Plant genetic diversity in the Canary Islands: a conservation perspective

The Canary Islands are an Atlantic volcanic archipelago with a rich flora of ～570 endemic species. The endemics represent ～40% of the native flora of the islands, and ～20% of the endemics are in the E (endangered) category of the International Union for Conservation of Nature. A review of allozyme variation in 69 endemic species belonging to 18 genera and eight families is presented. The average species-level genetic diversity (H(T)) at allozyme loci is 0.186, which is twice as high as the mean reported for endemics of Pacific archipelagos. Possible factors contributing to this higher diversity are discussed, but the reasons remain obscure. An average of 28% of the allozyme diversity within species resides among populations, indicating a high level of interpopulational differentiation. Studies of reproductive biology indicate that many of the endemic species are outcrossers. The high total diversity within species, the relatively high differentiation among populations, and the outcrossing breeding systems have implications for species conservation. Decreased population sizes in outcrossing species would promote biparental inbreeding and increase inbreeding depression. The relatively high proportion of allozyme diversity among populations indicates that the most effective strategy for preserving genetic variation in species is to conserve as many populations as possible. The genetic diversity in many Canary Island endemics is endangered by: (1) overgrazing by introduced animals, such as barbary sheep, goats, mouflons, rabbits, and sheep; (2) interspecific hybridization following habitat disturbance or planting of endemics along roadsides or in public gardens; (3) competition with alien plant species; and (4) decline of population size because of urban development and farming.     

Origin and evolution of endemic plants of the Bonin (Ogasawara) Islands

The Bonin Islands are typical oceanic islands, located at the western part of the North Pacific Ocean and approximately 1,000 km south of mainland Japan. This archipelago consists of about 20 small islands. Although floristic diversity is low due to the small area and limited environmental diversity, the Bonin Islands harbor unique endemic flora as in other well-known oceanic islands. This paper presents a brief summary of the results obtained from recent studies on the endemic flora of the Bonin Islands. The results are reviewed in relation to the four stages of the evolution of endemic flora in the oceanic islands; migration, establishment, enlargement and diversification. The ancestors of the flora originated mostly from tropical and subtropical Southeast Asia or mainland Japan by rare events of long distance dispersal. The proportion of bird-dispersed species is relatively high as for other oceanic islands. Genetic data sets obtained from allozyme variation in some endemic species suggest that migration occurred several million years ago and genetic diversity is correlated with current population size. At the time of establishment, self-compatible plants are expected to have an advantage. However, the percentage of dioecious plants is relatively high. This is partly due to evolutionary changes from hermaphroditic ancestors to dioecy which occurred in two genera in the Bonin Islands. In addition, there are some examples of evolutionary changes from herbaceous ancestors to woody endemics. Adaptive radiation is found in some genera, although the number of congeneric endemic species is less than five. Studies of allozyme variation inPittosporum, Symplocos andCrepidiastrum showed that genetic identity is generally very high between congeneric species in spite of their distinct morphologies. This result suggests that divergence of these species occurred rather recently and distinct morphological differences are based on a limited number of genetic changes.     

The utility of automated analysis of inter-simple sequence repeat (ISSR) loci for resolving relationships in the Canary Island species of Tolpis (Asteraceae)

Plants of oceanic islands, often remarkably divergent morphologically from continental relatives, are useful models for studying evolution and speciation because evolution is telescoped in time and space. Prior studies revealed little DNA sequence variation within the clade of ca. 10 Canary Island species of Tolpis, which precluded resolving species relationships. The present study assessed the utility of automated analysis of inter-simple sequence repeat (ISSR) loci for resolving relationships within the clade using 264 individuals from 36 populations of all recognized species and three undescribed morphological variants. Similarity (Dice coefficient) and Fitch parsimony were used to generate neighbor-joining (NJ) and strict consensus trees (MP), respectively. All individuals of the morphologically distinct endemic species formed clusters in both trees. There is also support for clusters of two undescribed variants in the NJ tree. Individuals from a morphologically variable complex consisting primarily of two species are not well resolved at population or species levels. The NJ and MP trees are not congruent at deeper levels, including relationships among species. Results are interpreted in terms of the biology of the species, and the utility of automated analysis of ISSR markers for interpreting patterns of evolution of Tolpis in the Canary Islands is discussed.     

