Data from: Organismal responses to habitat change: herbivore performance, climate, and leaf traits in regenerating tropical dry forests

1. The ecological effects of large-scale climate change have received much attention, but the effects of the more acute form of climate change that results from local habitat alteration have been less explored. When forest is fragmented, cut, thinned, cleared or otherwise altered in structure, local climates and microclimates change. Such changes can affect herbivores both directly (e.g., through changes in body temperature) and indirectly (e.g., through changes in host plant traits). 2. We advance an eco-physiological framework to understand the effects of changing forests on herbivorous insects. We hypothesize that if tropical forest caterpillars are climate and resource specialists, then they should have reduced performance outside of mature forest conditions. 3. We tested this hypothesis with a field experiment contrasting the performance of Rothschildia lebeau (Saturniidae) caterpillars feeding on the host plant Casearia nitida (Salicaceae) in two different aged and structured tropical dry forests in Area de Conservación Guanacaste, Costa Rica. 4. Compared to more mature closed-canopy forest, in younger secondary forest we found that: (1) ambient conditions were hotter, drier, and more variable; (2) caterpillar growth and development were reduced; and (3) leaves were tougher, thicker, and drier. Further, caterpillar growth and survival were negatively correlated with these leaf traits, suggesting indirect host-mediated effects of climate on herbivores. 5. Based on the available evidence, and relative to mature forest, we conclude that reduced herbivore performance in young secondary forest could have been driven by changes in climate, leaf traits (which were likely climate induced), or both. However, additional studies will be needed to provide more direct evidence of cause-and-effect and to disentangle the relative influence of these factors on herbivore performance in this system.

1. 大规模气候变化的生态效应已受到广泛关注，但由局部生境改变引发的更为剧烈的气候变化类型，其影响却较少被探究。当森林发生片段化、砍伐、疏伐、清理或其他结构改变时，局地气候与微气候会发生变化。此类变化可通过直接途径（如体温改变）与间接途径（如宿主植物性状改变）对植食性动物产生影响。
2. 我们提出一套生理生态学框架，以解析森林结构变化对植食性昆虫的影响。我们提出假说：若热带森林毛虫为气候与资源特化物种，则它们在成熟森林以外的生境中表现会下降。
3. 我们依托一项野外实验对该假说进行验证：在哥斯达黎加瓜纳卡斯特保护区的两片不同林龄与结构的热带旱林中，以宿主植物Casearia nitida（Salicaceae，杨柳科）饲养Rothschildia lebeau（Saturniidae，天蚕蛾科）幼虫，对比其表现。
4. 相较于更为成熟的密闭冠层森林，我们在幼龄次生林中观测到：（1）环境条件更炎热、更干燥且波动幅度更大；（2）毛虫的生长与发育进程受阻；（3）宿主叶片更坚韧、更厚且含水量更低。进一步分析表明，毛虫的生长速率与存活率与上述叶片性状呈负相关，这暗示气候可通过宿主介导的间接途径对植食性动物产生影响。
5. 结合现有研究证据，相较于成熟森林，我们认为幼龄次生林中植食性动物表现下降，可能由气候变化、叶片性状改变（其变化大概率由气候驱动）或二者共同作用导致。不过，仍需开展更多研究以获取二者因果关系的直接证据，并厘清这两类因素在该研究系统中对植食性动物表现的相对影响。