Collevatti R G, Grattapaglia D, Hay J D
Pós-Graduação em Biotecnologia e Recursos Genéticos, Universidade Católica de Brasília, Brasília, SGAN 916, Mod. B, Asa Norte, Brasília, D.F. Brasil, 70790-160.
Mol Ecol. 2001 Feb;10(2):349-56. doi: 10.1046/j.1365-294x.2001.01226.x.
We report the population genetic structure of the endangered tropical tree species Caryocar brasiliense, based on variability at 10 microsatellite loci. Additionally, we compare heterozygosity and inbreeding estimates for continuous and fragmented populations and discuss the consequences for conservation. For a total of 314 individuals over 10 populations, the number of alleles per locus ranged from 20 to 27 and expected and observed heterozygosity varied from 0.129 to 0.924 and 0.067 to 1.000, respectively. Significant values of theta and R(ST) showed important genetic differentiation among populations. theta was much lower than R(ST), suggesting that identity by state and identity by descent have diverged in these populations. Although a significant amount of inbreeding was found under the identity by descent model (f = 0.11), an estimate of inbreeding for microsatellite markers based on a more adequate stepwise mutation model showed no evidence of nonrandom mating (R(IS) = 0.04). Differentiation (pairwise F(ST)) was positively correlated with geographical distance, as expected under the isolation by distance model. No effect of fragmentation on heterozygosity or inbreeding could be detected. This is most likely due to the fact that Cerrado fragmentation is a relatively recent event (approximately 60 years) compared to the species life cycle. Also, the populations surveyed from both fragmented and disturbed areas were composed mainly of adult individuals, already present prior to ecosystem fragmentation. Adequate hypothesis testing of the effect of habitat fragmentation will require the recurrent analysis of juveniles across generations in both fragmented and nonfragmented areas.
我们基于10个微卫星位点的变异性，报告了濒危热带树种巴西坚果（Caryocar brasiliense）的群体遗传结构。此外，我们比较了连续群体和破碎化群体的杂合性和近亲繁殖估计值，并讨论了其对保护工作的影响。在10个群体中的总共314个个体中，每个位点的等位基因数量在20到27之间，预期杂合度和观察到的杂合度分别在0.129至0.924和0.067至1.000之间变化。显著的θ值和R(ST)值表明群体间存在重要的遗传分化。θ远低于R(ST)，这表明在这些群体中，状态同一性和血统同一性已经出现分歧。尽管在血统同一性模型下发现了显著的近亲繁殖（f = 0.11），但基于更合适的逐步突变模型对微卫星标记的近亲繁殖估计未显示出非随机交配的证据（R(IS) = 0.04）。正如距离隔离模型所预期的那样，分化（成对F(ST)）与地理距离呈正相关。未检测到破碎化对杂合性或近亲繁殖的影响。这很可能是由于与该物种的生命周期相比，塞拉多（Cerrado）破碎化是一个相对较新的事件（约60年）。此外，从破碎化和受干扰地区调查的群体主要由成年个体组成这些个体在生态系统破碎化之前就已存在。对栖息地破碎化影响进行充分的假设检验将需要对破碎化和未破碎化地区的几代幼体进行反复分析。
