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Research

 

 

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.

 

 

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 species.

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.

 

 

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.

 

 

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.