Trait evolution and historical biogeography shape assemblages of annual killifish

Abstract

Aim Different species assemblages of annual killifish possess replicated body size distributions yet have unique sets of species in each area of endemism. Here, we use models of trait evolution and historical biogeography to discover how size variation originated and has been restructured. Location South America. Taxon Austrolebias (Cyprinodontiformes). Methods We sampled 63 individuals from 26 Austrolebias species. Using phylogenetic trees (BEAST2), data on environmental variables at sampling locations and size data, we compare different models for trait evolution (SURFACE, l1OU) of body size and niche traits. We model the historical biogeography of the areas of endemism (BioGeoBEARS) and use both analyses in combination to reconstruct the history of four species assemblages. Results We present new phylogenetic trees for Austrolebias and use them to show that large size principally arose within a single area driven by a shifted selection optimum for a subset of the species in that area. We suggest that ecological interactions triggered size divergence and that this large‐bodied lineage subsequently spread to two other areas. A second assemblage may have been shaped by adaptation to a new environment without an associated increase in size divergence. A third assemblage, which has the smallest size range and the most recent origin, is phylogenetically clustered, and we found no evidence of environmental filtering. Main conclusions Assemblage similarity in Austrolebias is the result of contrasting ecological, evolutionary and historical processes. Modelling trait evolution together with historical biogeography can help to disentangle the complex histories of multispecies assemblages. This approach provides context to commonly used tests investigating the role of ecological processes from phylogenetic data and generates new testable hypotheses on the processes that generated trait diversity and assemblage similarity.

Patterns and drivers of Nothobranchius killifish diversity in lowland Tanzania

“…It is typically recorded in assemblages with four Nothobranchius species (range 3-5) and apparently requires the presence of congeners that serve as its prey (Wildekamp, 2004). Similar evolution of giant predatory species in annual fish assemblages has been reported from the Neotropics (Helmstetter et al, 2020) and demonstrates that wetland killifish assemblages from various regions converge to a common pattern (García et al, 2009(García et al, , 2019Loureiro et al, 2015) through adaptations to specialized ecological niches. While the body morphology of Nothobranchius species is relatively conserved (Wildekamp, 2004) and species evolve toward three major body size optima (Lambert et al, 2019), there is preliminary evidence of trophic niche (Polačik et al, 2014;Polačik & Reichard, 2010) and trophic-related morphology (Costa, 2018;Reichard, 2015) differentiation within local Nothobranchius assemblages.…”

Embryonic development of natural annual killifish populations of the genus Austrolebias: Evolutionary parallelism and the role of environment

“…Temporary pools are characterised by extensive seasonal fluctuation, but their fundamental characteristics, such as the shifting wet and dry phases, gradual filling and desiccation, and hypoxic substrate remain very similar worldwide (Williams, 2006). For instance, similar selective forces repeatedly resulted in characteristic body size structuring in adult killifish communities (Canavero et al, 2014; Helmstetter et al, 2020). Consequently, we hypothesise that the selective pressures imposed by temporary pool seasonality acting on embryos of annual killifish are very similar regardless of geography.…”