Floral odour chemistry defines species boundaries and underpins strong reproductive isolation in sexually deceptive orchids

Peakall, Rod; Whitehead, Michael R.

doi:10.1093/aob/mct199

Cited by 71 publications

(99 citation statements)

References 76 publications

(129 reference statements)

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“…; Schiestl & Schlüter, ; Urru et al ., ). In some sexually deceptive orchids, floral isolation is mediated solely by the production of different floral scent bouquets (Xu et al ., ) or the production of few different scent compounds (Peakall et al ., ; Peakall & Whitehead, ).…”

Section: Discussionmentioning

confidence: 97%

Floral isolation is the major reproductive barrier between a pair of rewarding orchid sister species

Sun

Schlüter

Gross

et al. 2015

J of Evolutionary Biology

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The crucial role of reproductive isolation in speciation has long been recognized; however, a limited number of studies quantify different isolation barriers and embed reproductive isolation in a phylogenetic context. In this study, we investigate reproductive isolation between the often sympatrically occurring orchid species, Gymnadenia conopsea and G. odoratissima. We examine the phylogenetic relationship between the two species and analyse floral isolation, fruit set and seed viability from interspecies crosses, as well as the ploidy level. Additionally, we quantify interspecies differences in floral signals and morphology. The results suggest that the two species have a sisterspecies relationship. In terms of reproductive isolation, we found complete floral isolation between the two species, but little to no post-pollination isolation; the species also mostly had the same ploidy level in the studied populations. We also show clear distinctions in floral signals, as well as in floral size and spur length. We propose that respective adaptation to shortvs. long-tongued pollinators was the driver of speciation in the here studied Gymnadenia species. Our study supports the key role of floral isolation in orchid speciation and shows that floral isolation is not restricted to highly specialized pollination systems, but can also occur between species with less specialized pollination.

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Section: Discussionmentioning

confidence: 97%

Floral isolation is the major reproductive barrier between a pair of rewarding orchid sister species

Sun

Schlüter

Gross

et al. 2015

J of Evolutionary Biology

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“…Floral nectar tube length is also sometimes considered a key innovation which enhances diversification rates [28] because long tubes reduce the number of pollinators able to use a flower and this consequent specialization is expected to intensify selection by pollinators [29]. In addition, diversification rates may be enhanced because specialization upon different pollinators may lead to reproductive isolation [30].…”

Section: Introductionmentioning

confidence: 99%

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

et al. 2014

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Floral tubes are often thought to be a consequence of adaptive specialization towards pollinator morphology. We explore floral tube length evolution within Tritoniopsis revoluta (Iridaceae), a species with considerable geographical tube length variation. We ask whether tube lengths of T. revoluta populations are associated with pollinator proboscis lengths, whether floral divergence occurs in the presence of different pollinators and whether floral convergence occurs between distantly related populations pollinated by the same pollinator. Finally, we ask whether tube length evolution is directional. Shifts between morphologically different pollinators were always associated with shifts in floral morphology, even when populations were very closely related. Distantly related populations had similar tube lengths when they were pollinated by the same pollinator. Shifts in tube length tended to be from short to long, although reversals were not infrequent. After correcting for the population-level phylogeny, there was a strong positive, linear relationship between floral tube length and pollinator proboscis length, suggesting that plants are functionally specialized on different pollinators at different sites. However, because tube length evolution in this system can be a bidirectional process, specialization to the local pollinator fauna is unlikely to result in evolutionary or ecological dead-ends such as canalization or range limitation.

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“…Accordingly, it would be of interest to determine the genetic variability within the complex and how it compares to other orchid groups, such as the C. reticulata complex which comprises many narrow range endemic morphospecies. By contrast many cryptic pollinator-specific sexually deceptive orchids (Bower 1996(Bower , 2006Brown 1997, Peakall andWhitehead 2013) exhibit few or no morphological differences between sibling species. Such taxa may have diverged relatively recently.…”

Section: Discussionmentioning

confidence: 97%

Pollinator sharing by the sexually deceptive Green-comb Spider Orchids, Caladenia phaeoclavia, C. parva and C. villosissima (Orchidaceae: Caladeniinae): taxonomic considerations

Bower¹

2015

Telopea

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Sexually deceptive orchids are pollinated when male insects perform mating behaviours on the femalemimicking labellum. Such orchids are characterised by extreme pollinator specificity, having only one, or occasionally a few, closely related insect species as pollen vectors. Sharing of a sexually deceived pollinator species between two or more orchid species is rare among Australian orchids in the Drakaeinae and Caladeniinae pollinated by male Thynnid wasps. In this paper putative pollinator sharing within a complex of three morphologically similar species of Greencomb Spider Orchids, Caladenia parva G.W. Carr, C. phaeoclavia D.L. Jones and C. villosissima G.W. Carr, was investigated using pollinator baiting and choice testing in the field. The three orchid taxa are shown to share the same thynnid wasp pollen vector, Lophocheilus anilitatus (Smith) over the entire geographic range of the complex in New South Wales and Victoria. Pollinator baiting and choice testing at 42 locations revealed no evidence for the existence of cryptic pollinator species in L. anilitatus. The close morphological similarity of the three orchids, their sharing of the same pollinator and lack of evidence of a reproductive isolating mechanism, suggest they belong to the same biological species, C. parva. However, phylogenetic analysis is desirable to confirm the monophyly of the three morphospecies and the possible existence of polyploidy in C. villosissima merits investigation.

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Floral odour chemistry defines species boundaries and underpins strong reproductive isolation in sexually deceptive orchids

Cited by 71 publications

References 76 publications

Floral isolation is the major reproductive barrier between a pair of rewarding orchid sister species

Floral isolation is the major reproductive barrier between a pair of rewarding orchid sister species

Intraspecific divergence and convergence of floral tube length in specialized pollination interactions

Pollinator sharing by the sexually deceptive Green-comb Spider Orchids, Caladenia phaeoclavia, C. parva and C. villosissima (Orchidaceae: Caladeniinae): taxonomic considerations

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