Evolution / Phylogenetics
Sunday March 13:
10:00am-11:30am
Back to Concurrent Session
III
ABSTRACTS |
PHYLOGENY AND POPULATION ANALYSIS
OF AN ENDANGERED TROPICAL TREE (Guaiacum spp.)
Dertien, J.R., Duvall, M.R., and
Beck, H.T.
Department of Biological Sciences,
Northern Illinois University, DeKalb, IL 60115
Lignum-vitae or guayacán (Guaiacum
spp., Zygophyllaceae) are trees and shrubs endemic
to the New World dry tropics. Regarded for their unique
wood and various medicinal properties, they are of
increasing conservation concern due to historical
exploitation, active trade, and reduced habitat. Previous
morphological studies have failed to adequately resolve
key taxonomic questions or establish clear geographic
boundaries for species or populations. The goal of
this research is to use comparative DNA sequence analysis
to understand the taxonomic boundaries, genetic structure,
and geographical distribution of Guaiacum. This information
is important for the proper management of remnant
populations, effective trade regulation, and future
restoration and reintroduction efforts. In addition
to its direct application to conservation, this study
engages an inadequately studied and poorly understood
area of plant evolution. The establishment of distinct
evolutionary lineages in plants can be complicated
given their capacity for hybridization and introgression;
which often poses problems to the traditional separations
of systematics, population genetics, and phylogeography.
These problems may be overcome; and analysis of multiple
loci of highly variable DNA sequences may elucidate
the roles of both historic and contemporary genetic
exchange among Guaiacum species and populations, thereby
identifying distinct genetic lineages of conservation
concern as well as providing insight into their evolution.
Keywords: Plant Evolution, Phylogenetics,
Population Genetics, Conservation
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MOLECULAR PHYLOGENY AND CLASSIFICATION
OF SANTALACEAE
Der, J.P. and Nickrent, D.L.
Department of Plant Biology, Southern
Illinois University, Carbondale, IL 62901
Santalaceae is a cosmopolitan family
of root and stem hemiparasitic plants in the Sandalwood
order (Santalales). The family is paraphyletic with
respect to Viscaceae and previous classifications
recognize 38 genera (ca. 450 spp.) in four tribes:
Amphorogyneae, Anthoboleae, Santaleae, and Thesieae.
A molecular phylogeny is presented here based on nuclear
SSU rDNA and chloroplast rbcL and matK DNA sequence
data with nearly complete generic-level sampling.
These data were analyzed using parsimony, likelihood
and Bayesian methods. Five well-supported clades are
resolved, but deep-level relationships among these
clades remain ambiguous. Tribe Santaleae is polyphyletic
and the mistletoe family Eremolepidaceae is monophyletic,
but embedded within one clade of Santaleae. Tribe
Amphorogyneae is sister to Viscaceae and contains
both root parasites and mistletoes. Anthobolus is
excluded from Santalaceae and allied with Opiliaceae.
The mistletoe habit has evolved independently twice
in Santalaceae and in three other families in Santalales
(Misodendraceae, Loranthaceae, and Viscaceae). Preliminary
work on other genes show promise for resolving deep-level
nodes, at which time main clades will be recognized
as a formal family-level classification.
Keywords: Santalaceae, Santalales,
molecular phylogeny, classification
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FUNCTIONAL
CONSTRAINT UNDERLIES 60 MILLION YEAR STASIS OF DROSOPHILID
TESTIS-SPECIFIC BETA TUBULIN
Nielsen, M.
University of Dayton, 300 College Park
Dayton, OH 45469
How do proteins evolve while maintaining
their function? Previous studies find a highly stringent
structure/function relationship between the Drosophila
melanogaster testis-specific tubulin beta2 and the spermtail
axoneme, such that small changes in the beta2 protein
render it unable to generate a motile axoneme. This
raises the question, How does beta2 evolve while maintaining
its function? To answer, we cloned full and partial-length
beta2 sequences from 17 species of Drosophilids spanning
60my of evolution. Not a single amino acid difference
is coded among them – beta2 maintains its function
by not evolving. We also performed phylogenetic analyses
to determine ortholog/paralog relationships among insect
tubulins. We find that the Lepidopteran and Dipteran
testis-specific beta-tubulins are orthologs, and surprisingly,
despite functioning in the same structure, the Lepidopteran
orthologs are evolving rapidly. We argue that differences
in tubulin isoform use in the testes cause the Dipteran
axoneme to be less evolvable, which has facilitated
the evolution of a unique amino acid synergism in Drosophilid
beta2 that is resistant to change, resulting in its
evolutionary stasis.
Keywords: tubulin, Drosophila,
axoneme, constraint
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THE
INFLUENCE OF GENOTYPE ON ATLANTIC SALMON SURVIVORSHIP
(Honorable mention!)
