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iNaturalist defines itself as an “online social network of people sharing biodiversity information to help each other learn about nature” and it is likely one of the largest citizen science web portals in the world, as every year millions of observations across thousands of species are gathered and collectively compiled by an engaged community of nearly 3 million users (November 2023). The strengths and potentialities that explain the success of the platform are reviewed and include, among others, its usability and low technical requirements, immediacy, open-access, the possibility of interacting with other users, artificial-intelligence-aided identification, versatility and automatic incorporation of the validated records to GBIF. iNaturalist has, however, features that scientists need to carefully consider when using it for their research, making sure that the quality of observations does not limit or hinder its usefulness in plant research. While these are identified (e.g., the lack of representative photographs for many observations or the relatively frequent identification errors), we provide some suggestions to overcome them and, by doing so, improve the use and add value to iNaturalist for plant research.

iNaturalist defines itself as an “online social network of people sharing biodiversity information to help each other learn about nature” and it is likely one of the largest citizen science web portals in the world, as every year millions of observations across thousands of species are gathered and collectively compiled by an engaged community of nearly 3 million users (November 2023). The strengths and potentialities that explain the success of the platform are reviewed and include, among others, its usability and low technical requirements, immediacy, open-access, the possibility of interacting with other users, artificial-intelligence-aided identification, versatility and automatic incorporation of the validated records to GBIF. iNaturalist has, however, features that scientists need to carefully consider when using it for their research, making sure that the quality of observations does not limit or hinder its usefulness in plant research. While these are identified (e.g., the lack of representative photographs for many observations or the relatively frequent identification errors), we provide some suggestions to overcome them and, by doing so, improve the use and add value to iNaturalist for plant research.

Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

Biological invasions in remote areas that experience low human activity provide unique opportunities to elucidate processes responsible for invasion success. Here we study the most widespread invasive plant species across the isolated islands of the Southern Ocean, the annual bluegrass, Poa annua. To analyse geographical variation in genome size, genetic diversity and reproductive strategies, we sampled all major sub-Antarctic archipelagos in this region and generated microsatellite data for 470 individual plants representing 31 populations. We also estimated genome sizes for a subset of individuals using flow cytometry. Occasional events of island colonization are expected to result in high genetic structure among islands, overall low genetic diversity and increased self-fertilization, but we show that this is not the case for P. annua. Microsatellite data indicated low population genetic structure and lack of isolation by distance among the sub-Antarctic archipelagos we sampled, but high population structure within each archipelago. We identified high levels of genetic diversity, low clonality and low selfing rates in sub-Antarctic P. annua populations (contrary to rates typical of continental populations). In turn, estimates of selfing declined in populations as genetic diversity increased. Additionally, we found that most P. annua individuals are probably tetraploid and that only slight variation exists in genome size across the Southern Ocean. Our findings suggest multiple independent introductions of P. annua into the sub-Antarctic, which promoted the establishment of genetically diverse populations. Despite multiple introductions, the adoption of convergent reproductive strategies (outcrossing) happened independently in each major archipelago. The combination of polyploidy and a mixed reproductive strategy probably benefited P. annua in the Southern Ocean by increasing genetic diversity and its ability to cope with the novel environmental conditions.

Acaulon mediterraneum es un musgo acrocárpico con una estrategia vital fugitiva presente especialmente en la cuenca mediterránea occidental, pero con registros verificados en otras regiones de Europa como la costa balcánica (Sabovljević et al. 2008), Escandinavia (Hassel 2003) o las Islas Británicas (Blockeel et al. 2021). Además, se ha citado en Canarias (González-Mancebo et al. 2007), Australia (Stone 1988) y California (Toren 2015). Su presencia en territorio ibérico es más bien dispersa por el centro y sur de la Península: Ab, Al, Cs, H, Hu, Ma, Sa, Se, Z, Ag, BAl, BB, E y R (Guerra 2006; Guerra et al. 2023) y las citas aportadas para la provincia de Madrid coinciden con las preferencias generales del taxon por terrenos ácidos en zonas de matorral abierto., Depto. de Biodiversidad, Ecología y Evolución, Fac. de Ciencias Biológicas, TRUE, pub

