臺灣熱帶火蟻收集種子之初探

Preliminary Study of Seed Harvesting by the Tropical Fire Ant, ＂Solenopsis geminata＂ (Hymenoptera: Formicidae), in Taiwan

10.6661/TESFE.2014014

陳佑蓁(Yu-Chen Chen)；吳文哲(Wen-Jer Wu)；賴麗娟(Li-Chuan Lai)

非蟻佈植物 ； 熱帶火蟻 ； 食種子現象 ； 禾本科 ； 偏好 ； non-myrmecochorous ； ＂Solenopsis geminate＂ ； dyszoochory ； Poaceae ； preference

台灣昆蟲

34卷3-4期（2015 / 03 / 01）

167 - 182

繁體中文

螞蟻被認為是種子的取食者或傳播者，螞蟻傳播種子常被視為螞蟻與植物交互關係中的互利共生；然而，螞蟻也可能同時是非蟻佈植物種子的取食者兼傳播者。熱帶火蟻（＂Solenopsis geminata＂）具有食種子現象，會收集其棲地中多種非蟻佈植物的種子。本研究從臺中、雲林、嘉義和臺南四地區熱帶火蟻蟻巢內部挖掘火蟻所收集的種子，並進行鑑定。結果顯示四地區熱帶火蟻收集的種子，共計12科，37種。非蟻佈草本植物種子佔多數，其中禾本科占16種。臺中熱帶火蟻收集大量大黍；雲林主要為飛揚草、兩耳草和牛筋草；嘉義以飛揚草、霧水葛和雙花草為主；臺南以青莧、龍爪茅和馬唐數量居多。關於熱帶火蟻對種子偏好之試驗，結果顯示熱帶火蟻偏好先搬運雙花草、大黍和圓果雀稗等3種種子。種子的單顆重量似乎影響火蟻的選擇，火蟻偏好先搬運大於0.56 mg的種子，最後搬運重量介於0.07～0.43 mg的種子。種子發芽試驗結果顯示，火蟻蟻巢內的霧水葛、龍爪茅、大黍和兩耳草種子的發芽率顯著較高於植株上的成熟種子；青莧種子的發芽率則顯著較低。值得注意的是，熱帶火蟻似乎偏好外來種植物種子。火蟻大量搬運、收集並取食其偏好的種子種類，可能影響火蟻入侵地區的植物族群豐度與組成，尤其是本土禾草植物。

Ants are considered both predators and dispersers of seeds. Seed dispersal by ants is usually regarded as part of the ant-plant mutualism. However, ants may play a dual role as both predator and disperser of non-myrmechorous seeds. Tropical fire ants (＂Solenopsis geminata＂) have a granivorous habit (dyszoochory), with workers having been observed attempting to collect seeds from numerous non-myrmechorous plant species. We excavated fire ant nests from four counties (Taichung, Yunlin, Chiayi and Tainan) in Taiwan. We then gathered the seeds that were harvested by the ants, and found seeds of 37 species belonging to 12 plant families. Most of the seeds were nonmyrmechorous herb seeds, including 16 species of the Poaceae family. The majority of the seeds harvested in Taichung by the fire ants was ＂Panicum maximum＂, in Yunlin it was ＂Chamaesyce hirta, Eleusine indica and Paspalum conjugatum, in Chiayi it was Pouzolzia zeylanica, Chamaesyce hirta and Dichanthium annulatum, and in Tainan it was Amaranthus patulus, Dactyloctenium aegyptium＂ and ＂Digitaria sanguinalis＂. We conducted seed preference experiments, and found that grass seeds such as ＂Dichanthium annulatum, Panicum maximum＂, and ＂Paspalum orbiculare＂ were readily removed by the fire ants. The ant's choices seemed to be influenced by the weight of the seed. Seeds heavier than 0.56 mg were harvested preferentially, while seeds weighing between 0.07-0.43 mg were rarely retrieved. In our seed germination experiments, the germination rates of seeds from ＂Pouzolzia zeylanica, Dactyloctenium aegyptium, Panicum maximum＂ and ＂Paspalum conjugatum＂ collected by the fire ants were significantly higher than those from mature seeds left on the plants, while the germination rate of seeds from ＂Amaranthus patulus＂ was significantly lower. It is worth noting that fire ants seemed to prefer the seeds of introduced species to those of native species. The results in this study show that seed removal and harvesting by workers of ＂S. geminate＂ may impact the abundance and composition of a plant community in Taiwan, especially that of native grasses in fields infested with ＂S. geminate＂.