Chloroplast DNA evidence for the roles of island colonization and extinction in Tolpis (Asteraceae: Lactuceae)

Tolpis consists of ～13 species native to Africa, Europe, and Macaronesia, with at least one species endemic to each of the four major archipelagos of the Azores, Madeira Islands, Canary Islands, and Cape Verde Islands. All but two of these species develop woody stems by maturity. Chloroplast DNA restriction site variation was analyzed for all species of Tolpis and four outgroups in order to understand the patterns of island colonization and evolution of woodiness in this genus. Parsimony analyses revealed a strongly supported monophyletic Tolpis. Within the genus, the following three well-supported groups were detected: all species from the Canary Islands and Cape Verde Islands, both Azorean species, and both continental species. The Canary Island/Cape Verde clade was sister to the two continental species, and the Azorean clade was sister to this group. The two Madeiran species of Tolpis occupied the basalmost positions within the genus. When biogeography was mapped onto this phylogeny, nine equally parsimonious reconstructions (five steps each) of dispersal history were detected, which fell into two groups: eight reconstructions implied that Tolpis colonized Madeira from the continent, followed by continental extinction and subsequent continental recolonization, while one reconstruction implied that Tolpis colonized Macaronesia four times. Two of the reconstructions involving continental extinction required the least amount of overall dispersal distance. The cpDNA phylogeny also suggests that woodiness arose in the common ancestor of all extant Tolpis, followed by two independent reversals to an herbaceous habit. Assuming that one of the eight reconstructions favoring continental extinction and recolonization is true, our results suggest that Tolpis may represent the first documented example of a woody plant group in Macaronesia that has recolonized the mainland in herbaceous form.     

ALLOZYME DIVERSITY WITHIN AND DIVERGENCE AMONG FOUR SPECIES OF ROBINSONIA (ASTERACEAE: SENECIONEAE), A GENUS ENDEMIC TO THE JUAN FERNANDEZ ISLANDS,CHILE

Enzyme electrophoresis was employed to assess genetic diversity within and divergence among four species of Robinsonia (R. evenia, R. gayana, R. gracilis, R. thurifera), a genus endemic to the Juan Fernandez Islands, Chile. The genus consists of treelike perennial plants, and all species are dioecious. Morphological diversity within the genus is reflected by recognition of two subgenera, with three sections in one subgenus. Total gene diversity is highest in the two species (R. gayana and R. gracilis) that are most common and have the largest population sizes. Robinsonia evenia has only half and the rare R. thurifera only 20% of the diversity detected in the other two species. The diversity measured in R. gayana and R. gracilis is comparable to the values typical of continental species of flowering plants with similar life history attributes. The genetic identities between species range from 0.560 to 0.706, which is similar to or below many values for congeneric species, but much lower than most reports for congeners on oceanic islands. The higher diversity within and divergence among species of Robinsonia compared to many insular endemics may result from several factors. The genus probably arose from selfincompatible plants of the genus Senecio, which means that several to perhaps many colonizers carried considerable allozymic variation to the Islands. Large population sizes and obligate outcrossing are additional factors that would account for higher diversity. Sorting of alleles during radiation and the process of mutation probably combined to produce divergence among the species. Estimated divergence times calculated for the species from allozyme data range from 1.7 to 5.5 million years depending on the assumptions made in the calculations; the age of the island (Masatierra) on which these four species are confined is approximately 4.0 million years. The electrophoretic data suggest that Robinsonia arrived early in the archipelago, and radiated and speciated rapidly after colonization.     

