GENETIC DIVERSITY IN SIX GOVENIA (ORCHIDACEAE) SPECIES WITH DIFFERENT POLLINATOR ATTRACTION STRATEGIES

A few generalizations have been made about the amount of genetic diversity and life-history traits in plants, and a number of studies have reported contrasting results, indicating that these generalizations are not necessarily reliable. Six Govenia species belonging to three groups characterized by different pollinator attraction strategies were studied: (a) small inflorescences with three to eight whitish or greenish flowers, (b) medium-sized inflorescences with 15-30 white flowers, and (c) large inflorescences with 30-50 or more yellowish flowers. Genetic variation was assessed using starch gel electrophoresis to resolve 17 allozyme loci in 13 populations, to determine the level and distribution of genetic variation, and to evaluate the association between genetic diversity and pollinator attraction strategy. A high level of genetic variation and a low genetic differentiation among species were found. The mean number of alleles per locus was higher among species with strategy c than species with strategy a (A = 2.23 vs. 2.0), and the genetic diversity within populations was higher among taxa with strategy a than with strategy c (H-o = 0.72 vs. 0.46), while population differentiation was lower for strategy a than for strategy c (F-st = 0.056 vs. 0.155). Our results suggest that the amount and distribution of genetic variation observed in Govenia are the result of incipient divergence and have been significantly affected by drift. Pollinator attraction strategy plays an important role in the genetic identity and genetic structure of Govenia and could be the main cause of the differences between species; the different strategies have an effect on reproductive success and therefore on gene flow.