Data from: Non-additive effects of intra- and interspecific competition between two larval salamanders

1) Assessment of the relative strengths of intra- and interspecific competition has increased in recent years, and is critical to understanding the importance of competition. Yet, whether intra- and interspecific competition can have non-additive effects has rarely been tested. The resulting fitness consequences of such non-additive interactions are important to provide the context necessary to advance our understanding of competition theory. 2) We compared the strength of additive and non-additive intra- and interspecific competition by manipulating densities of a pair of larval salamanders (Ambystoma talpoideum and A. maculatum) in experimental mesocosms within a response surface design. 3) Intraspecific density had the strongest effect on the strength of competition for both species, and few observed comparisons indicated interspecific competition was an important factor in predicting body size, growth or larval period length of either species. 4) Non-additive effects of intra- and interspecific competition influenced some response variables, including size and mass at metamorphosis in A. maculatum, but at a reduced strength compared to intraspecific effects alone. 5) Intraspecific competition was thus the dominant biotic interaction, but non-additive effects also impact the outcome of competition in these species, validating the importance of testing for and incorporating non-additive density effects into competition models.1) 近年来，种内竞争（intraspecific competition）与种间竞争（interspecific competition）的相对强度评估研究愈发增多，这对于明晰竞争的生态学意义至关重要。然而，种内与种间竞争是否能够产生非加性效应（non-additive effects），迄今极少得到实证检验。这类非加性相互作用所带来的适合度后果，可为推进竞争理论的认知提供必要的研究语境。 2) 本研究依托响应面设计（response surface design），在实验中宇宙装置（experimental mesocosms）中操控两种幼虫蝾螈（Ambystoma talpoideum与A. maculatum）的种群密度，以此对比加性与非加性种内、种间竞争的强度。 3) 对于两个受试物种而言，种内密度对竞争强度的影响均最为显著；且仅在极少数观测案例中，种间竞争可作为预测任一物种体型大小、生长速率或幼虫期时长的关键因子。 4) 种内与种间竞争的非加性效应，会对部分响应变量产生影响，其中包括A. maculatum变态发育时的体型与体重，但该效应的强度相较于单纯的种内效应有所减弱。 5) 综上，种内竞争是主导性的生物相互作用（biotic interaction），但非加性效应同样会影响这两个物种的竞争结局，这证实了在竞争模型中纳入并检验非加性密度效应的必要性与重要性。