無論在人類的社會還是自然生物系統中，近代的研究發(fā)現合作行為可能是個體間相互作用的基本形式之一,。英國科協主席Robert May在2005年的任職演說中,，將生物進化過程和人類的社會學中合作關系演化及其系統維持列為進化生物學或社會科學中最為重要的、未被解決的科學問題,。從上世紀60年代陸續(xù)提出的群選擇理論,、親選擇理論以及互惠選擇等理論認為合作雙方由于合作雙方之間存在親緣關系、利益互換或群體間競爭等因素,，個體選擇合作的策略將總是比其它任何策略的收益都高,，合作雙方將穩(wěn)定的合作納什均衡。然而,，后來的試驗與觀測發(fā)現：在幾乎所有的合作系統,，合作雙方實際都存在沖突或競爭，部分個體將會采取欺騙的策略,，甚至演化為系統的寄生者,。上述經典理論因而無法解釋合作系統普遍存在的沖突或投機現象。
中國科學院昆明動物所的王瑞武和云南大學數學系教授李耀堂,、博士研究生賀軍州等在2004年Nature發(fā)表模型的基礎上,，將經典的鷹-鴿博弈從對稱性轉化非對稱性后，模型驚奇地發(fā)現：合作雙方的非對稱性程度越高,，雙方的合作頻率也將越高,。系統中優(yōu)勢方通過對投機的懲罰而獎勵誠實合作者，從而維持合作系統地局域穩(wěn)定性。優(yōu)勢方對合作方或劣勢方的懲罰可信性將依賴于合作方從該系統退出成本大小或擴散到其它系統的可能性,。其分析發(fā)現：經典合作理論與實際觀測結果之間的悖論可能是由于經典理論對稱性的前提假設不合理所致,，現實的合作系統可能是從一個對稱性系統演化而來。該理論模型將發(fā)表在近期的《中國科學》中,。
課題組同時以著名的榕樹-榕小蜂之間的合作為模式系統對該思想進行了驗證,。其實驗結果發(fā)現：經典的基于對稱思想，認為生態(tài)位分化維持合作或生態(tài)系統穩(wěn)定性的理論可能是不可信的,。其實驗結果顯示：合作系統內的投機者或寄生物種完全會導致合作的個體或物種滅絕,，從而導致榕樹與傳粉小蜂之間合作關系的解體。然而,，投機或寄生物種過度增長又將導致植物懲罰,，從而又會致使投機或寄生物種的滅絕，誠實合作的個體或物種又從其它種群中擴散過來,，重新建立其種群,。當誠實合作者種群數量得以建立并擴張后，投機或寄生者的又可以在合作系統中得到擴散,，整個生態(tài)或合作系統將通過上述非對稱性的相互作用而出現擾動,，系統也將通過其內部個體間的非對稱性相互作用而維持其合作關系的局域性穩(wěn)定。
該研究結果同時表明生態(tài)學中“島嶼”效應可能通過物種的非對稱性相互作用而產生,。在生態(tài)學理論中， Preston1962年提出“島嶼”理論后,，普遍認為“島嶼”效應只能通過空間異質性產生,，此項研究結果表明：物種的相互非對稱性相互作用也將會導致物種的局域性滅絕，物種分布將因此在某些局域環(huán)境的出現“真空”的“斑塊”,，其它局域或斑塊的物種從而遷徙過來填補其分布的空白,，合作系統通過物種的非對稱性相互作用產生“島嶼”或“斑塊”效應，通過“島嶼”或“斑塊間的相互移動實現物種間相互關系的混沌性擾動,。而這一重要的“島嶼效應”產生機制在過去的生態(tài)學研究中完全被忽略了,。
這一實驗結果由王瑞武和他的兩名碩士研究生孫寶發(fā)和鄭琪合作完成。結果于2010年5月發(fā)表在國際著名雜志Ecology上,。
該項研究結果將是對老莊哲學思想的一次科學的詮釋：任何一個物種或個體的過度增長或擴張反過來將會導致自身滅絕或種群減少,。“禍兮福之所倚，福兮禍之所伏”,，或“樂極生悲,，否去泰來”的思想在生態(tài)系統得到驗證。(生物谷Bioon.com)
生物谷推薦原文出處：
Ecology doi: 10.1890/09-1446.1
Diffusive coevolution and mutualism maintenance mechanisms in a fig–fig wasp system
Rui-Wu Wang1,4, Bao-Fa Sun1,2, and Qi Zheng1,3
1 Ecology, Conservation, and Environment Center (ECEC), State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Science, Kunming, Yunnan 650223 China
2 Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Science, Beijing 100101 China
3 School of Medicine, Zhejiang University, Zhejiang 310000 China
In reciprocal mutualism systems, the exploitation events by exploiters might disrupt the reciprocal mutualism, wherein one exploiter species might even exclude other coexisting exploiter species over an evolutionary time frame. What remains unclear is how such a community is maintained. Niche partitioning, or spatial heterogeneity among the mutualists and exploiters, is generally believed to enable stability within a mutualistic system. However, our examination of a reciprocal mutualism between a fig species (Ficus racemosa) and its pollinator wasp (Ceratosolen fusciceps) shows that spatial niche partitioning does not sufficiently prevent exploiters from overexploiting the common resource (i.e., the female flowers), because of the considerable niche overlap between the mutualists and exploiters. In response to an exploiter, our experiment shows that the fig can (1) abort syconia-containing flowers that have been galled by the exploiter, Apocryptophagus testacea, which oviposits before the pollinators do; and (2) retain syconia-containing flowers galled by Apocryptophagus mayri, which oviposit later than pollinators. However, as a result of (2), there is decreased development of adult non-pollinators or pollinator species in syconia that have not been sufficiently pollinated, but not aborted. Such discriminative abortion of figs or reduction in offspring development of exploiters while rewarding cooperative individuals with higher offspring development by the fig will increase the fitness of cooperative pollinating wasps, but decrease the fitness of exploiters. The fig–fig wasp interactions are diffusively coevolved, a case in which fig wasps diversify their genotype, phenotype, or behavior as a result of competition between wasps, while figs diverge their strategies to facilitate the evolution of cooperative fig waps or lessen the detrimental behavior by associated fig wasps. In habitats or syconia that suffer overexploitation, discriminative abortion of figs or reduction in the offspring development of exploiters in syconia that are not or not sufficiently pollinated will decrease exploiter fitness and perhaps even drive the population of exploiters to local extinction, enabling the evolution and maintenance of cooperative pollinators through the movement between habitats or syconia (i.e., the metapopulations).