[Aim] The afroalpine sky-islands present one of the most interesting models to study discrete biogeographic patterns in a terrestrial island system. Here, we performed range-wide sampling of the afroalpine clade of fine-leaved Festuca grasses and address a set of hypotheses on its origin and dispersal. We focus on the widespread species F. abyssinica and explore the role of the eastern and western African sky-islands., [Location] Tropical Africa, [Taxon] Afroalpine Festuca, [Methods] We combine data from field surveys, phylogeography, coalescence-based dispersal modelling, and environmental niche and dispersal costs analyses to infer patterns of genetic diversity, genealogical relationships, colonization routes and range shifts under two Quaternary climates (current – to represent warm periods; and Last Glacial Maximum (LGM) – to represent cold periods)., [Results] The westernmost populations in East Africa show higher genetic diversity and higher similarities with the West African populations and the Ethiopian Simen Mountains than with the more closely situated East African populations. Dispersal models and ecological niche predictions of F. abyssinica supported multiple long-distance dispersals (LDD) among the eastern African sky-islands, and at least two dispersal events between the two sides of Africa (0.86 Ma and 0.52 Ma), probably facilitated by bridging suitable habitats during the coldest periods of the Pleistocene., [Main conclusions] We reconstruct an afroalpine mountain-hopping dispersal model, with migrations occurring between adjacent sky-islands in eastern Africa, and through a Central Africa–Sudan pathway connecting afroalpine patches on the two sides of the continent.

The link between the successful establishment of alien species and propagule pressure is well-documented. Less known is how humans influence the post-introduction dynamics of invasive alien populations. The latter requires studying parallel invasions by the same species in habitats that are differently impacted by humans. We analysed microsatellite and genome size variation, and then compared the genetic diversity and structure of invasive Poa annua L. on two sub-Antarctic islands: human-occupied Marion Island and unoccupied Prince Edward Island. We also carried out niche modelling to map the potential distribution of the species on both islands. We found high levels of genetic diversity and evidence for extensive admixture between genetically distinct lineages of P. annua on Marion Island. By contrast, the Prince Edward Island populations showed low genetic diversity, no apparent admixture, and had smaller genomes. On both islands, high genetic diversity was apparent at human landing sites, and on Marion Island, also around human settlements, suggesting that these areas received multiple introductions and/or acted as initial introduction sites and secondary sources (bridgeheads) for invasive populations. More than 70 years of continuous human activity associated with a meteorological station on Marion Island led to a distribution of this species around human settlements and along footpaths, which facilitates ongoing gene flow among geographically separated populations. By contrast, this was not the case for Prince Edward Island, where P. annua populations showed high genetic structure. The high levels of genetic variation and admixture in P. annua facilitated by human activity, coupled with high habitat suitability on both islands, suggest that P. annua is likely to increase its distribution and abundance in the future.

Premise Genera that are widespread, with geographically discontinuous distributions and represented by few species, are intriguing. Is their achieved disjunct distribution recent or ancient in origin? Why are they species-poor? The Rand Flora is a continental-scale pattern in which closely related species appear codistributed in isolated regions over the continental margins of Africa. Genus Camptoloma (Scrophulariaceae) is the most notable example, comprising three species isolated from each other on the northwest, eastern, and southwest Africa. Methods We employed Sanger sequencing of nuclear and plastid markers, together with genomic target sequencing of 2190 low-copy nuclear genes, to infer interspecies relationships and the position of Camptoloma within Scrophulariaceae by using supermatrix and multispecies-coalescent approaches. Lineage divergence times and ancestral ranges were inferred with Bayesian Markov chain Monte Carlo (MCMC) approaches. The population history was estimated with phylogeographic coalescent methods. Results Camptoloma rotundifolium, restricted to Southern Africa, was shown to be a sister species to the disjunct clade formed by C. canariense, endemic to the Canary Islands, and C. lyperiiflorum, distributed in the Horn of Africa-Southern Arabia. Camptoloma was inferred to be sister to the mostly South African tribes Teedieae and Buddlejeae. Stem divergence was dated in the Late Miocene, while the origin of the extant disjunction was inferred as Early Pliocene. Conclusions The current disjunct distribution of Camptoloma across Africa was likely the result of fragmentation and extinction and/or population bottlenecking events associated with historical aridification cycles during the Neogene; the pattern of species divergence, from south to north, is consistent with the "climatic refugia" Rand Flora hypothesis.

