An assessment of genetic diversity in Desmodium sumichrastii (Fabaceae) of central Mexico

Abstract

The genus Desmodium contains ca. 450 species, distributed in Eastern Asia, Mexico, and Brazil, with 40 endemic species in Mexico, including Desmodium sumichrastii (Schinder) Standley. Randomly amplified polymorphic DNA (RAPD) variation was used to assess genetic variation within and among five populations of D. sumichrastii from west-central Mexico, constituting the first assessment in the tribe Desmodieae. Ninety percent of all bands were polymorphic for the 10 decamer RAPD primers used. Sixty-one percent of the variation was within populations, and 39% was among them. This pattern of higher variation within than among populations is unusual, but can be attributed to ethological characteristics of pollinators. The unweighted pair-group method with arithmetic averages (UPGMA) dendrogram based on Nei's genetic distances plots populations from Jalisco together, whereas populations from Aguililla in the neighboring state of Michoacan are separated and next to the San Miguel del Monte population (also in Michoacan). However, the dendrogram based on Dice's similarity coefficient calculated for all individuals separately groups the populations from Aguililla. We also found a significant correlation between genetic and geographic distances, which is in agreement with Dice's UPGMA dendrogram, where closer populations are more genetically similar. Interestingly the most diverse populations are located within a Biosphere Preserve, and the least diverse populations are located in heavily disturbed sites.