Classen Alice, Eardley Connal D, Hemp Andreas, Peters Marcell K, Peters Ralph S, Ssymank Axel, Steffan-Dewenter Ingolf
Department of Animal Ecology and Tropical Biology Biocenter University of Würzburg Würzburg Germany.
Unit of Environmental Sciences and Management North West University Potchefstroom South Africa.
Ecol Evol. 2020 Feb 5;10(4):2182-2195. doi: 10.1002/ece3.6056. eCollection 2020 Feb.
Species differ in their degree of specialization when interacting with other species, with significant consequences for the function and robustness of ecosystems. In order to better estimate such consequences, we need to improve our understanding of the spatial patterns and drivers of specialization in interaction networks.
Here, we used the extensive environmental gradient of Mt. Kilimanjaro (Tanzania, East Africa) to study patterns and drivers of specialization, and robustness of plant-pollinator interactions against simulated species extinction with standardized sampling methods. We studied specialization, network robustness and other network indices of 67 quantitative plant-pollinator networks consisting of 268 observational hours and 4,380 plant-pollinator interactions along a 3.4 km elevational gradient. Using path analysis, we tested whether resource availability, pollinator richness, visitation rates, temperature, and/or area explain average specialization in pollinator communities. We further linked pollinator specialization to different pollinator taxa, and species traits, that is, proboscis length, body size, and species elevational ranges.
We found that specialization decreased with increasing elevation at different levels of biological organization. Among all variables, mean annual temperature was the best predictor of average specialization in pollinator communities. Specialization differed between pollinator taxa, but was not related to pollinator traits. Network robustness against simulated species extinctions of both plants and pollinators was lowest in the most specialized interaction networks, that is, in the lowlands.
Our study uncovers patterns in plant-pollinator specialization along elevational gradients. Mean annual temperature was closely linked to pollinator specialization. Energetic constraints, caused by short activity timeframes in cold highlands, may force ectothermic species to broaden their dietary spectrum. Alternatively or in addition, accelerated evolutionary rates might facilitate the establishment of specialization under warm climates. Despite the mechanisms behind the patterns have yet to be fully resolved, our data suggest that temperature shifts in the course of climate change may destabilize pollination networks by affecting network architecture.
物种在与其他物种互动时的专业化程度存在差异，这对生态系统的功能和稳健性具有重大影响。为了更好地评估这些影响，我们需要加深对互动网络中专业化的空间格局及其驱动因素的理解。
在此，我们利用乞力马扎罗山（坦桑尼亚，东非）广泛的环境梯度，采用标准化采样方法研究专业化的格局和驱动因素，以及植物 - 传粉者相互作用对模拟物种灭绝的稳健性。我们沿着3.4公里的海拔梯度，研究了由268个观测小时和4380次植物 - 传粉者相互作用组成的67个定量植物 - 传粉者网络的专业化、网络稳健性及其他网络指标。通过路径分析，我们测试了资源可用性、传粉者丰富度、访花率、温度和/或面积是否能解释传粉者群落的平均专业化程度。我们还进一步将传粉者专业化与不同的传粉者类群以及物种特征（即喙长、体型和物种海拔范围）联系起来。
我们发现，在不同生物组织水平上，专业化程度随海拔升高而降低。在所有变量中，年平均温度是传粉者群落平均专业化程度的最佳预测指标。传粉者类群之间的专业化程度存在差异，但与传粉者特征无关。在最专业化的互动网络中，即低地地区，植物和传粉者模拟物种灭绝时的网络稳健性最低。
我们的研究揭示了植物 - 传粉者专业化沿海拔梯度变化的格局。年平均温度与传粉者专业化密切相关。寒冷高海拔地区活动时间短所导致的能量限制，可能迫使变温物种拓宽其饮食谱。或者此外，加速的进化速率可能有助于在温暖气候下建立专业化。尽管这些格局背后的机制尚未完全解决，但我们的数据表明，气候变化过程中的温度变化可能通过影响网络结构使传粉网络不稳定。