Genetic differentiation and speciation in Stomion (Goleoptera: Tenebrionidae): flightless beetles of the Galápagos Islands, Ecuador

Stomion is a swarm of 13 tenebrionid beetle taxa endemic to the Galápagos Islands. The taxa show marked morphological variation, and all are flighdess. They can be divided into three divergent morphological groups based on external sculpturing of the elytra. Eleven taxa were examined electrophoretically at 20 enzyme loci to measure the extent of genetic differentiation which accompanied morphological differentiation and speciation. Stomion are shown to be ideal candidates for allopatric and founder event speciation, with their limited dispersal ability, narrow distributions, and incidence of single-island endemics. Accordingly, individual heterozygosities were low in most taxa, and gene pool divergence was apparent among populations of single taxa occupying different islands. Both interspecific and intraspecific genetic identities were high, with an average 1 = 0.88 and I = 0.96, respectively. The relatively young age of the genus and the allopatric mode of speciation may account for high genetic relatedness. No clear relationship was found between allozyme phenotypes and the three morphological groups, thus, the evolution of these traits may have been facilitated by similar selection among islands of similar age and geography. The geographical distributions of the morphological groups can be used to suggest a general pattern of speciation for the group.     

Scrophularia arguta,a widespread annual plant in the Canary Islands: a single recent colonization event or a more complex phylogeographic pattern?

Many studies have addressed evolution and phylogeography of plant taxa in oceanic islands, but have primarily focused on endemics because of the assumption that in widespread taxa the absence of morphological differentiation between island and mainland populations is due to recent colonization. In this paper, we studied the phylogeography of Scrophularia arguta, a widespread annual species, in an attempt to determine the number and spatiotemporal origins of dispersal events to Canary Islands. Four different regions, ITS and ETS from nDNA and psbA‐trnH and psbJ‐petA from cpDNA, were used to date divergence events within S. arguta lineages and determine the phylogenetic relationships among populations. A haplotype network was obtained to elucidate the phylogenetic relationships among haplotypes. Our results support an ancient origin of S. arguta (Miocene) with expansion and genetic differentiation in the Pliocene coinciding with the aridification of northern Africa and the formation of the Mediterranean climate. Indeed, results indicate for Canary Islands three different events of colonization, including two ancient events that probably happened in the Pliocene and have originated the genetically most divergent populations into this species and, interestingly, a recent third event of colonization of Gran Canaria from mainland instead from the closest islands (Tenerife or Fuerteventura). In spite of the great genetic divergence among populations, it has not implied any morphological variation. Our work highlights the importance of nonendemic species to the genetic richness and conservation of island flora and the significance of the island populations of widespread taxa in the global biodiversity.     

Diversification of the forest beetle genus Tarphius on the Canary Islands, and the evolutionary origins of island endemics

The flightless beetle genus Tarphius Erichson (Coleoptera: Colydiidae) is a distinctive element of the beetle fauna of the Canary Islands with 29 species distributed across the five western islands. The majority of Tarphius species are rare and intimately associated with the monteverde forest and only two species occur on more than one island. In this study we investigate the phylogeography of the Canary Island Tarphius, and their relationship to Tarphius from the more northerly archipelagos of Madeira and the Azores using maximum parsimony and Bayesian inference analysis of mitochondrial cytochrome oxidase I and II sequence data. We use geological datings for the Canary Islands, Azores, and Madeira to calibrate specific nodes of the tree for the estimation of divergence times using a penalized likelihood method. Data suggest that the Canary Island species assemblage is of some antiquity, however, much of this species diversity is relatively recent in origin. The phylogenetic relationships of species inhabiting the younger islands of El Hierro and La Palma indicate that colonization events between islands have probably been a significant factor in the evolutionary history of the Canary Island species assemblage. A comparison of molecular phylogenetic studies of arthropods on the Canary Islands suggests that, in the evolution of the arthropod species community of an island, the origin of endemic species is initially the result of colonizing lineages differentiating from their source populations. However, as an island matures a greater proportion of endemic species originate from intra-island speciation.     

