Unimodal head-width distribution of the European eel ( Anguilla anguilla L.) from the Zeeschelde does not support disruptive selection

PeerJ

article

Pieterjan Verhelst¹  Jens De Meyer⁵  Jan Reubens⁴  Johan Coeck²  Peter Goethals³  Tom Moens¹  Ans Mouton² 

[1] Marine Biology Research Group, Ghent University;Research Institute for Nature and Forest;Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent University;Flanders Marine Institute;Evolutionary Morphology of Vertebrates, Ghent University

关键词: Maturation stages;    Head dimorphism;    Telemetry;    Speed;    Disruptive selection;    Condition;    European eel;    Unimodality;    Bimodality;   

DOI  :  10.7717/peerj.5773

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Since the early 20th century, European eels (Anguilla anguilla L.) have been dichotomously classified into ‘narrow’ and ‘broad’ heads. These morphs are mainly considered the result of a differential food choice, with narrow heads feeding primarily on small/soft prey and broad heads on large/hard prey. Yet, such a classification implies that head-width variation follows a bimodal distribution, leading to the assumption of disruptive selection. We investigated the head morphology of 272 eels, caught over three consecutive years (2015–2017) at a single location in the Zeeschelde (Belgium). Based on our results, BIC favored a unimodal distribution, while AIC provided equal support for a unimodal and a bimodal distribution. Notably, visualization of the distributions revealed a strong overlap between the two normal distributions under the bimodal model, likely explaining the ambiguity under AIC. Consequently, it is more likely that head-width variation followed a unimodal distribution, indicating there are no disruptive selection pressures for bimodality in the Zeeschelde. As such, eels could not be divided in two distinct head-width groups. Instead, their head widths showed a continuum of narrow to broad with a normal distribution. This pattern was consistent across all maturation stages studied here.

【 授权许可】

CC BY