Premise: Genera that are widespread, with geographically discontinuous distributions and represented by few species, are intriguing. Is their achieved disjunct distribution recent or ancient in origin? Why are they species-poor? The Rand Flora is a continental-scale pattern in which closely related species appear codistributed in isolated regions over the continental margins of Africa. Genus Camptoloma (Scrophulariaceae) is the most notable example, comprising three species isolated from each other on the northwest, eastern, and southwest Africa. Methods: We employed Sanger sequencing of nuclear and plastid markers, together with genomic target sequencing of 2190 low-copy nuclear genes, to infer interspecies relationships and the position of Camptoloma within Scrophulariaceae by using supermatrix and multispecies-coalescent approaches. Lineage divergence times and ancestral ranges were inferred with Bayesian Markov chain Monte Carlo (MCMC) approaches. The population history was estimated with phylogeographic coalescent methods. Results: Camptoloma rotundifolium, restricted to Southern Africa, was shown to be a sister species to the disjunct clade formed by C. canariense, endemic to the Canary Islands, and C. lyperiiflorum, distributed in the Horn of Africa–Southern Arabia. Camptoloma was inferred to be sister to the mostly South African tribes Teedieae and Buddlejeae. Stem divergence was dated in the Late Miocene, while the origin of the extant disjunction was inferred as Early Pliocene. Conclusions: The current disjunct distribution of Camptoloma across Africa was likely the result of fragmentation and extinction and/or population bottlenecking events associated with historical aridification cycles during the Neogene; the pattern of species divergence, from south to north, is consistent with the “climatic refugia” Rand Flora hypothesis.

[Aim] Species with widespread distributions offer excellent opportunities for investigating recent biogeographical patterns across broad scales. Here, we tested the hypothesis that, due to its intermediate geographical location, NW Africa is pivotal in explaining the phylogeographical patterns of taxa with Mediterranean–Macaronesian distributions using a legume species with short generation times., [Location] Mediterranean, with a focus on NW Africa and the Canary Islands., [Taxon] Pitch trefoil (Bituminaria bituminosa)., [Methods] We generated genetic data and performed phylogeographical and demographic analyses at two geographical scales: Mediterranean Basin (MB), using plastid sequences (115 individuals), and Macaronesia, using plastid sequences (182 individuals) and 10 nuclear microsatellite loci (220 individuals). We also performed a literature survey focusing on phylogeographical studies of other circum-Mediterranean taxa., [Results] Northwest Africa was identified as a centre of genetic diversity (19 out of 38 haplotypes) and demographic expansion of B. bituminosa in the MB during the Pleistocene. Our literature review revealed two main phylogeographical patterns in widespread species: pre-Mediterranean evergreen sclerophylls versus Pleistocene facultative-deciduous (including Bituminaria) taxa, but on average, both functional groups show a similar, large genetic diversity (~40% of haplotypes) in NW Africa. At the Macaronesian scale, we found that Canarian Bituminaria is composed of two genetic sublineages that coexist and hybridize on the central islands and in the mainland Macaronesian enclave (Anti-Atlas region). Demographic analyses rejected the progression rule as the model of island colonization but strongly suggested that Anti-Atlas populations are the result of back-colonization from the easternmost islands before the Last Glacial Maximum (LGM)., [Conclusions] Bituminaria displays a pattern of Quaternary eastward expansion in the MB that appears to be paralleled by several members of its functional plant group. Thus, our study reveals a previously undescribed dual role of NW Africa in plant biogeography, acting both as a source of species expansion to the rest of the MB and a LGM refugium of plant populations with a Macaronesian island origin.

Geographic range shifts are one major organism response to climate change, especially if the rate of climate change is higher than that of species adaptation. Ecological niche models (ENM) and biogeographic inferences are often used in estimating the effects of climatic oscillations on species range dynamics. ENMs can be used to track climatic suitable areas over time, but have often been limited to shallow timescales; biogeographic inference can reach greater evolutionary depth, but often lacks spatial resolution. Here, we present a simple approach that treats them as independent and complementary sources of evidence, which, when used in partnership, can be employed to reconstruct geographic range shifts over deep evolutionary timescales. For testing this, we chose two extreme African disjunctions: Camptoloma (Scrophulariaceae) and Canarina (Campanulaceae), each comprising of three species disjunctly distributed in Macaronesia and eastern/southern Africa. Using inferred ancestral ranges in tandem with preindustrial and paleoclimate ENM hindcastings, we show that the disjunct pattern was the result of fragmentation and extinction events linked to Neogene aridification cycles. Our results highlight the importance of considering temporal resolution when building ENMs for rare endemics with small population sizes and restricted climatic tolerances such as Camptoloma, for which models built on averaged monthly variables were more informative than those based on annual bioclimatic variables. Additionally, we show that biogeographic information can be used as truncation threshold criteria for building ENMs in the distant past. Our approach is suitable when there is sparse sampling on species occurrences and associated patterns of genetic variation, such as in the case of ancient endemics with widely disjunct distributions as a result of climate change

