Laboratorio de Zoología de Invertebrados I, Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan No. 670, B8000ICN Bahía Blanca, Buenos Aires, Argentina; MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France.
Mol Phylogenet Evol. 2021 Apr;157:107035. doi: 10.1016/j.ympev.2020.107035. Epub 2020 Dec 4.
Cryptic species can present a significant challenge to the application of systematic and biogeographic principles, especially if they are invasive or transmit parasites or pathogens. Detecting cryptic species requires a pluralistic approach in which molecular markers facilitate the detection of coherent taxonomic units that can then be analyzed using various traits (e.g., internal morphology) and crosses. In asexual or self-fertilizing species, the latter criteria are of limited use. We studied a group of cryptic freshwater snails (genus Galba) from the family Lymnaeidae that have invaded almost all continents, reproducing mainly by self-fertilization and transmitting liver flukes to humans and livestock. We aim to clarify the systematics, distribution, and phylogeny of these species with an integrative approach that includes morphology, molecular markers, wide-scale sampling across America, and data retrieved from GenBank (to include Old World samples). Our phylogenetic analysis suggests that the genus Galba originated ca. 22 Myr ago and today comprises six species or species complexes. Four of them show an elongated-shell cryptic phenotype and exhibit wide variation in their genetic diversity, geographic distribution, and invasiveness. The remaining two species have more geographically restricted distributions and exhibit a globose-shell cryptic phenotype, most likely phylogenetically derived from the elongated one. We emphasize that no Galba species should be identified without molecular markers. We also discuss several hypotheses that can explain the origin of cryptic species in Galba, such as convergence and morphological stasis.
隐种可能对系统学和生物地理学原理的应用构成重大挑战，尤其是如果它们具有入侵性或传播寄生虫或病原体的话。检测隐种需要采用多元化的方法，其中分子标记有助于检测具有一致性的分类单元，然后可以使用各种特征（例如内部形态）和杂交来分析这些分类单元。在无性或自交的物种中，后一种标准的使用受到限制。我们研究了一组来自圆口螺科的隐生淡水蜗牛（属 Galba），这些蜗牛几乎已经入侵了所有大陆，主要通过自交繁殖并将肝吸虫传播给人类和家畜。我们旨在通过整合形态学、分子标记、在美洲广泛采样以及从 GenBank 检索数据（包括旧世界样本）的方法，阐明这些物种的系统发育、分布和进化关系。我们的系统发育分析表明，Galba 属大约在 2200 万年前起源，今天包含六个种或种复合体。其中四个种表现出长壳隐生表型，在遗传多样性、地理分布和入侵性方面表现出广泛的变异。其余两个种的地理分布更为局限，表现出球形壳隐生表型，很可能是从长壳表型进化而来的。我们强调，没有分子标记，就不应识别任何 Galba 种。我们还讨论了几个可以解释 Galba 隐种起源的假说，例如趋同和形态停滞。
