Data from: Coupled range dynamics of brood parasites and their hosts responding to climate and vegetation changes

As populations shift their ranges in response to global change, local species assemblages can change, setting the stage for new ecological interactions, community equilibria, and evolutionary responses. Here we focus on the range dynamics of four avian brood parasite species and their hosts in southern Africa, in a context of bush encroachment (increase in woody vegetation density in places previously occupied by savanna-grassland mosaics) favouring some species at the expense of others. We first tested whether hosts and parasites constrained each other's ability to expand or maintain their ranges. Second, we investigated whether range shifts represented an opportunity for new host-parasite and parasite-parasite interactions.
We used multi-species dynamic occupancy models with interactions, fitted to citizen-science data, to estimate the contribution of interspecific interactions to range shifts and to quantify the change in species co-occurrence probability over a 25-year period. Parasites were able to track their hosts’ range shifts. We detected no deleterious effect of the parasites’ presence on either the local population viability of host species or the hosts’ ability to colonize newly suitable areas. In the recently diversified indigobird radiation (Vidua spp.), following bush encroachment, the new assemblages presented more potential opportunities for speciation via host switch, but also more potential for hybridization between extant lineages, also via host switch. Multi-species dynamic occupancy models with interactions brought new insights into the feedbacks between range shifts, biotic interactions, and local demography: brood parasitism had little detected impact on extinction or colonization processes, but inversely the latter processes affected biotic interactions via the modification of co-occurrence patterns.

当种群为响应全球变化而改变分布范围时，局域物种组合会发生改变，为新型生态相互作用、群落平衡以及演化响应奠定了基础。本研究聚焦于南非地区4种鸟类巢寄生物种及其宿主的分布动态，研究背景为灌丛扩张——即原本为稀树草原-草地镶嵌体的区域内木本植被密度增加——该过程有利于部分物种，却以其他物种为代价。首先，我们检验了宿主与巢寄生者是否会相互限制对方扩张或维持分布范围的能力；其次，我们探究了分布范围的转移是否为新型宿主-寄生者以及寄生者-寄生者相互作用提供了契机。

我们采用带有相互作用项的多物种动态占据模型（multi-species dynamic occupancy models），拟合公民科学观测数据，以估算种间相互作用对分布范围转移的贡献，并量化25年间物种共存概率的变化。研究发现，巢寄生鸟类能够追踪宿主的分布范围转移。我们未检测到寄生者的存在对宿主物种的局域种群存续能力，或是宿主开拓新适宜生境的能力产生任何有害影响。在近期发生辐射演化的维达雀属（Vidua spp.）类群中，灌丛扩张后形成的新物种类群不仅通过宿主转换为物种形成提供了更多潜在可能，同时也通过宿主转换为现存支系间的杂交创造了更多契机。

带有相互作用项的多物种动态占据模型为分布范围转移、生物相互作用与局域种群动态间的反馈机制提供了新的认知：育雏寄生现象对物种灭绝或拓殖过程的可检测影响极微，反之，后者（灭绝与拓殖过程）则通过改变物种共存模式对生物相互作用产生影响。