Out of Africa: evidence of the obligate mutualism between long corolla tubed plant and long‐tongued fly in the Himalayas

Abstract

Summary Mutualism between long corolla tubed plants and their potential pollinators, long‐tongued flies, is a classic example of coevolution, but to date, has only been reported from the regions of southern Africa. Many plant species from the Himalayas also show botanical characteristics that could be consistent with pollination by long‐tongued flies. Here, we seek the evidence of the “long‐tongued‐long tubed fly/flower” mutualism out of Africa, in a different continent and climatic region, the Himalayas.Floral traits of Himalayan region endemic alpine genus, Roscoea, indicate possible mutualism with long‐tongued flies for pollination success; however, effective pollinators of this genus are yet unknown. This study investigates whether long‐tongued flies and Roscoea purpurea in Nepal Himalayas show exclusive mutualism for their survival/reproduction.We made extensive observations of floral visitors of R. purpurea and food source of Philoliche longirostris across their wide ranges of populations in Nepal Himalayas for three consecutive years (2012–2014). To confirm the obligate reliance of R. purpurea upon P. longirostris for pollination success, manipulated pollination experiments were conducted at two populations for 2 years. Similarly foraging behavior, visitation frequency, and pollination efficiency of P. longirostris were assessed at two populations for 2 years, and its contribution for the reproductive success of R. purpurea was evaluated. Our results indicate that R. purpurea is self‐compatible but lacks autonomous selfing and obligatorily relies on P. longirostris for reproductive success. Across all populations, P. longirostris was observed as an exclusive and highly efficient pollinator of R. purpurea, while P. longirostris exclusively depends up on R. purpurea for food source.Out of Africa, this study provides the first evidence of long‐tongued fly pollination system and indicates the possibility of additional instances of such a rare phenomenon in the Himalayas. Finding of specialized pollinator of Roscoea only at its evolutionary center indicates that Roscoea species are originally pollinated by long‐tongued flies. Spatial mismatch with specialized pollinators may have induced the evolution of autonomous selfing in North Indochinese clades of Roscoea. This finding thus substantiates how geographic disjunction causes the shifting of pollination mechanism in closely related plant species.

A preliminary species‐level phylogeny of the alpine ginger Roscoea: Implications for speciation

“…Roscoea species are largely endemic to the Himalayas and the Hengduan Mountains, and exhibit extremely diverse floral traits that may link to local adaptations and/or distinct pollination syndromes (Zhang & Li, 2008;Zhang et al, 2011;Fan & Li, 2012;Paudel et al, 2015Paudel et al, , 2016. Compared to previous phylogenetic results (Ngamriabsakul et al, 2000), this study produced a more informative phylogenetic backbone using nrDNA and cpDNA from which testable hypotheses can be drawn for future in-depth speciation studies for this group.…”

Coevolutionary elaboration of pollination‐related traits in an alpine ginger (Roscoea purpurea) and a tabanid fly in the Nepalese Himalayas

“…and Philoliche longirostris Hardwicke. At all sites, R. purpurea was the most abundant species in flower during our observation period and P. longirostris was observed to be its exclusive floral visitor (Paudel et al ., ). Each site covers c .…”

“…Our preliminary field observations indicated that inflorescence height, floral display area, and corolla tube length of R. purpurea , as well as proboscis length of P. longirostris , varied across the wide range of habitats in which the populations occur. Moreover, the variation in floral length and fly proboscis length appeared to be concomitant, in a manner consistent with coevolution (Paudel et al ., ).…”

“…We examined the interaction between an alpine ginger, Roscoea purpurea (Zingiberaceae), and its obligate pollen vector, Philoliche longirostris (Diptera: Tabanidae) (Paudel et al, 2015). Our preliminary field observations indicated that inflorescence height, floral display area, and corolla tube length of R. purpurea, as well as proboscis length of P. longirostris, varied across the wide range of habitats in which the populations occur.…”

Phenotypic selection on flowering phenology and pollination efficiency traits between Primula populations with different pollinator assemblages

“…As previous studies have suggested, an increase in the number of flowers is always selected because of the upper limit to seed production and attractiveness to pollinators (Grindeland, Sletvold, & Ims, ; Mitchell, Karron, Holmquist, & Bell, ; Sandring & Ågren, ). Selection on corolla tube or spur length can be attributed to interactions with local pollinators (Huang, Wang, & Sun, ), for example, coevolutionary elaboration between corolla tube length of Roscoea purpurea and its local pollinators (Paudel et al., , ). However, our results support these hypotheses at only one of our studied populations.…”