Species richness and genetic diversity in Dysopsis hirsuta (Euphorbiaceae) and Nothomyrcia fernandeziana (Myrtaceae), endemic species of the Juan Fernández Archipelago, Chile.

Abstract

The Juan Fernández Archipelago is located 667 kilometers west of continental Chile and consists of tluee islands: Santa Claia, Robinson Crusoe, and Alejandro Seikirk, with a geológica! age estimated bcrween 1-4 my. The Archipelago is a natural laboratory, charactcrized by a high percentagc of spccific cndcmism. Human activity, involving degradation of the forests as well as introduction of exotic animáis and alien plants, has caused a significant reduction in popularion number and size, as well as genetic variation within endemic plant species. The objective of this contiibution is to present inforraation on genetic diversity in two endemic species from the Juan Fernández Archipelago, one an herb and another a tree, in conjunction with general species richness valúes to determine áreas of greater interest for conservalion. Samples of Dysopsis hirsuta (Mull. Arg.) Skottsb. and Nothomyrcia fernandeziana (Hook. et Am.) Kausel in Rtjbinson Crusoe Island were col- — 44 — ABSTRACT BOOK IT Posters lected from 10 and 18 populations, respectively. After extraction of DNA, AFLPs were obtained for genetic analysis. Scoring was done with the program GeneMarker ver. 1.85, and a binary matrix was generated for each species. The data were analyzed using Genalex and the software Are 9.3. In parallel, an analysis of richness of thirteen tree species was performed in Diva-Gis using a circular neighborhood method. In Dysopsis hirstiUt the valúes of number of effective alíeles (Ne = 1.078), percentage of polymorphism (% P = 50.6%), Shannon-Weaver Index (I = 0.237), and expected heterozygosity (He = 0.154) were lower in populations with less species richness (<7 species) and invaded sites. The highest valúes of genetic diversity (Ne = 1.3, %P = 65, I = 0.272, He = 0.170) were found in sites with high species richness (>9 species) and in fragments of native forest. Nothomyrcia fernandeziana does not evidence a relationship between genetic diversity and species richness, and it has high valúes of genetic diversity in invaded áreas (%P invaded = 61.2%, %P native = 54.8%). We discuss the levéis of genetic diversity in D. hirsuta in relatíon to forest fragmentation, isolation, low gene flow between populations, and mode of speciation. Homogeneous genetic diversity within N. fernandeziana may be associated, among oiher factors, wiih tlie coniinuous distribution of this species on Robinson Ciusoe Island.