
distance, male discrimination
Oral presentation
X chromosomes evolution in Stegodyphus
spiders
Jesper Bechsgaard1, Mads Fristrup Schou 1, Bram
Vanthournout 1, Frederik Hendrickx2,3, Bjarne Knudsen4,
Virginia Settepani1, Mikkel Heide Schierup1,5, Trine Bilde1
1Department of Bioscience, Aarhus University, 8000
Aarhus C, Denmark; 2Royal Belgian Institute of Natural
Sciences, Brussels, Belgium; 3Terrestrial Ecology Unit
(TEREC), Biology Department, Ghent University, Gent,
Belgium; 4Qiagen; 5Bioinformatics Research Center
(BiRC), Aarhus University, 8000 Aarhus C, Denmark
Substitution patterns (between species) and diversity
(within species) of spider X chromosomes is predicted to
differ from autosome evolution due to their hemizygous
state in males. If new beneficial mutations on average are
recessive or partially recessive more adaptive substitutions
are expected on the X chromosomes, so-called faster-X evo-
lution. Also, since populations carry more autosomes than
X chromosomes less diversity is predicted on X chromo-
somes; if everything being equal, 75% of the autosomes.
However, both substitution patterns and diversity levels may
be influenced by life-history and ecological factors such as
sex ratio bias and population size fluctuations. Here we use
transcriptome and RAD sequencing to explore the substitu-
tion patterns and diversity levels of X chromosomes and
autosomes in two Stegodyphus species (S. mimosarum and
S. africanus) with contrasting sex ratio and population
dynamics. We found evidence of faster-X evolution in both
species. Furthermore, we found that mutation rates are
higher on autosomes, consistent with more cell-divisions in
male gametes than female gametes. X to A diversity levels
were highly similar among the two species suggesting that
female bias and population size fluctuations in S. mimosa-
rum have similar but oppositely directed effects.
Keywords: faster-X evolution, X chromosomes, popula-
tion genetics, social spider
Student - oral presentation
Increased temperature alters beetle
behavior to increase predator effects and
decrease herbivory
*Orsolya Beleznai1, Jamin Dreyer2, Mark Williams2 ,
Ferenc Samu1, James D. Harwood2
1Zoology Department, Plant Protection Institute,
Centre for Agricultural Research, Hungarian Academy
of Sciences, 26-30 Nagykovácsi Road, HU-1029, Buda-
pest, Hungary; 2Department of Entomology, University
of Kentucky, S-225 Agricultural Science Center North,
KY 40546-0091 Lexington, Kentucky, USA
Predators can limit the abundance and/or activity levels
of their prey, and the magnitudes of these effects are
contingent on predator and prey traits that may change
with environmental conditions. Aberrant thermal regimes
could disrupt pest (herbivore prey) suppression through
asymmetric effects, i.e. heat-sensitive predator vs. heat-tol-
erant prey. To explore the potential effects of warming on
suppressing pests and controlling herbivory in a vegetable
20th International Congress of Arachnology