The distribution of genetic variation in species is governed by factors that act differently across spatial scales. To tease apart the contribution of different processes, especially at intermediate spatial scales, it is useful to study simple ecosystems such as those on sub-Antarctic oceanic islands. In this study, we characterize spatial genetic patterns of two keystone plant species, Azorella selago on sub-Antarctic Marion Island and Azorella macquariensis on sub-Antarctic Macquarie Island. Although both islands experience a similar climate and have a similar vegetation structure, they differ significantly in topography and geological history. We genotyped six microsatellites for 1,149 individuals from 123 sites across Marion Island and 372 individuals from 42 sites across Macquarie Island. We tested for spatial patterns in genetic diversity, including correlation with elevation and vegetation type, and clines in different directional bearings. We also examined genetic differentiation within islands, isolation-by-distance with and without accounting for direction, and signals of demographic change. Marion Island was found to have a distinct northwest–southeast divide, with lower genetic diversity and more sites with a signal of population expansion in the northwest. We attribute this to asymmetric seed dispersal by the dominant northwesterly winds, and to population persistence in a southwestern refugium during the Last Glacial Maximum. No apparent spatial pattern, but greater genetic diversity and differentiation between sites, was found on Macquarie Island, which may be due to the narrow length of the island in the direction of the dominant winds and longer population persistence permitted by the lack of extensive glaciation on the island. Together, our results clearly illustrate the implications of island shape and geography, and the importance of direction-dependent drivers, in shaping spatial genetic structure.

[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.

Subtropical islands are often viewed as refuges where Quaternary climatic shifts driving global episodes of extinction were buffered. Island biodiversity, however, may have been impacted by climatic fluctuations at local scales, particularly in spatially heterogeneous island systems. In this study, we generated a conceptual framework for predicting the potential impact of Pleistocene extinctions on the biogeographical pattern of the Canarian spermatophyte flora, with a focus on the easternmost Canarian islands (ECI). Then, we performed an exhaustive bibliographic revision (270 studies) to examine whether taxonomic, phylogenetic and phylogeographical data support our predictions. Although molecular information is limited for many lineages, the available data suggest that the majority of extant ECI plant taxa may be the result of relatively recent (<1 Ma) dispersal from surrounding insular and mainland areas. Different lines of evidence are compatible with the idea of a Pleistocene period of frequent lineage extirpation on ECI. Extinction may thus have provided new ecological opportunities for recent (re)colonization, with some cases of recent establishment mediated by facilitation. Considering background extinction on ECI, we describe five general patterns of colonization for Canarian plant lineages. In addition to factors related to island ontogeny and long-distance dispersal, we suggest that Pleistocene extinctions may have significantly contributed to extant biogeographical patterns in the Canarian archipelago, such as the biased distribution ranges of island plants and the low endemic richness on ECI. This new scenario provides testable hypotheses for future studies dealing with the phylogeography, taxonomy and conservation of terrestrial biodiversity on the Canarian islands, and possibly, on other near-shore islands.

The distribution of genetic variation in species is governed by factors that act differently across spatial scales. To tease apart the contribution of different processes, especially at intermediate spatial scales, it is useful to study simple ecosystems such as those on sub-Antarctic oceanic islands. In this study, we characterize spatial genetic patterns of two keystone plant species, Azorella selago on sub-Antarctic Marion Island and Azorella macquariensis on sub-Antarctic Macquarie Island. Although both islands experience a similar climate and have a similar vegetation structure, they differ significantly in topography and geological history. We genotyped six microsatellites for 1,149 individuals from 123 sites across Marion Island and 372 individuals from 42 sites across Macquarie Island. We tested for spatial patterns in genetic diversity, including correlation with elevation and vegetation type, and clines in different directional bearings. We also examined genetic differentiation within islands, isolation-by-distance with and without accounting for direction, and signals of demographic change. Marion Island was found to have a distinct northwest-southeast divide, with lower genetic diversity and more sites with a signal of population expansion in the northwest. We attribute this to asymmetric seed dispersal by the dominant northwesterly winds, and to population persistence in a southwestern refugium during the Last Glacial Maximum. No apparent spatial pattern, but greater genetic diversity and differentiation between sites, was found on Macquarie Island, which may be due to the narrow length of the island in the direction of the dominant winds and longer population persistence permitted by the lack of extensive glaciation on the island. Together, our results clearly illustrate the implications of island shape and geography, and the importance of direction-dependent drivers, in shaping spatial genetic structure.

