We have been focusing our research on two mountainous regions, the Middle American Highlands and Northwestern North America

A. Middle American Highlands.

The Middle American Highlands include several distinct mountain ranges in upper Central America and central and southern Mexico. This region is characterized by very high rates of endemism and is considered "hyperdiverse." Since I began my master's thesis research, I have been examining genetic variation in several mesoamerican murid rodent species, some of which are widespread across the highlands and some of which are restricted to just a single mountain range. Two widespread complexes that have almost perfectly congruent widespread distributions in pine/oak and cloud forests are the Peromyscus aztecus/P. hylocetes complex, and the Reithrodontomys sumichrasti complex. Analyses of mtDNA data for multiple samples within each of these complexes indicate that there are strong similarities between the two phylogeographies. In both complexes, populations from each of several mountain ranges represent monophyletic assemblages of haplotypes, and the Isthmus of Tehuantepec is a strong phylogeographic barrier. However there are also instances of strong phylogeographic incongruence. These mixed results indicate that these two taxa have responded to Pleistocene climatic fluctuations neither completely independently, as would be predicted by the current paradigm in biogeography, nor in a completely concerted fashion. These findings will have broad implications regarding both conservation biology of the region and assembly of modern communities. Collaborators on these projects include Dr. Elizabeth Arellano (CEAMISH), Dr. Duke Rogers ( Brigham Young University), and Dr. Bill Kilpatrick (University of Vermont).

A third species complex under investigation, Peromyscus furvus, is restricted to the Sierra Madre Oriental. Preliminary analyses of mtDNA indicate that there may be a cryptic species included in this taxon. This project is an extension of the MS thesis that former graduate student Danny Harris conducted at Brigham Young University.

B. Northwestern North America.

Several general ecological/distributional patterns recur in northwestern North America forest endemic species. These include: species widespread in xeric forests (e.g., Ponderosa pine forests); species that have populations in the mesic forests (i.e., cedar-hemlock forests) of the coastal ranges and separate (disjunct) populations in the northern Rocky Mountains; and species that are restricted to forests of the northern Rocky Mountains. Because both xeric and mesic forests are the foundation of resource-based industries, which often place conflicting demands on ecosystems (e.g., recreation/tourism and timber), assessing the genetic structure of multiple elements of these ecosystems is critical to the economy of the region. Comparative phylogeography for these systems can provide for a wealth of research opportunities; we have begun by conducting research on the comparative phylogeography of several representative species representing each of these ecological/distributional patterns.

1. Mesic Forest Disjuncts.

Northwestern North America contains the world's greatest extent of mesic temperate coniferous forests. These forests are characterized by the late successional dominance of western hemlock (Tsuga heterophyla) and western redcedar (Thuja plicata), and cedar-hemlock ecosystems occur in two isolated bands. One occupies the Coast and Cascade Ranges of British Columbia, Washington, and Oregon; the second occupies the northern Rocky Mountains of Idaho, northeastern Washington, northwestern Montana, and southeastern B. C. The two bands are separated from each other by xeric forests as well as the shrub/steppe and high desert of the Columbia Basin (i.e., mesic forests are disjunct). Because over 150 species have been reported to exhibit this disjunct distribution (including plant, animal and fungal taxa), several hypotheses have been erected regarding the genesis of this disjunction. We are ultimately interested in examining testing these hypotheses in as many species as possible.

To date, we have data for tailed frogs (Ascaphus truei & A. montanus), water voles (Microtus richardsoni), and the Plethodon vandykei species group of salamanders (including P. vandykei and P. idahoensis). Both amphibian species fit the predictions of the ancient vicariance hypothesis, whereas waters voles appear to have achieved the disjuct distribution by dispersal from the northern Rockies into the Northern Cascades. In addition, we are collaborating with Steve Brunsfeld (UofI, Department of Forest Resources) to examine several plant species, including dusky willow (Salix melanopsis), western white pine (Pinus monticola) and a phlox (Collomia heterophylla).

2. Northern Rocky Mountain Endemics.

In addition, there are many plants and animals that are restricted to the inland portions of the mesic forests, and we are examining several of these. These include Red-tailed chipmunks (Tamias ruficaudus), Columbian ground squirrels (Spermophilus columbianus), and Idaho giant salamanders (Dicamptodon aterrimus). We are also collaborating with Steve Brunsfeld to examine Constance's bittercress (Cardamine constancei).

3. Widespread Xeric Forests

Xeric forests are widespread in northwestern North America and are dominated by Ponderosa pine. These ecosystems are characterized by patchy stands of timber separated by intervening grassy areas. We've begun comparative phylogeography of xeric forest species by examining two widespread taxa endemic to northwestern North America: montane voles (Microtus montanus) and yellow-pine chipmunks (Tamias amoenus). Two xeric forest taxa endemic to northwestern North America, Montane voles (Microtus montanus) and Yellow-pine chipmunks (T. amoenus) are being examined examined. Mitochondrial sequence data indicate that T. amoenus harbors extensive genetic diversity that partitions among mountain ranges. We're also beginning work on the wandering shrew (Sorex vagrans).

The long-term goal for this aspect of our research is to develop a center for ecosystem genetics for northwestern North American forest ecosystems. The Northwestern North America comparative phylogeography project is currently funded by NSF/EPSCoR. There is a great deal of room on these projects for graduate students.