Evolution in Sinocyclocheilus cavefish is marked by rate shifts, reversals, and origin of novel traits


SOCIETY FOR INTEGRATIVE AND COMPARATIVE BIOLOGY
2021 VIRTUAL ANNUAL MEETING (VAM)
January 3 – Febuary 28, 2021

Meeting Abstract


2-4  Sat Jan 2  Evolution in Sinocyclocheilus cavefish is marked by rate shifts, reversals, and origin of novel traits Mao, TR; Liu, YW; Meegaskumbura, M*; Ellepola, G; Fu, CH; Gross, JB; Pie, MR; Guangxi University; University of Cincinnati; Universidade Federal do Paraná madhava_m@mac.com http://www.ecoevodevo.org

Sinocyclocheilus of China, the most diverse cavefish clade in the world (75 species), provide unique opportunities to understand recurrent evolution of stereotypic traits. However, they remain poorly understood in terms of morphological evolution. We constructed phylogenies and categorized 49 species based on eye-related condition (Blind, Micro-eyed, and Normal-eyed), habitat types (Troglobitic – cave-restricted; Troglophilic – cave-associated; Surface – outside caves) and existence of horns. Geometric-morphometric analyses show Normal-eyed morphs with fusiform shapes segregating from Blind/Micro-eyed deeper bodied morphs (1st PC axis); 2nd PC axis accounts for shape complexity related to horns. Ancestral reconstructions suggest at least three independent origins of Blind morphs, each with different levels of modification in relation to their ancestral Normal-eyed morphs; Sinocyclocheilus are also pre-adapted for cave dwelling. A geophylogeny shows an east-to-west diversification spanning Pliocene and Pleistocene, with Troglobitic species dominating karstic plains and Surface forms inhabiting western hills. Evolutionary rates analyses suggest that lineages leading to Blind morphs were characterized by significant rate shifts, such as a slowdown in body size evolution and a 3-12 fold increase in rate of eye regression, possibly explained by limited resource availability. Body size and eye size have undergone reversals, but not horns, a trait entailing considerable time to form.

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