Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa.
The Compton Herbarium, Kirstenbosch Research Centre, South African National Biodiversity Institute, Newlands, Cape Town, South Africa.
Ann Bot. 2019 Jan 23;123(2):277-288. doi: 10.1093/aob/mcy126.
As most plants rely on pollination for persistence in communities, pollination interactions should be important determinants of plant community assembly. Here, trait and phylogenetic null modelling approaches were combined with pollinator interaction networks to elucidate the processes structuring flower colour assembly patterns in Asteraceae communities in Namaqualand, South Africa.
Plant species were assigned to flower colour pattern categories (CPCs) that incorporate the complexity of the bulls-eye colour pattern, using pollinator vision models. Null models were used to assess whether daisy communities exhibit clustering (driven by filtering, facilitation or convergence) or overdispersion (driven by competitive exclusion or character displacement) of CPCs. Next, flower visitor networks were constructed for communities with non-random CPC assembly to confirm the functional role of pollinators in determining floral trait assembly.
Plant species are unevenly distributed across CPCs, the majority of which are not phylogenetically conserved, suggesting that certain CPCs have a selective advantage. Clustering of CPCs in communities is more frequent than overdispersion, and this does not reflect non-random phylogenetic assembly. In most communities at least one CPC is overrepresented relative to null assemblages. Interaction networks show that each community has a single dominant pollinator that strongly interacts with the overrepresented CPC, suggesting a role for pollinator preferences in driving clustered assembly of CPCs within daisy communities.
This novel approach, which demonstrates non-random assembly of complex flower colour patterns and corroborates their functional association with particular pollinators, provides strong evidence that pollinators influence plant community assembly. Results suggest that in some community contexts the benefits of pollinator sharing outweigh the costs of heterospecific pollen transfer, generating clustered assembly. They also challenge the perception of generalized pollination in daisies, suggesting instead that complex daisy colour patterns represent a pollination syndrome trait linked to specific fly pollinators.
由于大多数植物依赖传粉来维持其在群落中的生存，因此传粉相互作用应该是植物群落组装的重要决定因素。在这里，性状和系统发育零模型方法与传粉者相互作用网络相结合，阐明了南非纳马夸兰 Asteraceae 群落中花色组装模式的形成过程。
利用传粉者视觉模型，将植物物种分配到花色图案类别 (CPC) 中，这些类别包含了靶心颜色图案的复杂性。零模型用于评估雏菊群落是否表现出 CPC 的聚类（由过滤、促进或趋同驱动）或过分散（由竞争排斥或特征置换驱动）。接下来，为具有非随机 CPC 组装的群落构建花访客网络，以确认传粉者在确定花色性状组装中的功能作用。
植物物种在 CPC 中分布不均匀，其中大多数物种在系统发育上没有保守性，这表明某些 CPC 具有选择性优势。群落中 CPC 的聚类比过分散更为频繁，这并不反映非随机的系统发育组装。在大多数群落中，至少有一种 CPC 相对于零集装是过代表的。相互作用网络表明，每个群落都有一种主要的传粉者与过代表的 CPC 强烈相互作用，这表明传粉者偏好在驱动雏菊群落中 CPC 的聚类组装中发挥作用。
这种新颖的方法证明了复杂花色图案的非随机组装，并证实了它们与特定传粉者的功能关联，为传粉者影响植物群落组装提供了强有力的证据。结果表明，在某些群落环境中，传粉者共享的好处超过了异交花粉转移的成本，从而产生了聚类组装。它们还挑战了雏菊中普遍传粉的观念，表明复杂的雏菊颜色模式代表了与特定蝇传粉者相关的传粉综合征性状。
