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

Peakall, Rodney; Whitehead, Michael

Description

Background and AimsThe events leading to speciation are best investigated in systems where speciation is ongoing or incomplete, such as incipient species. By examining reproductive barriers among incipient sister taxa and their congeners we can gain valuable insights into the relative timing and importance of the various barriers involved in the speciation process. The aim of this study was to identify the reproductive barriers among sexually deceptive orchid taxa in the genus...[Show more]

dc.contributor.authorPeakall, Rodney
dc.contributor.authorWhitehead, Michael
dc.date.accessioned2015-12-10T23:18:37Z
dc.identifier.issn0305-7364
dc.identifier.urihttp://hdl.handle.net/1885/65710
dc.description.abstractBackground and AimsThe events leading to speciation are best investigated in systems where speciation is ongoing or incomplete, such as incipient species. By examining reproductive barriers among incipient sister taxa and their congeners we can gain valuable insights into the relative timing and importance of the various barriers involved in the speciation process. The aim of this study was to identify the reproductive barriers among sexually deceptive orchid taxa in the genus Chiloglottis.MethodsThe study targeted four closely related taxa with varying degrees of geographic overlap. Chemical, morphological and genetic evidence was combined to explore the basis of reproductive isolation. Of primary interest was the degree of genetic differentiation among taxa at both nuclear and chloroplast DNA markers. To objectively test whether or not species boundaries are defined by the chemistry that controls pollinator specificity, genetic analysis was restricted to samples of known odour chemistry.Key ResultsFloral odour chemical analysis was performed for 600+ flowers. The three sympatric taxa were defined by their specific chiloglottones, the semiochemicals responsible for pollinator attraction, and were found to be fully cross-compatible. Multivariate morphometric analysis could not reliably distinguish among the four taxa. Although varying from very low to moderate, significant levels of genetic differentiation were detected among all pairwise combinations of taxa at both nuclear and chloroplast loci. However, the levels of genetic differentiation were lower than expected for mature species. Critically, a lack of chloroplast DNA haplotype sharing among the morphologically indistinguishable and most closely related taxon pair confirmed that chemistry alone can define taxon boundaries.ConclusionsThe results confirmed that pollinator isolation, mediated by specific pollinator attraction, underpins strong reproductive isolation in these taxa. A combination of large effective population sizes, initial neutral mutations in the genes controlling floral scent, and a pool of available pollinators likely drives diversity in this system.
dc.publisherAcademic Press
dc.sourceAnnals of Botany
dc.titleFloral odour chemistry defines species boundaries and underpins strong reproductive isolation in sexually deceptive orchids
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume113
dc.date.issued2014
local.identifier.absfor060311 - Speciation and Extinction
local.identifier.absfor060411 - Population, Ecological and Evolutionary Genetics
local.identifier.ariespublicationu9511635xPUB1147
local.type.statusPublished Version
local.contributor.affiliationPeakall, Rodney, College of Medicine, Biology and Environment, ANU
local.contributor.affiliationWhitehead, Michael, College of Medicine, Biology and Environment, ANU
local.description.embargo2037-12-31
local.bibliographicCitation.startpage341
local.bibliographicCitation.lastpage355
local.identifier.doi10.1093/aob/mct199
local.identifier.absseo970106 - Expanding Knowledge in the Biological Sciences
dc.date.updated2015-12-10T10:07:49Z
local.identifier.scopusID2-s2.0-84892729500
local.identifier.thomsonID000330193100012
CollectionsANU Research Publications



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