My research program is focused on a number of ecological and evolutionary questions
at the interface of intra- and interspecific processes. My research program is heavily
collections-based and integrates traditional field and morphological data with molecular
and genomic methods to elucidate pattern and process at several spatial and temporal
scales. Much of my work and that of my students continues to focus on members of
the genus Neotoma.
My studies at the broadest spatial scale in the N. fuscipes complex
suggest that a combination of topographic barriers and the expansion and contraction
of suitable habitat during glacial cycles along particular mountain ranges in California
have played a major role in the diversification of this group (Matocq 2002a). More
recent habitat shifts associated with Holocene warming trends appear to be associated
with the expansion of these woodrats into northern California and the contraction
of the range in southern California (Smith et al. 2000)..
The Granite Mountains of the East Mojave desert where we discovered an isolated
population of N. macrotis (Smith et al. 2000) . N. lepida and N. macrotis are sympatric
at this site.
Transition Zone Dynamics
The two major mitochondrial clades uncovered in my early phylogeographic studies
come into geographic proximity of one another in several different areas in the
current range of this complex. As such, this is an excellent system in which to
study contact/transition zone dynamics between genetically differentiated lineages
(Matocq 2002b). Thus far, I have examined three independent areas of transition
between the two most divergent lineages in the complex. I have uncovered several
trenchant morphological differences between these genetic lineages. One of the most
striking differences is highly divergent male genitalia (see below). Although we
do not observe broad-scale introgression of characters from one species into the
other, these lineages do have the capacity to interbreed. Using both laboratory
and field studies, we are currently investigating the behavioral, ecological, genetic,
and morphological factors that contribute to resproductive isoloation between these
Three areas of transition between the deepest clades within the N. fuscipes complex.
Differences in cranial morphology and genitalia across a transition zone. Phallus
images by Karen Klitz.
Systematics and character evolution
In order to further understand the evolution of genital morphology in woodrats,
we have recently completed a phylogenetic analysis of the entire genus Neotoma using
four mitochondrial and four nuclear genes (Matocq et al., in review). Using ancestral
state reconstruction methods, our analyses suggest that a common genital form in
woodrats has evolved more than once and that sister taxa can have highly divergent
genital morphologies. We are beginning to study the underlying developmental genetic
processes that generate the various genital morphologies observed in Neotoma. Furthermore,
we are examining the functional significance of these genital differences in terms
of their role in reproductive isolation.
Behavior and demography
In order to determine how local scale processes such as reproductive success, survivorship,
and dispersal influence the effective population size of woodrats (Matocq 2004),
and ultimately, the maintenance and distribution of genetic diversity within and
among populations, I have studied a population of woodrats at the Hastings Natural
History Reservation in Carmel Valley, California. I developed microsatellite primers
(Matocq 2001) in order to examine the spatial distribution of genetically related
individuals (Matocq and Lacey 2004) and to test hypotheses concerning mating patterns
(Matocq 2004). Our ongoing demographic and behavioral studies in this system are
largely focused in contact zones between major lineages of Neotoma.