Aim: The loss of dispersal on islands hypothesis (LDIH) posits that wind-dispersed plants should exhibit reduced dispersal potential, particularly if island populations are old. In this study, we tested this hypothesis using a detailed phylogeographical framework across different geographical scales. Location: Mainland and island areas of the Atlantic and Mediterranean regions, including Macaronesia (Canary Islands and Cape Verde) and Mediterranean islands in the strait of Sicily. Methods: Forty-five populations of Periploca laevigata, a wind-dispersed shrub, were sampled. Plastid and nuclear microsatellite data were used to reconstruct spatio-temporal patterns of island colonization, and estimates of seed terminal velocity used as a surrogate for dispersal ability under both field and common garden conditions. Results: Our findings did not provide evidence of loss of dispersability in any island lineage. In all of the regions considered, dispersal ability was similar on island and mainland populations, or higher on islands. Contrary to LDIH expectations, lineages inferred as the oldest (western Canaries and Cape Verde) converged towards the most dispersive seed phenotype. This pattern was supported by data obtained under common garden conditions. Within the western Canarian lineage, successful dispersal was shown to be very rare among islands and extensive within islands, but dispersability did not vary significantly from older to more recent sublineages. Considering all the study islands, we found a strong, positive correlation between dispersal ability and estimates of within-island habitat availability. Main conclusions: This study suggests that dispersal ability can be favoured on islands, possibly because traits enhancing wind dispersal are positively selected when habitat availability is high. Our results challenge broad generalizations of the LDIH, but we discuss how overlooking species′ phylogeographical history may give rise to misleading conclusions.

Aim: The disjunct distribution patterns of sister taxa can arise when previously continuous distribution ranges are fragmented by environmental changes such as major climatic events. Populations become isolated on either side of the newly established environmental barrier, and absence of gene flow promotes allopatric speciation, in a process that is known as ecological vicariance. If climate change altered the ancestral range gradually, such as along temporal temperature or moisture gradients, the age of divergence of disjunct species should be related to the lineage tolerance to climatic conditions. Here, we investigate this hypothesis using as a study model the African Rand Flora, a continental-scale floristic pattern that relates sister taxa distributed on either side of the Saharan Desert. Location: Africa, Macaronesia, Mediterranean Basin and the Middle East. Methods: We estimated the extant climatic tolerances of 14 Rand Flora lineages based on present occurrence data, and correlated the phylogenetic age of divergence between vicariant clades. We tested whether the tempo of the vicariance in the Rand Flora lineages was associated with the average values of their climatic niches in agreement with niche-driven divergence. We hindcasted species ranges using species distribution models combined with palaeoclimate simulations to infer the potential distribution of each lineage's ancestors. Results: We found a positive relationship between the lineage temperature niche and the age of the Rand Flora disjunction: lineages with subtropical affinities diverged first, whereas those with a higher tolerance to drier conditions (temperate or sub-xeric adaptations) exhibited younger disjunctions. The range reconstructions showed the existence of climatic corridors south of the Sahara in the wetter Late Miocene, which became interrupted during the mid-Pliocene warming event. Main conclusions: Our results suggest that climate change leading to the formation of the Sahara Deser

The Eastern African Afromontane forest is getting increased attention in conservation studies because of its high endemicity levels and shrinking geographic distribution. Phylogeographic studies have found evidence of high levels of genetic variation structured across the Great Rift System. Here, we use the epiphytic plant species Canarina eminii to explore causal explanations for this pattern. Phylogeographic analyses were undertaken using plastid regions and AFLP fragments. Population genetic analyses, Statistical Parsimony, and Bayesian methods were used to infer genetic diversity, genealogical relationships, structure, gene flow barriers, and the spatiotemporal evolution of populations. A strong phylogeographic structure was found, with two reciprocally monophyletic lineages on each side of the Great Rift System, high genetic exclusivity, and restricted gene flow among mountain ranges. We explain this pattern by topographic and ecological changes driven by geological rifting in Eastern Africa. Subsequent genetic structure is attributed to Pleistocene climatic changes, in which sky-islands acted as long-Term refuges and cradles of genetic diversity. Our study highlights the importance of climate change and geographic barriers associated with the African Rift System in shaping population genetic patterns, as well as the need to preserve the high levels of exclusive and critically endangered biodiversity harboured by current patches of the Afromontane forest.

