Genetic variation facilitates both natural range expansions and anthropogenic invasions. Contrary to expectations, hybridization does not always impact negatively on biodiversity. Increasing evidence indicates advantageous roles for introgressive hybridization in maintaining standing genetic variation. Hypothesizing that hybridization may contribute to the evolutionary and invasive success of a diverse group of freshwater snails (Ampullariidae, commonly known as apple snails), we estimated the frequency of hybridization between two globally invasive species of Pomacea, Pomacea canaliculata (Lamarck, 1822) and P. maculata Perry, 1810, in their native range. While previous work in Asia has uncovered the occurrence of extensive hybridization, we provide the first phylogenetic evidence of a high degree of hybridization (30%) between these species in Uruguay and Brazil. Hybrids carried both heterozygous and homozygous combinations of elongation factor 1-α (EF1α) nuclear alleles in both mating directions, indicating that hybridization has occurred over multiple generations and likely preceded introductions outside the native range. Among the five sites in Brazil previously documented as containing only P. maculata, one far northern population (Careiro Castanho), which is thousands of kilometres from the northern range of P. canaliculata, unexpectedly contained hybrids. This may be the result of human-facilitated introductions. Together with recent work from Asia, our investigations in the native range of apple snails support a reframing of historical perspectives of hybridization as a driver of extinction and diversity loss towards a modern paradigm where hybridization may promote diversification and contribute to the survival of evolutionary lineages such as molluscs.

中文翻译：

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苹果蜗牛（Pomacea spp.）在其原生范围内渐进杂交的第一个证据

遗传变异促进了自然范围的扩大和人为入侵。与预期相反，杂交并不总是对生物多样性产生负面影响。越来越多的证据表明渐进杂交在维持常设遗传变异方面的有利作用。假设杂交可能有助于多种淡水蜗牛（Ampullariidae，通常称为苹果蜗牛）的进化和入侵成功，我们估计了两种全球入侵物种 Pomacea、Pomacea canaliculata（Lamarck，1822）和P. maculata Perry，1810 年，在它们的原生范围内。虽然之前在亚洲的工作已经揭示了广泛杂交的发生，我们提供了乌拉圭和巴西这些物种之间高度杂交 (30%) 的第一个系统发育证据。杂交体在两个交配方向都携带延伸因子 1-α (EF1α) 核等位基因的杂合子和纯合子组合，表明杂交已经发生了多代，并且可能先于天然范围之外的引入。在巴西先前记录为仅包含 P. maculata 的五个地点中，一个距离 P. canaliculata 北部范围数千公里的远北种群 (Careiro Castanho) 出人意料地包含杂交种。这可能是人为引入的结果。加上最近来自亚洲的作品，