A sterol-mediated gleaner–opportunist trade-off underlies the evolution of grazer resistance to cyanobacteria

Abstract

The human-caused proliferation of cyanobacteria severely impacts consumers in freshwater ecosystems. Toxicity is often singled out as the sole trait to which consumers can adapt, even though cyanobacteria are not necessarily toxic and the lack of nutritionally critical sterols in cyanobacteria is known to impair consumers. We studied the relative significance of toxicity and dietary sterol deficiency in driving the evolution of grazer resistance to cyanobacteria in a large lake with a well-documented history of eutrophication and oligotrophication. Resurrecting decades-old Daphnia genotypes from the sediment allowed us to show that the evolution and subsequent loss of grazer resistance to cyanobacteria involved an adaptation to changes in both toxicity and dietary sterol availability. The adaptation of Daphnia to changes in cyanobacteria abundance revealed a sterol-mediated gleaner–opportunist trade-off. Genotypes from peak-eutrophic periods showed a higher affinity for dietary sterols at the cost of a lower maximum growth rate, whereas genotypes from more oligotrophic periods showed a lower affinity for dietary sterols in favour of a higher maximum growth rate. Our data corroborate the significance of sterols as limiting nutrients in aquatic food webs and highlight the applicability of the gleaner–opportunist trade-off for reconstructing eco-evolutionary processes.

A test of the gleaner–opportunist trade‐off among photosynthetic traits in cryptophyte algae

“…We took a novel approach to evaluate the potential origin of this type of trade‐off through evolutionary diversification of the traits themselves by using phylogenetic comparative methods to control for the evolutionary history of our focal species. As we did not find a gleaner–opportunist trade‐off between photosynthetic traits, our work supports the view that this trade‐off may not be as widespread as previously assumed (Isanta‐Navarro et al, 2022; Litchman et al, 2007; Yamamichi & Letten, 2022).…”

A test of the gleaner-opportunist trade-off among photosynthetic traits in Cryptophyte algae

“…We took a novel approach to evaluate the potential origin of this type of trade-off through evolutionary diversification of the traits themselves by using phylogenetic comparative methods to control for the evolutionary history of our focal species. As we did not find a gleaner-opportunist trade-off between photosynthetic traits our work supports the view that this trade-off may not be as widespread as previously assumed (Litchman et al, 2007;Isanta-Navarro et al, 2022;Yamamichi & Letten, 2022).…”