Abstract
The isolated watersheds of the southwestern Andean Altiplano constitute a natural laboratory to study the evolutionary divergence of freshwater biota. Field observations showed that Biomphalaria snails from Parinacota, Colpa, and Caquena have different shell sizes. We performed morphometric analysis and common garden experiment to evaluate whether the observed shell variation has a genetic base and if this variation is manifested in other morphological characters and life history traits. Network analysis revealed that the snails of Parinacota form a lineage genetically distinct from Caquena and Colpa. The morphometric analysis of the shell showed that the Parinacota snails were larger than Caquena and Colpa, both in nature and laboratory conditions, but there was no evidence of difference in the shape of the shell when compared using multivariate analyses. The number of eggs per ovicapsule was the only life history trait that was significantly different between lineages, although this difference may be also attributed to size of the progenitor; the oviposition rate did not differ between lineages or localities, and the hatching size and growth rate differed only at the locality level, not lineages. The results suggest that shell size of the snails has a genetic basis associated to the phenotype, while the expression and evolution of life history traits in extreme high environments are highly influenced by proximal causes.
Highlights
The isolated watersheds of the southwestern Andean Altiplano constitute a natural laboratory to study the evolutionary divergence of freshwater biota
Haplotype network Previous molecular phylogenetic analyses suggest that Biomphalaria snails from the Caquena basin and those from the Lauca basin belong to different lineages (Collado et al 2011)
In this paper we evaluated genetic, morphological, and life history traits variation in snails of the genus Biomphalaria from different populations of the Chilean Altiplano
Summary
The isolated watersheds of the southwestern Andean Altiplano constitute a natural laboratory to study the evolutionary divergence of freshwater biota. One way to evaluate how much of the observed variation among populations is due to differences between genotypes and how much is due to environmental influence is to perform ‘common garden experiments', in which individuals from contrasting environments are raised under the same conditions (Conover and Schultz 1995). Considering that its aquatic life cycle links them directly with the evolution of the hydrologic systems, these snails provide an ideal model to evaluate the variation in morphological and life history traits between populations spanned in fragmented habitats. These snails are hermaphrodite capable of selfing, a preference for outbreeding has been reported in the group (Barbosa and Barbosa 1994). They have direct development and limited vagility increasing the possibility of divergence among populations since juvenile emerges as miniature adults in the habitat occupied by their parents
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