Department of Biology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA.
Oecologia. 2020 Jul;193(3):749-759. doi: 10.1007/s00442-020-04705-w. Epub 2020 Jul 11.
Climate change is creating warmer, earlier springs, which are causing the phenology of many organisms to shift. Additionally, as temperatures increase, the body size of many ectotherms is decreasing. However, phenological and body size shifts are not occurring at the same rates across species, even in species that live in close proximity or have similar life history. Differing rates of phenological and body-size shifts may affect ecological interactions. We investigated whether shifts in phenology and body size had a predictable effect on interspecific competition. We tested three hypotheses. First, priority effects would indicate early arriving organisms gain a competitive advantage. Second, larger organisms would be competitively superior. Third, similarly sized organisms would compete more strongly. We manipulated aquatic larval conditions to create variation in wood frog (Rana sylvatica) size at and date of metamorphosis. Wood frogs were placed in terrestrial enclosures with unmanipulated juvenile American toads (Anaxyrus americanus) where we tracked amphibian growth over 3 months. Consistent with the size superiority hypothesis, initially smaller wood frogs did not compete as strongly with toads. However, the results of the phenological shift were the opposite of our priority effects prediction: early arrival by frogs increased toad mass. Our results could indicate that toads would experience fewer negative effects of competition with wood frogs that metamorphose earlier and smaller under climate change. Our study highlights the challenges of predicting how climate change will affect interspecific interactions and emphasizes the need to investigate the role of shifts in both phenology and body size.
气候变化正在导致春季变暖、提前到来，从而使许多生物的物候发生变化。此外，随着温度的升高，许多变温动物的体型正在变小。然而，即使在生活在相近环境或具有相似生活史的物种中，物候和体型的变化也不是以相同的速度发生的。物候和体型变化的不同速度可能会影响生态相互作用。我们研究了物候和体型的变化是否会对种间竞争产生可预测的影响。我们检验了三个假说。首先，优先效应表明，较早到达的生物体会获得竞争优势。其次，体型较大的生物在竞争中会更占优势。第三，体型相似的生物会竞争得更激烈。我们通过操纵水生幼虫的条件来改变林蛙（Rana sylvatica）在变态时的体型和日期。将林蛙放入未受人为干预的幼年美洲牛蛙（Anaxyrus americanus）的陆地围栏中，在 3 个月的时间里，我们跟踪了两栖动物的生长情况。与体型优势假说一致，最初体型较小的林蛙与牛蛙的竞争并不强烈。然而，物候变化的结果与我们的优先效应预测相反：青蛙的提前到达增加了牛蛙的体重。我们的结果可能表明，与那些更早、更小的林蛙相比，牛蛙在气候变化下与林蛙竞争时会受到较少的负面影响。我们的研究强调了预测气候变化将如何影响种间相互作用的挑战，并强调了需要研究物候和体型变化的作用。
