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广受学界关注，但由本地生境改变引发的更为剧烈的气候变化类型，其生态影响却较少得到探索。当森林被碎片化、砍伐、疏伐、开垦或以其他方式改变林分结构时，区域气候与微气候（microclimates）将发生改变。此类变化可通过直接途径（例如通过影响动物体温）与间接途径（例如通过改变宿主植物性状）对植食动物（herbivores）产生影响。
2. 我们提出一套生理生态学框架（eco-physiological framework），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专性物种，则其在成熟森林以外的生境中，适合度表现应会下降。
3. 我们依托哥斯达黎加瓜纳卡斯特保护区（Area de Conservación Guanacaste）内两处不同林龄与林分结构的热带干旱森林，开展野外实验，对比罗斯柴尔德天蚕蛾（Rothschildia lebeau，天蚕蛾科Saturniidae）幼虫取食宿主植物光叶脚骨脆（Casearia nitida，杨柳科Salicaceae）时的适合度表现。
4. 相较于成熟郁闭林（closed-canopy forest），幼龄次生林（younger secondary forest）内的环境条件具备以下特征：(1) 气温更高、湿度更低且波动更强；(2) 毛虫的生长与发育进程显著减缓；(3) 叶片更为坚韧、厚实且含水量更低。进一步分析显示，毛虫的生长速率与存活率与上述叶片性状呈负相关，这表明气候变化可通过宿主介导的间接途径对植食动物产生影响。
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动物适合度表现下降，可能由气候变化、宿主植物性状改变（其本身或由气候变化诱导），或二者共同驱动。不过，仍需开展更多研究以获取二者因果关系的直接证据，并厘清这两类因素对该研究系统内植食动物适合度表现的相对影响。