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Complex Behaviors of Arachnids
My research focuses on the evolution and
function of complex signaling, with an emphasis on inter- and
intra-specific communication among arachnids. The primary goal of my
research is to understand the selection pressures that drive the
evolution of secondary sexual traits and associated signals. The methods
I use to achieve this goal incorporate multiple levels of analysis
including broad comparative approaches concentrating on behavior as well
as more mechanistic neuroanatomical and neurophysiological approaches.
Current Projects
There are three main research programs on
which I am currently working: (1) complex signal evolution in the wolf
spider genus Schizocosa, (2) Sexual selection as a potential driving
force in the rapid diversification of jumping spiders on the sky islands
of Southeastern Arizona, and (3) sensory ecology, neurobiology and
behavior of amblypygids (Arachnida, Amblypygids).
- Complex
signal evolution in the wolf spider genus Schizocosa - While
there exists a substantial conceptual and empirical framework for
studying and understanding signal evolution, this framework is based
almost entirely on studies of signals in isolation or on sensory
specialists. However, most animal displays are complex, consisting
of multiple components sent serially and often overlapping. My
research on Schizocosa wolf spiders brings a comparative approach to
the analysis of complex courtship signaling, specifically multimodal
signaling. Male courtship displays within this genus are either
unimodal (only vibratory signals) or multimodal (visual and
vibratory signals). Within multimodal species, there is further
variation in the degree to which different species are ornamented.
Unimodal signaling is ancestral in this group, raising the question
of why a second modality has been added. My research then focuses on
such questions as: What are the costs and benefits associated with
multiple signaling for both signalers and receivers? What is the
information content of the multiple signals and how does this
influence complex signal evolution? How do both content-driven and
efficacy-driven selection pressures influence the evolution of
complex signals?
Variation in the degree
of ornamentation in male Schizocosa forelegs
In a recent study, I found that subadult female experience in one
species of Schizocosa influences adult female mating behavior,
suggesting a role of learning and memory in mate choice. Future studies
examining the evolutionary consequences of social influences on mate
choice as well as studies examining the cognitive abilities of spiders
are currently being planned.
- Jumping
spider diversification - Populations of the jumping spider Habronattus
pugillis isolated atop mountain ranges in southeastern Arizona
display tremendous secondary sexual trait diversification. As
recently as 10,000 or as long as 400,000 years ago, these
populations were likely contiguous. Among the currently allopatric
populations, males vary greatly in both their courtship behavior and
the related ornamentation while females from the populations are not
easily distinguished. Due to the restriction of population
differences to male secondary sexual traits in conjunction with
population genetic data, it is thought that sexual selection is
responsible for the population differences. In collaboration with
colleagues such as Wayne Maddison, we use a comparative approach to
conduct reciprocal crosses between populations in an attempt to
distinguish among different processes of sexual selection that could
potentially be driving such a rapid and recent diversification.
- Sensory
ecology, neuroanatomy, and behavior of amblypygids - Amblypygids
are bizarre arachnids characterized by a dorso-ventrally flattened
body, heavily spinded pedipalps, and modified first legs. Due to
their nocturnal lifestyle and bizarre appearance, very little is
known about this arachnid order. My initial studies of amblypygids
are aimed at gaining basic insights into the natural history and
field behavior of these animals and involve field studies in Costa
Rica, the Florida Keys, as well as Puerto Rico. Amblypygids stand
out among arachnids in that they possess extremely large mushroom
bodies as well as giant interneurons located in their antenniform
legs. Ultimately, a goal of my research program on amblypygids is to
shed light onto the function of both the giant interneurons and the
enlarged mushroom bodies of this group as well as to gain more
general information about their natural history.
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