The emblematic "Captaincookia" in New Caledonia (Rubiaceae), a divergent Ixora species showing adaptive variability from humid to sclerophyll forests
Abstract:Background and aims – Ixora margaretae, endemic to New Caledonia, is a flagship for the archipelago's sclerophyllous forests. Recently, three populations of an Ixora resembling I. margaretae were found in humid forest.
Methods – Genetic studies using SSR markers and morpho-anatomical studies of vegetative and reproductive features are provided.
Results – Molecular results show that the genetic distances between and within Ixora margaretae dry and humid stands vary similarly. Accordingly, humid stands are interpreted as a part of the broad newly delimited I. margaretae, occurring in fragmented habitats. Morpho-anatomical data show that several features, such as the bark types, the individual height, and the fruit fleshiness result from genetic variability expressed under environmental constraints. However, other features are interpreted as acclimatisation of populations to local conditions, such as the convergent erected receptaculum pollinis for dry and humid stands, obtain by two different anatomical processes. All data suggest that I. margaretae is a species showing genetic isolation and relative adaptations to environments of populations in both humid and sclerophyll forests. This illustrates potential ongoing speciation processes for several populations in both forest types. A scenario showing the successive habitat modifications from humid to sclerophyll forests that can explain the persistence of the species in sclerophyll areas is proposed.
Document Type: Regular Paper
Publication date: 2016-03-01
Plant Ecology and Evolution (a continuation of Belgian Journal of Botany, incorporating Systematics and Geography of Plants) is an international journal devoted to ecology, phylogenetics and systematics of all 'plant' groups in the traditional sense (including algae, cyanobacteria, fungi, myxomycetes), also covering related fields such as comparative and developmental morphology, conservation biology, ecophysiology, evolution, phytogeography, pollen and spores, population biology, and vegetation studies. It is published by the Royal Botanical Society of Belgium and the Botanic Garden Meise and contains original research papers, review articles, checklists, short communications and book reviews.
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