Teaching

Fort Lewis College Courses

Bio 112: Intro. to Organismic & Evolutionary Biology 

Bio 206: General Botany (Syllabus, Winter 2012)

Bio 302: Systematic Botany  

(Syllabus, Fall 2011)

Bio 390: Plant Speciation and Evolution

Bio 407: Evolution 

(Syllabus, Winter 2012)

Bio 496/497: Senior Thesis: Quercus Hybridization (Fall 2009/Winter 2010)

Bio 496/497: Senior Thesis: Viola ecotypes (Winter 2011/Fall 2011

Workshop: Universidad Nacional Autónoma de México (Summer 2009):

Introdución a la Ecología Molecular en Plantas

Publications

Herbarium

Department of Biology

Research Summary

I'm interested in developing a broad understanding of the ecological and organismal factors which contribute to the creation and maintenance of plant biodiversity.  Much of my work has involved the application of population genetics in a phylogeographic, phylogenetic or ecological context to  identify lineages and explore the evolutionary forces maintaining these lineages.  Currently I am involved in a variety of projects focusing on the evolution of plant biodiversity through reciprocal hybridization in Mexican Quercus, the evolution and conservation of rare taxa, the evolution of chromosomal races in widespread species, and ecotypic differentiation controlled by elevational gradients in the Southern Rockies.

Secondarily I am interested in traditional taxonomic studies focused on the circumscription and identification of taxa and using the available data to complete revisionary taxonomic treatments.  I have been working extensively on a monographic review of the genus Froelicha in the Amaranthaceae and am currently involved in the production of other taxonomic treatments and assisting with various flora projects. 

Student Research & Work Opportunities

Students interested in plants are encouraged to look into developing independent studies with me on the flora of SW Colorado.  These could be floristic-based studies or evolutionary-based studies. Work (funded via Financial Aid's work study program) is additionally available to work caring for plants in the college greenhouse.   Limited opportunities are available for paid work in the college herbarium assisting in the development of a digital publically-accessible database of the herbarium collections.

Current Research

Studies of Quercus biogeography and hybridization in Mexico and the S.W. United States

The genus Quercus is well known for frequent hybridization among closely related species and recurrent hybridization is an important evolutionary process in the generation of species biodiversity.  I have been studying the effects of this recurrent hybridization in one of the "hotspots" of oak diversity in the world. Of the approximately 500 species of Quercus Mexico shows a very high level of both species diversity at 160 along with a high level of species endimism.  Much of this diversity is likely due to recurrent hybridization and habitat changes during evolutionary history.

As a means of studying these processes I have been working with a natural group of red oaks known as the Subsection Racemiflorae consisting of four species (Q. conzattii Trel., Q. radiata Trel., Q. tarahumara Spellenb., J.R. Bacon, & Breedlove, Q. urbanii Trel.) which are united by the characteristic of producing acorns on racemose inflorescences. These species form a natural group of red oaks restricted to the western Sierra Madre and southern Cordillera of Mexico. There is an apparent segregation of the species based on edaphic factors and elevation with the more restricted species (Q. radiata, Q. tarahmara, Q. urbanii) being more or less specialists on highly sterile, often mineralized soils.

Q. conzattii                                                   Q. radiata

Q. tarahumara                                               Q. urbanii

Of particular interest in the group is the bicentric distribution of both Q. urbanii and Q. conzattii. Quercus urbanii is disjunct by approximately 700 km from mountain slopes near the Balsas Depression to the western Sierra Madre in Sinaloa and adjacent Durango. Across this distribution it occurs mostly in small "islands" of monospecific stands, however there are no quantifiable differences in morphology between the northern and southern portions of the range and there are no reports of it hybridizing with other oak species. Extending this pattern of range disjunction is Q. conzattii which is disjunct by approximately 850 km between its northern and southern regions of distribution. While occurring in ecologically similar habitats and often as the first black oak above xeric tropical or desert scrub, its large disjunction has resulted in slight morphological differences between the two portions of its range, although almost all differences can be viewed as a continuum of variation from south to north. An additional resulting characteristic of its wide disjunction is the presence of a different composition of sympatric species, particularly other Quercus.

