Genetic variation within and between populations of two endangered endemic species of the laurel forest from the Canary Islands, Myrica rivas-martinezii (Myricaceae) and Sideritis discolor (Lamiaceae)

Abstract

Myrica rivas-martinezii A.Santos and Sideritis discolor Bolle, two endangered endemic species of the laurel forest from the Canary Islands, were studied by using RAPD markers with the goal of assessing their within- and among-population apportionment of genetic variability. Ten- and 11-oligonucleotide primers assayed in three populations of each of M. rivas-martinezii and S. discolor resulted in 32 molecular markers in the former species and 49 in the latter (90.6% and 100% polymorphic, respectively). The value of the coefficient of genetic differentiation among populations was very high for M. rivas-martinezii (F_ST = 0.487) but only moderate for S. discolor (F_ST = 0.149). These results suggest that gene flow among populations is extremely low in M. rivas-martinezii and quite substantial in S. discolor. The UPGMA cluster obtained from Dice's coefficient mixed individuals from different populations in S. discolor but not in M. rivas-martinezii, where they were grouped by their island of occurrence. On the basis of these results and the vulnerability of these two species, we suggest protection of all natural populations. However, if habitat conservation is not possible, our results suggest that for S. discolor, the La Virgen population would make a good donor population because of geographical and genetic factors. The high genetic differentiation detected among populations of M. rivas-martinezii suggests that each island should be considered as a distinct management unit. However, considering the situation of this species on La Palma Island with only two isolated individuals, reintroductions of germoplasma from El Hierro may be a viable way to guarantee the existence of M. rivas-martinezii in that island.