Genetic variation in isolated Mexican populations of the endemic maple Acer skutchii Rehd.

摘要

Acer skutchii is an endemic tree species occurring in only six locations in Central America. We observed genetic variation of A. skutchii in three small populations from two locations at five nuclear microsatellite loci (simple sequence repeats, nSSRs), ten chloroplast microsatellites (cpSSRs), and 161 AFLP loci (Amplified Fragment Length Polymorphisms). The total variation of the studied populations was low: No variation was detected at cpSSRs, a total of 2.6 alleles per locus and a total expected heterozygosity of 0.112 was observed at nSSRs, and a total expected heterozygosity of 0.174 was computed for AFLPs. The smallest population Manantlan (N = 26) consistently exhibited the lowest levels of genetic variation, contributed least to the total genetic diversity, and contained the lowest number of unique variants both at nSSRs and at AFLPs. The low level of genetic variation in particular in population Manantlan is explained by genetic drift. Contrasting patterns of genetic differentiation amongpopulations were observed at nSSRs and at AFLPs. Two neighbouring populations at the location Talpa showed the highest genetic similarity at AFLPs, but not at nSSRs. The high number of polymorphic loci make AFLP markers more appropriate to assess patterns of genetic differentiation among populations. Efforts for in situ conservation of genetic resources should primarily focus on the larger populations in Talpa. A mixed plantation with progenies from all populations should be established as a complementary ex situ conservation measure.