Oye Brian K, Hill Ryan I
Department of Biological Sciences, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA.
Insects. 2025 Jan 11;16(1):64. doi: 10.3390/insects16010064.
Habitat fragmentation and land use changes threaten neotropical habitats and alter patterns of diversity at forest edges. Like other arthropod assemblages, neotropical fruit-feeding butterfly communities show strong vertical stratification within forests, with some recent work showing its potential role in speciation. At forest edges, species considered to be forest canopy specialists have been observed descending to the forest understory, with the similarity in light conditions between the canopy and understory strata at edges hypothesized to be responsible for this phenomenon. We conducted a study using standardized sampling to document and quantify this edge effect, characterize edge and forest strata, and estimate the relative contributions of temperature and light conditions to changes in nymphalid butterfly stratification at forest edges. We found strong evidence of an edge effect in these butterflies and confirmed strong differences in light and temperature, showing that the edge understory differs little from forest canopy conditions. Of 41 species common to both forests and edges, 28 shifted to have a lower canopy probability at the edge, and our model detected a decrease in canopy probability of 0.165. Furthermore, our analysis indicated the relative abundance of canopy taxa increased at the edge, and the tribes Haeterini and Morphini were especially sensitive to edge effects. However, the analyses here did not clearly implicate temperature or light magnitude in causing changes in neotropical nymphalid vertical stratification at forest edges. Instead, our results point to other mediator variables as being important for changes at tropical forest edges. From our data, edge-responsive species can be separated into two different categories, which likely relates to their resilience to anthropogenic disturbance. We also note that structural causal models have a potential place in future work on tropical conservation, given they can provide causal estimates with observational data.
栖息地破碎化和土地利用变化威胁着新热带地区的栖息地，并改变了森林边缘的多样性模式。与其他节肢动物群落一样，新热带地区以果实为食的蝴蝶群落在森林中表现出强烈的垂直分层现象，最近的一些研究表明这种分层现象在物种形成中可能发挥作用。在森林边缘，被认为是树冠层专家的物种被观察到下降到森林下层，据推测边缘处树冠层和下层之间光照条件的相似性是造成这种现象的原因。我们进行了一项研究，采用标准化采样来记录和量化这种边缘效应，描述边缘和森林分层特征，并估计温度和光照条件对森林边缘蛱蝶分层变化的相对贡献。我们发现了这些蝴蝶存在边缘效应的有力证据，并证实了光照和温度存在显著差异，表明边缘下层与树冠层条件差异不大。在森林和边缘都常见的41个物种中，有28个在边缘处转移到树冠层的概率降低，我们的模型检测到树冠层概率下降了0.165。此外，我们的分析表明树冠层类群的相对丰度在边缘处增加，并且Haeterini族和Morphini族对边缘效应特别敏感。然而，这里的分析并没有明确表明温度或光照强度是导致新热带地区森林边缘蛱蝶垂直分层变化的原因。相反，我们的结果指出其他中介变量对热带森林边缘的变化很重要。根据我们的数据，对边缘有反应的物种可以分为两类，这可能与它们对人为干扰的恢复力有关。我们还指出，结构因果模型在未来热带保护工作中可能会有一席之地，因为它们可以利用观测数据提供因果估计。
