Data from: Spatial patterns of the frog Oophaga pumilio in a plantation system are consistent with conspecific attraction

The conspecific attraction hypothesis predicts that individuals are attracted to conspecifics because conspecifics may be cues to quality habitat and/or colonists may benefit from living in aggregations. Poison frogs (Dendrobatidae) are aposematic, territorial, and visually oriented – three characteristics which make dendrobatids an appropriate model to test for conspecific attraction. In this study, we tested this hypothesis using an extensive mark-recapture dataset of the strawberry poison frog (Oophaga pumilio) from La Selva Biological Station, Costa Rica. Data were collected from replicate populations in a relatively homogenous Theobroma cacao plantation, which provided a unique opportunity to test how conspecifics influence spatial ecology of migrants in a controlled habitat with homogeneous structure. We predicted that (1) individuals entering a population would aggregate with resident adults, (2) migrants would share sites with residents at greater frequency than expected by chance, and (3) migrant home-ranges would have shorter nearest-neighbor distances (NND) to residents than expected by chance. The results were consistent with these three predictions: relative to random simulations, we observed significant aggregation, home-range overlap, and NND distribution functions in four, five, and six, respectively, of the six migrant-resident groups analyzed. Conspecific attraction may benefit migrant O. pumilio by providing cues to suitable home sites and/or increasing potential for social interactions with conspecifics; if true, these benefits should outweigh the negative effects of other factors associated with aggregation. The observed aggregation between migrant and resident O. pumilio is consistent with conspecific attraction in dendrobatid frogs, and our study provides rare support from a field setting that conspecific attraction may be a relevant mechanism for models of anuran spatial ecology.

同种吸引假说（Conspecific Attraction Hypothesis）预测，个体之所以会被同种个体吸引，是因为同种个体可作为优质栖息地的指示线索，且/或集群生活的拓殖者可从中获益。箭毒蛙科（Dendrobatidae）蛙类兼具警戒色、领地性与视觉依赖性三大特征，使其成为检验同种吸引效应的理想模式类群。本研究以哥斯达黎加拉塞尔瓦生物站的草莓箭毒蛙（Oophaga pumilio）为研究对象，基于其大范围标记重捕（mark-recapture）数据集对该假说展开验证。研究数据采自相对均质的可可（Theobroma cacao）种植园中的多个重复种群，这为我们在结构均一的可控生境中检验同种个体如何影响拓殖者的空间生态特征提供了独特契机。我们提出三项预测：1）迁入种群的个体将与居留成体集群；2）拓殖者与居留个体共享微生境的频率将显著高于随机概率；3）拓殖者的家域与居留个体的最近邻距离（Nearest-Neighbor Distance, NND）将小于随机预期值。研究结果与三项预测均相符：相较于随机模拟结果，在6个分析的拓殖者-居留者组中，分别有4组、5组和6组呈现出显著的集群效应、家域重叠以及符合预期的最近邻距离分布特征。同种吸引可通过为草莓箭毒蛙拓殖者提供适宜生境的指示线索，以及/或者提升其与同种个体进行社会互动的概率，使其获益；若该效应成立，这些益处应超过集群相关的其他负面因素带来的代价。本研究观测到的草莓箭毒蛙拓殖者与居留个体间的集群现象，与箭毒蛙科蛙类存在同种吸引效应的结论相符，同时本研究从野外场景中提供了罕见的实证支持，表明同种吸引或许是无尾两栖类空间生态模型中的关键作用机制。