ABSTRACT

To understand patterns of genetic and morphological variability, population structure and dispersal dynamics of the invasive bivalve Pinctada imbricata radiata (Leach, 1814) in Tunisian waters, we studied 200 individuals from five different sites (natural, polluted and/or subjected to environmental and anthropogenic pressures) using 10 enzymatic systems and six shell measurements. In this study, we attempt to elucidate the relationship between the spreading ability and the adaptive potential of the species under various environmental stresses. Fourteen putative enzyme-coding loci were resolved, six of which were polymorphic at the level of 99%. P. imbricata radiata maintains a relatively consistent level of polymorphism at the genetic markers studied, since 10% of individuals were heterozygous. The mean F_IS value was positive and significant in two samples. However, the remaining samples collected from the disturbed marine sites (polluted, urban and lagoon areas) were at Hardy–Weinberg equilibrium. Highly significant genetic (mean F_ST = 0.022, P < 0.001) and morphological (Wilks’ lambda = 0.0814, approximate F_{20, 627} = 35.484, P < 0.001) differentiations between samples were observed, with no evidence of isolation caused by geographic distance. However, the Mantel test performed between genetic and morphological distances revealed a significant correlation. Our results indicate that natural selection seems to have a greater influence on genetic differentiation in P. imbricata radiata than genetic drift. The combination of genetic and morphological data provided important theoretical information for determining the invasion mechanisms of the species.

摘要

为了了解突尼斯水域中入侵双壳类Pinctada imbricata radiata（Leach，1814 年）的遗传和形态变异模式、种群结构和扩散动态，我们研究了来自五个不同地点（自然、污染和/或受到环境和人为影响的地点）的 200 名个体。压力）使用 10 个酶促系统和 6 个外壳测量。在这项研究中，我们试图阐明物种在各种环境压力下的传播能力与适应潜力之间的关系。解析了 14 个推定的酶编码位点，其中 6 个多态性达到 99%。P. imbricata radiata在所研究的遗传标记上保持相对一致的多态性水平，因为 10% 的个体是杂合的。两个样本的平均F _IS值为正且显着。然而，从受干扰的海洋地点（污染区、城市区和泻湖区）收集的其余样本处于哈代-温伯格平衡。高度显着的遗传（平均F _ST  = 0.022，P  < 0.001）和形态学（Wilks' lambda = 0.0814，近似F _{20, 627}  = 35.484，P < 0.001) 观察到样品之间的差异，没有证据表明地理距离造成隔离。然而，在遗传和形态距离之间进行的 Mantel 检验揭示了显着的相关性。我们的结果表明，与遗传漂变相比，自然选择似乎对P. imbricata radiata 的遗传分化具有更大的影响。遗传学和形态学数据的结合为确定该物种的入侵机制提供了重要的理论信息。