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Background and Aims Archipelagos provide a valuable framework for investigating phenotypic evolution under different levels of geographical isolation. Here, we analysed two co-distributed, widespread plant lineages to examine if incipient island differentiation follows parallel patterns of variation in traits related to dispersal and colonization. Methods Twenty-one populations of two anemochorous Canarian endemics, Kleinia neriifolia and Periploca laevigata, were sampled to represent mainland congeners and two contrasting exposures across all the main islands. Leaf size, seed size and dispersability (estimated as diaspore terminal velocity) were characterized in each population. For comparison, dispersability was also measured in four additional anemochorous island species. Plastid DNA data were used to infer genetic structure and to reconstruct the phylogeographical pattern of our focal species. Key Results In both lineages, mainland–island phenotypic divergence probably started within a similar time frame (i.e. Plio-Pleistocene). Island colonization implied parallel increases in leaf size and dispersability, but seed size showed opposite patterns of variation between Kleinia and Periploca species pairs. Furthermore, dispersability in our focal species was low when compared with other island plants, mostly due to large diaspore sizes. At the archipelago scale, island exposure explained a significant variation in leaf size across islands, but not in dispersability or seed size. Combined analyses of genetic and phenotypic data revealed two consistent patterns: (1) extensive within-island but very limited among-island dispersal, and (2) recurrent phenotypic differentiation between older (central) and younger (peripheral) island populations. Conclusions Leaf size follows a more predictable pattern than dispersability, which is affected by stochastic shifts in seed size. Increased dispersability is associated with high population connectivity at the island scale, but does not preclude allopatric divergence among islands. In sum, phenotypic convergent patterns between species suggest a major role of selection, but deviating traits also indicate the potential contribution of random processes, particularly on peripheral islands. [ABSTRACT FROM AUTHOR]

Ecological studies have shown that island taxa often display novel phenotypic ranges relative to mainland congeners (i.e. character shift), but most examples come from behavioural and morphological traits in animals. In this study, I hypothesize that high levels of habitat diversity on oceanic islands would also provide opportunities for character shift in plant taxa with strong colonization ability. Habitat differentiation and phenotypic variation in two resource-use traits (leaf size and specific leaf area) were analysed in taxa showing widespread distributions in the Canary Islands and across mainland Mediterranean areas: Lavandula, Olea, Periploca and Cistus. Preliminary analysis of bioclimatic data indicated that islands show subtropical conditions that are not found among the mainland habitats occupied by these taxa, which could have favoured phenotypic differentiation between these two regions. Strong evidence of character shift, however, was only found in two cases. Phenotypic data in Lavandula suggested that evolution of growth form in the island setting was associated with the expression of novel leaf traits. Evidence of character shift was also related to ecological release, most notably in Periploca, when island populations occupy a range of ecological zones distant from typical mainland conditions (e.g. zones influenced by the humid, north-east trade winds). This study shows that widespread island taxa display convergent phenotypic responses to habitat shift, which strongly suggest an adaptive pattern and stress the deterministic nature of phenotypic variation. I further discuss how the identification of these patterns provides a promising framework for the testing of hypotheses on the evolutionary mechanisms involved in phenotypic adaptation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 399-411. [ABSTRACT FROM AUTHOR]

Ecological conditions, such as high habitat diversity and the absence of competitors, have been proposed as key determinants of the patterns of speciation observed in oceanic island floras. However, the relationship between plant traits and lineage diversification has received less attention. Here, we review 120 published phylogenetic and population genetic studies of three well-studied oceanic archipelagos ( Canary Islands, Galápagos and Hawai'i) to investigate potential associations between life history characters (growth form and fruit type) and patterns of diversification. The available data suggest that the phenotypic syndrome 'herbaceous-dry fruited' was predominant among ancestors of species-rich lineages, although the Hawaiian flora also shows a substantial proportion of 'woody-fleshy fruited' ancestors. Growth form, unlike fruit type, is shown to be a labile character strongly selected for woodiness, particularly in radiating lineages. Dry fruits, although representative of diverse dispersal modes and efficacies, are generally associated with a low incidence of inter-island colonization, and the analysis of population genetic data confirms strong genetic differentiation among islands for dry fruited species of radiating lineages. In contrast, fleshy fruited species of monotypic lineages typically show widespread distributions coupled with extensive gene flow among islands, which probably impedes speciation. Our analyses suggest that fruit types associated with limited evidence of dispersal promote recurrent speciation within lineages, although particular character states related to speciation appear to be context dependent. This study reinforces the idea that plant traits associated with island colonization and population persistence are, in addition to ecological conditions, important factors in understanding the patterns of diversification on islands. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 334-348. [ABSTRACT FROM AUTHOR]

Strong geographical isolation within the distribution of a species may result in differentiated lineages exhibiting conspicuous phenotypic differences. In the present paper, we investigate whether plastid and phenotypic variation is geographically structured within the Olea europaea complex in Macaronesia, which comprises three subspecies separated by oceanic barriers: maroccana (south-west Morocco), guanchica (Canary Islands) and cerasiformis (Madeira archipelago). Plastid variation showed a significant pattern of geographical structure (NST > GST = 0.56), because of the lack of shared haplotypes among subspecies and the presence of a single and private haplotype in the eastern Canary Islands. Such a clear molecular structure, however, was not reflected in a congruent pattern of phenotypic differentiation among taxa in leaf morpho-functional traits. Despite the substantial genetic differentiation observed between the subspecies from Madeira and the Canary Islands, they displayed both higher leaf size (leaf area) and specific leaf area (leaf surface area-to-mass ratio) than their continental counterparts, probably as a result of oceanic conditions in subtropical environments. Unlike most of the plant groups previously studied in the Macaronesian region, the lineages of Olea illustrate how low phenotypic differentiation can be also related to a clear molecular differentiation in oceanic island enclaves. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162, 54–63. [ABSTRACT FROM AUTHOR]