Mexican Conifers
Six conifer families, 10 genera, and approximately 85 species occur naturally in Mexico, making it a world center of diversity.
Pines
Pinus nelsonii, San Luis Potosí.
With 110-120 species, the genus Pinus (pines) includes more living species than any other genus of conifer, and Mexico has more native pine species than any other country. Pinus is the most ecologically important tree genus in the Northern Hemisphere.
The number of pine species in Mexico is an active area of investigation. Recent treatments have included between 45 and 60 species. An intermediate number may be more reasonable, somewhere around 50. A list of our currently recognized species can be found here.
Conifer phylogeny
Arbol de Tule (Taxodium mucronatum), Oaxaca.
The main research interest of our lab group is in the systematics and evolution of conifers, particularly New World members of the pine family (Pinaceae).
We sequence DNA and use the pattern of substitutions between different species (and individuals) to infer species relationships and to reconstruct their evolutionary history. We are also tying these DNA based inferences with the fossil record to estimate the time of diversification of Pinaceae lineages.
Conservation genetics
Guadalupe cypress (photo by Patricia Rosas).
For a century, the viability of the only population of the Guadalupe cypress (Callitropsis guadalupensis), located on Isla Guadalupe, Baja California, was threatened from grazing by introduced goats. The goats were eradicated a few years ago, but last fall a large fire burned much of the forest.
Using chloroplast markers, we have found high genetic diversity in the endangered Guadalupe cypress.
DNA barcodes
Pinus maximartinezii, an endangered conifer.
An international effort is underway to generate short, standardized DNA sequence reads that are supposed to permit the identification of species. One question of interest to us is whether the DNA markers being used will be adequate for distinguishing endangered Mexican plants, including conifers.
We are assembling a reference database of DNA barcodes for a few hundred species of conifers, agaves, cacti, and orchids. The DNA sequences come from the chloroplast genes rbcL and matK, and we are looking for two more spacer regions. The sequences will be released in the Barcode of Life database by the end of the 2010.