Environmental determinants of genetic diversity in Caragana microphylla (Fabaceae) in northern China.

The sand-fixing shrub Caragana microphylla (Fabaceae) is extensively used for vegetation restoration in areas of northern China undergoing desertification. Although the understanding of its genetic variation and related determinants is an important component of plant conservation and ecological restoration in the face of a changing global environment, the relationship between genetic diversity in C. microphylla and climatic factors is unknown. In this study, we assessed population genetic variation in C. microphylla along temperature and humidity gradients in northern China using inter-simple sequence repeat ( ISSR) markers. In general, high levels of genetic diversity were uncovered in the 13 populations studied. The number of polymorphic loci ranged from 14 to 63 and polymorphism percentages ranged from 8.75 to 39.38%. Observed and effective allele numbers were 1.09-1.40 and 1.06-1.30, respectively. Nei's genetic diversity index ( h) was calculated as 0.0340-0.1663 and Shannon's diversity index ( I) was 0.0502-0.2403. At the species level, h and I were 0.2579 and 0.3965, respectively. Populations from low hydrothermal level areas, experiencing severe desertification and habitat fragmentation, exhibited the greatest genetic diversity. Genetic diversity in C. microphylla was positively correlated with annual temperature range, cold index, mean annual rainfall and hydrothermal synthesis index, whereas a negative association was found with mean annual temperature. Using redundancy analysis, we found that mean annual rainfall and cold index explained 87.8% of observed genetic variation, suggesting that genetic diversity in C. microphylla depends primarily on these two factors. Our data are relevant to the restoration and management of degraded ecosystems in arid and semiarid regions. [ABSTRACT FROM AUTHOR]