杭州石荠苎和石香薷(唇形科)的传粉生物学比较研究

COMPARATIVE STUDIES ON POLLINATION BIOLOGY OF MOSLA HANGCHOUENSIS AND M. CHINENSIS (LABIATAE)

杭州石荠苎 (Mosla hangchouensis Matsuda)和石香薷 (M.chinensis Maxim.)是一对种对 ,前者零星分布于浙江 ,后者广布于长江流域以南地区。杭州石荠苎以异花传粉为主 ,花粉 /胚珠 (P/ O)为 756～6163;石香薷以自花传粉为主 ,P/ O=110。杭州石荠苎的花部特征适于异花传粉 :花冠筒长 5～ 10 mm,口部直径 3～ 5mm,鲜红色 ;花柱长 6～ 15mm,柱头伸出花冠筒外 ,高出花药 1.5～ 2 .0 mm,柱头在花朵开放以后才有受粉能力 ;花药在花朵开放后纵裂 ;自交结实率 11.6% ;自然状态下结实率 77.5%。石香薷的花部器官明显退化 :花冠筒长 3mm,口部直径 1.0～ 1.5mm,白色或淡粉红色 ;花柱长 2 .5mm,柱头不伸出花冠筒外 ,紧靠花药 ,自花传粉现象频繁 ;套袋自交结实率 75.0 % ,自然状态下结实率 95.0 %。杭州石荠苎的传粉昆虫主要是三条熊蜂 (Bombus trifascitus Smith.)、中华蜜蜂 (Apis cerana Fabricius)、叶舌蜂 (H ylaeussp.)和淡脉隧蜂 (L asioglossum eidmanni Bluthgen)等 ,体长多在 5～ 15mm,胸部直径在1.5～ 5.0 mm之间 ,口器长 1.0～ 6.0 mm。当昆虫将身体伸入花冠筒中时 ,其头胸背部的毛丛与从上唇裂片下伸出的柱头接触 ,毛丛上的花粉粒即粘附到柱头上 ,同时毛丛与花药接触 ,花粉粒粘附到毛丛上。

Mosla hangchouensis Matsuda and M. chinensis Maxim. are sibling species. The former is endemic to the coastal areas of Zhejiang Province, and the latter occupies southern China. Their morphological differences were associated with their different breeding systems indicated by pollen ovule ratio (P/O). M. hangchouensis was predominantly outcrossing with P/O ranging from 756 to 6163 due to the variation among populations. Floral characters also showed that M. hangchouensis is an outcrosser: corolla tube 5～10 mm long, 3~5 mm wide, bright red; style 6~15 mm long; stigma 1 5~2 0 mm horizontally away from anthers. On the contrary, M. chinensis was predominantly a selfer with a low P/O ratio (P/O=110). Its floral parameters contrasted sharply with M. hangchouensis: corolla tube 3 0 mm long, 1 0~1 5 mm wide, pale colored; style 2 5 mm long, stigma close to or touching anthers. The pollinators of M. hangchouensis most frequently seen are:Bombus trifascitus Smith., Scolia spp., Apis cerana Fabricius, Hylaeus sp.and Lasioglossum spp. These pollinators began to visit flowers at about 8:00 am, when flower buds were ready to open. When insects entered corolla tube for honey and (or) pollen, the stigmata touched the insects' body hairs to which pollen grains adhered, and pollen grains were transferred to the stigmata. Meanwhile the hairs collected pollen from anthers under the upper lips of corolla as the insects thrusted their bodies forward. Bumble bees and honey bees were considered more efficient pollinators because they were hair rich and their body size fitted corolla tube fairly well. Due to the short flight distance of pollinators between two visits (average flight distances of honey bees and solitary bees were 0 52 m and 0 32 m respectively), pollen dispersal was probably restricted. Pollen vectors were important for the reproductive success of M. hangchouensis because 84 3% of its seed set depended on the pollinators' visitation. Although insects did pay visits to M. chinensis occasionally, such visitation was insignificant in seed set due to cleistogamy. Discussions are made on the evolutionary significance of breeding system divergence between M. hangchouensis and M. chinensis, and the contribution of studies on pollination biology to conservation biology. Further studies are suggested for more thorough understanding of pollination biology of M. hangchouensis.