Data from: Reciprocal intraguild predation and predator coexistence

1. Intraguild predation is a mix of competition and predation, and occurs when one species feeds on another species that uses similar resources. Theory predicts that intraguild predation hampers coexistence of species involved, but it is common in nature. It has been suggested that increasing habitat complexity and the presence of alternative food may promote coexistence. Reciprocal intraguild predation limits possibilities for coexistence even further. Habitat complexity and the presence of alternative food are believed to promote coexistence. 2. We investigated this using two species of predatory mites, Iphiseiodes zuluagai and Euseius concordis, by assessing co-occurrence in the field and on arenas differing in spatial structure in the laboratory. 3. The predators co-occured on the same plants in the field. In the laboratory, adults of the two mites fed on juveniles of the other species, both in the presence and the absence of a shared food source, showing that the two species are involved in reciprocal intraguild predation. Adults of I. zuluagai also attacked adults of E. concordis This suggests limited possibilities for coexistence of the two species. Indeed, E. concordis invariably went extinct extremely rapidly on arenas without spatial structure with populations consisting of all stages of the two predators and with a shared resource. Coexistence was prolonged on host plant leaves with extra food sources, but E. concordis still went extinct. On small, intact plants, coexistence of the two species was much longer, and ended with the other species, I. zuluagai, often going extinct. 4. These results suggest that spatial structure and the presence of alternative food increase the coexistence period of intraguild predators.

1. 集团内捕食（intraguild predation）是竞争与捕食的混合生态交互类型，指一种物种取食另一种利用相似资源的物种。理论预测，集团内捕食会阻碍所涉物种的共存，但该现象在自然界中却极为普遍。已有研究表明，生境复杂性提升与替代食物的存在或可促进物种共存；而双向集团内捕食则会进一步限制物种共存的可能性。此前观点认为，生境复杂性与替代食物的存在可助力物种共存。
2. 本研究以两种捕食螨——Iphiseiodes zuluagai与Euseius concordis为研究对象，通过野外调查其共现分布情况，并在实验室中利用空间结构不同的实验单元开展实验。
3. 野外调查显示，两种捕食螨可在同一植株上共现。实验室条件下，无论是否存在共享食物源，两种捕食螨的成体均会取食对方物种的幼体，证实二者存在双向集团内捕食；且I. zuluagai的成体还会攻击E. concordis的成体。这表明二者的共存空间十分有限。事实确实如此：在仅包含两种捕食螨各虫态且存在共享食物源、无空间结构的实验单元中，E. concordis始终会极快速地灭绝。在添加额外食物源的寄主植物叶片上，二者的共存时间得以延长，但E. concordis最终仍会灭绝。而在小型完整植株上，二者的共存时间显著更长，但最终通常以I. zuluagai灭绝告终。
4. 上述结果表明，空间结构与替代食物的存在，可延长集团内捕食者的共存时长。