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，但由局地生境改变引发的更为剧烈的气候变化形式，其影响却较少得到探索。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（microclimates）会发生变化。此类变化可通过直接途径（例如通过体温改变）和间接途径（例如通过宿主植物性状改变）对植食性动物（herbivores）产生影响。
2. 我们提出一套生态生理学框架，用以解析森林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，则它们在成熟森林生境之外的适合度表现会下降。
3. 我们依托哥斯达黎加瓜纳卡斯特保护区（Area de Conservación Guanacaste）内两处不同林龄与结构的热带旱林，以取食宿主植物光果嘉赐树（Casearia nitida，杨柳科Salicaceae）的Rothschildia lebeau（天蚕蛾科Saturniidae）毛虫为研究对象，通过野外对照实验检验了上述假说。
4. 与更为成熟的郁闭林相比，在幼龄次生林中我们发现：(1) 环境条件更炎热、更干燥且波动更大；(2) 毛虫的生长与发育速率减缓；(3) 叶片更坚韧、更厚实且含水量更低。进一步研究发现，毛虫的生长速率与存活率与上述叶片性状呈负相关，这表明气候通过宿主介导对植食性动物产生了间接影响。
5. 基于现有证据，相较于成熟森林，我们认为幼龄次生林中植食性动物适合度表现下降，可能由气候变化、叶片性状改变（其变化大概率由气候诱导）或二者共同驱动。不过，仍需开展更多研究以提供更直接的因果关系证据，并厘清这两类因素在该研究系统中对植食性动物适合度表现的相对影响程度。