The Legacy of Ecosystem Effects Caused by Adaptive Radiation
There is increasing evidence that closely related species have contrasting ecosystem effects, but very little is known about the temporal scale of these effects. When organisms' ecosystem-effects persist beyond or emerge after their presence in the ecosystem, this might increase the potential for eco-evolutionary feedbacks to accompany evolutionary diversification. Here we studied lab-raised whitefish of a benthic-limnetic species pair from a postglacial adaptive radiation to test whether closely related species have contrasting effects on mesocosm ecosystems (hereafter ecosystem effects). We found that the presence of whitefish (ecological effect) had strong effects on some ecosystem components, for example by reducing snail and mussel abundance and increasing phytoplankton abundance. Whitefish species had contrasting effects (evolutionary effect) on benthic algal cover, dissolved organic carbon, and zooplankton community composition, but these effects only emerged several months after whitefish were removed from the ecosystem. The effects of plasticity and the interactive effects of species and plasticity were relatively weak and, with one exception, not significant. Ecological and evolutionary effect sizes were uncorrelated over both phases of the experiment, as were effect sizes between phases for both ecological and evolutionary contrasts. Overall, our results suggest that adaptive radiation can have effects on the structure and functioning of ecosystems, but that the temporal dynamics and mechanistic basis of these effects are insufficiently understood.
Variation in ecosystem metrics (Table 1) among treatments for both phases of the experiment. Each dot is a mesocosm, and the five treatment combinations are Benthic whitefish raised on either benthic (BB) or limnetic (BL) food, Limnetic whitefish reared on either benthic (LB) or limnetic food (LL), and no fish (NF). In phase 1, the effect of fish presence/absence was significant (squares vs. stars and circles), and in phase 2, the species effect was significant (stars vs. circles) and the effect of fish presence/absence was marginally significant (P = 0.05).
Variation in zooplankton species composition among treatments for both phases of the experiment, with the same treatment combinations as in Figure 1. In phase 1 (Panel A), there was only a strong effect of fish presence/absence (squares vs. stars and circles), and in phase 2 (Panel B), none of the contrasts were significant.
Comparison of effect sizes between (A) the presence/absence of whitefish (Ecological effect) versus the species of whitefish (Evolutionary effect), and between (B) ecosystem metrics from phase 1 and phase 2. Metrics with significant differences for either contrast are labeled with codes found in Table 1.
Contributor Notes
Associate Editor: A. Hendry.
From “Eco-Evolutionary Dynamics in Cold Blood,” an ASIH-sponsored symposium at the 2016 Joint Meeting of Ichthyologists and Herpetologists in New Orleans, Louisiana.