Microgeographic adaptation to toxic cyanobacteria in two aquatic grazers

Abstract

The hypothesis that zooplankton display local adaptations to toxic cyanobacteria was tested by investigating the performance of 24 clones from six populations of the large-bodied Daphnia pulex and 13 clones from four populations of the small-bodied Chydorus sphaericus. They were fed a pure nutritious green alga Chlorella pyrenoidosa (good food) and a mixed diet with a toxic cyanobacterium Microcystis aeruginosa (poor food). The grazer performances feeding on the poor food significantly differed among their populations over a small geographic scale (7-10 km for D. pulex and 15-20 km for C. sphaericus). Both the absolute tolerance (performance on poor food) and relative tolerance (performance on poor food relative to good food) to toxic M. aeruginosa were enhanced with increasing microcystin concentrations in the sediments and finally reached the maximum values. Additionally, the significant food 3 clone interactions indicated that phenotypic plasticity in response to toxic cyanobacteria had a genetic basis in two grazers. The significant food 3 population interactions and correlations between growth plasticity and microcystin concentrations indicated that this phenotypic plasticity evolved across grazer populations. The reduced plasticity was evidenced by both the reduced slope of reaction norms and the enhanced mean performance for both diets. D. pulex had more evolutionary potential for the reduced plasticity than C. sphaericus. These results suggest that zooplankton populations developed evolutionary tolerance to toxic cyanobacteria on a microgeographic level.

Transcriptomic analysis dissects the mechanistic insight into the Daphnia clonal variation in tolerance to toxic Microcystis

“…On the other hand, zooplankton often exist mutually with harmful algal blooms (HABs), suggesting that they have multiple abilities to behaviorally reduce the ingestion of hazardous doses and to be physiologically tolerant to the ingested toxin. In line with the previous studies (Hietala et al ; Chislock et al ; Jiang et al , ), the present population‐level results clearly showed clonal variation in Daphnia fitness in response to toxic Microcystis . Of note, the clones were cultured individually under identical conditions.…”

Cyanobacteria facilitate parasite epidemics in Daphnia

“…) and for Daphnia pulex from small Chinese ponds and rivers with different trophic states (Jiang et al. ). However, cyanobacteria tolerance is costly and might be associated with tradeoffs such as being more vulnerable to starvation for more tolerant individuals (Hairston et al.…”

Increasing dominance of small zooplankton with toxic cyanobacteria

“…The green alga Chlorella pyrenoidosa (Chlorellaceae) (FACHB-15) and the microcystin-producing cyanobacterium Microcystis aeruginosa (Microcystaceae) (FACHB-905) were obtained from the Freshwater Algae Culture Collection at the Institute of Hydrobiology (FACHB-collection), the Chinese Academy of Sciences. The FACHB-905 strain produces microcystin-LR and microcystin-RR at a total concentration of 24 fg cell À1 (Jiang et al, 2015). The cultures were grown in BG-11 medium at 25°C under fluorescent light at 50 lmol m À2 s À1 on a 12:12 light:dark cycle.…”

“…Total microcystin concentration was measured with an enzyme linked immunosorbent assay (ELISA). The detailed ELISA protocol has been described in our previous study (Jiang et al, 2015).…”