How an Ecological Race Is Forming: Morphological and Genetic Disparity among Thermal and Non-Thermal Populations of Aquatic Lymnaeid Snails (Gastropoda: Lymnaeidae)

Hot (geothermal) pools and streams, a specific type of aquatic biotopes having almost worldwide distribution, maintain rich faunas animals belonging to various taxa. Snails (Gastropoda) represent one such groups, which form populations in geothermal waterbodies all continents. Some freshwater snail species produce morphologically distinct hot-water populations, whose rank is often debated (full or thermal ‘ecotype’, ‘race’). In this study, we used six pond snails (family Lymnaeidae) investigate the morphological genetic consequences infiltration into habitats. particular, aimed at studying changes shell shape proportions as well formation unique haplotypes occurrence latter beyond waterbodies. All studied demonstrate diminutive body size hot sites accompanied, four species, by apparent alterations proportions. A phenomenon phenotypic ‘juvenilization’, when adult able reproduce individuals characteristic for full-grown living under ‘normal’ conditions, described. Unique ‘thermal’ haplotypes, not found sites, were normally restricted single locality, no signs frequent ‘travels’ from habitat another are seen. vast majority cases, these exclusive separated their ancestors only few (1–3) mutational steps, may indicate relatively recent origin. We inclined relate both reduction ‘juvenilization’ life-cycle re-adjustment following penetration lymnaeids The ecological (‘thermal’) intraspecific races different forming habitats, exhibit, great extent, evolutionary predictability (=convergent evolution; =parallelisms). dilemma ‘ecological race vs. young species’ application taxonomy briefly discussed.