Data from: High temperature intensifies negative density dependence of fitness in red flour beetles

Competition for food, space, or other depletable resources has strong impacts on the fitness of organisms and can lead to a pattern known as negative density dependence, where fitness decreases as population density increases. Yet, many resources that have strong impacts on fitness are nondepletable (e.g., moisture or temperature). How do these nondepletable resources interact with depletable resources to modify negative density dependence? We tested the hypothesis that negative density dependence is modulated by temperature in red flour beetles and tested the prediction that the strength of negative density dependence should decrease as temperature decreases. We measured the number of eggs laid, offspring development time, and the number of offspring that reached maturity at three temperatures and two food treatment combinations as we simultaneously manipulated adult population density. We demonstrated that low temperatures weaken negative density dependence in the number of eggs laid; this pattern was most evident when food was abundant. Density had no effect on development time, but low temperatures increased development time. The percent of eggs that emerged as adults decreased with both density and temperature and increased with food. Temperature, an abiotic driver, can thus modulate density-dependent processes in ectotherms. Therefore, models of population growth for ectotherms should incorporate the effects of temperature.针对食物、空间或其他可耗尽资源的竞争，会对生物的适合度（fitness）产生强烈影响，并可能催生一种被称为负密度依赖（negative density dependence）的模式：即生物适合度随种群密度升高而下降。然而，诸多对适合度具有显著影响的资源却是不可耗尽的，例如水分与温度。那么这些不可耗尽资源与可耗尽资源会如何相互作用，进而改变负密度依赖的效应？我们以红面粉甲虫（red flour beetles）为实验对象，验证了“温度会调控负密度依赖”这一假说，并检验了“负密度依赖的强度应随温度降低而减弱”这一预测。我们在三种温度条件与两种食物处理组合下，通过同步调控成虫种群密度，测量了成虫产卵量、后代发育时长以及成功达到成熟的后代数量。研究结果表明，低温会减弱产卵量相关的负密度依赖效应，这一模式在食物充足时最为显著；种群密度对后代发育时长无显著影响，但低温会延长发育时长；卵孵化为成虫的比例随种群密度与温度升高而降低，随食物供给增加而升高。作为非生物驱动因子的温度，能够调控外温动物（ectotherms）的密度依赖过程，因此外温动物的种群增长模型应当纳入温度的影响效应。