Data from: Evidence for general size-by-habitat rules in actinopterygian fishes across nine scales of observation

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
32000+ species, fulfil these criteria for the fundamental habitat
divisions in water. With four datasets of body size (ranging 10905–27226
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.