The bracts of the alpine ‘glasshouse’ plantRheum alexandrae(Polygonaceae) enhance reproductive fitness of its pollinating seed-consuming mutualist

Abstract

Environmental conditions are known to affect the reproductive fitness of insects, as do host plants. Although the highly specialized bracts of Himalayan ‘glasshouse’ plants are thought to be an adaptive morphology that allows the plant to reproduce in harsh alpine environments, little information appears to exist concerning the benefit of these bracts for the pollinating insects. In this study, we examine whether the semi‐translucent bracts of Rheum alexandrae, a giant herb endemic to the alpine zone of the Hengduan Mountains in south‐western China, enhance the reproductive fitness of its pollinator. Rheum alexandrae depends mainly on mutualistic seed‐consuming Bradysia flies for pollination. Bracts increased interior temperature on sunny days, acted as a buffer against fluctuating air humidity, greatly decreased the intensities of ultraviolet B/C radiation and provided shelter from strong winds. Bract removal significantly decreased adult oviposition and offspring performance of pollinators during flowering and fruiting, respectively. Our results indicate that the bracts of R. alexandrae enhance the reproductive fitness of its pollinating seed‐consuming mutualist in alpine environments, which may be attributed to the positive effects of the bracts on the interior microenvironment. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179, 349–359.

Host specificity of two pollinating seed‐consuming fly species is not related to soil moisture of host plant in the high Himalayas

“…For example, if a larva must move to complete development, the cues available at the oviposition site may have very little predictive value about the quality of microhabitat for pupation and adult emergence (Craig & Itami, ). This might be the case of the two Bradysia species as their eggs are laid in flowers whereas pupation and adult eclosion take place in soils around the host plants (Song et al., , ). In addition, season variation in rainfall because of prevailing monsoon climate in alpine zone of the eastern Himalayas may aggravate the habitat complexity in terms of soil moisture.…”

“…(e–h). Flowering plants (a, e), female flies visiting flowers (b, f), fruits infested by fly larvae (c, g), Fly pupae in soil (d, h) (modified from Song et al., , )…”

“…(Diptera: Sciaridae), respectively (Figure 1b,f;Song et al, 2014;Song, Stöcklin, Peng, Gao, & Sun, 2015). After feeding on developing seeds in parasite fruits (Figure 1c,g), fly larvae exited from the fruits and burrowed into the soil around the plants (Figure 1d,h), where they overwinter as pupae (Song et al, 2014(Song et al, , 2015. Thus, pupation and adult emergence are completed in the soil.…”

Advances in the studies of plant diversity and ecological adaptation in the subnival ecosystem of the Qinghai-Tibet Plateau

“…此外, 在青藏高原北部高山区 域, 囊种草也具有显著的提升植物群落物种丰富度、 密度和多样性的能力 [52] . [11,55,56] . 除了提供种子作为幼虫的食物, 塔黄和水 黄高度特化的巨大半透明苞片形成的"温室结构"具有 增温、防风和防雨等作用, 还为蕈蚊提供交配的场 所、成虫的食物(花粉)以及成虫产卵和幼虫发育适宜 的微环境条件 [11,56] .…”

“…[11,55,56] . 除了提供种子作为幼虫的食物, 塔黄和水 黄高度特化的巨大半透明苞片形成的"温室结构"具有 增温、防风和防雨等作用, 还为蕈蚊提供交配的场 所、成虫的食物(花粉)以及成虫产卵和幼虫发育适宜 的微环境条件 [11,56] . 由于蕈蚊的繁殖完全依赖这类植 物, 但也提供了"超级传粉服务", 形成了"我为你育儿, 你为我传粉"的互惠关系, 使塔黄和水黄坐果率分别高 达95%和90%以上, 且不存在花粉限制 [55,56] .…”