New publication: Fine‐scale population differences in Atlantic cod reproductive success: A potential mechanism for ecological speciation in a marine fish

By Nancy E. Roney, Rebekah A. Oomen*, Halvor Knutsen*, Esben M. Olsen, and Jeffrey A. Hutchings* in Ecology and Evolution


Successful resource‐management and conservation outcomes ideally depend on
matching the spatial scales of population demography, local adaptation, and threat
mitigation. For marine fish with high dispersal capabilities, this remains a fundamental
challenge. Based on daily parentage assignments of more than 4,000 offspring,
we document fine‐scaled temporal differences in individual reproductive success for
two spatially adjacent (<10 km) populations of a broadcast‐spawning marine fish.
Distinguished by differences in genetics and life history, Atlantic cod (Gadus morhua)
from inner‐ and outer‐fjord populations were allowed to compete for mating and reproductive
opportunities. After accounting for phenotypic variability in several traits,
reproductive success of outer‐fjord cod was significantly lower than that of innerfjord
cod. This finding, given that genomically different cod ecotypes inhabit innerand
outer‐fjord waters, raises the intriguing hypothesis that the populations might be
diverging because of ecological speciation. Individual reproductive success, skewed
within both sexes (more so among males), was positively affected by body size, which
also influenced the timing of reproduction, larger individuals spawning later among
females but earlier among males. Our work suggests that spatial mismatches between
management and biological units exist in marine fishes and that studies of reproductive
interactions between putative populations or ecotypes can provide an
informative basis on which determination of the scale of local adaptation can be

First published: 31 October 2018
Publication webpage.

Tags: Ecology and Evolution;
Published Nov. 7, 2018 1:51 PM - Last modified Nov. 7, 2018 1:54 PM