Data from: Evolution of complex asexual reproductive strategies in jellyfish

Many living organisms in terrestrial and aquatic ecosystems rely on multiple reproductive strategies to reduce the risks of extinction in variable environments. Examples are provided by the polyp stage of several bloom-forming jellyfish species, which can reproduce asexually using different "budding" strategies. These strategies broadly fall into three categories: 1) fast localized reproduction, 2) dormant cysts, or 3) motile and dispersing buds. Similar functional strategies are also present in other groups of species. However, mechanisms leading to the evolution of this rich reproductive diversity are yet to be clarified. Here we propose an evolutionary model for jellyfish polyps and determine how local population extinction and unequal fitness of the three modes can drive the evolution of multiple reproductive strategies. Depending on environmental parameters, we find that evolution leads to a unique evolutionary stable strategy, where in general multiple reproductive modes coexist. As the extinction risk increases, this strategy shifts from a pure budding mode to a dual strategy, and finally to one characterized by allocation into all three modes. We determine the existence of relative fitness-dependent thresholds in extinction risk where these transitions can occur and discuss our predictions in light of observations on polyp reproduction in laboratory and natural systems.陆地与水生生态系统中的诸多生物，均会依托多种繁殖策略以降低多变环境下的灭绝风险。例如多种水华型水母物种的水螅体（polyp）阶段，便可通过不同的“出芽”（budding）策略进行无性繁殖。此类繁殖策略大致可分为三类：1）快速局域繁殖；2）休眠孢囊（cyst）；3）可移动且具备扩散能力的出芽体。其他物种类群中也存在类似的功能性繁殖策略。然而，催生这类丰富繁殖多样性的演化机制尚未阐明。本研究针对水母水螅体构建了一套演化模型，旨在明确局域种群灭绝与三种繁殖模式的适合度（fitness）差异，如何驱动多种繁殖策略的演化。研究发现，依据环境参数的不同，演化会导向唯一的演化稳定策略：通常情况下多种繁殖模式会共存。随着灭绝风险升高，该策略会从单一的出芽模式逐步转向双模式策略，最终演变为同时分配至三类繁殖模式的策略。本研究确定了依赖相对适合度的灭绝风险阈值区间，该区间可触发上述策略转变，并结合实验室与自然系统中关于水螅体繁殖的观测结果，对本研究的预测展开讨论。