Wildfire reveals transient changes to individual traits and population responses of a native bumble bee ( Bombus vosnesenskii ),Journal of Animal Ecology

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Wildfire reveals transient changes to individual traits and population responses of a native bumble bee ( Bombus vosnesenskii )
Journal of Animal Ecology ( IF 3.5 ) Pub Date : 2020-05-19 , DOI: 10.1111/1365-2656.13244
John M Mola _{1,

2} , Michael R Miller _{2,

3} , Sean M O'Rourke ₃ , Neal M Williams _{2,

4}

Affiliation

Fire-induced changes in the abundance and distribution of organisms, especially plants, can alter resource landscapes for mobile consumers driving bottom-up effects on their population sizes, morphologies, and reproductive potential. We expect these impacts to be most striking for obligate visitors of plants, like bees and other pollinators, but these impacts can be difficult to interpret due to the limited information provided by forager counts in the absence of survival or fitness proxies. Increased bumble bee worker abundance is often coincident with the pulses of flowers that follow recent fire. However, it is unknown if observed postfire activity is due to underlying population growth or a stable pool of colonies recruiting more foragers to abundant resource patches. This distinction is necessary for determining the net impact of disturbance on bumble bees: are there population-wide responses or do just a few colonies reap the rewards? We estimated colony abundance before and after fire in burned and unburned areas using a genetic mark-recapture framework. We paired colony abundance estimates with measures of body size, counts of queens, and estimates of foraging and dispersal to assess changes in worker size, reproductive output, and landscape-scale movements. Higher floral abundance following fire not only increased forager abundance, but also the number of colonies from which those foragers came. Importantly, despite a larger population size we also observed increased mean worker size. Two years following fire, queen abundance was higher in both burned and unburned sites, potentially due to the dispersal of queens from burned into unburned areas. The effects of fire were transient; within two growing seasons, worker abundance was substantially reduced across the entire sampling area and body sizes were similar between burned and unburned sites. Our results reveal how disturbance can temporarily release populations from resource limitation, boosting the genetic diversity, body size, and reproductive output of populations. Given that the effects of fire on bumble bees acted indirectly through pulsed resource availability, it is likely our results are generalizable to other situations, such as habitat restorations, where resource density is enhanced within the landscape.

中文翻译：

野火揭示了本地熊蜂 (Bombus vosnesenskii) 个体特征和种群反应的短暂变化

火灾引起的生物（尤其是植物）丰度和分布的变化可以改变移动消费者的资源景观，从而推动对其种群规模、形态和繁殖潜力的自下而上的影响。我们预计这些影响对于植物的专性访问者（如蜜蜂和其他传粉者）来说最为显着，但由于在缺乏生存或健康代理的情况下，觅食者计数提供的信息有限，因此这些影响可能难以解释。大黄蜂工人数量的增加通常与最近火灾后的花朵脉冲相吻合。然而，尚不清楚观察到的火灾后活动是否是由于潜在的人口增长或稳定的殖民地池招募更多的觅食者到丰富的资源斑块。这种区别对于确定干扰对大黄蜂的净影响是必要的：是否有全种群的反应，还是只有少数蜂群获得了回报？我们使用遗传标记重新捕获框架估计了燃烧和未燃烧区域火灾前后的菌落丰度。我们将群体丰度估计值与体型、蚁后数量以及觅食和散布估计值相结合，以评估工人大小、繁殖产量和景观尺度运动的变化。火灾后更高的花卉丰度不仅增加了觅食者的丰度，而且增加了这些觅食者的群体数量。重要的是，尽管人口规模较大，但我们也观察到平均工人规模有所增加。火灾发生两年后，燃烧和未燃烧地点的蜂王丰度更高，可能是由于蚁后从燃烧到未燃烧区域的分散。火灾的影响是短暂的；在两个生长季节内，整个采样区域的工人数量显着减少，燃烧和未燃烧地点的体型相似。我们的结果揭示了干扰如何暂时使种群摆脱资源限制，提高种群的遗传多样性、体型和繁殖能力。鉴于火灾对大黄蜂的影响是通过脉冲资源可用性间接起作用的，我们的结果很可能适用于其他情况，例如栖息地恢复，其中景观中的资源密度增加。整个采样区域的工人数量显着减少，燃烧和未燃烧地点之间的体型相似。我们的结果揭示了干扰如何暂时使种群摆脱资源限制，提高种群的遗传多样性、体型和繁殖能力。鉴于火灾对大黄蜂的影响是通过脉冲资源可用性间接起作用的，我们的结果很可能适用于其他情况，例如栖息地恢复，其中景观中的资源密度增加。整个采样区域的工人数量显着减少，燃烧和未燃烧地点之间的体型相似。我们的结果揭示了干扰如何暂时使种群摆脱资源限制，提高种群的遗传多样性、体型和繁殖能力。鉴于火灾对大黄蜂的影响是通过脉冲资源可用性间接起作用的，我们的结果很可能适用于其他情况，例如栖息地恢复，其中景观中的资源密度增加。

更新日期：2020-05-19

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