Do canal-cutting behaviours facilitate host-range expansion by insect herbivores?Biological Journal of the Linnean Society, 2009, 96, 715–731.
DAVID E. DUSSOURD*
根據共演化理論中物種數逐漸增加之輻射演化模型，能克服植物防禦能力的植食性昆蟲可進入一個新的適應區域(adaptation zone)並因此在演化上得到較高的物種多樣性。目前關於植食者如何對植物防禦產生逆適應可能導致的種化所知甚少。根據蛺蝶的研究結果推測食性的擴張可能是關鍵的一步。本文檢測能以切斷管道 (canal -cutting)方法撤消植物防禦的食葉性昆蟲是否通常有比較廣的食性範圍。作者從文獻中鑑定出92種會切斷管道的昆蟲(canal cutters)，其中包括8種新的切斷通道者。已知寄主範圍的 canal cutters 中只有27%取食跨越多個科的寄主植物，此比例接近或低於整體植食性昆蟲中評估為廣食性者的比例。至多只有5種 canal cutters 專一性地取食具有分泌管的植物。廣食者數量不高有一部份可歸因於具有分泌管道的植物在親緣關係上距離相當遙遠，以及其對應之化學物質的特殊性。許多canal-cutting 物種對於從寄主植物的化學物質獲得防禦能力的倚賴，也會偏好種化發生。
Abstract
According to the escalation–radiation model of co-evolution, insect herbivores that acquire the ability to circumvent a plant defence enter a new adaptive zone and increase in species. How herbivore counter-adaptations to plant defences might lead to speciation is poorly understood. Studies of nymphalid butterflies suggest that the evolution of a broadened host range may be a critical step. This paper examines if leaf-feeding insects capable of deactivating defensive plant canals with canal cutting often have broad host ranges. A total of 94 species of canal-cutting insects were identified from the literature, including eight new canal cutters described in this paper. Only 27% of canal cutters with known host ranges are generalists that feed on plants in multiple families. The proportion of generalist canal cutters is similar or lower than estimates of generalists among phytophagous insects overall. Only five species, at most, of the canal-cutting generalists feed exclusively on plants with secretory canals. The paucity of generalists can be attributed in part to the considerable taxonomic distance separating canal-bearing plant families and to their corresponding chemical distinctiveness. The dependence of many canal-cutting species on host chemicals for defence would also favour specialization.
DAVID E. DUSSOURD*
根據共演化理論中物種數逐漸增加之輻射演化模型，能克服植物防禦能力的植食性昆蟲可進入一個新的適應區域(adaptation zone)並因此在演化上得到較高的物種多樣性。目前關於植食者如何對植物防禦產生逆適應可能導致的種化所知甚少。根據蛺蝶的研究結果推測食性的擴張可能是關鍵的一步。本文檢測能以切斷管道 (canal -cutting)方法撤消植物防禦的食葉性昆蟲是否通常有比較廣的食性範圍。作者從文獻中鑑定出92種會切斷管道的昆蟲(canal cutters)，其中包括8種新的切斷通道者。已知寄主範圍的 canal cutters 中只有27%取食跨越多個科的寄主植物，此比例接近或低於整體植食性昆蟲中評估為廣食性者的比例。至多只有5種 canal cutters 專一性地取食具有分泌管的植物。廣食者數量不高有一部份可歸因於具有分泌管道的植物在親緣關係上距離相當遙遠，以及其對應之化學物質的特殊性。許多canal-cutting 物種對於從寄主植物的化學物質獲得防禦能力的倚賴，也會偏好種化發生。
Abstract
According to the escalation–radiation model of co-evolution, insect herbivores that acquire the ability to circumvent a plant defence enter a new adaptive zone and increase in species. How herbivore counter-adaptations to plant defences might lead to speciation is poorly understood. Studies of nymphalid butterflies suggest that the evolution of a broadened host range may be a critical step. This paper examines if leaf-feeding insects capable of deactivating defensive plant canals with canal cutting often have broad host ranges. A total of 94 species of canal-cutting insects were identified from the literature, including eight new canal cutters described in this paper. Only 27% of canal cutters with known host ranges are generalists that feed on plants in multiple families. The proportion of generalist canal cutters is similar or lower than estimates of generalists among phytophagous insects overall. Only five species, at most, of the canal-cutting generalists feed exclusively on plants with secretory canals. The paucity of generalists can be attributed in part to the considerable taxonomic distance separating canal-bearing plant families and to their corresponding chemical distinctiveness. The dependence of many canal-cutting species on host chemicals for defence would also favour specialization.
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