無論在人類的社會還是自然生物系統(tǒng)中,，近代的研究發(fā)現(xiàn)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(xié)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(xué)中合作關(guān)系演化及其系統(tǒng)維持列為進化生物學(xué)或社會科學(xué)中最為重要的,、未被解決的科學(xué)問題,。從上世紀(jì)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(rèn)為合作雙方由于合作雙方之間存在親緣關(guān)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(xiàn)：在幾乎所有的合作系統(tǒng),，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(tǒng)的寄生者,。上述經(jīng)典理論因而無法解釋合作系統(tǒng)普遍存在的沖突或投機現(xiàn)象。
中國科學(xué)院昆明動物所的王瑞武和云南大學(xué)數(shù)學(xué)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(chǔ)上,，將經(jīng)典的鷹-鴿博弈從對稱性轉(zhuǎn)化非對稱性后，模型驚奇地發(fā)現(xiàn)：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(tǒng)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(tǒng)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(tǒng)退出成本大小或擴散到其它系統(tǒng)的可能性,。其分析發(fā)現(xiàn)：經(jīng)典合作理論與實際觀測結(jié)果之間的悖論可能是由于經(jīng)典理論對稱性的前提假設(shè)不合理所致，現(xiàn)實的合作系統(tǒng)可能是從一個對稱性系統(tǒng)演化而來,。該理論模型將發(fā)表在近期的《中國科學(xué)》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(tǒng)對該思想進行了驗證,。其實驗結(jié)果發(fā)現(xiàn)：經(jīng)典的基于對稱思想,，認(rèn)為生態(tài)位分化維持合作或生態(tài)系統(tǒng)穩(wěn)定性的理論可能是不可信的。其實驗結(jié)果顯示：合作系統(tǒng)內(nèi)的投機者或寄生物種完全會導(dǎo)致合作的個體或物種滅絕,，從而導(dǎo)致榕樹與傳粉小蜂之間合作關(guān)系的解體,。然而，投機或寄生物種過度增長又將導(dǎo)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(dāng)誠實合作者種群數(shù)量得以建立并擴張后,，投機或寄生者的又可以在合作系統(tǒng)中得到擴散，整個生態(tài)或合作系統(tǒng)將通過上述非對稱性的相互作用而出現(xiàn)擾動,，系統(tǒng)也將通過其內(nèi)部個體間的非對稱性相互作用而維持其合作關(guān)系的局域性穩(wěn)定,。
該研究結(jié)果同時表明生態(tài)學(xué)中“島嶼”效應(yīng)可能通過物種的非對稱性相互作用而產(chǎn)生。在生態(tài)學(xué)理論中,， Preston1962年提出“島嶼”理論后,，普遍認(rèn)為“島嶼”效應(yīng)只能通過空間異質(zhì)性產(chǎn)生,，此項研究結(jié)果表明：物種的相互非對稱性相互作用也將會導(dǎo)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(xiàn)“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(tǒng)通過物種的非對稱性相互作用產(chǎn)生“島嶼”或“斑塊”效應(yīng)，通過“島嶼”或“斑塊間的相互移動實現(xiàn)物種間相互關(guān)系的混沌性擾動,。而這一重要的“島嶼效應(yīng)”產(chǎn)生機制在過去的生態(tài)學(xué)研究中完全被忽略了,。
這一實驗結(jié)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(jié)果于2010年5月發(fā)表在國際著名雜志Ecology上,。
該項研究結(jié)果將是對老莊哲學(xué)思想的一次科學(xué)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(dǎo)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(tǒng)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).
