Data from: Metapopulation dynamics of species with cryptic life stages

Quantifying metapopulation dynamics is a challenging task. Difficulties particularly arise in species that possess unobservable resistance forms that bias the estimation of colonization and persistence rates. Here, we develop a general multistate occupancy model that allows estimation of species persistence for both normal and resistant forms, even when the latter are not detectable. We apply this model to an 11-year data set on the tropical freshwater snail Drepanotrema depressissimum in a network of 229 ponds. These ponds frequently dry out, and the snails can persist by aestivating in the ground, where they are not detected. Our model adequately captures this feature because it infers a high persistence rate for the resistant form, while models ignoring aestivation tend to overestimate extinction and colonization. In addition, we find that, surprisingly, colonization and persistence are even higher in sites prone to desiccation and during years with low rainfall than in more humid sites and years, suggesting that D. depressissimum favors unstable sites where competitors are rare and where it can rely on aestivation to persist. Our model has the potential to provide valuable insights into the metapopulation dynamics of many species that otherwise could hardly be studied because of the existence of undetectable life forms.

量化集合种群动态（metapopulation dynamics）是一项极具挑战性的任务。难点尤其体现在那些拥有不可观测抗性形态的物种上，这类形态会干扰定殖率与存续率的估算。在此，我们构建了一款通用的多状态占据模型（multistate occupancy model），即便抗性形态无法被检测到，该模型仍可估算物种在正常形态与抗性形态下的存续率。我们将此模型应用于一项为期11年的数据集，该数据集针对229个池塘构成的网络中的热带淡水螺光滑盘卷螺（Drepanotrema depressissimum）展开研究。这些池塘时常干涸，螺类可通过在土壤中夏蛰得以存续，而此时它们无法被观测到。本模型能够充分捕捉这一特征：其推断出的抗性形态存续率较高，而忽略夏蛰过程的模型往往会高估灭绝与定殖速率。此外，我们意外发现：相较于湿润生境与多雨年份，易干旱生境及少雨年份的定殖与存续速率反而更高，这表明光滑盘卷螺（Drepanotrema depressissimum）更偏好竞争物种稀少、且可依靠夏蛰存续的不稳定生境。本模型有望为诸多因存在不可观测生活史形态而难以开展研究的物种的集合种群动态研究提供宝贵见解。