Complex population genetic structure in the endemic Canary Island pine revealed using chloroplast microsatellite markers

The Canary archipelago, located on the northwestern Atlantic coast of Africa, is comprised of seven islands aligned from east to west, plus seven minor islets. All the islands were formed by volcanic eruptions and their geological history is well documented providing a historical framework to study colonization events. The Canary Island pine (Pinus canariensis C. Sm.), nowadays restricted to the westernmost Canary Islands (Gran Canaria, Tenerife, La Gomera, La Palma and El Hierro), is considered an old (Lower Cretaceous) relic from an ancient Mediterranean evolutionary centre. Twenty seven chloroplast haplotypes were found in Canary Island pine but only one of them was common to all populations. The distribution of haplotypic variation in P. canariensis suggested the colonization of western Canary Islands from a single continental source located close to the Mediterranean Basin. Present-day populations of Canary Island pine retain levels of genetic diversity equivalent to those found in Mediterranean continental pine species, Pinus pinaster and Pinus halepensis. A hierarchical analysis of variance (AMOVA) showed high differentiation among populations within islands (approximately 19%) but no differentiation among islands. Simple differentiation models such as isolation by distance or stepping-stone colonization from older to younger islands were rejected based on product-moment correlations between pairwise genetic distances and both geographic distances and population-age divergences. However, the distribution of cpSSR diversity within the islands of Tenerife and Gran Canaria pointed towards the importance of the role played by regional Pliocene and Quaternary volcanic activity and long-distance gene flow in shaping the population genetic structure of the Canary Island pine. Therefore, conservation strategies at the population level are strongly recommended for this species.Communicated by D.B. NealeA. Gómez and S.C. González-Martínez as joint authors     

Index to Vegetatio,volumes 74–110 (1988–1994)

Chamaecytisus proliferus (L.fil.) Link (Fabaceae: Genisteae) represents a species complex in the Canary Islands. Floristic data from 147 releves from the whole complex were collected and analysed by classification (TWINSPAN) and ordination (DECORANA) methods. Results indicate that white escobon of Tenerife, escobon of El Hierro, white escobon of Gran Canaria and typical tagasaste in La Palma are associated with those plant communities from the north of these islands which are under the influence of the north-eastern trade winds. Narrow-leaved escobon in Tenerife and La Gomera, escobon of southern Gran Canaria and white tagasaste of La Palma are found in those areas which are not under the direct influence of these winds. Morphological forms from the more easterly islands (Gran Canaria and Tenerife-La Gomera) have the broadest ecological range and they have played an important role in the floristic changes which have taken place after the destruction of the forests in these islands. The highest priorities for in situ conservation should be given to wild populations of typical tagasaste, white escobon of Tenerife and escobon of El Hierro.Abbreviations IBPGR International Board for Plant Genetic Resources - DECORANA Detrended Correspondence Analysis - OTU Operational Taxonomic Unit - TWINSPAN Two Way Indicator Species Analysis     

Phylogeography and genetic structure of the Canarian common chaffinch (Fringilla coelebs) inferred with mtDNA and microsatellite loci

The widespread common chaffinch (Fringilla coelebs) inhabits five of the seven Canary Islands. Sequences of the mitochondrial cytochrome b gene (1002 bp) revealed new insights into the systematics and phylogeography of this taxon. Additionally, a set of microsatellite loci were analyzed to examine the structure of these populations. Our results suggest that a new species of the genus Fringilla is present in the Canary Islands, which comprises at least three subspecies, but with a different distribution to that which has been morphologically accepted. The specimens from Gran Canaria are genetically distinct from those of La Gomera and Tenerife (F. c. canariensis), which suggests the existence of an undescribed taxon. Furthermore, nuclear microsatellite data suggest an ongoing incipient speciation process in this population. This study provides both important conservationist implications and a basis for re-evaluating the taxonomic status of the Canarian Fringilla coelebs populations.     

Colonisation and diversification of the blue tits (Parus caeruleus teneriffae-group) in the Canary Islands

The blue tit (Parus caeruleus teneriffae group) is proposed to have colonised the Canary Islands from North Africa according to an east-to-west stepping stone model, and today, the species group is divided into four subspecies, differing in morphological, acoustic, and ecological characters. This colonisation hypothesis was tested and the population structure between and within the islands studied using mitochondrial DNA sequences of the non-coding and relatively fast evolving control region. Our results suggest that one of the central islands, Tenerife, was colonised first and the other islands from there. Three of the presently recognised four subspecies are monophyletic, exception being the subspecies teneriffae, which consists of two monophyletic groups, the one including birds of Tenerife and La Gomera and the other birds of Gran Canaria. The Gran Canarian birds are well differentiated from birds of the other islands and should be given a subspecies status. In addition, the teneriffae subspecies group is clearly distinct from the European caeruleus group, and therefore the blue tit assemblage should be divided into two species.     

