Abstract
Organisms respond to climate change in many different ways and their local extinction risk may vary widely among taxa. Crustaceans from freshwater temporary ponds produce resting eggs to cope with environmental uncertainty and, as a consequence, egg banks have a fundamental role for population persistence. The egg bank dynamics of six clonal lineages of Heterocypris incongruens (Ostracoda) from Northern Italy were simulated. Clonal lineages W1 and W2 are the most common “winter ecotypes”, clonal lineages S1 and S2 are allochthonous “summer ecotypes” and clonal lineages I1 and I2 are relatively rare and generalist in terms of seasonality. Fecundity and proportion of resting eggs vary by clonal lineage, temperature and photoperiod. The clonal extinction risk was estimated in present climate conditions and under climate change. For comparison, and to assess the potential colonization of northern ponds, clonal lineages from Lampedusa Island (Southern Italy), L, were considered. Cohen’s general model was used for simulating egg bank dynamics and the extinction rate of each clonal lineage was estimated with uncertainty analysis. A 30 year simulation in present and climate change conditions was carried out. Extinction rates were lower in climate change conditions than in present conditions. Hydroperiod, hatching rate and egg deterioration rate were the critical factors that affected extinction rates. Extinction rates varied among clonal lineages. This suggests that H. incongruens might be able to have multiple responses to climate change due to its genetic diversity. In climate change conditions, W clonal lineages underwent a niche expansion, while a mismatch between photoperiod and hydroperiod might generate a detrimental effect on the phenology of summer S clonal lineages that might cause their extinction. Southern clonal lineages L, showing an intermediate extinction rate, might colonize northern temporary ponds.
Highlights
Climate change may be an important threat to global biodiversity, but the extent of species loss will depend on the details of how species respond to changing climates and predicting how species will respond may be very difficult
To obtain the probability of extinction and viability of the egg bank, Latin Hypercube Sampling (LHS) [58] was performed 1000 times, assuming the estimated prior distribution for each factor (Table S2). The results made it possible to quantify the extinction rate of each clone under 2 climate conditions (R script S1 in Regionalized sensitivity analysis (RSA) was performed to evaluate the rank of each factor (H, P, Y and D) in determining the extinction or viability of the egg bank
In climate change conditions, extinction rates should decline for all different clonal lineages and the extinction risk may vary widely depending on both genetic and ecological diversity
Summary
Climate change may be an important threat to global biodiversity, but the extent of species loss will depend on the details of how species respond to changing climates and predicting how species will respond may be very difficult. The partial hatching from the egg bank during each new inundation is part of a bet-hedging strategy that buffers environmental fluctuations, preventing demographic catastrophes when the hatchlings are unable to complete their life cycle and produce new resting eggs [27,28,29,30] Environmental cues, such as temperature and photoperiod, as well as maternal effects, may act as signals of a suitable environment that allow synchronizing hydroperiod and life cycle, and reduce extinction risk. We used the general model proposed by Cohen [22] to simulate egg bank dynamics of H. incongruens in vernal temporary ponds on Lampedusa Island (Southern Italy) [46]. The simulated egg bank dynamics of six different clonal lineages of H. incongruens from Northern Italy, in present climate conditions and in future climate change conditions, are reported. Uncertainty, regionalized sensitivity (RSA) and global sensitivity analysis (GSA) were carried out to evaluate the model in terms of output uncertainty, interaction terms and importance of factors for the model output [47,48,49,50]
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