Department of Biology, University of Ottawa, Ottawa, ON, Canada.
Rocky Mountain Biological Laboratory, Crested Butte, CO, USA.
J Anim Ecol. 2021 May;90(5):1353-1366. doi: 10.1111/1365-2656.13460. Epub 2021 Mar 19.
Reproductive timing can affect an organism's production of offspring and its offspring's success, both of which contribute to its overall fitness. In seasonal environments, the timing of reproductive activity may be restricted to short periods of the year owing to numerous potential selective pressures such as variation in daylength, weather, food availability, predation or competition. We documented the relationships between reproductive timing and individual reproductive success (total reproductive output and offspring success) in subalpine populations of five cavity-nesting solitary bee species. We also examined the relationships between bee reproductive success and environmental variables that are likely ultimate drivers of bee phenology in subalpine environments (i.e. seasonality of floral resource abundance and temperature). Over 6 years, we recorded solitary bee nesting timing, egg production and offspring success using artificial nesting structures ('trap-nests') established at multiple study sites. We also quantified floral resources and recorded temperature throughout growing seasons. Bees nesting earlier in the season exhibited greater reproductive success. Reproductive output generally increased with floral abundance, although this relationship was weak and only significant for some bee species. Elevated temperatures were associated with increased nest construction rate, but not with greater reproductive output. These contrasting effects of temperature may have been driven by the negative relationship between temperature and bee longevity. Bees who nested for shorter durations of time (a proxy for longevity) produced fewer offspring, and individuals exhibiting the shortest nesting durations were also those that began nesting late in the season. Overall, bees who initiated nesting early and sustained activity for a long duration had the highest reproductive output. This work documents the relationship between reproductive phenology and fitness in wild insect populations and highlights the ways in which organisms can cope with the challenges of living in seasonal and highly variable environments.
繁殖时机可以影响生物的繁殖数量及其后代的成功，而这两者都有助于生物的整体适应性。在季节性环境中，由于多种潜在的选择压力，如日长、天气、食物供应、捕食或竞争的变化，繁殖活动的时间可能会受到限制，只能集中在一年中的短时间内。我们记录了 5 种洞穴筑巢独居蜜蜂物种的亚高山种群中繁殖时机与个体繁殖成功（总繁殖量和后代成功）之间的关系。我们还研究了蜜蜂繁殖成功与环境变量之间的关系，这些环境变量可能是亚高山环境中蜜蜂物候学的最终驱动因素（即花卉资源丰富度和温度的季节性）。在 6 年多的时间里，我们使用在多个研究地点建立的人工筑巢结构（“陷阱巢”）记录了独居蜜蜂的筑巢时间、产卵和后代成功。我们还量化了花卉资源并记录了整个生长季节的温度。在季节早期筑巢的蜜蜂表现出更高的繁殖成功率。繁殖输出通常随着花卉丰富度的增加而增加，尽管这种关系较弱，仅对一些蜜蜂物种有意义。较高的温度与筑巢速度的增加有关，但与繁殖输出的增加无关。温度的这种相反影响可能是由温度与蜜蜂寿命之间的负相关关系驱动的。筑巢时间较短（寿命的代理）的蜜蜂繁殖的后代较少，而筑巢时间最短的个体也是在季节后期开始筑巢的个体。总的来说，那些早期开始筑巢并长时间持续活动的蜜蜂繁殖输出最高。这项工作记录了野生昆虫种群中繁殖物候学与适应性之间的关系，并强调了生物体应对在季节性和高度可变环境中生活的挑战的方式。
