由寄主植物、氣候與微環境探討癭蚋科Daphnephila屬昆蟲在台灣樟科楨楠屬植物之分布

Abstract

造癭昆蟲由於具有寄主專一性，容易隨著寄主的種化而增加多樣性。為測試植物科群大小假說，分析331種台灣產癭的寄主植物，將蟲癭多樣性與植物科內種數進行迴歸分析，結果受到樟科和殼斗科兩大優勢造癭寄主植物科內蟲癭多樣性偏高，以及蘭科、禾本科等大的植物科群內蟲癭多樣性少的影響，並無顯著相關性。而依植物科群地質年齡假說，將造癭植物依拓展歷史，區分為產癭特有種、非特有原生種和外來種寄主植物來探討蟲癭種類出現的多樣性，結果顯示，台灣特有種植物上的蟲癭多樣性較非特有原生種高，外來種因為蟲癭少導致不顯著，除了優勢造癭植物如樟科、殼斗科外，大多數寄主植物上僅有單一種蟲癭，樟科中最優勢的造癭屬是楨楠屬 (37.3%)，僅有8種植物，卻可採集到57形態種蟲癭，主要造癭者為雙翅目癭蚋科 (Cecidomyiidae) (50形態種)，其餘為半翅目蟲癭。相同蟲癭形態種具有種專一性，其中紅楠 (Machilus thunbergii) 上包含9種形態種蟲癭，除小西氏楠 (M. konishii) 僅有2種形態種蟲癭外，其餘6種楨楠屬植物均有6種以上不同形態種蟲癭。針對樟科楨楠屬蟲癭調查台灣126個樣區，以蟲癭種類數、蟲癭數量與氣候因子逐一進行相關性分析，結果發現兩者僅與秋雨量呈顯著正相關，推測可能是Daphnephila蟲癭在秋季的高生長量導致。經由典型對應分析 (CCA) 檢驗楨楠屬蟲癭群聚與氣候因子的關係，整體趨勢顯示，氣候因子影響寄主植物分布，蟲癭群聚受氣候因子的影響不顯著。以福山地區楨楠屬樣樹的蟲癭進行微棲地分析，不同樹高層的蟲癭數量與優勢種類有明顯差異；樹冠上層蟲癭數量較中下層多，而偏好在上層的尖卵型與鐘型蟲癭，經常單生在單葉上，偏好中下層出現的長棒型與鳥型，則多顆聚集在單葉上。香楠鐘型蟲癭一年一世代，出現數量受寄主春季抽芽期和秋季的癭體發育期兩個季節影響。全穿透光率、春季均溫與鐘型蟲癭量呈正相關，溼度則為負相關，溼度變動大且輻射光強的高層，有利鐘型蟲癭生長。

Since galling insects are host-specific, they diverse with the host speciation. Regression analysis was used to test of the plant family size hypothesis for 331 galling hosts in Taiwan. The result showed no significant relationship between gall species richness and host plant family’s size. It was probably because small plant families, such as Lauraceae and Fagaceae, are more diverse than big families, such as Orchidaceae and Poaceae, in galling host plants. To test plant family geological age hypothesis, examing galling plants in native, endemic, and exotic host species. The result shows highest gall diversity in the endemic hosts, and exotic hosts are the least. During the investigation in Taiwan, most host-plants are found having only one gall species on it, except dominant galling hosts, such as Lauraecae and Fagaceae. Among those families, the highest GSR is the genus Machilus (37.3%). Fifty-seven gall morphospecies were collected in 8 spp. of the genus Machilus. Most gallers are gall midges (Diptera: Cecidomyiid) (50 spp.), the others are Hemiptera. The gall morphospecies represent species specific. Among 8 Machilus species in Taiwan, there are 9 mophospecies galls being found on M. thunbergii; 2 mophospecies galls on M. konishii; and 6 morphospecies galls on the rest of hosts respectively. In 126 sampling sites of Machilus host in Taiwan, environmental variables were analysized to find correlations to gall species richness and abundance. The result shows only significant correlation in sum of the precipitation from September to November. The result probably because high production of Daphnephila galls are in autumn. Canonical correspondence analysis indicates climate variables are more influencial on hosts than gall communities. For the analysis of microhabitat variables on 10 sampling host Machilus trees at Fushan. The result shows that gall amount is higher at upper canopy stratum. The emergence of univoltine bell-liked Daphnephila galls on M. zuihoenensis was affected by two phenology stages: budburst of host plants in spring and gall development during autumn. Bell-like galls are positively correlated to illumination and spring mean temperature, but negatively correlated to humidity. The larger fluctuation of humidity and higher radiation of upper canopy benefits the development of bell-like galls.