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.

生物入侵可导致本土物种被取代，进而改变本土猎物的可获得性与本土捕食者的捕食选择。我们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），研究其对入侵贻贝Mytilus galloprovincialis、Semimytilus algosus以及本土贻贝Aulacomya atra、Choromytilus meridionalis的猎物选择偏好。鉴于龙虾与海星的食性广泛，且已有研究表明其捕食选择可反映猎物可获得性，我们提出假说：两种捕食者会优先取食数量最多的猎物，而不考虑该猎物的本土或入侵属性。实验室实验中，我们为捕食者设置了不同比例的本土与入侵贻贝组合，以模拟入侵前与入侵后的群落场景。我们比较了各贻贝物种的多项可能影响捕食者选择的参数：壳体强度、闭壳肌大小与能量含量。两种捕食者均表现出对本土贻贝Choromytilus meridionalis的偏好，即便该物种在实验中数量最少。尽管贻贝参数显示入侵物种更易被取食，但捕食者仍选择了本土物种。本研究结果凸显了猎物入侵被促进的潜在可能——尤其是当捕食者避开外来猎物，转而选择可通过种间竞争抵御入侵的本土同类猎物时。目前尚不清楚这种缺乏捕食者介导的生物抵抗的情况与间接促进作用共同发生的频率，但解析驱动此类结果的捕食行为，将有助于我们深化对成功入侵机制的理解。