On the identity of Riccia teneriffae S.W.Arnell (Marchantiophyta: Ricciaceae) and a note on R. cavernosa Hoffm. in the Canary Islands

Abstract

We revised both the holotype and an isotype of Riccia teneriffae S.W.Arnell 1962 and additionally revised our own collections of Riccia cavernosa Hoffm. 1795 from the Canary Islands. Since the types of R. teneriffae represent R. cavernosa, and the latter name precedes the former, R. teneriffae should be treated as a synonym of R. cavernosa. In the Canary Islands, R. cavernosa appears to be rare. It has been found on La Gomera, Gran Canaria, Lanzarote, and Tenerife. We report it as new to Fuerteventura. R. cavernosa inhabits ephemeral, thin layers of mud. Very rarely it occurs on basaltic pyroclasts. SEM images of spores are presented. The local distribution is mapped.     

Reconciling gene trees with organism history: the mtDNA phylogeography of three Nesotes species (Coleoptera: Tenebrionidae) on the western Canary Islands

The processes of island colonization and speciation are investigated through mtDNA studies on Canary Island beetles. The genus Nesotes (Coleoptera: Tenebrionidae) is represented by 19 endemic species on the Canary Islands, the majority of which are single island endemics. Nesotes conformis is the most widespread, occurring on Gran Canaria, Tenerife, La Palma and El Hierro. Nesotes conformis forms a paraphyletic assemblage, with a split between Gran Canaria and the other three islands. Nesotes conformis of the western Canary Islands cluster with Nesotes altivagans and Nesotes elliptipennis from Tenerife. Fifty‐two individuals from this western islands species complex have been sequenced for 675 base pairs of the mtDNA cytochrome oxidase II gene, representing Tenerife, La Palma and El Hierro. A neighbour joining analysis of maximum likelihood distances resulted in three distinct mtDNA lineages for N. conformis, two of which also include mitotypes of N. altivagans and N. elliptipennis. Through application of parametric bootstrap tests, we are able to reject hypotheses of monophyly for both N. conformis and N. altivagans. Nesotes altivagans and N. elliptipennis are poorly separated morphologically and mtDNA sequence data adds support to this being one species with a highly variable morphology. We propose that N. altivagans/N. elliptipennis is recently derived from two ancestral mtDNA lineages within N. conformis from the Teno region of Tenerife. We further propose colonization of the younger islands of La Palma and El Hierro by N. conformis from a mitochondrial lineage within the Teno massif (colonization; diversification; mitochondrial DNA; Canary Islands; Coleoptera).     

Phylogenetic relationships among the Canary Island Steganacaridae (Acari, Oribatida) inferred from mitochondrial DNA sequence data

The mite genus Steganacarus is represented in the Canary Islands by three endemic species, one recently discovered species, and several morphotypes of uncertain taxonomic position. We used a fragment of the mitochondrial cytochrome oxidase I gene to reconstruct the phylogenetic relationships among representatives of the different taxa from the three central islands of the archipelago, Tenerife, La Gomera and Gran Canaria. Sequence data were analysed by both maximum parsimony and maximum likelihood methods. The inferred phylogenetic relationships do not correlate well with current morphological taxonomy but reveal four deeply divergent and geographically coherent lineages, one each on Gran Canaria and La Gomera and two on Tenerife. No pattern of molecular differentiation was observed among different morphotypes. Possible explanations for this incongruence are suggested in relation to the ecology and biogeography of the group. A recently discovered Steganacarus species from La Gomera, morphologically quite distinct from the other Canarian Steganacarus, is clearly identified as a taxon distantly related to all the other Canarian samples.     

