Phenotypic plasticity can explain evolution of sympatric polymorphism in the hairy snailTrochulus hispidus(linnaeus, 1758)

Abstract

Morphological variation of snails from the genus Trochulus is so huge that their taxonomy is unclear. The greatest variability concerns forms hispidus and sericeus/plebeius, which are often considered as separate species. To evidence the species barriers, we carried out crossbreeding experiments between these two sympatric morphs. Moreover, we compared the shell morphology of laboratory-bred offspring with their wild parents to test if the variation can be explained by the phenotypic plasticity model. We found that the two Trochulus morphs show no reproductive barriers. The fecundity rates, the mean clutch size, and F1 viability observed for all crosses were not significantly different. In hybrid crosses (in F2 generation), we also recorded reproduction compatibility, similar fecundity, and hatching success as in their parents. Accordingly, phylogenetic analyses revealed the significant grouping of sequences from these different morphs and supported no constrains in reproduction between them. Comparison of shell morphology between wild and laboratory samples showed that various characters appeared highly plastic. The average shell shape of the hispidus morph changed significantly from flat with wide umbilicus to elevated with narrower umbilicus such as in the sericeus/plebeius morph. All these findings indicate that the examined morphs do not represent separate biological species and the evolutionary process is not advanced enough to separate their genetic pool. Therefore, phenotypic plasticity has played a significant role in the evolution of Trochulus shell polymorphism. The two morphs can evolve independently in separate phylogenetic lineages under the influence of local environmental conditions.

Speciation in sympatric species of land snails from the genus Trochulus (Gastropoda, Hygromiidae)

“…Disregarding the incorrect assignment of the samples, these results can be interpreted into two ways. Following our previous findings, showing the influence of local environment on shell shape in Trochulus taxa (Proćków et al, 2017a(Proćków et al, , 2017b(Proćków et al, , 2018, we can assume that these outstanding cases represent individuals genetically related with others in the population but having different shell morphology due to such a phenotypic plasticity and the environmental influence. It means that the same or similar shell morphology can occur independently in different genetic lineages.…”

“…Moreover, recent studies have provided an even more confusing picture, revealing that T. sericeus/hispidus constitutes a complex of morphologically similar but genetically divergent species in the Sarine valley in Swiss Western Prealps (Dépraz et al, 2009) and the snails morphologically resembling T. sericeus sometimes form genetically separate clades (Duda et al, 2014;Proćków et al, 2014Proćków et al, , 2017c or conversely, two morphologically different shells assigned to T. hispidus and T. sericeus do not form phylogenetically distinct clades (Duda et al, 2014;Proćków et al, 2013); hence, these snails are often described as the T. hispidus complex (Kruckenhauser et al, 2014). Furthermore, T. hispidus and T. sericeus appeared to be phenotypically plastic and showed no interbreeding constraints (Proćków et al, 2017a). Since their shell morphology strictly depends on microhabitat, they were regarded ecophenotypes (Proćków et al, 2018).…”

Molecular phylogeny reveals high diversity and endemism in the limestone karst‐restricted land snail genus Sophina Benson, 1859 from Myanmar (Eupulmonata: Helicarionidae), with description of four new species

“…Arboreal species tend to have a narrow umbilicus and a relatively tall shell, while ground‐dwelling species have a wide umbilicus and flat shell (Hirano, Kameda, Kimura, & Chiba, 2015). In contrast, the variation of umbilicus width could also be a result of phenotypic plasticity (Proćków, Kuźnik‐Kowalska, & Mackiewicz, 2017).…”

Integrative systematics reveals the new land-snail genus Taphrenalla (Eupulmonata: Ariophantidae) with a description of nine new species from Thailand

“…Several reports (e.g., Hausdorf, 1998;Hirano et al, 2014;Hyman et al, 2017) have suggested that genital traits are more likely to reflect the actual phylogenetic relationships than morphological appearances. On one hand, phenotypic plasticity in snail shells is a well-documented phenomenon and is probably a response to environmental variation (Emberton, 1991(Emberton, , 1995Gustafson et al, 2014;Proćków et al, 2017). The other is convergence and parallelism in the character states of the shell morphology and other anatomical structures that are generally known in land snails (Hirano et al, 2014(Hirano et al, , 2015Köhler & Criscione, 2015;Hyman et al, 2017).…”