Given the combination of broad and narrow range species, the clear range disjunction, and occasional gene flow through hybridization present within the subsection Racemiflorae it is thought that this group can act as a good model system within the Mexican oaks for the detection of historical patterns of gene flow and past species distributions. I have collected and analyzed the genetic structure of 49 populations of the group throughout its range using a combination of nuclear and chloroplast microsatellites. Results indicate recurent gene flow via hybridization and genome sharing among at least three of the species. Bayesian admixture analysis also suggests extensive hybridization, likely with other species, particularly in the most widespread Q. conzattii. 

Poster Presentation presented at the IVIII Botanical Congress, Melbourne Australia: "Genetic Structure and Speciation in a Lineage of Mexican Red Oaks: A Phylogeographic Study of Quercus Section Lobatae Subsection Racemiflorae." 

Closer to home I have been working to understand patterns of hybridization among the oak species of the Four Corners region which is principally dominated by Q. gambelii, Q. turbinella, and Q. havardii.  Initial work with Senior Thesis students during the 2009-2010 school year compared populations of pure and mixed species using a combination of detailed morphometric analysis and Inter-simple sequence repeat (ISSR) genetic markers. This work showed a high level of gene exchange among the taxa, most evident in lower elevation zones, while morphological characters were consistent and taxon-specific - even in the light of high levels of gene sharing. Further work is hoped to identify a set of specific genetic traits which identify specific taxon groups. For more information on this project see the Senior Seminar page under the heading teaching to the left.

Biogeography and conservation genetics of Guaiacum (Zygophyllaceae) in Western Mexico

The genus Guaiacum or Lignum Vitae is a group of six species native to the dry forests of the American tropics and subtropics which have been used for a variety of purposes spanning from medicinal to timber products for centuries. Today utilization of Guaiacum is principally for its wood which is one of the heaviest currently in trade with a mass of approximately 1303 kg/m3 and has a self-lubricating quality making it useful for mechanical purposes. Past overexploitation in conjunction with habitat loss and a slow rate of regeneration has left most species of Guaiacum threatened and are today listed on the IUCN Red List of Threatened Species and their trade controlled under CITES. Two species of Guaiacum occur in western Mexico G. coulteri, a shrub to small tree endemic to the seasonally dry forests of the Pacific Coast of Mexico ranging from Sonora to Oaxaca and G. unijugum, a small shrub endemic to the Cape of Baja California.

To date my work with western Mexican Guaiacum has identified the evolutionary relationships of the Baja California endemic and surveyed the genetic diversity and structure of G. coulteri to assist in conservation measures. The work with G. coulteri has additionally uncovered potential instances of cryptic speciation within the species range likely do to chromosomal rearrangements.  I am currently investigating the patterns of chromosome number across the species range using flow cytometry.

Studies in Western North American Viola

I have recently begun a series of new investigations into species distinctions and speciation of Viola in the Southern Rockies and SW US.  I am initially focusing my attention on ecotypic differentiation and potential ecological speciation in the Viola adunca complex in the San Juan Mountains of SW Colorado.  This work is being performed with undergraduate students (see Senior Thesis Viola ecotypes for more info) and is currently funded by the Colorado Native Plant Society. 

Additionally I have been working to describe a new species of Viola endemic to the Guadalupe Mountains of SE New Mexico and SW Texas. This new species, to be described as V. calcicola R.A. McCauley & H.E. Ballard, is restricted to cracks of limestone along the southeastern extent of the range.

Systematics of the genus Froelichia (Amaranthaceae)

The genus Froelichia is a group of 16 species of small herbs and shrubs native to a variety of habitats in the Western Hemisphere. I have worked extensively with this group over the past ten years on topics ranging from strict taxonomic description of new species, to biogeography, population ecology, and phylogenetic reconstructions and am currently working on a taxonomic monograph of the group. To facilitate dispersion of this taxonomic information much of this is being compiled into an electronic monograph.  

© 2012 Ross A McCauley