The comparative pollination biology of a population of Primula beesiana, a population ofP bulleyana, and an overlapping population of these two species in Yulong Shan, Yunnan Province, China, was studied in 2004 and 2005. The results indicate that both P beesiana and P bulleyana are typical heterostylous and obligate outcrossing species; the main pollinators of the two species were bees and butterflies. At the sites of all three populations, the main pollinating visitors of the two species showed preference for one of the two species, resulting in the ethological isolation of the two species by the pollinators. This ethological isolation contributes to the reproductive isolation of the two species, which supports the hypothesis that P beesiana and P bulleyana are two distinct species. The reproductive isolation of the two species （ethological isolation） is probably an important mechanism in maintaining species boundaries in the genus and has contributed to the species diversification of Primula in the area. In addition, gene exchanges between P beesiana and P bulleyana has occurred to some extent in the overlapping population, but whether natural hybridization has contributed to species diversification in Primula remains to be determined.
Omphalogramma souliei Franch. is an endangered perennial herb only distributed in alpine areas of SW China. ISSR markers were applied to determine the genetic variation and genetic structure of 60 individuals of three populations of O. souliei in NW Yunnan, China. The genetic diversity at the species level is low with P=42.5% （percentage of polymorphic bands） and Hsp=0.1762 （total genetic diversity）. However, a high level of genetic differentiation among populations was detected based on different measures （Nei＇s genetic diversity analysis： Gst=0.6038; AMOVA analysis： Fst=0.6797）. Low level of genetic diversity within populations and significant genetic differentiation among populations might be due to the mixed mating system in which xenogamy predominated and autogamy played an assistant role in O. souliei. The genetic drift due to small population size and limited current gene flow also resulted in significant genetic differentiation. The assessment of genetic variation and differentiation of the endangered species provides important information for conservation on a genetic basis. Conservation strategies for this rare endemic species are proposed.
