Nuclear and chloroplast microsatellites reveal high genetic diversity and structure in Platonia insignis Mart., an endangered species native to the Brazilian Amazon

ABSTRACT Bacurizeiro (Platonia insignis) is a fruit of the Amazon that, due to anthropic actions, has been suffering serious damage to its genetic diversity. We analyzed the genetic diversity and structure of seven bacurizeiro populations distributed among four Brazilian states and two biomes, the Amazon and Cerrado, based on eight nuclear (ncSSR) and three chloroplast (cpSSR) microsatellite markers. Higher heterozygosity values were found for the Northern populations of Japurá and Marapanim, and the Northeast population of Chapadinha when using ncSSR. Higher diversity indices were also observed for these populations with cpSSR, although higher haplotypic diversity parameters were detected for the two Northern populations. Genetic structure analysis showed the formation of two well defined groups: I - populations from Maranhão and Piauí (Cerrado) and II - populations from Amazonas and Pará (Amazon). Positive and significant correlations were identified between genetic and geographical distances for both ncSSR (r = 0.09; p = 0.0010) and cpSSR (r = 0.11; p = 0.0008), in agreement with the genetic structure analysis. The high genetic structure among populations probably reflects the divergent natural and human selection pressures to which bacurizeiros are subjected in both the Amazon and Cerrado biomes, with higher diversity maintained in the Amazon populations.

摘要 巴库里果（Bacurizeiro，学名*Platonia insignis*）是亚马逊原生果实，因人为活动干扰，其遗传多样性正遭受严重破坏。本研究依托8个核微卫星（ncSSR, nuclear simple sequence repeat）标记与3个叶绿体微卫星（cpSSR, chloroplast simple sequence repeat）标记，对分布于巴西4个州、涵盖亚马逊与塞拉多（Cerrado）2个生物群落的7个巴库里果种群的遗传多样性及种群遗传结构展开分析。基于ncSSR标记的分析结果显示，北部的雅普拉（Japurá）、马拉帕尼姆（Marapanim）种群以及东北部的查帕迪尼亚（Chapadinha）种群具有更高的杂合度水平。基于cpSSR标记的分析中，上述种群同样表现出更高的多样性指数，不过两个北部种群的单倍型多样性参数更为优异。种群遗传结构分析表明，供试种群可划分为两个特征鲜明的类群：类群Ⅰ——来自马拉尼昂州（Maranhão）与皮奥伊州（Piauí）的塞拉多种群；类群Ⅱ——来自亚马孙州（Amazonas）与帕拉州（Pará）的亚马逊种群。无论是ncSSR（r=0.09；p=0.0010）还是cpSSR（r=0.11；p=0.0008），均检测到遗传距离与地理距离间存在显著正相关，该结果与种群遗传结构分析结论一致。种群间显著的遗传分化，大概率反映了巴库里果在亚马逊与塞拉多生物群落中所承受的差异化自然与人为选择压力，其中亚马逊种群维持了更高水平的遗传多样性。