Integrative taxonomy reveals Europe's rarest songbird species,the Gran Canaria blue chaffinch Fringilla polatzeki

The conservation of endangered taxa often critically depends on accurate taxonomic designations. The status of the Gran Canaria population of the blue chaffinch Fringilla teydea polatzeki has not been reevaluated since the early 1900s when this taxon was described as a subspecies and combined with the much more common Tenerife blue chaffinch F. t. teydea in a single species. We show that multiple diagnostic differences in plumage, songs, calls and morphometrics distinguish F. t. polatzeki from F. t. teydea. Preliminary playback experiments suggest that F. t. polatzeki is able to discriminate between songs of both taxa. Along with previously reported differences in mitochondrial DNA, these findings show that the blue chaffinches on Gran Canaria and Tenerife represent two distinctive species: F. polatzeki and F. teydea. Gran Canaria blue chaffinch is Europe's rarest passerine species and should be classified as critically endangered. Its long‐term survival in the wild currently depends on a very small (< 20 km²) area in southwest Gran Canaria. Reclassification of Gran Canaria blue chaffinch as a species increases the urgency of ongoing conservation efforts. Our study underscores the critical importance of taxonomic clarification of threatened taxa that are currently classified as ‘subspecies’.     

A Bryophyte Flora of Kent. IV. Addenda and Corrigenda

Abstract

Based on a revision of Andreaea from the Canary Islands, the occurence of two species is confirmed. A key is provided. A. crassifolia Luisier occurs on Gran Canaria, La Palma and Tenerife. A. heinemannii Hampe &; Müll.Hal. occurs on La Palma. Former records of A. heinemannii s.l. for Gran Canaria and Tenerife refer to A. crassifolia.     

Morphological variation in the Chamaecytisus proliferus (L.f.) Link complex (Fabaceae: Genisteae) in the Canary Islands

FRANCISCO-ORTEGA, J., JACKSON, M. T., SANTOS-GUERRA, A. & FORD-LLOYD, B. V., 1993. Morphological variation in the Chamaecytisus proliferus (L.f.) Link complex (Fabaceae: Genisteae) in the Canary Islands . A multivariate study (Principal Component Analysis and Cluster Analysis, Warďs method) of 47 morphological traits from 164 populations of Chamaecytisus proliferus (L.f.) Link from the Canary Islands confirmed that this species complex is formed by seven morphological types. At least eight traits discriminated between these types. Patterns of variation follow a cline within Gran Canaria, Tenerife and La Palma. These results also show that morphological variation is greater in the eastern islands (i.e. Gran Canaria and Tenerife) than in the western islands (La Gomera, El Hierro and La Palma) and that no morphological differences are found between plants of typical tagasaste from wild and cultivated populations.     

Phylogeography of skinks (Chalcides) in the Canary Islands inferred from mitochondrial DNA sequences

Mitochondrial DNA (mtDNA) evolution was investigated in skinks of the genus Chalcides found in the Canary Islands ( Ch. sexlineatus, Ch. viridanus and Ch. simonyi ), together with some North African congenerics ( Ch. polylepis and Ch. mionecton ). Several sites were included within islands to cover areas of known within-island geographical variation in morphology. Skinks from the islands of El Hierro and La Gomera appear to be sister taxa. The relationships between this clade and the Tenerife and Gran Canarian skinks were not fully resolved, although the best working hypothesis indicated monophyly with the former, with the latter forming a closely related outgroup. Ch. simonyi from Fuerteventura was more distantly related to the Western Canary Island skinks and did not show close relationships with the North African species Ch. mionecton and Ch . polylepis . Possible colonization sequences for the four most Western Canary Islands were considered. El Hierro appears to have been colonized relatively recently from La Gomera, commensurate with the recent origin of this island, while dispersal between La Gomera and Tenerife and between Gran Canaria and Tenerife or La Gomera appears to have taken place considerably earlier. Substantial within-island haplotype divergence was found in Gran Canaria and Tenerife. This may be a result of recent periods of intense volcanic activity found within these two islands. Lower levels of within-island differentiation are found in La Gomera and El Hierro and may be explained by lower levels of volcanic activity during recent geological history and a more recent colonization, respectively.     

Microsatellite loci development in endangered pamphagid grasshoppers endemic to the Canary Islands (Orthoptera)

The five recognized endemic pamphagid species (Orthoptera) of the Canary Islands have restricted and fragmented ranges due to habitat decline. Seven polymorphic microsatellite markers have been developed for Acrostira tamarani, and the performance of primer pairs amplifying these loci in related taxa has been tested. The number of alleles in A. tamarani samples taken from two distant localities in the island of Gran Canaria ranged from two to eight per locus. Observed heterozygosities were from 0.151 to 0.559. Up to four primer pairs amplified in related species with moderate heterozigosities (maximum of 0.687 and 10 alleles for Ata67 locus in Purpuraria erna). These markers could be useful tools to study the population structure and management of endemic threatened pamphagids of the Canary archipelago.     

