Bees and crops in Spain: an update for melon, watermelon and almond

Pollinators of most of the plants cultivated in the Mediterranean regions of Europe are still unknown. We provide new data and we review previously available information on bees (Apoidea) associated with three economically important crops in Spain: melon (<i>Cucumis melo</i> L.), watermelon (<i>Citrullus lanatus</i> (Thunb.) Matsum. &amp; Nakai) and almond (<i>Prunus dulcis</i> (Mill.) D.A.Webb). We found that, overall, 98 bee species spanning four families visit flowers of the studied crop species, and 46 additional species were sampled within the crops with pan-traps. The bee assemblages visiting melon include 7–33 species, with moderate to high importance of small <i>Lasioglossum</i> (Halictidae) and of honey bee (<i>Apis mellifera</i> Linnaeus, 1758: Apidae), and in one case of small <i>Ceratina</i>: Apidae. Watermelon flowers are visited by 11–14 species of bees, with highest abundance of honey bees or of small <i>Lasioglossum</i>, depending on the locality. Bees collected on almond trees included 12–37 species, with the honey bee and medium-size to large <i>Andrena</i> (Andrenidae) and <i>Osmia</i> (Megachilidae) being predominant. The new samples expanded the geographical distributions of nearly one-fourth of the collected species. Diversity estimators slightly varied even within fields of the same crop, and a cluster analysis suggested both a certain overlap between melon and watermelon and a role of geographical distance on similarity among bee assemblages, though these patterns were much clearer using presence data rather than abundances. Below-ground-nesting and solitary species were more frequently collected than above-ground-nesting and eusocial species, but for melon and watermelon the highest abundances were recorded for eusocial species. Almost exclusively polylectic species visited the flowers of the three studied crops. The results of this study could help in planning conservation actions to maintain this important diversity of potential pollinators in Spanish areas covered by these crops.

欧洲地中海区域多数栽培植物的传粉者仍未被探明。本研究提供全新调研数据，并系统梳理了西班牙三种经济重要作物相关的蜂总科（Apoidea）类群的已有资料：甜瓜（<i>Cucumis melo</i> L.）、西瓜（<i>Citrullus lanatus</i> (Thunb.) Matsum. & Nakai）以及扁桃（<i>Prunus dulcis</i> (Mill.) D.A.Webb）。研究共记录到隶属于4个科的98种蜂类造访上述三种作物的花部，另有46个物种通过色陷阱诱捕（pan-traps）在作物田中被采集到。造访甜瓜花的蜂类类群包含7至33个物种，小型隧蜂属（<i>Lasioglossum</i>，隧蜂科（Halictidae））与西方蜜蜂（<i>Apis mellifera</i> Linnaeus, 1758，蜜蜂科（Apidae））的重要性从中等到较高不等，部分样点中小型芦蜂属（<i>Ceratina</i>，蜜蜂科（Apidae））同样占据重要地位。西瓜花的造访蜂类有11至14个物种，根据采样地点不同，优势类群为西方蜜蜂或小型隧蜂属。扁桃树上采集到的蜂类包含12至37个物种，其中西方蜜蜂、中到大型的地蜂属（<i>Andrena</i>，地蜂科（Andrenidae））以及壁蜂属（<i>Osmia</i>，切叶蜂科（Megachilidae））为优势类群。本次新采集的样本扩展了近四分之一已采集物种的地理分布范围。即便在同一作物的不同田块中，多样性估算量（diversity estimators）结果也存在小幅差异；聚类分析（cluster analysis）结果显示，甜瓜与西瓜的蜂类群落存在一定重叠，且地理距离对蜂类群落的相似性存在影响，不过基于物种存在数据而非多度数据时，上述模式会更为显著。地下筑巢的独居蜂类比地上筑巢的真社会性蜂类更常被采集到，但在甜瓜与西瓜田块中，真社会性蜂类的多度最高。三种供试作物的花部几乎仅被多食性蜂类造访。本研究结果可为制定针对性保护策略提供参考，以维持西班牙上述作物种植区内潜在传粉蜂类的重要多样性。