Department of Biological Sciences, University of South Carolina, 715 Sumter St, Columbia, SC 29208, USA.
Am J Bot. 2022 Jun;109(6):1047-1055. doi: 10.1002/ajb2.1857. Epub 2022 May 21.
A switch in pollinator can occur when a plant lineage enters a new habitat where the ancestral pollinator is less common, and a novel pollinator is more common. Because pollinator communities vary according to environmental tolerances and availability of resources, there may be consistent associations between pollination mode and specific regions and habitats. Such associations can be studied in lineages that have experienced multiple pollinator transitions, representing evolutionary replicates.
Our study focused on a large clade of Penstemon wildflower species in western North America, which has repeatedly evolved hummingbird-adapted flowers from ancestral bee-adapted flowers. For each species, we estimated geographic ranges from occurrence data and inferred environmental niches from climate, topographical, and soil data. Using a phylogenetic comparative approach, we investigated whether hummingbird-adapted species occupy distinct geographic regions or habitats relative to bee-adapted species.
Hummingbird-adapted species occur at lower latitudes and lower elevations than bee-adapted species, resulting in a difference in their environmental niche. Bee-adapted species sister to hummingbird-adapted species are also found in relatively low elevations and latitudes, similar to their hummingbird-adapted sister species, suggesting ecogeographic shifts precede pollinator divergence. Sister species pairs-regardless of whether they differ in pollinator-show relatively little geographic range overlap.
Adaptation to a novel pollinator may often occur in geographic and ecological isolation from ancestral populations. The ability of a given lineage to adapt to novel pollinators may critically depend on its ability to colonize regions and habitats associated with novel pollinator communities.
当一个植物谱系进入一个新的栖息地，那里祖先传粉者较少，而新的传粉者更为常见时，传粉者可能会发生转变。由于传粉者群落因环境耐受性和资源可利用性而有所不同，因此在经历了多次传粉者转变的谱系中，可能存在与特定地区和栖息地之间的一致关联，这些转变可以作为进化的复制品进行研究。
我们的研究集中在北美的西部，一个大型的风铃草野生花卉物种进化枝，它从祖先的蜜蜂适应花多次进化为蜂鸟适应花。对于每个物种，我们根据出现数据估计了地理范围，并根据气候、地形和土壤数据推断了生态位。利用系统发育比较方法，我们调查了相对于蜜蜂适应物种，蜂鸟适应物种是否占据了独特的地理区域或栖息地。
蜂鸟适应物种的分布纬度和海拔都低于蜜蜂适应物种，导致它们的生态位不同。与蜂鸟适应物种亲缘关系最近的蜜蜂适应物种也存在于相对较低的海拔和纬度，与它们的蜂鸟适应姐妹物种相似，这表明生态地理转变先于传粉者的分歧。无论是否在传粉者方面存在差异，姐妹种对之间的地理范围重叠相对较少。
对新传粉者的适应往往可能与祖先种群在地理和生态上是隔离的。给定谱系适应新传粉者的能力可能严重依赖于其在与新传粉者群落相关的地区和栖息地进行殖民的能力。
