Strugariu Alexandru, Martin Ryan Andrew
Department of Exact and Natural Sciences, Institute of Interdisciplinary Research, Alexandru Ioan Cuza University of Iași, 700057 Iași, Romania.
Department of Biology, Case Western Reserve University, Cleveland, OH 44106, USA.
Animals (Basel). 2023 Apr 6;13(7):1264. doi: 10.3390/ani13071264.
Disruptive selection arises when extreme phenotypes have a fitness advantage compared to more-intermediate phenotypes. Theory and evidence suggest that intraspecific resource competition is a key driver of disruptive selection. However, while competition can be indirect (exploitative) or direct (interference), the role of interference competition in disruptive selection has not been tested, and most models of disruptive selection assume exploitative competition. We experimentally investigated whether the type of competition affects the outcome of competitive interactions using a system where disruptive selection is common: Mexican spadefoot toads (). tadpoles develop into alternative resource-use phenotypes: carnivores, which consume fairy shrimp and other tadpoles, and omnivores, which feed on algae and detritus. Tadpoles intermediate in phenotype have low fitness when competition is intense, as they are outcompeted by the specialized tadpoles. Our experiments revealed that the presence of carnivores significantly decreased foraging behavior in intermediate tadpoles, and that intermediate tadpoles had significantly lower growth rates in interference competition treatments with carnivores but not with omnivores. Interference competition may therefore be important in driving disruptive selection. As carnivore tadpoles are also cannibalistic, the 'fear' effect may have a greater impact on intermediate tadpoles than exploitative competition alone, similarly to non-consumptive effects in predator-prey or intraguild relationships.
当极端表型比更中间的表型具有适应性优势时，就会出现间断性选择。理论和证据表明，种内资源竞争是间断性选择的关键驱动因素。然而，虽然竞争可以是间接的（剥削性的）或直接的（干扰性的），但干扰性竞争在间断性选择中的作用尚未得到检验，并且大多数间断性选择模型都假定为剥削性竞争。我们使用一个常见间断性选择的系统，通过实验研究了竞争类型是否会影响竞争相互作用的结果：墨西哥锄足蟾（）。蝌蚪会发育成不同的资源利用表型：食肉动物，以仙女虾和其他蝌蚪为食；杂食动物，以藻类和碎屑为食。当竞争激烈时，表型处于中间状态的蝌蚪适应性较低，因为它们会被特化的蝌蚪击败。我们的实验表明，食肉动物的存在显著降低了中间型蝌蚪的觅食行为，并且在与食肉动物而非杂食动物的干扰性竞争处理中，中间型蝌蚪的生长速度显著较低。因此，干扰性竞争在推动间断性选择方面可能很重要。由于食肉动物蝌蚪也是同类相食的，“恐惧”效应可能对中间型蝌蚪的影响比对单纯的剥削性竞争更大，这类似于捕食者 - 猎物或同资源集团关系中的非消费性效应。