Patterns of genetic divergence of three Canarian endemic Lotus (Fabaceae): implications for the conservation of the endangered L. kunkelii

We examined data for 11 allozyme loci in 14 populations that represent the distribution of the endangered Lotus kunkelii, the narrowly distributed L. arinagensis (both endemic to Gran Canaria), and the broad-ranging L. lancerottensis (endemic to the easternmost Canary Islands, Fuerteventura and Lanzarote) to explore and construe patterns of genetic variation and use this data to assess the controversial taxonomic status of L. kunkelii relative to L. lancerottensis. While L. kunkelii maintains low levels of variation, presumably as a consequence of prolonged inbreeding due to very low population size and sharp geographic isolation, the other two taxa have much higher indicators of polymorphism than those reported for other oceanic island endemics. Lotus arinagensis has the highest genetic polymorphism and the lowest interpopulation differentiation, presumably because of its considerable antiquity and habitat stability, despite recent fragmentation. The high interpopulation differentiation in L. lancerottensis is attributed to the Atlantic acting as a barrier, reducing gene flow within islands. Evolutionary analysis of the allozyme evidence indicates that L. kunkelii is genetically closer to L. arinagensis than to L. lancerottensis, thereby dispelling the taxonomic uncertainty and supporting L. kunkelii as a distinct species, warranting legal protection in the forthcoming catalog of threatened Canarian species.     

RAPD marker diversity within and divergence among species of Dendroseris (Asteraceae: Lactuceae)

Random Amplified Polymorphic DNA (RAPD) markers were used to measure genetic diversity within and divergence among species of Dendroseris (Asteraceae: Lactuceae), a genus endemic to the Juan Fernandez Islands, Chile. Results were compared to previous studies employing allozymes. For five of the species, RAPD banding patterns distinguished all individuals examined, and different mutilocus genotypes were found even in species exhibiting no allozyme diversity. RAPD band diversities ranged from 0.003 to 0.022 within species; >90% of total diversity was among species and <10% within them. Relative levels of allozyme and RAPD diversity were similar for some species, particularly those with highest and lowest diversities, but overall there was no significant correlation. Relationships inferred from a neighbor-joining tree generated from RAPD bands were similar to results obtained from morphology, chloroplast DNA (cpDNA) restriction site mutations, and sequences from the internal transcribed spacer regions of nuclear ribosomal DNA (ITS), but somewhat better resolution was achieved. Relationships shown by allozymes differed from trees based on other data; this ostensibly is a result of the sharing of ancestral alleles and the absence of alleles generated subsequent to speciation. Dendroseris represents an example where RAPD markers, because of their greater variability, provide a useful alternative to allozymes for assessing diversity in rare species endemic to oceanic islands and for resolving relationships among the species.     

Effects of climate change on the distribution of plant species and plant functional strategies on the Canary Islands

Aim

Oceanic islands possess unique floras with high proportions of endemic species. Island floras are expected to be severely affected by changing climatic conditions as species on islands have limited distribution ranges and small population sizes and face the constraints of insularity to track their climatic niches. We aimed to assess how ongoing climate change affects the range sizes of oceanic island plants, identifying species of particular conservation concern.

Location

Canary Islands, Spain.

Methods

We combined species occurrence data from single-island endemic, archipelago endemic and nonendemic native plant species of the Canary Islands with data on current and future climatic conditions. Bayesian Additive Regression Trees were used to assess the effect of climate change on species distributions; 71% (n = 502 species) of the native Canary Island species had models deemed good enough. To further assess how climate change affects plant functional strategies, we collected data on woodiness and succulence.

Results

Single-island endemic species were projected to lose a greater proportion of their climatically suitable area (x ̃ = −0.36) than archipelago endemics (x ̃ = −0.28) or nonendemic native species (x ̃ = −0.26), especially on Lanzarote and Fuerteventura, which are expected to experience less annual precipitation in the future. Moreover, herbaceous single-island endemics were projected to gain less and lose more climatically suitable area than insular woody single-island endemics. By contrast, we found that succulent single-island endemics and nonendemic natives gain more and lose less climatically suitable area.

Main Conclusions

While all native species are of conservation importance, we emphasise single-island endemic species not characterised by functional strategies associated with water use efficiency. Our results are particularly critical for other oceanic island floras that are not constituted by such a vast diversity of insular woody species as the Canary Islands.     

