Barnacle recurit density, biomass, and reproductive output measured in rocky intertidal habitats in Glasgow Head, on the Atlantic coast of Nova Scotia, Canada@en

Through a field experiment, we show that a predator has negative nonconsumptive effects (NCEs) on different life-history stages of the same prey species. Shortly before the recruitment season of the barnacle Semibalanus balanoides (May–June), we established experimental cages in rocky intertidal habitats in Nova Scotia, Canada. The cages were used to manipulate the presence and absence of dogwhelks, Nucella lapillus, the main predators of barnacles. At the centre of each cage, we installed a tile where barnacle pelagic larvae could settle and the resulting recruits grow. Mesh prevented caged dogwhelks from accessing the tiles, but allowed waterborne dogwhelk cues to reach the tiles. Results in May indicated that barnacle larvae settled preferentially on tiles from cages without dogwhelks. In November, at the end of the dogwhelk activity period and once the barnacle recruits had grown to adult size, barnacle body mass was lower in the presence of dogwhelks. This limitation may have resulted from a lower barnacle feeding activity with nearby dogwhelks, as found by a previous study. The observed larval and adult responses in barnacles are consistent with attempts to decrease predation risk. November data also indicated that dogwhelk cues limited barnacle reproductive output, a possible consequence of the limited growth of barnacles. Overall, this study suggests that a predator species might influence trait evolution in a prey species through NCEs on different life-history stages.本研究通过野外实验证实，捕食者可对同一猎物种的不同生活史阶段产生负面非消耗性效应（nonconsumptive effects, NCEs）。在纹藤壶（Semibalanus balanoides）幼体招募季（5至6月）来临前，我们于加拿大新斯科舍省的潮间带岩滩生境中搭建了实验笼。该实验笼用于调控狗岩螺（Nucella lapillus，藤壶的主要捕食者）的有无。每个实验笼的中心均布设一块陶片，以供藤壶浮游幼体附着并完成后续幼体发育。笼体网孔可阻隔笼内饲养的狗岩螺接触陶片，但允许水体中携带的狗岩螺化学信号传递至陶片处。5月的观测结果显示，藤壶幼体优先选择无狗岩螺的实验笼内陶片进行附着。11月，即狗岩螺活动周期结束且藤壶幼体生长至成体规格时，有狗岩螺信号组的藤壶体质量显著更低。该生长限制效应可能源于此前一项研究的发现：当附近存在狗岩螺时，藤壶的摄食活动会受到抑制。观测到的藤壶幼体与成体响应，与其为降低捕食风险而采取的适应性策略相一致。11月的观测数据还显示，狗岩螺信号会抑制藤壶的繁殖输出，这可能是藤壶生长受限的间接结果。综上，本研究表明，捕食者可通过对猎物不同生活史阶段施加非消耗性效应，进而影响猎物种的性状进化。