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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., (© The Author(s) 2018. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background and Aims: Various studies and conservationist reports have warned about the contraction of the last subtropical Afro-Macaronesian forests. These relict vegetation zones have been restricted to a few oceanic and continental islands around the edges of Africa, due to aridification. Previous studies on relict species have generally focused on glacial effects on narrow endemics; however, little is known about the effects of aridification on the fates of previously widespread subtropical lineages., Methods: Nuclear microsatellites and ecological niche modelling were used to understand observed patterns of genetic diversity in two emblematic species, widely distributed in these ecosystems: Canarina eminii (a palaeoendemic of the eastern Afromontane forests) and Canarina canariensis (a palaeoendemic of the Canarian laurel forests). The software DIYABC was used to test alternative demographic scenarios and an ensemble method was employed to model potential distributions of the selected plants from the end of the deglaciation to the present., Key Results: All the populations assessed experienced a strong and recent population decline, revealing that locally widespread endemisms may also be alarmingly threatened., Conclusions: The detected extinction debt, as well as the extinction spiral to which these populations are subjected, demands urgent conservation measures for the unique, biodiversity-rich ecosystems that they inhabit.

Insular species are expected to have low genetic diversity, for their populations are often small and isolated, and characterized by restricted gene flow and increased incidence of inbreeding. However, empirical results do not always match this expectation. For example, population genetic analyses of several Canarian endemics, based mainly on allozymes, show levels of genetic diversity exceptionally high for insular species. To investigate whether genetic variation in rare species endemic to Canary Islands is low, as predicted by theoretical expectations, or high, as documented in some previous studies, we analysed genetic diversity of the endangered Ruta oreojasme, a rare endemic of the island of Gran Canaria, using microsatellite markers, which are more variable than allozymes. Our analyses identified very high levels of genetic diversity (A = 7.625, P = 0.984, H o = 0.558, H e = 0.687) for R. oreojasme. Even though the distribution of the species is restricted to the South of Gran Canaria, only one population shows low genetic diversity, isolation and signs of a recent bottleneck/founder event. Some intrinsic characteristics of R. oreojasme (hermaphroditism, proterandry and polyploidy), the relative climatic stability of the Canarian archipelago during Quaternary glacials/interglacials, the size of most populations (thousands of individuals), its age, and the relative proximity of the archipelago to the mainland might have contributed to the high diversity that characterises this endemic. As expected, given the marked topographic complexity of Gran Canaria, we found marked genetic structure in R. oreojasme populations. Our results support the observation that Canarian endemics are characterised by unexpectedly high genetic diversity and provides important insights for potential applications to the conservation of R. oreojasme.

Premise of the Study: Endemic plants on oceanic islands have long served as model systems for studying patterns and processes of evolution. However, phylogenetic studies of island plants frequently illustrate a decoupling of molecular divergence and ecological/morphological diversity, resulting in phylogenies lacking the resolution required to interpret patterns of evolution in a phylogenetic context. The current study uses the primarily Macaronesian flowering plant genus Tolpis to illustrate the utility of multiplexed shotgun genotyping (MSG) for resolving relationships at relatively deep (among archipelagos) and very shallow (within archipelagos) nodes in this small, yet diverse insular plant lineage that had not been resolved with other molecular markers., Methods: Genomic libraries for 27 accessions of Macaronesian Tolpis were generated for genotyping individuals using MSG, a form of reduced-representation sequencing, similar to restriction-site-associated DNA markers (RADseq). The resulting data files were processed using the program pyRAD, which clusters MSG loci within and between samples. Phylogenetic analyses of the aligned data matrix were conducted using RAxML., Key Results: Analysis of MSG data recovered a highly resolved phylogeny with generally strong support, including the first robust inference of relationships within the highly diverse Canary Island clade of Tolpis., Conclusions: The current study illustrates the utility of MSG data for resolving relationships in lineages that have undergone recent, rapid diversification resulting in extensive ecological and morphological diversity. We suggest that a similar approach may prove generally useful for other rapid plant radiations where resolving phylogeny has been difficult., (© 2015 Botanical Society of America, Inc.)

Ecological and evolutionary studies largely assume that island populations display low levels of neutral genetic variation. However, this notion has only been formally tested in a few cases involving plant taxa, and the confounding effect of selection on genetic diversity (GD) estimates based on putatively neutral markers has typically been overlooked. Here, we generated nuclear microsatellite and plastid DNA sequence data in Periploca laevigata, a plant taxon with an island-mainland distribution area, to (i) investigate whether selection affects GD estimates of populations across contrasting habitats; and (ii) test the long-standing idea that island populations have lower GD than their mainland counterparts. Plastid data showed that colonization of the Canary Islands promoted strong lineage divergence within P. laevigata, which was accompanied by selective sweeps at several nuclear microsatellite loci. Inclusion of loci affected by strong divergent selection produced a significant downward bias in the GD estimates of the mainland lineage, but such underestimates were substantial (>14%) only when more than one loci under selection were included in the computations. When loci affected by selection were removed, we did not find evidence that insular Periploca populations have less GD than their mainland counterparts. The analysis of data obtained from a comprehensive literature survey reinforced this result, as overall comparisons of GD estimates between island and mainland populations were not significant across plant taxa (N = 66), with the only exception of island endemics with narrow distributions. This study suggests that identification and removal of markers potentially affected by selection should be routinely implemented in estimates of GD, particularly if different lineages are compared. Furthermore, it provides compelling evidence that the expectation of low GD cannot be generalized to island plant populations., (© 2015 John Wiley & Sons Ltd.)

Background and Aims Allozyme and reproductive data sets for the Canarian flora are updated in order to assess how the present levels and structuring of genetic variation have been influenced by the abiotic island traits and by phylogenetically determined biotic traits of the corresponding taxa; and in order to suggest conservation guidelines. Methods Kruskal-Wallis tests are conducted to assess the relationships of 27 variables with genetic diversity (estimated by A, P, Ho and He) and structuring (GST) of 123 taxa representing 309 populations and 16 families. Multiple linear regression analyses (MLRAs) are carried out to determine the relative influence of the less correlated significant abiotic and biotic factors on the genetic diversity levels. Key Results and Conclusions The interactions between biotic features of the colonizing taxa and the abiotic island features drive plant diversification in the Canarian flora. However, the lower weight of closeness to the mainland than of (respectively) high basic chromosome number, partial or total self-incompatibility and polyploidy in the MLRAs indicates substantial phylogenetic constraint; the importance of a high chromosome number is feasibly due to the generation of a larger number of linkage groups, which increase gametic and genotypic diversity. Genetic structure is also more influenced by biotic factors (long-range seed dispersal, basic chromosome number and partial or total self-incompatibility) than by distance to the mainland. Conservation-wise, genetic structure estimates (FST/GST) only reflect endangerment under intensive population sampling designs, and neutral genetic variation levels do not directly relate to threat status or to small population sizes. Habitat protection is emphasized, but the results suggest the need for urgent implementation of elementary reproductive studies in all cases, and for ex situ conservation measures for the most endangered taxa, even without prior studies. In non-endangered endemics, multidisciplinary research is needed before suggesting case-specific conservation strategies. The molecular information relevant for conservation should be conserved in a standardized format to facilitate further insight.