Evidence for general size‐by‐habitat rules in actinopterygian fishes across nine scales of observation. (10th June 2021)

• Record Type: Journal Article
• Authors: Clarke, John T.
• Editors: Mouillot, David
• Is Part Of: Ecology letters. Volume 24:Number 8(2021)
• Page Start: 1569
• Page End: 1581
• Publication Date: 2021-06-10
• Subjects: size evolution -- actinopterygian fishes -- marine -- freshwater -- phenotypic evolution; Ecology -- Periodicals; 577
• DOI: 10.1111/ele.13768
• Languages: English
• ISSNs: 1461-023X

Abstract

Abstract: Identifying environmental predictors of phenotype is fundamentally important to many ecological questions, from revealing broadscale ecological processes to predicting extinction risk. However, establishing robust environment—phenotype relationships is challenging, as powerful case studies require diverse clades which repeatedly undergo environmental transitions at multiple taxonomic scales. Actinopterygian fishes, with 32, 000+ species, fulfil these criteria for the fundamental habitat divisions in water. With four datasets of body size (ranging 10, 905–27, 226 species), I reveal highly consistent size‐by‐habitat‐use patterns across nine scales of observation. Taxa in marine, marine‐brackish, euryhaline and freshwater‐brackish habitats possess larger mean sizes than freshwater relatives, and the largest mean sizes consistently emerge within marine‐brackish and euryhaline taxa. These findings align with the predictions of seven mechanisms thought to drive larger size by promoting additional trophic levels. However, mismatches between size and trophic‐level patterns highlight a role for additional mechanisms, and support for viable candidates is examined in 3439 comparisons. Abstract : Establishing environmental predictors of body size is of fundamental importance to ecology. With data from over 27, 000 species of fishes, I establish general size rules between the major aquatic habitat types, revealing that various marine‐influenced environments contain larger taxa than those in freshwaters. The findings align with the predictions of seven mechanisms thought to drive larger size by promoting additional trophic levels, yet I demonstrate a need for additional mechanisms, and support for viable candidates is examined in 3439 comparisons.