Wang Chun-Chieh, Rogers D Christopher
Marine Biology Institute, Shantou University, 243 Daxue Road, Shantou, 515063, Guangdong Province, China.
Kansas Biological Survey, The Biodiversity Institute, Kansas University, Higuchi Hall, 2101 Constant Avenue, Lawrence, KS, 66047-3759, USA.
Oecologia. 2018 Dec;188(4):1081-1093. doi: 10.1007/s00442-018-4272-6. Epub 2018 Oct 23.
Organisms evolve to maintain fitness across generations, while short-term fitness in stochastic habitats such as temporary wetlands may be highly varied. As typical temporary wetland inhabitants, large branchiopods rely on bet hedging hatching that helps them survive throughout generations. An optimal hatching rate is predicted to be approximate to the successful reproduction probability (SRP). We tested the difference between hatching rate and SRP of large branchiopods Branchinella kugenumaensis and Eulimnadia braueriana in a temporary wetland in Taiwan, through field surveys and climatic records to evaluate their SRP. Comparisons were performed under two proposed scenarios, where a population's hatching was bet hedged for a hydroperiod or for a wet season (with several hydroperiods), respectively. Population size fluctuations were simulated for these two scenarios under assumed egg mortalities and reproductive replenishments. Results showed that the hatching rates only fitted to SRP for E. braueriana under the scenario of bet hedging on a wet season, not for B. kugenumaensis, nor for both species under the scenario of bet hedging on a hydroperiod. Bet hedging on a wet season would have a smaller range of population size fluctuation and a lower rate of population size decrease. This implies that large branchiopods adopt a conservative hatching strategy, lowering the hatching fraction in each hydroperiod to reduce long-term egg bank size fluctuation. Bet hedging strategies could occur during other life cycle stages, coexist with other life history strategies, and lead to the diversified hatching fraction distribution rather than a single, optimal fraction throughout hydroperiods.
生物进化以维持世代间的适应性，而在诸如临时湿地等随机栖息地中的短期适应性可能差异很大。作为典型的临时湿地居民，大型鳃足类动物依靠风险分摊孵化，这有助于它们世代生存。预计最佳孵化率接近成功繁殖概率（SRP）。我们通过实地调查和气候记录，测试了台湾一个临时湿地中大型鳃足类动物库氏鳃足虫和布氏真仙女虫的孵化率与SRP之间的差异，以评估它们的SRP。在两种假设情景下进行了比较，在这两种情景中，种群的孵化分别针对一个水文周期或一个湿季（包含几个水文周期）进行风险分摊。在假定的卵死亡率和繁殖补充情况下，对这两种情景下的种群大小波动进行了模拟。结果表明，仅在针对湿季进行风险分摊的情景下，布氏真仙女虫的孵化率才符合SRP，库氏鳃足虫不符合，在针对水文周期进行风险分摊的情景下，两种物种均不符合。针对湿季进行风险分摊会使种群大小波动范围更小，种群大小下降速率更低。这意味着大型鳃足类动物采取保守的孵化策略，降低每个水文周期的孵化比例，以减少长期卵库大小的波动。风险分摊策略可能在其他生命周期阶段出现，与其他生活史策略共存，并导致孵化比例分布多样化，而不是在整个水文周期内保持单一的最佳比例。