Patterns of cladogenesis in the venomous marine gastropod genus Conus from the Cape Verde islands

Isolated oceanic archipelagos are excellent model systems to study speciation, biogeography, and evolutionary factors underlying the generation of biological diversity. Despite the wealth of studies documenting insular speciation, few of them focused on marine organisms. Here, we reconstruct phylogenetic relationships among species of the marine venomous gastropod genus Conus from the Cape Verde archipelago. This small island chain located in the Central Atlantic hosts 10% of the worldwide species diversity of Conus. Analyses were based on mtDNA sequences, and a novel nuclear marker, a megalin-like protein, member of the low-density lipoprotein receptor gene family. The inferred phylogeny recovered two well-defined clades within Conus. One includes Cape Verde endemic species with larger shells, known as the "venulatus" complex together with C. pulcher from the Canary Islands. The other is composed of Cape Verde endemic and West Africa and Canary Island "small" shelled species. In both clades, nonendemic Conus were resolved as sister groups of the Cape Verde endemics, respectively. Our results indicate that the ancestors of "small" and "large" shelled lineages independently colonized Cape Verde. The resulting biogeographical pattern shows the grouping of most Cape Verde endemics in monophyletic island assemblages. Statistical tests supported a recent radiation event within the "small shell" clade. Using a molecular clock, we estimated that the colonization of the islands by the "small" shelled species occurred relatively close to the origin of the islands whereas the arrival of "large" shelled Conus is more recent. Our results suggest that the main factor responsible for species diversity in the archipelago may be allopatric speciation promoted by the reduced dispersal capacity of nonplanktonic lecithotrophic larvae.     

Spatial and ecological population genetic structures within two island‐endemic Aeonium species of different niche width

The Crassulacean genus Aeonium is a well‐known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra‐island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island‐endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.     

The phylogeography of the darkling beetle,Hegeter politus,in the eastern Canary Islands.

We investigated the phylogeography of Hegeter politus, a saprophagous, flightless darkling beetle endemic to the eastern Canary Islands, using a fragment of the mitochondrial COI gene. Distance and parsimony based gene trees of the mitotypes identified revealed a striking association between mitotype clades and sampling locations. The branching order of the clades suggested that the colonization of the islands by Hegeter politus proceeded from the southern part of Fuerteventura in a north-northeast direction to Lanzarote and the smaller islands. Based on this, a colonization scenario compatible with the reported geological ages and volcanisms of the various parts of the islands has been proposed. The high divergence of the beetles collected from the extreme south of Fuerteventura (the Jandía peninsula) from all other samples has led us to propose that they may be from a new species that has not been described previously. The ecological isolation of Jandía from the rest of Fuerteventura by the sand dunes that cover its narrow isthmus in the north, and the existence of many plant and animal endemisms unique to Jandía, lend supportive evidence to our proposal. The similarities between the evolution of island endemics in the Hawaiian and Canary archipelagos have been discussed. We conclude that many endemics in the Canary archipelago, like the Hawaiian Islands, are most likely to have originated from post-colonization differentiation and divergence.     

Tracking colonization and diversification of insect lineages on islands: mitochondrial DNA phylogeography of Tarphius canariensis (Coleoptera: Colydiidae) on the Canary Islands.

The genus Tarphius Erichson (Coleoptera: Colydiidae) is represented by 29 species on the Canary Islands. The majority are rare, single-island endemics intimately associated with the monteverde (laurel forest and fayal-brezal). The Tarphius canariensis complex is by far the most abundant and geographically wide-spread, occurring on Gran Canaria, Tenerife and La Palma. Eighty-seven individuals from the T. canariensis complex were sequenced for 444 bp of the mitochondrial DNA cytochrome oxidase I gene (COI), 597 bp of the COII gene and the intervening tRNA(leu) gene. A neighbour-joining analysis of maximum-likelihood distances put La Palma as a single monophyletic clade of haplotypes occurring within a larger clade comprising all Tenerife haplotypes. Gran Canarian haplotypes were also monophyletic occurring on a separate lineage. Using a combination of the phylogeographic pattern for T. canariensis, geological data, biogeography of the remaining species and estimated divergence times, we proposed a Tenerifean origin in the old Teno massif and independent colonizations from here to north-eastern Tenerife (Anaga), Gran Canaria and La Palma. New methods of estimating diversification rates using branching times were applied to each island fauna. All islands exhibited a gradually decreasing rate of genetic diversification similar to that seen for Brachyderes rugatus (Coleoptera: Curculionidae) from the Canary Islands.     

