Island- and lake-like parallel adaptive radiations replicated in rivers

Area of Science:

• Evolutionary Biology
• Ecology
• Ichthyology

Background:

• Parallel adaptive radiation is well-documented in island lizards and lake fishes.
• It arises from ecological opportunities in novel ecosystems and similar adaptive landscapes.
• This leads to similar ecomorphs despite independent evolutionary histories.

Purpose of the Study:

• To investigate parallel adaptive radiations in South American riverine cichlid fishes.
• To determine if similar evolutionary patterns observed in islands and lakes also occur in rivers.
• To examine the diversification of pike cichlids (Crenicichla) in the Uruguay and Paraná Rivers.

Main Methods:

• Comparative analysis of cichlid fish communities.
• Examination of speciation patterns and ecomorph evolution.
• Analysis of phenotypic evolution and morphospace expansion.

Main Results:

• Pike cichlids (Crenicichla) independently diversified into similar ecomorphs in the Uruguay and Paraná Rivers.
• Ecomorphs include crevice feeders, periphyton grazers, and molluscivores.
• Bursts of phenotypic evolution were associated with river colonization and morphospace expansion.

Conclusions:

• Parallel adaptive radiations are feasible in labile riverine ecosystems, not just islands and lakes.
• Riverine cichlid radiations exhibit characteristics typical of classic parallel adaptive radiations.
• This expands our understanding of evolutionary processes in diverse environments.