DOI: 10.5061/dryad.67c7q
title: Data from: Eco-evolution in size-structured ecosystems: simulation case study of rapid morphological changes in alewife

description: Background: Over the last 300 years, interactions between alewives and
 zooplankton communities in several lakes in the U.S. have caused the
 alewives’ morphology to transition rapidly from anadromous to landlocked.
 Lakes with landlocked alewives contain smaller-bodied zooplankton than
 those without alewives. Landlocked adult alewives display smaller body
 sizes, narrower gapes, smaller inter-gill-raker spacings, reach maturity
 at an earlier age, and are less fecund than anadromous alewives.
 Additionally, landlocked alewives consume pelagic prey exclusively
 throughout their lives whereas anadromous alewives make an ontogenetic
 transition from pelagic to littoral prey. These rapid, well-documented
 changes in the alewives’ morphology provide important insights into the
 morphological evolution of fish. Predicting the morphological evolution of
 fish is crucial for fisheries and ecosystem management, but the
 involvement of multiple trophic interactions make predictions difficult.
 To obtain an improved understanding of rapid morphological change in fish,
 we developed an individual-based model that simulated rapid changes in the
 body size and gill-raker count of a fish species in a hypothetical,
 size-structured prey community. Model parameter values were based mainly
 on data from empirical studies on alewives. We adopted a functional trait
 approach; consequently, the model explicitly describes the relationships
 between prey body size, alewife body size, and alewife gill-raker count.
 We sought to answer two questions: (1) How does the impact of alewife
 populations on prey feed back to impact alewife size and gill raker number
 under several alternative scenarios? (2) Will the trajectory of the
 landlocked alewives’ morphological evolution change after 150–300 years in
 freshwater? Results: Over the first 250 years, the alewives’ numbers of
 gill-rakers only increased when reductions in their body size
 substantially improved their ability to forage for small prey.
 Additionally, alewives’ gill-raker counts increased more rapidly as the
 adverse effects of narrow gill-raker spacings on foraging for large prey
 were made less severe. For the first 150–250 years, alewives’ growth
 decreased monotonically, and their gill-raker number increased
 monotonically. After the first 150–250 years, however, the alewives
 exhibited multiple evolutionary morphological trajectories in different
 trophic settings. In several of these settings, their evolutionary
 trajectories even reversed after the first 150–250 years. Conclusions:
 Alewives affected the abundance and morphology of their prey, which in
 turn changed the abundance and morphology of the alewives. Complex
 low-trophic-level interactions can alter the abundance and characteristics
 of alewives. This study suggests that the current morphology of recently
 (∼300 years)-landlocked alewives may not represent an evolutionarily
 stable state.
description: Alewife Model
 CodeComputer code used to
 generate this paperalewifeModel_Code.tar.gzSimul_FoodWeb.tarDirectory structure with all parameter files to re-generate the data used for this study. You can thus generate the data for a subset of the parameter space, or the entire data set.