Hierarchical structure of ecological and non-ecological processes of differentiation shaped ongoing gastropod radiation in the Malawi Basin

Abstract

Ecological processes, non-ecological processes or a combination of both may cause reproductive isolation and speciation, but their specific roles and potentially complex interactions in evolutionary radiations remain poorly understood, which defines a central knowledge gap at the interface of microevolution and macroevolution. Here I examine genome scans in combination with phenotypic and environmental data to disentangle how ecological and non-ecological processes contributed to population differentiation and speciation in an ongoing radiation of gastropods from the Malawi Basin. I found a remarkable hierarchical structure of differentiation mechanisms in space and time: neutral and mutation-order processes are older and occur mainly between regions, whereas more recent adaptive processes are the main driver of genetic differentiation and reproductive isolation within regions. The strongest differentiation occurs between habitats and between regions, i.e. when ecological and non-ecological processes act synergistically. The structured occurrence of these processes based on the specific geographical setting and ecological opportunities strongly influenced the potential for evolutionary radiation. The results highlight the importance of interactions between various mechanisms of differentiation in evolutionary radiations, and suggest that non-ecological processes are important in adaptive radiations, including those of cichlids. Insight into such interactions is critical to understanding large-scale patterns of organismal diversity.

Evolution of population structure in an estuarine‐dependent marine fish

“…Basic habitat differences, initiated by glacial retreat and perpetuated by contemporary oceanic and atmospheric forces interacting with the geomorphology of the northeastern Gulf basin, followed by selection, appear to have led to reduced gene flow across the region, reinforcing accrued differences and resulting in continued genomewide divergence. This process, termed isolation by adaptation or IBA (Nosil, Egan, & Funk, ), has been observed in animal and plant species (Van Bocxlaer, ; Funk, Egan, & Nosil, ; Mallet, Martos, Blambert, Martos, Blambert, Pailler, & Humeau, ) and, potentially, is a harbinger of incipient speciation (Schemske, ). The same dynamic may pertain to other coastal or nearshore fishes (18 species in 14 families) where genetically or morphologically defined sister taxa (species, subspecies, populations) occur in the three regions (Supplemental Table ; Portnoy & Gold, ).…”

Role of ancient lakes in genetic and phenotypic diversification of freshwater snails

“…Various evolutionary phenomena such as adaptive radiation, parallel evolution, and hybrid speciation have been documented in some ancient lakes (e.g., Seehausen, ; Sturmbauer & Meyer, ). In these circumstances, mollusks are an excellent model to compare the relationships among morphology, phylogeny, and geographical distribution patterns (Glaubrecht, ; Miura, Urabe, Nishimura, Nakai, & Chiba, ; von Rintelen, Wilson, Meyer, & Glaubrecht, ; Van Bocxlaer, ; Van Bocxlaer & Hunt, ). Because mollusks are less mobile they are more likely to become geographically isolated (Miura et al, ).…”

Recent lake expansion triggered the adaptive radiation of freshwater snails in the ancient Lake Biwa

“…The cichlids in the Great East African Lakes have caused a major development in models for adaptive radiation (Albertson et al 1999;Sturmbauer et al 2001;Kocher 2004;Seehausen 2006;Sturmbauer et al 2011). While these species flocks exhibit intralacustrine radiations and will certainly help in obtaining more information on evolutionary dynamics of species diversification, the intralacustrine radiations of endemic invertebrates such as mollusks may also have a great potential in contributing to our knowledge on species diversification (von Rintelen et al 2004;Albrecht et al 2006;Albrecht et al 2008;Glaubrecht 2008;Schultheiß et al 2009;Van Bocxlaer and Hunt 2013;Van Bocxlaer 2017). Because mollusks are less mobile, they are likely to become geographically isolated to a higher degree.…”