Sponsler Douglas B, Hamilton Murray, Wiesneth Michael, Steffan-Dewenter Ingolf
Department of Animal Ecology and Tropical Biology, Biocenter University of Würzburg Würzburg Germany.
Ecol Evol. 2024 Jun 18;14(6):e11531. doi: 10.1002/ece3.11531. eCollection 2024 Jun.
Concerns about competition between pollinators are predicated on the assumption of floral resource limitation. Floral resource limitation, however, is a complex phenomenon involving the interplay of resource production by plants, resource demand by pollinators, and exogenous factors-like weather conditions-that constrain both plants and pollinators. In this study, we examined nectar limitation during the mass flowering of rosaceous fruit trees in early spring. Our study was set in the same region as a previous study that found severe nectar limitation in summer grasslands. We used this seasonal contrast to evaluate two alternative hypotheses concerning the seasonal dynamics of floral resource limitation: either (H1) rates of resource production and consumption are matched through seasonal time to maintain a consistent degree of resource limitation, or (H2) a mismatch of high floral resource production and low pollinator activity in early spring creates a period of relaxed resource limitation that intensifies later in the year. We found generally much lower depletion in our spring study compared to the near 100% depletion found in the summer study, but depletion rates varied markedly through diel time and across sampling days, with afternoon depletion rates sometimes exceeding 80%. In some cases, there were also pronounced differences in depletion rates across simultaneously sampled floral species, indicating different degrees of nectar exploitation. These findings generally support the seasonal mismatch hypothesis (H2) but underscore the complex contingency of nectar depletion. The challenge of future work is to discern how the fluctuation of resource limitation across diel, inter-diel, and seasonal time scales translates into population-level outcomes for pollinators.
对传粉者之间竞争的担忧是基于花卉资源有限的假设。然而，花卉资源有限是一个复杂的现象，涉及植物的资源生产、传粉者的资源需求以及诸如天气条件等限制植物和传粉者的外部因素之间的相互作用。在本研究中，我们调查了早春蔷薇科果树大量开花期间的花蜜限制情况。我们的研究与之前一项发现夏季草原存在严重花蜜限制的研究在同一地区进行。我们利用这种季节对比来评估关于花卉资源限制季节动态的两个替代假设：要么（H1）资源生产和消耗率在季节时间上相匹配，以维持一致的资源限制程度，要么（H2）早春花卉资源高产与传粉者活动低的不匹配导致了一段资源限制宽松的时期，而这一时期在当年晚些时候会加剧。我们发现，与夏季研究中接近100%的消耗相比，我们春季研究中的消耗普遍要低得多，但消耗率在昼夜时间和不同采样日之间有显著差异，下午的消耗率有时超过80%。在某些情况下，同时采样的花卉物种之间的消耗率也存在明显差异，这表明花蜜利用程度不同。这些发现总体上支持季节不匹配假说（H2），但强调了花蜜消耗的复杂偶然性。未来工作的挑战是要弄清楚资源限制在昼夜、日间和季节时间尺度上的波动如何转化为传粉者的种群水平结果。
