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51
DENVER MUSEUM OF NATURE & SCIENCE
REPORTS
|
No. 3, July 2, 2016
Niche theory and the principle of competitive exclusion
dictate that species which occupy the same niche, e.g., use
the same resource and occupy the same habitat in the same
manner, cannot coexist. Spiders belonging to the southern
African genus
Ammoxenus
(Araneae, Ammoxenidae) are
specialists, feeding exclusively on termites. Up to four
Ammoxenus
species were found to coexist in sympatry. These
species are cryptic, and can be separated only by the struc-
ture of the palp and epigyne, sometimes only very slightly so.
Collection data indicate that these spiders utilize the same
termite food source in a seemingly identical manner in space
and time. One plausible explanation for the high levels of
sympatry in these spiders could be that the abundance of the
termite food source mitigate competition, resulting in little
to no niche partitioning, in accord with ecological neutral
theory model predictions. Conversely, given that the spiders
hide in the small, soft soil mounds made by the termites,
which allow them to correlate their activity patterns with
that of termites, the limiting resource could be microhabitat
(termite mounds) availability, which might have driven
niche partitioning. Field observations on behavior and
microhabitat use are needed to establish possible cryptic
niche partitioning. For example, anecdotal evidence in the
literature indicate differences in post-capture termite process-
ing. This could have implications for differential predatory
pressures. Even if evidence for niche partitioning is found,
however, it would only partially explain the distribution
patterns seen in
Ammoxenus
. Our aim is to provide pos-
sible explanations, including the still contentious sympatric
speciation that could be further investigated to explain the
distribution and the level of sympatry seen in these spiders.
Keywords: biogeography, competitive exclusion, niche
partitioning, sympatric speciation
Student - poster presentation
Biogeography of two Caribbean ochyroc-
eratid genera:
Theotima
and
Ochyrocera
*Sasha Bishop
1
, Greta Binford
1
, Abel Pérez-González
2
,
Ingi Agnarsson
3
1
Department of Biology, Lewis & Clark College,
Portland, OR, USA;
2
División Aracnología, Museo
Argentino de Ciencias Naturales - CONICET, Buenos
Aires, Argentina;
3
Department of Biology, University
of Vermont, Burlington, VT, USA
sashab@lclark.eduThe Caribbean island system is a region of high biological
diversity. The islands are home to much unknown arach-
nid diversity that has evolved in the context of complex
biogeographical histories of the islands and associated
land masses. This study analyzes patterns of diversity in
the family Ochyroceratidae, a relatively uncharacter-
ized group in the Caribbean. Sampling is centered on
two genera:
Theotima
, a smaller, parthenogenic genus,
and
Ochyrocera
, a non-parthenogenic genus. Though
there is minimal documented evidence of their dispersal
capabilities, both genera are small, leaf-litter dwelling
spiders with biologies consistent with poor dispersers. We
use phylogenetic analyses to comparatively assess genetic
structure and biogeographic pattern of these two genera.
Phylogenies use two mitochondrial genes (COI and 16s)
and two nuclear genes (28s and H3) with representation
of a total of 200 individuals collected from across the
Caribbean islands and southern Mexico. Both genera
display high levels of genetic depth, however patterns
of relatedness in
Ocherocera
reflect more island-, and
region-level genetic structure than
Theotima
. These pat-
terns suggest the possibility of higher dispersal rates in
Theotima
relative to
Ochyrocera
. Genetic structure of COI
suggests approximately 29 distinct genetic lineages within
our sampled taxa, greatly expanding the sampling beyond
16 known species within the region.
Keywords: Ochyroceratidae, biogeography, biodiversity
hotspot
Oral presentation
Intelligent adhesives: the structure and
function of humidity responsive spider
aggregate glues
Todd A. Blackledge
1
, Matjaz Gregoric
2
, Angela M.
Alicea-Serrano
1
, Dharamdeep Jain
3
, Gaurav Amarpuri
3
,
Brent D. Opell
4
, Ali Dhinojwala
3
1
Department of Biology, The University of Akron, Akron
OH 44325-3908, USA;
2
Institute of Biology, Scientific
20
th
International Congress of Arachnology