Pollen fertility of synthetic intra- and interspecific F1 hybrids in Canary Island Tolpis (Asteraceae)

Pollen fertility was determined for synthetic F₁ hybrids between members of the genus Tolpis endemic to the Canary Islands. Mean fertility varies from 1 to nearly 100%. High hybrid sterility is unusual for island lineages. Surprisingly, the fertility of hybrids between morphologically distinct species was generally higher than some crosses within the morphologically variable group that includes the Tolpis laciniata and T. lagopoda complexes. Within this group, fertility was lower particularly in hybrids involving one recognized segregate species (T. webbii), but none of the four potentially new species had reduced hybrid fertility. Despite the overall fertility differences between groupings within the T. laciniata and T. lagopoda complexes there is variation in fertility within groups; sterility factors have a complex inter-populational distribution. The cause of hybrid sterility is unknown, but preliminary data suggest that both chromosomal and genetic factors are involved.     

Biogeographical and evolutionary patterns in the Macaronesian shield-backed katydid genus Calliphona Krauss, 1892 (Orthoptera: Tettigoniidae) and allies as inferred from phylogenetic analyses of multiple mitochondrial genes

Abstract.  We investigated the phylogenetic patterns, evolutionary processes, and their taxonomic implications, of two closely related shield-backed katydid genera endemic to the Macaronesian archipelagos: the monotypic Psalmatophanes Chopard, 1938 endemic to Madeira and Calliphona Krauss, 1892, which includes three species restricted to the Canary Islands. Two main hypotheses have been proposed to explain the origin and colonization pathways of these two genera: a single origin with subsequent sequential colonization of the islands, or three independent colonization waves from continental Africa. We used DNA sequence information from the mitochondrial genes cox1, tRNAleucine, rrnL and nad1 to infer phylogenetic relationships among Psalmatophanes and Calliphona species. Our results provide support for the independent colonization of Madeira and the Canary Islands, and suggest that Psalmatophanes is actually more closely related to the continental genus Tettigonia than to the Canarian representatives. Deep genetic divergence among Canarian species provides further support for the assignment of the Canarian species into two subgenera. Tree topology along with Bayesian-based estimates of lineage age suggest a pattern of colonization from Tenerife to La Palma, and from Tenerife to Gran Canaria with subsequent dispersal to La Gomera. We report the first collection of a Calliphona specimen in the island of El Hierro, which molecular data suggest is a recent immigrant from La Gomera. We hypothesize that the patterns of distribution and genetic divergence exhibited by Calliphona in the Canary Islands are compatible with a taxon cycle process. Our results have further implications for the higher level phylogeny of the subfamily Tettigoniinae and suggest that some of the tribes as currently delimited may not correspond to natural groups.     

Notes on the Poaceae of the Robinson Crusoe (Juan Fernández) Islands, Chile

Notes on the Poaceae of the Robinson Crusoe (Juan Fernández) Islands, Chile, Brittonia 54: 154–163. 2001.—Poaceae in the Robinson Crusoe (=Juan Fernández) Islands number 53 species in 32 genera, of which 9% of the species are endemic, 9% indigenous, and 81% adventitious. The endemic taxa (and their conservation status) are:Agrostis masafuerana (rare),Chusquea fernandeziana (not endangered),Megalachne berteroana (not endangered),M. masafuerana (not endangered), andPodophorus bromoides (extinct).Megalachne andPodophorus are endemic genera. Comparisons with Poaceae in the Bonin and Volcano Islands, Canary Islands, Galápagos Islands, and Hawaiian Islands show different levels of endemism: number of endemic taxa, respectively, 5, 10, 12, 40; percent specific endemism, 8, 6, 21, 19. No endemic genera occur.Anthoxanthum odoratum, Avena barbata andHordeum murinum are noxious weeds in the Robinson Crusoe Islands. Many adventives are shared among floras of the archipelagos, with the highest ties of Robinson Crusoe being to the Canaries (53% of total Poaceae known in Juan Fernández) and the Hawaiian Islands (47%). Low levels of adventives occur within the Bonin (5%) and Galápagos (7%) Islands. In contrast, there are many endemic genera of Asteraceae in these same archipelagos: Bonin and Volcano Islands (1), Canary Islands (8), Galápagos Islands (5), and Hawaiian Islands (6); percent of specific endemism is also higher (20, 53, 54 and 56, respectively). Hypotheses for greater levels of endemics among oceanic island Asteraceae include more efficient dispersal mechanisms by wind and birds, animal pollination systems that result in greater degrees of geographic populational genetic isolation, and a vascular cambium that offers enhanced growth-form evolutionary opportunities.     

