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My
research
focuses on monogamous birds and mammals. I am interested in genetic
population structure and gene flow within isolated populations, and the
genetic consequences of mate choice and dispersal.
Current
Project
MHC-Based Mate Choice in Dark-Eyed Juncos (Junco hyemalis)
The major
histocompatibility complex (MHC), a gene family involved in immune
function, has been shown to play a role in mate choice in several
species, though studies to date have given varying results. MHC
genotype may be detected via odor, in sweat and urine and mammals and
potentially in preen oil in birds. The following mate choice hypotheses
have been suggested: 1) inbreeding avoidance, as individuals with
different MHC types will be non-relatives, 2) compatible genotypes, as
disassortative mating will produce heterozygous and therefore fitter
offspring, or 3) “good genes,” as condition-dependent traits may rely
on underlying MHC genotype. Further, even if females in a monogamous
species choose a social mate on the basis of other characteristics such
as habitat quality, she may still choose an extra-pair male on the
basis of MHC genotype. Although balancing selection likely plays a role
in maintaining MHC diversity, a bottlenecked population may lose
substantial levels of variation at this locus as at other loci. I am
testing these mate choice hypotheses with respect to MHC in a
well-studied songbird, the Dark-Eyed Junco, and also testing whether an
isolated population with few migrants employs a different mate choice
strategy than a migrating, outbred population. Specifically, I expect
that inbreeding avoidance is more important in an isolated population.
To accomplish these goals, I am sequencing MHC Class IIB loci in
samples collected from socially mated male-female pairs and extra-pair
males in
two populations in southern California: one a normal, migrating
population in a mountain
habitat, the other a recently established isolated, sedentary
population in an urban habitat.
A
small isolated population of Dark-Eyed Juncos that became established
on the campus of University of California in San Diego (UCSD) in the
early 1980s has diverged morphologically and behaviorally from the
closest breeding population at Laguna Mountain. Founding population
size has been estimated at fewer than 10 breeding pairs, resulting in a
higher than usual level of inbreeding. I explored mating patterns in
both populations with respect to both social and extra-pair partners
and the relation of these patterns to the major histocompatibility
complex (MHC) Class IIB genotype. Mating is disassortative with respect
to MHC, yet extra-pair fertilizations were more frequent in pairs with
the highest levels of MHC sequence difference, supporting the
“compatible genes” hypothesis and selection for optimal outbreeding. At
UCSD, individuals had a higher risk of inbreeding, and were more likely
to avoid mating with close relatives than at LM. I am further examining
the relationship between genetic and spatial distance within these two
populations.
This
research is supported by a grant from the Indiana Academy of Science.
Past Projects
Evolutionary
Genetics of Kloss's Gibbons (Hylobates klossii): Systematics,
Phylogeography, and Conservation
This was my dissertation
research at the City University of New York.
(The dissertation abstract may be viewed here,
or you can download
the full 3.0 MB dissertation pdf.)
For this project, I investigated the genetic diversity of the Kloss's
gibbon, endemic to the Mentawai Islands of Indonesia. These gibbons are
a poorly studied species, and little is understood about their
phylogenetic position within the gibbon radiation and patterns of
genetic diversity within the species. The other endemic Mentawai
primates (Macaca pagensis, Presbytis potenziani, and Simias
concolor)
have been suggested to be divided into two subspecies based on
variation in coat color: one on Siberut in the northern end of the
chain, and one subspecies on the three southern islands. The Kloss's
gibbon shows no obvious variation, as all individuals are completely
black. Furthermore, the primates of the Mentawai Islands are threatened
by logging and hunting, and the conservation status of the Kloss's
gibbon has not been evaluated since 1980.
I collected fecal samples from unhabituated gibbon groups at 7 sites on
all four Mentawai Islands in 2001 and 2003. I also conducted population
surveys based on loud calls (want to hear a Kloss's gibbon call?).
I extracted DNA from the fecal samples and amplified and sequenced the
hypervariable region I of the mitochondrial genome, and also genotyped
the samples at six microsatellite loci.
Systematics:
Based on mitochondrial
D-loop sequences and their congruence with morphological and vocal
characteristics as well as ND3-4 data, the Kloss's gibbon appears
to be a recently derived member of the lar
group of gibbons, clustering with the geographically close H. agilis
and H. moloch,
rather than a basal taxon as previous morphological studies have
suggested. These results are in press at Molecular Phylogenetics and Evolution.
Download
a pdf of the accepted manuscript.
Phylogeography:
Based on the mitochondrial
data, the Kloss's gibbon shows no genetic
differentiation between islands. I presented these data at a talk at
the IPS meetings in Torino, Italy, in August 2004 (abstract).
These results will be published in The
Gibbons: New Perspectives on Small Ape Socioecology and Population
Biology, edited by Susan Lappan, Danielle J. Whittaker, and Thomas
Geissmann.
Conservation:
Based on my surveys, there
are 20,000-25,000 Kloss's gibbons remaining
in the wild, with the largest proportion located on Siberut. These data
were published in Oryx in 2005 (PDF).
I evaluated the conservation status for all four
Mentawai primate species and published a conservation action plan (PDF).
I was invited to the 2006 Asian Primate Red List workshop and changed
the status of these species.
Funding
This
research was funded by:
New York
Consortium in Evolutionary Primatology
Molecular phylogenetic
affinities
of the simakobu monkey (Simias concolor) (with Nelson Ting)
The
simakobu monkey is endemic to the Mentawai Islands, and is considered
to be a member of the odd-nosed group of Asian colobines. However,
there is little agreement as to whether this species belongs to its own
genus, whether it is congeneric to the proboscis monkey of Borneo (Nasalis
larvatus), or whether it is basal to the colobine radiation. We
amplified the cytochrome b locus from Simias hairs, and found
that the level of differentiation between Simias concolor and Nasalis
larvatus does not support a genus-level distinction. These results
were published in the journal Molecular Phylogenetics and
Evolution (Corrected
proof PDF).
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