Barneche DR, Burgess SC, and Marshall DJ. Global environmental drivers of marine fish egg size. Global Ecology and Biogeography. (accepted)
Aim: To test long standing theory on the role of environmental conditions (both mean and predictability) in shaping global patterns in the egg sizes of marine fishes.
Location: Global (50˚ S to 50˚ N).
Time period: 1880 to 2015.
Major taxa studied: Marine fish.
Methods: We compiled the largest geo-located dataset of marine fish egg size (diameter) to date (n = 1,078 observations; 192 studies; 288 species; 242 localities). We decomposed sea surface temperature (SST) and chlorophyll-a time-series into mean and predictability (seasonality and colour of environmental noise – i.e. how predictable the environment is between consecutive time steps), and used these as predictors of egg size in a Bayesian phylogenetic hierarchical model. We test four specific hypotheses based on the classic discussion by Rass (1941), as well as contemporary life-history theory, and the conceptual model of Winemiller & Rose (1992).
Results: Both environmental mean and predictability correlated with egg size. Our parsimonious model indicated that egg size decreases by c. 2.0-fold moving from 1˚C to 30˚C. Environments that were more seasonal with respect to temperature were associated with larger eggs. Increasing mean chlorophyll-a, from 0.1 to 1 mg m-3, was associated with a c. 1.3-fold decrease in egg size. Lower chlorophyll-a seasonality and reddened noise were also associated with larger egg sizes – aseasonal but more temporally autocorrelated resource regimes favoured larger eggs.
Main conclusions: Our findings support results from Rass (1941) and some predictions from Winemiller & Rose (1992). The effects of environmental means and predictability on marine fish egg size are largely consistent with those observed in marine invertebrates with feeding larvae, suggesting important.