Flower colour adaptation in a mimetic orchid

Abstract

Although the tremendous variability in floral colour among angiosperms is often attributed to divergent selection by pollinators, it is usually difficult to preclude the possibility that floral colour shifts were driven by non-pollinator processes. Here, we examine the adaptive significance of flower colour in Disa ferruginea, a non-rewarding orchid that is thought to attract its butterfly pollinator by mimicking the flowers of sympatric nectar-producing species. Disa ferruginea has red flowers in the western part of its range and orange flowers in the eastern part-a colour shift that we hypothesized to be the outcome of selection for resemblance to different local nectar-producing plants. Using reciprocal translocations of red and orange phenotypes as well as arrays of artificial flowers, we found that the butterfly Aeropetes tulbaghia, the only pollinator of the orchid, preferred both the red phenotype and red artificial flowers in the west where its main nectar plant also has red flowers, and both the orange phenotype and orange artificial flowers in the east, where its main nectar plant has orange flowers. This phenotype by environment interaction demonstrates that the flower colour shift in D. ferruginea is adaptive and driven by local colour preference in its pollinator.

A pollinator shift explains floral divergence in an orchid species complex in South Africa

“…This study is unusual in that a whole suite of traits was considered, unlike many previous studies which focused on pollinatordriven evolution of single traits, such as spur length (Robertson and Wyatt, 1990;Johnson, 1997;Johnson and Steiner, 1997;Boyd, 2004), colour (Newman et al, 2012), scent chemistry (Pellmyr, 1986;Johnson et al, 2005b) and flowering phenology (Herrera et al, 2002), although see studies in this special issue (e.g. Sun et al, 2014;van der Niet et al, 2014).…”

“…It should also be noted that several studies have not found clear evidence that the distribution of floral forms corresponds to a geographical mosaic of pollinators (Robertson and Wyatt, 1990;Herrera et al, 2002Herrera et al, , 2006. In some recent studies, geographical variation in floral traits has been attributed to geographical variation in the behaviour of a single pollinator (Ellis and Johnson, 2009;Newman et al, 2012).…”

“…Such evidence can be derived from experiments where pollinators of one of the ecotypes are presented with an array of all the ecotypes to determine foraging preferences or pollination effectiveness (Ellis and Johnson, 2009;Newman et al, 2012). Arrays can be assembled under laboratory conditions and presented to captive insects (Galen, 1989;der Jager and Ellis, 2014) or arranged in the field by means of transplant experiments (Robertson and Wyatt, 1990;Newman et al, 2012;Sun et al, 2014) or by manipulating flowers within a population (Johnson and Steiner, 1997).…”

Plantas, polinizadores e algumas articulações da biologia da polinização com a teoria ecológica

“…Aplicado aos estudos com polinização, o mimetismo batesiano ocorreria quando flores que não oferecem recursos, ou recursos pouco compensadores, se beneficiam por emitir sinais semelhantes aos sinais emitidos por flores gratificantes, de forma que os agentes biológicos não conseguissem diferenciá-los (Anderson et al 2005;Newman et al 2012). O mimetismo batesiano tem sido o fenômeno mais evocado para explicar as interações em Orchidaceae, o táxon com maior número de espécies que não oferecem recursos aos polinizadores (Jersáková et al 2006).…”

Extrapolating from local ecological processes to genus-wide patterns in colour polymorphism in South AfricanProtea

“…20% of British flora; [15]), well documented and have a long history of study. Pollinators are commonly implicated in maintenance of polymorphisms because their colour preferences may differ among guilds or individuals, over time or space, or with morph frequency [16][17][18][19][20]. Even so, pollinator-mediated selection on colour may be absent or consistently favouring one morph, which should act with genetic drift to eliminate polymorphism [21][22][23].…”