Microsatellite loci isolation in the endangered Gran Canarian blue chaffinch (Fringilla teydea polatzeki) and their utility in closely related taxa

The blue chaffinch, Fringilla teydea, is an endemic species of the Canary Islands. This species is formed by two subspecies: The Teneriffean blue chaffinch (F. t. teydea), and the endangered Gran Canarian blue chaffinch, (F. t. polatzeki). Here we report the isolation and characterization of nine tetranucleotide microsatellites (AAAG and AAAT) from the Gran Canarian subspecies, using an enrichment protocol. An average of 7.8 alleles per locus and an average observed heterozygosity of 0.773 were found (n = 28). The loci were tested for their ability to cross amplify in the Teneriffean subspecies and in the common chaffinch (Fringilla coelebs). These microsatellites will be used to manage a captive breeding programme for the endangered Gran Canarian subspecies.     

Evolution and diversification of the forest and hypogean ground-beetle genus Trechus in the Canary Islands

The beetle genus Trechus (Carabidae) is represented in the Macaronesian Islands by 43 endemic species. The Canary Islands have 16 endemic species, with two adapted to hypogean life. Phylogenetic relationships among 177 individuals of 38 Canarian, Madeiran, Azorean and continental Trechus species were examined using mitochondrial DNA and nuclear internal transcribed spacer 2 (ITS2) sequence data. Results show two main lineages in the Canaries: one comprising two sister groups with species from the laurel forest of La Gomera and Tenerife, and the other containing the single species from Gran Canaria and a species complex in the four western islands including two troglobites. Calibrations were applied to a linearized tree using a relaxed molecular clock method to estimate the major evolutionary divergence times of the Canarian Trechus species. Although the species assemblage in this archipelago is relatively ancient (7-8 million years), much of the species diversity is recent. Transition to the hypogean environment is more consistent with the "adaptive shift" rather than with the competing "climatic relict" hypothesis.     

David Fairchild expeditions to the Canary Islands: Plant collections and research outcomes

Dr. David Fairchild (1869–1954) made four field trips to the Canary Islands. They took place in 1903 (supported by Barbour Lathrop) and in 1925, 1926, and 1927 (supported by Allison V. Armour). They represented the first extensive plant exploration expeditions ever undertaken by United States botanists targeting this archipelago. At least two of the trips were joined by other biologists from several disciplines. Four of the seven Canary Islands (Gran Canaria, Lanzarote, La Palma, and Tenerife) were visited. The four expeditions yielded eight publications, over 315 photographs, and 89 germplasm accessions (73 species). Two of these publications focused on invertebrates, one on plant mosaic viruses, and two on the pollination biology and propagation of Ficus auriculata (Moraceae). The remaining three works provided accounts on the natural history and plants of the islands and on the cropping systems and the rural life of the archipelago.     

Third molar agenesis in human prehistoric populations of the Canary Islands

The occurrence of third molar agenesis was recorded in a sample of 1,492 maxillary and 1,718 mandibular arches belonging to the prehistoric settlers of the Gan Canaria, Tenerife, and La Gomera Islands (Canary Islands). There were significant sex differences only in the Tenerife sample for the maxilla, the incidence in females being higher than in males. In the Gran Canaria sample, the total frequency (male and female combined) of third molar agenesis (individual count method) was 8.7% for the maxilla and 9.3% for the mandible. In the Tenerife and La Gomera samples, the frequencies were 11.1% and 10.7% for the maxilla and 14.6% and 13.3% for the mandible. In the Tenerife sample, the differences between both jaws were statistically significant. The incidence of missing third molars in the mandible was significantly higher in Tenerife than in Gran Canaria, but the other sample differences were statistically nonsignificant. Bilateral absence of third molars was observed in about two-thirds of the specimens examined. Some correlation between both jaws for the occurrence of third molar agenesis was found. The hypotheses that have been proposed in order to explain third molar agenesis in man are discussed. It is suggested that the loss of the third molar in Homo sapiens could be produced by a heterochronic phenomenon of postdisplacement, as a consequence of the phylogenetic tendency toward the delay of the onset of the third molar formation, and that the genetic factors responsible for the absence of these teeth could be related to the general process of delay in tooth formation.     

