Data from: Generalist predator’s niche shifts reveal ecosystem changes in an experimentally fragmented landscape

Habitat fragmentation can alter the trophic structure of communities and environmental conditions, thus driving changes in biodiversity and ecosystem functions. Quantifying niches of generalist predators can reveal how fragmentation alters ecosystems. In a habitat fragmentation experiment, we used stable isotopes of a generalist predator skink to test predictions from spatial theory on trophic structure and to quantify abiotic changes associated with fragmentation among continuous forest, fragments, and matrix habitats. We predicted that in fragments and the matrix, isotopic niches would shift due to decreases in skink trophic positions (δ15N) from reductions in trophic structure of arthropod food webs and abiotic changes over time (δ13C) relative to continuous forest. Contrary to theoretical predictions, we did not find evidence of reductions in trophic structure with fragmentation. In fact, skink δ15N values were higher in the matrix and fragments than continuous forest, likely due to changes in distributions of a detritivorous prey species. In addition, δ13C values in the matrix decreased over years since fragmentation due to abiotic changes associated with matrix tree maturation. We show how isotopic niches are influenced by fragmentation via shifts in biotic and abiotic processes. The potential for either or both spatial and abiotic effects of fragmentation present a challenge for theory to better predict ecological changes in fragmented landscapes.生境破碎化（habitat fragmentation）可改变群落的营养结构（trophic structure）与环境条件，进而引发生物多样性（biodiversity）与生态系统功能（ecosystem functions）的变化。对广食性捕食者的生态位进行量化，能够揭示破碎化对生态系统的影响路径。在一项生境破碎化实验中，我们以广食性捕食者石龙子（skink）的稳定同位素（stable isotopes）为研究载体，验证了空间理论关于营养结构的相关预测，并量化了连续森林、破碎化生境以及基质生境（matrix habitats）之间与破碎化相关的非生物环境变化。 我们做出如下预测：相较于连续森林，破碎化生境与基质生境中的同位素生态位将发生偏移，其原因在于节肢动物食物网（arthropod food webs）的营养结构缩减，以及随时间推移产生的非生物环境变化，这会导致石龙子的营养级位置（trophic positions，以δ¹⁵N表征）降低。 但实验结果与理论预测相悖：我们未发现任何证据表明破碎化会导致营养结构缩减。事实上，基质生境与破碎化生境中的石龙子δ¹⁵N值显著高于连续森林，这一现象大概率源于食碎屑猎物（detritivorous prey）物种的分布变化。此外，自生境破碎化发生以来，基质生境中的δ¹³C值随采样年份增加而逐渐降低，这与基质树木成熟所伴随的非生物环境变化密切相关。 本研究阐明了破碎化如何通过生物与非生物过程的改变，对同位素生态位产生影响。破碎化所带来的空间效应与非生物效应，二者单独或共同作用，为学界精准预测破碎化景观中的生态变化带来了挑战。