title: Pollen size strongly correlates with stigma depth among Pedicularis species.
abstract: Darwin proposed that pollen size should be positively correlated with stigma depth rather than style length among species given that pollen tubes first enter the stigma autotrophically, then grow through the style heterotrophically. However, studies often show a positive relationship between pollen size and style length. Five floral traits were observed to be correlated among 42 bumblebee-pollinated Pedicularis species (Orobanchaceae) in which stigmas are distinct from styles. The phylogenetic independent contrast analysis revealed that pollen grain volume was more strongly correlated with stigma depth than with style length, consistent with Darwin's functional hypothesis between pollen size and stigma depth.
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Xiang-Ping
authors.initials: XP
authors.lastname: Wang
authors.affiliation: Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China.
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Yu
authors.affiliation: School of Life Sciences, Central China Normal University, Wuhan 430079, China.
authors.forename: Shi-Guo
authors.initials: SG
authors.lastname: Sun
authors.affiliation: School of Life Sciences, Central China Normal University, Wuhan 430079, China. Hsq@mail.ccnu.edu.cn.
authors.forename: Shuang-Quan
authors.initials: SQ
authors.lastname: Huang
mesh_terms: D035264:Flowers / Q000254:growth & development; D032262:Pedicularis / Q000145:classification / Q000254:growth & development*; D010802:Phylogeny; D011058:Pollen / Q000033:anatomy & histology / Q000254:growth & development; D053205:Pollen Tube / Q000254:growth & development
keywords: Pedicularis; phylogenetic comparative analysis; pollen grain volume; pollen tube growth; stigma depth; style length; trait correlation