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.     

Colonization and speciation on volcanic islands: phylogeography of the flightless grasshopper genus Arminda (Orthoptera,Acrididae) on the Canary Islands

Abstract Volcanic archipelagos represent excellent areas to study colonization and speciation processes. The grasshopper genus Arminda is one of many endemic taxa of the Canary Islands. It consists of seven wingless species, most of which are single‐island endemics. We sequenced two mitochondrial (12s rRNA, ND5) and two nuclear gene fragments (28s rRNA, ITS2) to reconstruct the colonization pattern of the genus. Our results are in accordance with a stepping‐stone colonization model from east to west, corresponding to the prevailing ocean currents, but alternative hypotheses cannot be fully rejected. The populations of A. brunneri from Tenerife belong to two different lineages (east and west) consistent with the geological history of the island. It remains to be tested whether these lineages represent different species and whether further lineages exist on this island. The five clades of the four western islands (A. brunneri group) have approximately similar branch lengths. The short internodes between these lineages resulted in a poorer phylogenetic resolution. Specimens from La Palma were genetically distinct and are subsequently described as a new species, Arminda palmae sp.n. Our results suggest in situ speciation on Gran Canaria, which was accompanied by a stronger degree of morphological diversification than the inter‐island speciation processes. The aberrant species A. canariensis has formerly been assigned to a monotypic subgenus Chopardminda, which is now synonymized with Arminda syn.n. based on its phylogenetic position. Gran Canaria seems to be the only island where Arminda species occur sympatrically, although allopatric speciation seems likely due to the long history of volcanism and erosion on the island.     

Disentangling the complex evolutionary history of the Western Palearctic blue tits (Cyanistes spp.) – phylogenomic analyses suggest radiation by multiple colonization events and subsequent isolation

Isolated islands and their often unique biota continue to play key roles for understanding the importance of drift, genetic variation and adaptation in the process of population differentiation and speciation. One island system that has inspired and intrigued evolutionary biologists is the blue tit complex (Cyanistes spp.) in Europe and Africa, in particular the complex evolutionary history of the multiple genetically distinct taxa of the Canary Islands. Understanding Afrocanarian colonization events is of particular importance because of recent unconventional suggestions that these island populations acted as source of the widespread population in mainland Africa. We investigated the relationship between mainland and island blue tits using a combination of Sanger sequencing at a population level (20 loci; 12 500 nucleotides) and next‐generation sequencing of single population representatives (>3 200 000 nucleotides), analysed in coalescence and phylogenetic frameworks. We found (i) that Afrocanarian blue tits are monophyletic and represent four major clades, (ii) that the blue tit complex has a continental origin and that the Canary Islands were colonized three times, (iii) that all island populations have low genetic variation, indicating low long‐term effective population sizes and (iv) that populations on La Palma and in Libya represent relicts of an ancestral North African population. Further, demographic reconstructions revealed (v) that the Canary Islands, conforming to traditional views, hold sink populations, which have not served as source for back colonization of the African mainland. Our study demonstrates the importance of complete taxon sampling and an extensive multimarker study design to obtain robust phylogeographical inferences.     

Pollination of Habenaria tridactylites on the Canary Islands

We investigated the pollination of Habenaria tridactylites, an endemic orchid of the Canary Islands. The entirely green, widely open flowers have a long spur containing nectar. We carried out fieldwork, a molecular clock analysis, herbarium surveys, identified pollinators by both morphology and DNA barcoding, and measured the length of floral spurs and insect tongues using a combination of traditional and innovative micro‐CT scanning methods to 1) determine the pollinator of this orchid and 2) investigate correlations between local mean spur length and age, altitude and longitude of the island. Habenaria tridactylites was found to be pollinated on Tenerife by both small and intermediate sized moth species with variable tongue lengths and mostly belonging to Geometridae and to a lesser extent Crambidae, Erebidae, Noctuidae and Tortricidae. Of the sixteen moth species identified, nine are endemic to the Canary Islands or Macaronesia. The different local populations of H. tridactylites on the islands of Gran Canaria, El Hierro, La Gomera, La Palma and Tenerife with different ages and distances from mainland Africa, did not show a significant correlation of mean spur length and altitude, but did show a significant and positive linear correlation with longitude and the geological age of the island. The latter is congruent with the evolutionary arms race theory first proposed by Darwin, suggesting that flowers gradually evolve longer spurs and pollinators longer tongues.