The Rand Flora is a well-known floristic pattern in which unrelated plant lineages show similar disjunct distributions in the continental margins of Africa and adjacent islands—Macaronesia-northwest Africa, Horn of Africa-Southern Arabia, Eastern Africa, and Southern Africa. These lineages are now separated by environmental barriers such as the arid regions of the Sahara and Kalahari Deserts or the tropical lowlands of Central Africa. Alternative explanations for the Rand Flora pattern range from vicariance and climate-driven extinction of a widespread pan-African flora to independent dispersal events and speciation in situ. To provide a temporal framework for this pattern, we used published data from nuclear and chloroplast DNA to estimate the age of disjunction of 17 lineages that span 12 families and nine orders of angiosperms. We further used these estimates to infer diversification rates for Rand Flora disjunct clades in relation to their higher-level encompassing lineages. Our results indicate that most disjunctions fall within the Miocene and Pliocene periods, coinciding with the onset of a major aridification trend, still ongoing, in Africa. Age of disjunctions seemed to be related to the climatic affinities of each Rand Flora lineage, with sub-humid taxa dated earlier (e.g., Sideroxylon) and those with more xeric affinities (e.g., Campylanthus) diverging later. We did not find support for significant decreases in diversification rates in most groups, with the exception of older subtropical lineages (e.g., Sideroxylon, Hypericum, or Canarina), but some lineages (e.g., Cicer, Campylanthus) showed a long temporal gap between stem and crown ages, suggestive of extinction. In all, the Rand Flora pattern seems to fit the definition of biogeographic pseudocongruence, with the pattern arising at different times in response to the increasing aridity of the African continent, with interspersed periods of humidity allowing range expansions.

Geographical isolation by oceanic barriers and climatic stability has been postulated as some of the main factors driving diversification within volcanic archipelagos. However, few studies have focused on the effect that catastrophic volcanic events have had on patterns of within-island differentiation in geological time. This study employed data from the chloroplast (cpDNA haplotypes) and the nuclear (AFLPs) genomes to examine the patterns of genetic variation in Canarina canariensis, an iconic plant species associated with the endemic laurel forest of the Canary Islands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has Tenerife as its central axis and divides Canarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo-islands’ of Anaga, Teno and Roque del Conde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within Tenerife or the nearby islands using a Bayesian approach to phylogeographical clustering. Oceanic barriers, in contrast, appear to have played a lesser role in structuring genetic variation, with intra-island levels of genetic diversity larger than those between-islands. We argue that volcanic eruptions and landslides after the merging of the palaeo-islands 3.5 Ma played key roles in generating genetic boundaries within Tenerife, with the palaeo-islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.

Transoceanic distributions have attracted the interest of scientists for centuries. Less attention has been paid to the evolutionary origins of ‘continent-wide’ disjunctions, in which related taxa are distributed across isolated regions within the same continent. A prime example is the ‘Rand Flora’ pattern, which shows sister taxa disjunctly distributed in the continental margins of Africa. Here, we explore the evolutionary origins of this pattern using the genus Canarina, with three species: C. canariensis, associated with the Canarian laurisilva, and C. eminii and C. abyssinica, endemic to the Afromontane region in East Africa, as case study. We infer phylogenetic relationships, divergence times and the history of migration events within Canarina using Bayesian inference on a large sample of chloroplast and nuclear sequences. Ecological niche modelling was employed to infer the climatic niche of Canarina through time. Dating was performed with a novel nested approach to solve the problem of using deep time calibration points within a molecular dataset comprising both above-species and population-level sampling. Results show C. abyssinica as sister to a clade formed by disjunct C. eminii and C. canariensis. Miocene divergences were inferred among species, whereas infraspecific divergences fell within the Pleistocene–Holocene periods. Although C. eminii and C. canariensis showed a strong genetic geographic structure, among-population divergences were older in the former than in the latter. Our results suggest that Canarina originated in East Africa and later migrated across North Africa, with vicariance and aridification-driven extinction explaining the 7000 km/7 million year divergence between the Canarian and East African endemics.