Effects of genetic and environmental factors on clonal reproduction in old-growth natural populations of Cryptomeria japonica

Abstract

Clonal reproduction is a crucial factor shaping the demography and genetic structure of many plant populations. However, we still do not understand the extent to which environmental and genetic factors influence clonal reproduction. Natural forests of Cryptomeria japonica are distributed under a range of environmental conditions in the Japanese Archipelago. In this study, the spatial genetic structures of 13 natural old-growth C. japonica forest plots of about 0.25ha were investigated using eight nuclear microsatellite markers. Clonal reproduction was detected in 10 plots, the clonal frequency in each plot varied. Patterns of spatial genetic structure at the ramet level showed significant positive autocorrelation over short distances, which may reflect clonal reproduction and the limited extent to which seedlings establish in gaps. The clonality of individual genets was influenced by the Q value of cluster 1 of the results of STRUCTURE analysis as the genetic factor, snow depth as the environmental factor, the average basal area (BA) and the interaction between Q value and snow depth. This result indicated that clonal genets had low Q values for cluster 1 and small BA, especially in regions experiencing heavy snow. On the other hand, the average BA had a negative effect for a number of ramets, however the parameter estimate was small. Our results suggest that clonal reproduction may have been the most important of the strategies exploited in order to establish in harsh environments like frequent disturbance conditions such as heavy snow region in this species.