title: Extremely high proportions of male flowers and geographic variation in floral ratios within male figs of Ficus tikoua despite pollinators displaying active pollen collection.
abstract: Most plants are pollinated passively, but active pollination has evolved among insects that depend on ovule fertilization for larval development. Anther-to-ovule ratios (A/O ratios, a coarse indicator of pollen-to-ovule ratios) are strong indicators of pollination mode in fig trees and are consistent within most species. However, unusually high values and high variation of A/O ratios (0.096-10.0) were detected among male plants from 41 natural populations of Ficus tikoua in China. Higher proportions of male (staminate) flowers were associated with a change in their distribution within the figs, from circum-ostiolar to scattered. Plants bearing figs with ostiolar or scattered male flowers were geographically separated, with scattered male flowers found mainly on the Yungui Plateau in the southwest of our sample area. The A/O ratios of most F. tikoua figs were indicative of passive pollination, but its Ceratosolen fig wasp pollinator actively loads pollen into its pollen pockets. Additional pollen was also carried on their body surface and pollinators emerging from scattered-flower figs had more surface pollen. Large amounts of pollen grains on the insects' body surface are usually indicative of a passive pollinator. This is the first recorded case of an actively pollinated Ficus species producing large amounts of pollen. Overall high A/O ratios, particularly in some populations, in combination with actively pollinating pollinators, may reflect a response by the plant to insufficient quantities of pollen transported in the wasps' pollen pockets, together with geographic variation in this pollen limitation. This suggests an unstable scenario that could lead to eventual loss of wasp active pollination behavior.
authors: Ecological Security and Protection Key laboratory of Sichuan Province College of Life Science and Biotechnology Mianyang Normal University Mianyang Sichuan 621000 China.
authors: Jun-Yin
authors: JY
authors: Deng
authors: Ecological Security and Protection Key laboratory of Sichuan Province College of Life Science and Biotechnology Mianyang Normal University Mianyang Sichuan 621000 China.
authors: Rong-Hua
authors: RH
authors: Fu
authors: School of Biology University of Leeds Leeds LS2 9JT UK; Department of Zoology and Entomology Rhodes University Grahamstown 6140 South Africa.
authors: Stephen G
authors: SG
authors: Compton
authors: Ecological Security and Protection Key laboratory of Sichuan Province College of Life Science and Biotechnology Mianyang Normal University Mianyang Sichuan 621000 China.
authors: Dai-Mei
authors: DM
authors: Hu
authors: Ecological Security and Protection Key laboratory of Sichuan Province College of Life Science and Biotechnology Mianyang Normal University Mianyang Sichuan 621000 China.
authors: Lu-Shui
authors: LS
authors: Zhang
authors: Ecological Security and Protection Key laboratory of Sichuan Province College of Life Science and Biotechnology Mianyang Normal University Mianyang Sichuan 621000 China.
authors: Fan
authors: F
authors: Yang
authors: Ecological Security and Protection Key laboratory of Sichuan Province College of Life Science and Biotechnology Mianyang Normal University Mianyang Sichuan 621000 China.
authors: Yan
authors: Y
authors: Chen
authors: CEFE UMR 5175 CNRS Université de Montpellier Université Paul-Valéry Montpellier EPHE Montpellier France.
authors: Finn
authors: F
authors: Kjellberg
keywords: Active pollination; Ceratosolen; P/O ratios; anther‐to‐ovule ratios; fig wasp; inflorescence design; pollen limitation