Turner, S.M. and DeWoody, J.A.
Department of Forestry and Natural
Resources, Purdue University, West Lafayette, IN 47906
Atlantic salmon were introduced into
Lake Huron from a variety of source populations in the
early 1980s. Since then 1.5 year old salmon have been
stocked annually, into the St. Marys River in Michigan.
Although salmon returning to the St. Marys River comprise
a large portion of the adults used for broodstock each
year, strains from other locations (e.g., Maine) are
often used to supplement the "natural" broodstock.
We quantified the influence of genome-wide relatedness
and major histocompatibility complex (MHC) genotype
on the mortality of young Atlantic salmon. Eggs from
a single female were fertilized with milt from a single
male to produce full-sib embryos; 32 families were created
in this manner. We monitored embryo survivorship in
each family and found that hatching success averaged
72%, but the variance was high—some families had
survivorship near 100% and others were near 0%. A suite
of 10 microsatellite loci was used to estimate relatedness
between parents. We found a significant negative relationship
between parental relatedness and juvenile survivorship.
Thus, our data are consistent with outbreeding depression,
the reduction in fitness due to the mating of two dissimilar
individuals. This is intriguing given the recent discovery
of outbreeding depression in crosses between wild and
farmed Atlantic salmon.
Keywords: MHC, relatedness, Atlantic
salmon
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CROSSING
BARRIERS: WHAT CAN WE LEARN FROM THE MULTIPLE HYBRIDIZATIONS
WITHIN THE PHRYNOCEPHALUS PRZEWALSKII COMPLEX?
Urquhart, J.W.1, Gozdzik, A.2, Bi,
K.1, and Fu, J.F.1
1Department of Integrative Biology,
University of Guelph, Guelph, ON, N1G 2W1
2Department of Zoology, University of Toronto, Toronto,
ON, M5S 3G5
The central Asian desert has a variety
of habitats and topological features that provide an
assortment of selection regimes and physical barriers.
As might be expected this diverse terrain offers several
opportunities to study speciation and hybridization.
One such system of isolation and secondary contact is
the Toad-Headed Lizards Phrynocephalus przewalskii complex.
Hybridization is common in at least four lineages. The
source of hybridization is currently unknown. It could
be that a few individuals cross barriers such as the
Yellow River or new connections have been made between
populations due to the past 300 years of desertification.
Microsatellite analyses will allow us to examine allele
and genotype distributions. This information will provide
evidence with which competing theories of the consequences
of hybridization can be tested. To date we have already
designed and optimized 13 microsatellite primers for
the next phase of our research.
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POST-PLEISTOCENE GLACIAL RETREAT,
COLONIZATION ROUTES,
AND GEOGRAPHIC VARIATION OF THE NORTHERN WATERSNAKE,
Nerodia sipedon, IN THE GREAT LAKES REGION
Robinson, J.W.1, King, R.B.1, Duvall,
M.R.1, Burghardt, G.M.2, Casper, G.S.3,
and Placyk, Jr, J.S.2
1 Department of Biological Sciences,
Northern Illinois University, De Kalb, IL 60115
2 Department of Psychology, University of Tennessee,
Knoxville, TN 37996
3 Vertebrate Zoology Section, Milwaukee Public Museum,
Milwaukee, WI 53233
Post-Pleistocene glacial retreat and
formation of the Great Lakes in North America had
a profound impact on the colonization routes of extant
reptiles and amphibians. These colonization routes
shaped the current distribution of reptiles and amphibians,
resulting in intraspecific geographic variation. This
research focuses on phylogeographic patterns of the
northern watersnake, Nerodia sipedon, in
the Great Lakes region resulting from post-Pleistocene
glacial retreat. Specifically, this study tests the
hypothesis that formation of Lake Michigan acted as
a geographic barrier, forcing a two-front colonization
into Wisconsin and Michigan. The northern watersnake
is widely distributed in eastern North America, making
it an ideal species in which to test this hypothesis.
Currently, complete mitochondrial DNA (mtDNA) sequences
for the gene ND2 have been obtained from 38 individuals.
From these sequences, 19 unique haplotypes were identified
from a total of 20 sites across Illinois, Wisconsin,
Michigan, Indiana, Kentucky, Ohio and Ontario, Canada.
Statistical parsimony analysis of mtDNA sequences
resulted in two genetically distinct networks that
could not be connected at the 95% significance level.
These clades represent a separation of eastern and
western groups, supporting a hypothesis of two-front
colonization. Maximum parsimony analysis, including
three congeneric outgroup sequences resulted in two
clades. These two clades are exactly analogous to
the two previously identified haplotype networks,
with bootstrap values for eastern and western clades
of 84 and 100, respectively.
Keywords: Great Lakes, Nerodia sipedon,
phylogeography, mitochondrial DNA
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III
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