The role of behavioral type composition on resource use and growth of a juvenile predator

Juvenile largemouth bass have distinct behavioral types that separate along the exploring behavioral axis and differ in diet. We used a mesoxosm experiement to test the hypothesis that groups composed of mixed behavioral types would have more efficient use of prey resources and reduced competition between individuals than experimental populations composed of similar behavioral types. Fish growth, diets and prey composition were quantified over a four-week period in mesocosms containing prey communities that were mixtures of zooplanktion and natural colonization by terrestrial insects. Mesocosms contained juvenile largemouth bass of either all fast exploratory-type, all slow exploratory-type or a 50/50 mix of the two behavioral types. Treatments with similar behavioral types had lower growth than treatments with mixed behavioral types. While evidence showed that slow explorers in homogeneous groups consumed fewer macroinvertebrates outside of refuge habitat, the same was not true of fast explorers. Results suggest that populations composed of different compositions of behavioral types may also differ in their food web interactions. The differences in growth suggest that individual performance can be higher in populations with a balanced mixture of behavioral types compared to more homogenous populations and adds to the growing knowledge that individual behavioral traits can have emergent population level effects.

大口黑鲈（largemouth bass）幼鱼具有鲜明的行为类型，这些类型沿探索行为轴分化，并在食性上存在显著差异。我们采用中宇宙实验（mesocosm experiment）检验了一项假说：相较于由单一行为类型个体组成的实验种群，由混合行为类型个体组成的种群能更高效地利用猎物资源，且个体间的竞争程度更低。我们在为期四周的实验周期内，对搭载了由浮游动物（zooplankton）与陆生昆虫自然迁入共同构成的猎物群落的中宇宙系统，开展了大口黑鲈幼鱼生长情况、食性以及猎物组成的量化测定工作。本次实验的中宇宙系统共设置三类处理组：全部个体为快速探索型、全部个体为慢速探索型，以及两种行为类型各占50%的混合组。单一行为类型组的个体生长速率显著低于混合行为类型组。尽管实验证据显示，单一行为类型组内的慢速探索型个体在庇护所生境外取食的大型无脊椎动物（macroinvertebrates）数量更少，但快速探索型个体并未表现出这一规律。研究结果显示，由不同行为类型组成的种群，其食物网相互作用模式也可能存在差异。生长速率的差异表明，相较于行为类型单一的种群，行为类型均衡混合的种群中个体的综合表现更佳；该研究也进一步丰富了当前的学术认知：个体行为性状能够产生种群水平的涌现效应。