Biology subjects

Savolainen, V.

Publications and source records attributed to Savolainen, V..

3 recordsLinked to original sources

bioRxiv2018

Trait evolution and historical biogeography shape assemblages of annual killifish

Reconstructions of evolutionary and historical biogeographic processes can improve our understanding of how species ssemblages developed and permit inference of ecological drivers affecting coexistence. We explore this approach in Austrolebias, a genus of annual fishes possessing a wide range of body sizes. Regional assemblages composed of different species with similar size distributions are found in four areas of eastern South America. Using phylogenetic trees, species distribution models and size data we show how trait evolution and historical biogeography have affected the composition of species assemblages. We extend age-range correlations to improve estimates of local historical biogeography. We find that size variation principally arose in a single area and infer that ecological interactions drove size divergence. This large-size lineage spread to two other areas. One of these assemblages was likely shaped by adaptation to a new environment, but this was not associated with additional size divergence. We found only weak evidence that environmental filtering has been important in the construction of the remaining assemblage with the smallest range of sizes. The repeated assemblage structures were the result of different evolutionary and historical processes. Our approach sheds light on how species assemblages were built when typical clustering approaches may fall short.

evolutionary biology↗

bioRxiv2017

The genetic basis and evolution of red blood cell sickling in deer

Crescent-shaped red blood cells, the hallmark of sickle cell disease, present a striking departure from the biconcave disc shape normally found in mammals. Characterized by increased mechanical fragility, sickled cells promote haemolytic anaemia and vaso-occlusions and contribute directly to disease in humans. Remarkably, a similar sickle-shaped morphology has been observed in erythrocytes from several deer species, without pathological consequences. The genetic basis of erythrocyte sickling in deer, however, remains unknown, limiting the utility of deer as comparative models for sickling. Here, we determine the sequences of human {beta}-globin orthologs in 15 deer species and identify a set of co-evolving, structurally related residues that distinguish sickling from non-sickling deer. Protein structural modelling indicates a sickling mechanism distinct from human sickle cell disease, coordinated by a derived valine (E22V) in the second alpha helix of the {beta}-globin protein. The evolutionary history of deer {beta}-globins is characterized by incomplete lineage sorting, episodes of gene conversion between adult and foetal {beta}-globin paralogs, and the presence of a trans-species polymorphism that is best explained by long-term balancing selection, suggesting that sickling in deer is adaptive. Our results reveal structural and evolutionary parallels and differences in erythrocyte sickling between human and deer, with implications for understanding the ecological regimes and molecular architectures that favour the evolution of this dramatic change in erythrocyte shape.

evolutionary biology↗

bioRxiv2017

A case for sympatric speciation by cannibalism in South-American annual killifish (Austrolebias)

A trophic radiation in the South-American annual killifish genus Austrolebias has led to the evolution of large specialized piscivores from small generalized carnivores. It has been proposed that this occurred in a single series of vicariant speciation events. An alternative hypothesis is denoted giant-dwarf speciation: piscivores would have evolved in sympatry by character displacement and cannibalism. We test the plausibility of both scenarios using size measures combined with distributional data and new phylogenetic trees based on mitochondrial and nuclear molecular markers.\n\nOur analysis uses historical biogeography models and Ornstein-Uehlenbeck processes describing trait evolution across the posterior distributions of phylogenetic trees. Large species most likely evolved three times from small ones. For the clade containing A. elongatus, we argue that vicariance was not involved in the origin of these large and specialized piscivores. They experience stabilizing selection with an optimum shifted towards larger bodies and longer jaws. The branch leading to this clade has the fastest evolving jaw lengths across the phylogeny, in agreement with expectations for giant-dwarf speciation. For A. wolterstorffi, the support for giant-dwarf speciation is weaker. When the species is placed at the root of Austrolebias, ancestral reconstructions are unreliable and vicariance cannot be ruled out. For the remaining large species, we can reject vicariance and giant dwarf speciation. Our results give rise to two new additional scenarios for the evolution of specialized piscivores. In the first, two successive speciation events in sympatry or parapatry produced large and piscivorous species. In the second, the immigration of a different annual killifish genus (Cynopoecilus) in the Patos area of endemism has contributed to in-situ diversification of Austrolebias species.

evolutionary biology↗