Radiation of the Spider Genus Dysdera (Araneae, Dysderidae) in the Canary Islands: Cladistic Assessment Based on Multiple Data Sets

The volcanic archipelago of the Canary Islands, 100 km off the northwestern coast of Africa, harbors 43 endemic species of the mostly circum-Mediterranean spider genus Dysdera (Araneae, Dysderidae). This amounts to approximately one-fourth of all known Dysdera species in an area that represents 0.1% of the range of the genus. In order to address the origin of this extraordinary number of endemic species, the phylogenetic relationships among all the endemic taxa and a sample of 27 continental species were reconstructed. A simultaneous cladistic analysis was performed on 66 morphological characters, 471 bp of the cytochrome oxidase I and 424 bp of the 16S rRNA mitochondrial genes. The preferred most parsimonious tree supports a single origin for most of the endemic species (84%), although this tree is ambiguous regarding the total number of overseas colonizations (allowing a minimum of two and a maximum of four colonization events). Our data suggest that the Canary Islands have been the source of the colonizers of some of the remaining Macaronesian archipelagoes (certainly for the Selvagem Islands and the Cape Verdes and possibly for Madeira); the Azores have been independently colonized by dysderids from the continent. The present study provides a phylogenetic framework for an exceptional case of insular species radiation, an essential tool for unraveling the factors that have promoted this amazing diversification. Species radiations in oceanic archipelagoes are excellent models for the study of speciation processes.     

Origin of Mediterranean insular endemics in the Boraginales: integrative evidence from molecular dating and ancestral area reconstruction

Aim The presence of numerous reliable fossils and the occurrence of many endemic island species make the Boraginales particularly suitable for integrative biogeographical studies. In this paper we aim to elucidate the time frame and events associated with the origin of selected borages endemic to the Mediterranean climate zone. More specifically, we describe and examine the alternative palaeo‐ and neoendemic hypotheses for their origin. Location Corsica and Sardinia (continental fragment islands) and the Canary Islands (an oceanic island archipelago). Methods Eighty‐nine accessions, representing 30 genera from five families ascribed to the Boraginales, were examined for six chloroplast DNA regions. We used an integrative approach including phylogenetic analyses (Mr Bayes ), Bayesian molecular dating (T3 package) with four fossil constraints on nodes, and biogeographical reconstructions (diva ) to elucidate the temporal and spatial origins of the Corso‐Sardinian and Canary Island endemics. Results Species of Echium endemic to the Canary Islands diverged from their continental sister clade during the Miocene (15.3 ± 5.4 Ma), probably after the rise of the oldest islands (c. 20 Ma). Corso‐Sardinian endemics of Borago diverged from their primarily North African sister clade during the late Miocene‐Pliocene (c. 6.9 ± 3.6 Ma), well after the initial fragmentation of the islands (c. 30 Ma). Similarly, Corso‐Sardinian endemics of Anchusa diverged from the South African Anchusa capensis during the Pliocene–Pleistocene (c. 2.7 ± 2.1 Ma). Main conclusions The present study reveals an Anatolian origin for Anchusa, Borago and Echium and underlines the importance of the Eastern Mediterranean region as a possible reservoir for plant evolution in the Mediterranean Basin. For Anchusa and Borago, the divergence from their respective sister clades on the two types of islands post‐dated the formation of the islands, thus supporting the neo‐endemic hypothesis, whereas the dating results for the origin of Echium endemics were less conclusive.