Plant Conservation Biology

Distribution, Population Size, and Reproductive Status of Chamaesyce jejuna in Nolan, Mitchell, and Pecos counties of Texas

This project is set to begin in spring 2013 and is funded by a Wildlife Conservation Grant from Texas Parks & Wildlife Department. Chamaesyce jejuna, commonly called Dwarf Sandmat, is a rare, endemic plant restricted to caliche uplands and limestone hills of the Great Plains and Chihuahuan Desert ecoregions of Texas.  This plant species is at risk for extirpation from its known range.

Dwarf Sandmat (Chamaesyce jejuna). Image of herbarium specimen of C. jejuna. (image source:

Distribution of Dwarf Sandmat. The yellow-colored counties in the map indicate Texas counties where populations of Chamaesyce jejuna have been known to occur. The southern-most set of counties are historic populations and have not been verified in recent years. 

Research goals for Spring 2013:
1. Verify the persistence of populations in Nolan, Mitchell, and Pecos counties of Texas.
2. Determine population sizes.
3. Survey individual populations at monthly intervals to determine if individual plants are producing flowers and seeds.
4. Search for additional populations in Nolan and Mitchell counties.

Future Research on C. jejuna:
Spring 2014: Conduct field surveys to locate and survey the historic populations (southernmost counties) shown on the map. These populations are in the Trans-Pecos and Big Bend Regions of southwest Texas. I am planning for this research to be the focus of my May Term 2014 course, BIOL 4099-A. Interested Hardin-Simmons students can contact me for more information.

Tropical Ecology in Costa Rica

I am teaching a tropical ecology course in Costa Rica during the May Term 2013 semester. Students participating in this course will take part in field studies of primary succession in Arenal Volcano National Park. I plan to offer this course again for May Term 2015. Interested HSU students should contact me for more information. The first image below shows primary or virgin rainforest. The second image below shows the author and Arenal Volcano in the background.

Recent Publications

Hammer, R.L, Hatch, S.L.,  Pepper, A.E., and Manhart, J.R. 2012. Concordance between Molecular and Morphological Evidence of Hybridization in the Dichanthelium acuminatum (Poaceae: Paniceae) Subspecies Complex. Description: full accessSouthwestern Naturalist, 57, 133-137.