Conservation and possible reintroduction of an endangered plant based on an analysis of community ecology: a case study of Primulina tabacum Hance

The distribution of the rare and endangered perennial herb Primulina tabacum Hance is restricted to eight karst caves in southern China. To conserve P. tabacum and to evaluate possible reintroduction, we studied its historical distribution and conducted field surveys of both its biotic and physical environment. We used detrended correspondence analysis and canonical correspondence analysis to investigate the plant community structure and to identify the major environmental factors associated with its presence at eight sites and absence from three other sites where it formerly grew. The results revealed differences in community structure among sites and close correlations between species composition and environmental conditions. The data indicate that P. tabacum has special ecological requirements, including alkaline soil, low soil content of N, P, K and organic matter, low light, a high soil water content and high relative humidity, and a high atmospheric CO2 concentration. Soil K content, relative humidity and atmospheric CO2 concentration were the three variables most strongly associated with the vegetation composition and structure of the 11 sites. It appears that as a result of reductions in humidity, some of the historical localities of P. tabacum may no longer be suitable for reintroduction. Pilea notata, Pteris cretica var. nervosa and two moss species, Heteroscyphus coalitus and Gymnostomiella longinervis, were strongly associated with P. tabacum. The first two plants could be useful as indicators of suitable environments for P. tabacum, and the moss species could be useful as nurse plants for the reintroduction of P. tabacum into wild habitats.