国际研究人员最近在南美洲发现一些内部关系特殊的鱼群，它们的外表非常相似，在一个群落里和谐共处、共御天敌，但它们却是不同的物种，在选择食物时各有偏好，与中国传统的“和而不同”理念不谋而合。
英国《自然》杂志1月6日刊登报告说，英国班戈大学等机构的研究人员和巴西同行在南美洲发现具有上述特点的甲鲶属鱼类。这种俗称“鼠鱼”的鱼种类很多，仅正式报告过的就有一百多种。过去人们知道，这些鱼喜欢集群生活，虽然一群鱼中有多个物种，但它们的外形却十分相似，有差不多的鳞片斑纹和尖利的鳍刺。
一个群落的鱼外表趋同可以互利，比如某个掠食者想吃其中一条鱼而尝过鳍刺的苦头后，就会对所有看起来差不多的鱼“敬而远之”，这种现象在生物学上称为“缪氏拟态”。以前曾在蝴蝶等生物中发现这种现象，但是这些生物往往因为彼此太相似而同时存在针对食物的内部竞争。
但本次研究发现了一种新型“缪氏拟态”关系，南美洲的这些鱼群为了维持集体内部的稳定关系而在食物选择上有所不同。研究人员捕获了共同生活的许多种“鼠鱼”，观察它们的嘴形，并通过分析其机体组织判断它们的摄食情况。结果显示，一个群落中的不同种“鼠鱼”的摄食对象存在差别，群落内部的食物竞争不大。
领导研究的马丁·泰勒博士说，这些“鼠鱼”看起来差不多，也在同一个地方生活，因此很容易认为它们存在食物竞争，但实际上它们却进化出各自选择不同食物的习性。正是这种“和而不同”的特点，增强了整个群体的生存能力。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature doi:10.1038/nature09660
Competition and phylogeny determine community structure in Müllerian co-mimics
Markos A. Alexandrou,Claudio Oliveira,Marjorie Maillard,Rona A. R. McGill,Jason Newton,Simon Creer& Martin I. Taylor
Until recently, the study of negative and antagonistic interactions (for example, competition and predation) has dominated our understanding of community structure, maintenance and assembly1. Nevertheless, a recent theoretical model suggests that positive interactions (for example, mutualisms) may counterbalance competition, facilitating long-term coexistence even among ecologically undifferentiated species2. Müllerian mimics are mutualists that share the costs of predator education3 and are therefore ideally suited for the investigation of positive and negative interactions in community dynamics. The sole empirical test of this model in a Müllerian mimetic community supports the prediction that positive interactions outweigh the negative effects of spatial overlap4 (without quantifying resource acquisition). Understanding the role of trophic niche partitioning in facilitating the evolution and stability of Müllerian mimetic communities is now of critical importance, but has yet to be formally investigated. Here we show that resource partitioning and phylogeny determine community structure and outweigh the positive effects of Müllerian mimicry in a species-rich group of neotropical catfishes. From multiple, independent reproductively isolated allopatric communities displaying convergently evolved colour patterns, 92% consist of species that do not compete for resources. Significant differences in phylogenetically conserved traits (snout morphology and body size) were consistently linked to trait-specific resource acquisition. Thus, we report the first evidence, to our knowledge, that competition for trophic resources and phylogeny are pivotal factors in the stable evolution of Müllerian mimicry rings. More generally, our work demonstrates that competition for resources is likely to have a dominant role in the structuring of communities that are simultaneously subject to the effects of both positive and negative interactions.
