Facultad de Ciencias, Universidad Autónoma de Baja California, Ensenada, Baja California, Mexico.
PLoS One. 2011 Jan 20;6(1):e16133. doi: 10.1371/journal.pone.0016133.
Callitropsis guadalupensis (Guadalupe cypress) is endemic to Guadalupe Island, Mexico, where it is the dominant species of the only forest. The species has suffered declining numbers following the introduction of goats to the island over 150 years ago. Callitropsis guadalupensis is closely related to Callitropsis forbesii (Tecate cypress), distributed in small isolated populations in mainland Baja California and southern California. The objective of the present study was to compare the genetic diversity of the island endemic to the continental species.
METHODOLOGY/PRINCIPAL FINDINGS: We measured genetic diversity in Callitropsis guadalupensis (n =54) from Guadalupe Island and in Callitropsis forbesii (n = 100) from five populations in mainland Baja California. The plastid DNA trnS-trnG spacer and the trnL-trnF region were chosen for characterization. Thirty-four haplotypes were observed, of which six were shared between both species. One of these haplotypes was also shared with three other species, Callitropsis lusitanica, Callitropsis montana, and Callitropsis stephensonii. Haplotype diversity (h) and nucleotide diversity (π) were significantly higher for Callitropsis guadalupensis (h = 0.698, π = 0.00071) than for Callitropsis forbesii (h = 0.337, π = 0.00024).
CONCLUSIONS/SIGNIFICANCE: Callitropsis guadalupensis shows no evidence of a founder effect or of a genetic bottleneck, and can be added to a growing list of insular species with higher genetic diversity than their mainland relatives.
瓜达卢佩柏（Guadalupe cypress）是墨西哥瓜达卢佩岛的特有种，是该岛唯一森林的优势物种。150 多年前，山羊被引入该岛后，该物种的数量一直在减少。瓜达卢佩柏与分布在加利福尼亚半岛和南加州小而孤立的种群中的 Tecate cypress（Callitropsis forbesii）密切相关。本研究的目的是比较岛屿特有种和大陆种的遗传多样性。
方法/主要发现：我们测量了来自瓜达卢佩岛的 54 株瓜达卢佩柏（Callitropsis guadalupensis）和来自加利福尼亚半岛五个种群的 100 株 Callitropsis forbesii 的遗传多样性。选择质体 DNA trnS-trnG 间隔区和 trnL-trnF 区进行特征描述。观察到 34 个单倍型，其中 6 个在两个物种中共享。其中一个单倍型也与其他三个物种 Callitropsis lusitanica、Callitropsis montana 和 Callitropsis stephensonii 共享。瓜达卢佩柏的单倍型多样性（h）和核苷酸多样性（π）显著高于 Callitropsis forbesii（h = 0.698，π = 0.00071）（h = 0.337，π = 0.00024）。
结论/意义：瓜达卢佩柏没有表现出奠基者效应或遗传瓶颈的迹象，可以加入到越来越多的岛屿物种名单中，这些物种的遗传多样性高于它们的大陆亲缘种。
