Teaching

Fort Lewis College Courses

(Links to current courses on Moodle require a valid FLC login)

Bio 112: Intro. to Organismic & Evolutionary Biology

Bio 206: General Botany (Moodle Site)

Bio 308: Plant Systematics (Moodle Site)

Bio 390: Plant Speciation and Evolution (Winter 2010)

Bio 496: Senior Seminar

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

Introdución a la Ecología Molecular en Plantas

Publications

Herbarium

(Coming Soon)

Greenhouse

(Coming Soon)

Department of Biology

Research Summary

My research works at the interface of three large areas of botanical research, 1) taxonomy, 2) phylogeny, and 3) population genetics.  I am principally interested in understanding the patterns that plants show across the landscape and across taxa to better understand plant biodiversity. Understanding the patterns seen in plant groups can then allow us to investigate the mechanisms of evolution which gave rise to that diversity.  Currently I am involved in a variety of projects focusing on the evolution of biodiversity through reciprocal hybridization in Mexican Quercus, the evolution and conservation of rare taxa, and the evolution of chromosomal races in widespread species.

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 taxonomic treatments for the Amaranthaceae and Fagaceae for the Flora of New Mexico. 

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.   I am also in the process of securing funding via an independent grant program for hiring student herbarium workers to work in herbarium curation and 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.
 

Closer to home I am working on a new project to understand the patterns of hybridization among the oak species of the Four Corners region which is principally dominated by Q. gambelii, Q. turbinella, and Q. havardii.  Much of this work is being undertaken by students in my Senior Seminar class in plant hybrids.  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.

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. For more information on this group see my specific pages on Froelichia.

 

© 2009 Ross A McCauley