Trees of the Magnoliaceae family are of scientific, cultural and socio-economic importance. Over 40% of all Magnoliaceae species occur in Southern China. A significant number of these are considered threatened because of habitat decline and, in some cases, overexploitation. Magnoliaceae species are increasingly attracting the interest of conservation biologists, and increasing efforts relevant to their conservation has been undertaken in recent years.
Kmeria septentrionalis Dandy (Magnoliaceae) is an endangered dioecious tree with a restricted distribution found in highly fragmented populations across Southern China. Kmeria septentrionalis is a relic species of the Tertiary period. The species is listed on the most endangered species in China, and a nature reserve has been established for its protection since 1991. However, the species is under a growing threat from illegal logging.
Assoc. Prof. LI Qiaoming and her team investigated the spatial genetic structure and genetic diversity of 161 individuals of K. septentrionalis collected from five natural populations using AFLP molecular markers. Within-population genetic variation was measured, with percentage of polymorphic bands (PPB) ranged from 63% to 87%, while HS (genetic diversity within population) varied from 0.185 to 0.244 with a mean of 0.215 ± 0.025. Their experiment demonstrated significant genetic differentiations were revealed between pairwise populations, indicating each population existing as an independent evolutionarily significant unit. Mantel test results showed no pattern of isolation-by-distance among populations separated by large distance. Fine scale spatial patterns of genetic variation suggested significant effects of isolation-by-distance within population at distances of 22 m. Their results suggest that the contrasting genetic structure at coarse and fine scale in K. septentrionalis may indicate restricted pollen flow and seed dispersal at fine scales, and separated evolution in isolated populations over long period of time at coarser scales.
Thus, the authors propose management practices must include a complete and reinforced ban on logging for this species. For those populations that have declined due to logging, conservation efforts, such as, re-introducing seedlings germinated from seeds from the same population, could provide assistance for a better and quick population recovery. However, introducing genetic material from other populations for restoration should be avoided since each population is likely an evolutionarily significant unit, under separated evolution over a long period of time. Ex situ collection for conservation, and establishing seed bank and DNA bank for K. septentrionalis should also be in the agenda.
The research result, entitled “Contrasting coarse and fine scale genetic structure among isolated relic populations of Kmeria septentrionalis”, has been published in Genetica 2010, 138: 939–944.