Data from: Do asynchronies in extinction debt affect the structure of trophic networks? A case study of antagonistic butterfly larvae–plant networks

Habitat loss and fragmentation affect species richness in fragmented habitats and can lead to immediate or time-delayed species extinctions. Asynchronies in extinction and extinction debt between interacting species may have severe effects on ecological networks. However, these effects remain largely unknown. We evaluated the effects of habitat patch and landscape changes on antagonistic butterfly larvae-plant trophic networks in Mediterranean grasslands in which previous studies had shown the existence of extinction debt in plants but not in butterflies. We sampled current species richness of habitat-specialist and generalist butterflies and vascular plants in 26 grasslands. We assessed the direct effects of historical and current patch and landscape characteristics on species richness and on butterfly larvae-plant trophic network metrics and robustness. Although positive species- and interactions-area relationships were found in all networks, structure and robustness was only affected by patch and landscape changes in networks involving the subset of butterfly specialists. Larger patches had more species (butterflies and host plants) and interactions but also more compartments, which decreased network connectance but increased network stability. Moreover, most likely due to the rescue effect, patch connectivity increased host-plant species (but not butterfly) richness and total links, and network robustness in specialist networks. On the other hand, patch area loss decreased robustness in specialist butterfly larvae-plant networks and made them more prone to collapse against host plant extinctions. Finally, in all butterfly larvae-plant networks we also detected a past patch and landscape effect on network asymmetry, which indicates that there were different extinction rates and extinction debts for butterflies and host plants. We conclude that asynchronies in extinction and extinction debt in butterfly-plant networks provoked by patch and landscape changes caused changes in species richness and network links in all networks, as well as changes in network structure and robustness in specialist networks.栖息地丧失与片段化（Habitat loss and fragmentation）会影响破碎化生境中的物种丰富度，并可能引发瞬时或滞后的物种灭绝。互作物种间的灭绝异步性与灭绝债务（extinction debt）可能对生态网络造成严重影响，但此类效应在很大程度上仍未明确。我们以地中海草原中的拮抗型蝶类幼虫-植物营养网络（trophic network）为研究对象，过往研究已证实该区域的植物类群存在灭绝债务，而蝶类类群则未表现出该特征。我们在26处草原样地中，调查了生境专性类群（habitat-specialist）与广适性类群（generalist）蝶类以及维管植物（vascular plants）的当前物种丰富度。我们评估了历史与当前的生境斑块及景观特征，对物种丰富度、蝶类幼虫-植物营养网络各项指标及鲁棒性（robustness）的直接影响。尽管所有网络中均存在正向的物种-面积关系与互作-面积关系，但仅在包含蝶类专性类群的网络中，其结构与鲁棒性才会受到生境斑块与景观变化的影响。更大的生境斑块拥有更多的物种（蝶类与寄主植物）与互作关系，同时也具有更多的网络模块（compartments），这虽降低了网络连通度（connectance），却提升了网络稳定性。此外，这一现象很可能源于拯救效应（rescue effect），生境斑块的连通性提升了专性网络中寄主植物的物种丰富度（而非蝶类）与总互作链路数，同时也提升了该类网络的鲁棒性。与之相对，生境斑块面积的缩减降低了专性蝶类幼虫-植物网络的鲁棒性，使其更易因寄主植物灭绝而发生崩溃。最后，在所有蝶类幼虫-植物网络中，我们均发现历史生境斑块与景观特征对网络不对称性存在影响，这表明蝶类与寄主植物的灭绝速率及灭绝债务均存在差异。综上，生境斑块与景观变化引发的蝶类-植物网络中灭绝异步性与灭绝债务，会导致所有网络的物种丰富度与互作链路发生改变，同时也会改变专性类群网络的结构与鲁棒性。