科研人員報(bào)告了一種寄生蟻物種與其種植真菌的宿主之間的關(guān)系的一種令人驚訝的共生特征,。寄生蟻Megalomyrmex的新近交配的蟻后悄悄進(jìn)入種植真菌的宿主蟻Sericomyrmex的真菌園并建立蟻群。這種寄生蟻通過食用宿主的后代從而妨礙宿主蟻群的生長，并且通過鉗制宿主未交配的蟻后的翼從而阻止蟻群的繁殖和擴(kuò)散,。Rachelle Adams及其同事報(bào)告說，這種寄生客蟻為它們的宿主帶來了一種此前沒有被認(rèn)識(shí)到的生存優(yōu)勢，因此也就解釋了它們在某些宿主種群中的高出現(xiàn)率。利用實(shí)驗(yàn)室實(shí)驗(yàn),，這組作者發(fā)現(xiàn)這種寄生蟻使用強(qiáng)大的生物堿保衛(wèi)宿主蟻群不受來襲的農(nóng)業(yè)掠食蟻Gnamptogenys hartmani的傷害，后者會(huì)強(qiáng)占Sericomyrmex的真菌園和蟻巢,。這組作者報(bào)告說,，這種寄生蟻比宿主能更有效地殺死這些來襲的掠食者，即便是數(shù)量不多的寄生蟻也可能保護(hù)它們不受掠食蟻的攻擊,，有效地減少了宿主蟻的死亡率,。此外，這組作者證明了這些掠食蟻的偵察蟻傾向于讓同巢的蟻前往氣味表明不存在那種寄生客蟻的Sericomyrmex蟻群,。這組作者說,，Megalomyrmex蟻可能充當(dāng)了保護(hù)其宿主的一種功能性兵蟻，這類似于某些中世紀(jì)城市持有的昂貴的雇傭兵部隊(duì),，這樣的部隊(duì)被用于抵御機(jī)動(dòng)部隊(duì)的入侵。（生物谷 Bioon.com）
生物谷推薦的英文摘要
PNAS doi: 10.1073/pnas.1311654110
Chemically armed mercenary ants protect fungus-farming societies
Rachelle M. M. Adamsa,b,1, Joanito Libertia, Anders A. Illuma, Tappey H. Jonesc, David R. Nasha,1, and Jacobus J. Boomsma
The ants are extraordinary in having evolved many lineages that exploit closely related ant societies as social parasites, but social parasitism by distantly related ants is rare. Here we document the interaction dynamics among a Sericomyrmex fungus-growing ant host, a permanently associated parasitic guest ant of the genus Megalomyrmex, and a raiding agro-predator of the genus Gnamptogenys. We show experimentally that the guest ants protect their host colonies against agro-predator raids using alkaloid venom that is much more potent than the biting defenses of the host ants. Relatively few guest ants are sufficient to kill raiders that invariably exterminate host nests without a cohabiting guest ant colony. We also show that the odor of guest ants discourages raider scouts from recruiting nestmates to host colonies. Our results imply that Sericomyrmex fungus-growers obtain a net benefit from their costly guest ants behaving as a functional soldier caste to meet lethal threats from agro-predator raiders. The fundamentally different life histories of the agro-predators and guest ants appear to facilitate their coexistence in a negative frequency-dependent manner. Because a guest ant colony is committed for life to a single host colony, the guests would harm their own interests by not defending the host that they continue to exploit. This conditional mutualism is analogous to chronic sickle cell anemia enhancing the resistance to malaria and to episodes in human history when mercenary city defenders offered either net benefits or imposed net costs, depending on the level of threat from invading armies.
