喜马拉雅地区藤本植物多样性及其地理格局

喜马拉雅山地是生物地理学研究的热点地区之一。本文对喜马拉雅地区的藤本植物多样性及其与毗邻地区的联系进行了统计分析, 并对该地区与印度河-恒河平原地区藤本植物多样性的地理格局及其成因进行了研究。结果显示: (1)喜马拉雅地区总计有1,083种藤本植物, 分属72科309属; 其中木质藤本725种, 草质藤本358种; 攀援方式主要为缠绕攀援(51.3%)。(2)该区域的藤本植物组成受相邻区域植物区系的显著影响, 其1,083种藤本植物中有74.1% (802种)在东南亚地区有分布, 50.6% (548种)在南亚有分布, 48.9% (530种)在中国西南地区有分布。本区藤本植物缺乏特有性, 仅125种(11.5%)为本区所特有, 没有特有含藤属。(3)藤本植物多样性及其在植物区系中的比例均自东向西逐渐降低; 木质藤本比例和缠绕攀援藤本比例均自东向西略呈上升趋势; 大多数含藤属的藤本多样性由东往西递减, 仅极少数含藤属由东往西逐渐增加, 如野豌豆属(Vicia)和菟丝子属(Cuscuta)。(4)藤本植物多样性在喜马拉雅和印度河-恒河平原地区呈现出自东向西递减的相似格局, 由东往西方向上含藤属递减率分别为8.4属/100 km和6.3属/100 km, 但喜马拉雅地区藤本植物多样性更高。喜马拉雅和印度河-恒河平原地区均有分布的272个含藤属中有196属在中亚及伊朗高原不再有分布, 其中31.1% (61属)在喜马拉雅地区的分布显著更偏西, 仅4.1% (8属)在印度河-恒河平原的分布显著更偏西。综合分析表明, 喜马拉雅地区藤本植物的多样性及其地理格局的特点与其特殊的地理位置、气候条件和生境的梯度变化以及毗邻地区植物区系的多元化有关; 水分条件的东西向梯度变化可能是藤本植物在喜马拉雅和印度河-恒河平原地区形成相似格局的主要原因。

Diversity and distribution patterns of climbing plants in the Himalayan region

The Himalayas are a biodiversity hotspot. In this study, the taxonomic diversity of climbing plants in the Himalayan region and its connection with neighbouring regions were analyzed, the distribution patterns of climbers in the Himalayas and the Indo-Gangetic Plain were compared, and mechanisms were discussed. Results showed that: (1) The Himalayan region harbored a total of 1,083 climbing species in 309 genera and 72 families. Approximately 66.9% (725 species) of these species were woody or semi-woody climbers (lianas) and the remaining 33.1% (358 species) were herbaceous (vines). Twining climbers accounted for 51.3% of the climbing plants in this region. (2) The climbing plant flora in the Himalayas was significantly affected by neighboring floras. About 74.1% (802 species) of the climbers in the Himalayas were also found in Southeast Asia, 548 species (50.6%) were found in South Asia, and 530 species (48.9%) were found in Southwest China. Only 125 climbers (11.5%) were endemic to this region and no endemic genus was recorded. (3) Species diversity of climbing plants and their proportion in the flora gradually decreased from east to west in the Himalayas. Twining climbers and lianas became more dominant in the western regions. At the genus level, species diversity of most climber-rich genera decreased westward across the Himalayas and species diversity of only a few genera (e.g. Vicia and Cuscuta) showed an increase from east to west. (4) The distribution patterns of climbing plants in the Himalayas and the Indo-Gangetic Plain were consistent. However, species diversity was higher in the Himalayas and its decreasing trend westward was more significant. At the genus level, the average decreasing rate of climber-containing genera from east to west is 8.4 genera per 100 km in the Himalayas and 6.3 genera per 100 km in the Indo-Gangetic Plain. A total of 272 climber-containing genera in the Himalayas were shared with the Indo-Gangetic Plain, and 196 genera were not found in the west regions (Central Asia and Iranian plateau). In the 196 genera, 61 genera (31.1%) were distributed more to the west in the Himalayas than in the Indo-Gangetic Plain, while only 8 genera (4.1%) were distributed more to the west in the Indo-Gangetic Plain than in the Himalayas. In conclusion, species diversity and distributional characteristics of climbers in the Himalayas were attributed in part to the geographical location of this region, the altitudinal and longitudinal gradients of climate and habitats, and the diversification of adjacent floras. The similarities of the distribution patterns of climbing plants in the Himalayas and the Indo-Gangetic Plain may be primarily due to similar east-west water gradients.