Antimicrobial strength increases with group size: implications for social evolution
Antimicrobial strength increases with group size: implications for social evolution
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DOI：
10.1098/rsbl.2010.0719
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发表时间：
2011-04-23
期刊：
影响因子：
3.3
通讯作者：
Beattie, Andrew
中科院分区：
文献类型：
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作者：
Turnbull, Christine;Hoggard, Stephen;Beattie, Andrew
我们假设，动物的聚集很可能会吸引病原微生物，尤其是半社会性和社会性昆虫，在这些昆虫中，选择最终导致数千甚至数百万的群体规模，吸引了绰号“超级生物”。在这里，我们分析了8种蓟马(昆虫纲：胸翅目)的个体抗菌力，发现种群规模最大的物种(100-700)的抗菌力最强，群体规模较小的物种(10-80)的抗菌活性较低，而单独的物种则没有。天然群体规模大的物种表现出很强的抗菌活性，而半社会性物种直到群体规模增加到足以检测到活性时才显示出活性。这种群居物种的行为方式类似，一旦种群规模超过120，就会出现可检测到的活动。这些分析表明，抗菌强度是由先天群体大小决定的。这表明，社会性的演变，根据定义，增加了群体规模，可能对防御微生物病原体有特殊的要求。因此，群体规模的增加，伴随着抗生素强度的增加，可能是在群居昆虫进化的早期，决定不归路点的关键因素，超过这一点，社会解剖和形态特征的进化是不可逆转的。我们的数据表明，通常情况下，增加群体规模的特征伴随着抗菌强度的增加，这对于从独居到社会和社会组织的转变至关重要。
We hypothesize that aggregations of animals are likely to attract pathogenic micro-organisms and that this is especially the case for semisocial and eusocial insects where selection ultimately led to group sizes in the thousands or even millions, attracting the epithet 'superorganism'. Here, we analyse antimicrobial strength, per individual, in eight thrips species (Insecta: Thysanoptera) that present increasing innate group sizes and show that species with the largest group size (100-700) had the strongest antimicrobials, those with smaller groups (10-80) had lower antimicrobial activity, while solitary species showed none. Species with large innate group sizes showed strong antimicrobial activity while the semisocial species showed no activity until group size increased sufficiently to make activity detectable. The eusocial species behaved in a similar way, with detectable activity appearing once group size exceeded 120. These analyses show that antimicrobial strength is determined by innate group size. This suggests that the evolution of sociality that, by definition, increases group size, may have had particular requirements for defences against microbial pathogens. Thus, increase in group size, accompanied by increased antibiotic strength, may have been a critical factor determining the 'point of no return', early in the evolution of social insects, beyond which the evolution of social anatomical and morphological traits was irreversible. Our data suggest that traits that increase group size in general are accompanied by increased antimicrobial strength and that this was critical for transitions from solitary to social and eusocial organization.