Data from: Impacts of mussel invasions on the prey preference of two native predators

Biotic invasions can result in the displacement of native species. This can alter the availability of native prey and the choices made by native predators. We investigated prey selection by two native South African predators, the west coast rock lobster Jasus lalandii and the starfish Marthasterias africana in response to the invasive mussels, Mytilus galloprovincialis and Semimytilus algosus, and native mussels Aulacomya atra and Choromytilus meridionalis. As the diets of lobsters and starfish are broad and have been suggested to reflect prey availability, we hypothesized that they would consume the most abundant prey, regardless of its native or alien status. Laboratory studies presented predators with varying proportions of native and invasive mussels that represented pre- and post-invasion scenarios. Mussel parameters (shell strength, adductor muscle size and energy content) that may be of importance in selection by predators were compared among species. Both predators exhibited preference towards the native mussel C. meridionalis, even when it was the least abundant prey. The selection of native species occurred despite mussel parameters suggesting invasive species would be easier to consume. These findings highlight the potential for facilitation of prey invasions, especially when predators avoid alien prey and select for native comparators that may offer resistance to the invasion through inter-specific competition. It is presently unclear how often such lack of predator-driven biotic resistance acts in combination with indirect facilitation, but interrogating the behaviors that drive such outcomes will advance our understanding of successful invasions.

生物入侵（biotic invasions）可导致本地物种（native species）遭到替代与排挤。这一过程会改变本地猎物的可获得性，并影响本地捕食者的取食选择。本研究针对南非本土的两种捕食者——西海岸岩龙虾（Jasus lalandii）与海星（Marthasterias africana），探究其对入侵性贻贝（地中海贻贝Mytilus galloprovincialis、Semimytilus algosus）以及本地贻贝（Aulacomya atra、Choromytilus meridionalis）的猎物选择（prey selection）偏好。鉴于岩龙虾与海星的食性较广，且已有研究表明其食性可反映猎物的可获得性，我们提出假说：两种捕食者会优先取食丰度最高的猎物，而不考虑该猎物是本地种还是外来种。本研究通过室内实验，为捕食者提供不同比例配比的本地与入侵性贻贝，以模拟入侵发生前与入侵发生后的群落场景。研究人员对不同贻贝物种的若干可能影响捕食者选择的参数进行了比较，包括壳体强度、闭壳肌大小与能量含量。尽管本地贻贝Choromytilus meridionalis在实验中始终为丰度最低的猎物，两种捕食者仍表现出对该物种的取食偏好。尽管贻贝的参数分析显示入侵性贻贝更易于被捕食者取食，但两种捕食者仍选择了本地物种。这些研究结果揭示了猎物入侵被促进的潜在可能性：当捕食者规避外来猎物、优先选择本地猎物时，本地猎物可通过种间竞争对生物入侵产生抵抗作用，此时该促进效应尤为显著。目前尚不清楚这种缺乏捕食者介导的生物抵抗作用，与间接促进效应共同发生的频率如何，但对驱动此类结果的捕食行为展开深入探究，将有助于我们加深对成功入侵机制的认知。