Occurrence and characterization of oils rich in gamma-linolenic acid (III): the taxonomical value of the fatty acids in Echium (Boraginaceae)

Fourteen species of the genus Echium (Fam. Boraginaceae) collected in the Macaronesia were surveyed in a search for high levels of gamma-linolenic acid (GLA, 18:3omega6) in the seed oil. High amounts of this fatty acid were found in all of them, ranging from 18.85% (E. pitardii var. pitardii) to 27.42% (E. gentianoides) on total seed fatty acids. The GLA content related to total seed weight was also significant, ranging from 1.26% (E. handiense) to 8.22% (E. gentianoides). In addition, considerable amounts of stearidonic acid (SA, 18:4omega3) were detected, ranging from 3.78% (E. bonnetii var. bonnetii) to 8.81% (E. pininana) on total fatty acids. Besides all the perennial species, the four herbaceous Echium taxa endemic to the Macaronesia also showed high GLA percentages. This is in contrast to the low GLA level found in continental Echium species, all of them bearing an herbaceous habit. These results are in good agreement with the available genetic data and show the ability of GLA to discriminate between Macaronesian and continental Echium species. The analysis of five other Macaronesian species belonging to plant families rich in GLA are also reported.     

Substrate specificity of acyl-Delta(6)-desaturases from Continental versus Macaronesian Echium species

Echium (Boraginaceae) species from the Macaronesian islands exhibit an unusually high level of gamma-linolenic acid (18:3n-6; GLA) and relatively low content of octadecatetraenoic acid (18:4n-3; OTA) in the seed, while the amounts of both fatty acids in their Continental (European) relatives are rather similar. We have tested the hypothesis of whether a different specificity of the acyl-Delta(6)-desaturases (D6DES) towards their respective usual substrates, linoleic acid (18:2n-6; LA) for GLA and alpha-linolenic acid (18:3n-3; ALA) for OTA, was partly responsible for this composition pattern. To this aim we have expressed in yeast the coding sequences of the D6DES genes for the Continental species Echium sabulicola, and the Macaronesian Echium gentianoides. When the yeast cultures are supplemented with the two fatty acid substrates (LA and ALA), a similar utilization of both compounds was found for the D6DES of E. sabulicola, while a preference for LA over ALA was observed for the enzyme of E. gentianoides. This substrate preference must contribute to the increased accumulation of GLA in the seeds of the Macaronesian Echium species. Comparison among the amino acid sequences of these desaturases and other related enzymes, allowed us the discussion about the possible involvement of some specific positions in the determination of substrate specificity.     

Occurrence and characterization of oils rich in gamma-linolenic acid Part I: Echium seeds from Macaronesia

Nineteen species of the genus Echium (Fam. Boraginaceae) collected in Macaronesia were surveyed in a search for new sources of gamma-linolenic acid (GLA, 18:3omega6). High amounts of this acid were found in all of them, ranging from 9.15% (E. plantagineum) to 26.31% (E. callithyrsum) of total seed fatty acids. The amounts of GLA related to total seed weight were also significant, ranging from 1.77% (E. sventenii) to 5.02% (E. nervosum). In addition, considerable amounts of stearidonic acid (SA, 18:4omega3) were detected, ranging from 3.03% (E. auberianum) to 12.94% (E. plantagineum) of total fatty acids. These data allow us to consider tile members of the genus Echium from Macaronesia as one of the richest sources of gamma-linolenic acid found so far in nature. The results obtained from multivariable data analysis and the taxonomic relationships among the species is discussed.     

Genome size variation in Macaronesian angiosperms: forty percent of the Canarian endemic flora completed

Genome sizes for 127 Macaronesian endemic angiosperms from 69 genera and 32 families were estimated using propidium iodide flow cytometry. Only about 30-fold variation in 1C-values was found, ranging from 0.32 pg in Echium bonnetii to 9.52 pg in Scilla dasyantha. Taxa with very small DNA amounts (1C 1.4 pg) were the most dominant group (71.7%), whereas the frequency of other categories was much lower (18.9% and 9.4% in taxa with small (1.41–3.50 pg) and intermediate 1C-values (3.51–14.00 pg), respectively). Comparisons of average C- and Cx-values between Macaronesian endemics and non-Macaronesian representatives always revealed significantly smaller amounts in the former group at various taxonomic levels (genus, family, major phylogenetic lineage). Potential relationship between nuclear DNA content and insular burst of speciation is suggested owing to the marked prevalence of very small genomes among angiosperms that underwent rapid adaptive radiation. Merging all the genome size data on Macaronesian angiosperms available shows that this flora represents the best covered plant assemblage from the phytogeographic point of view.     

873. ECHIUM NERVOSUM

The Madeiran endemic Echium nervosum W.T. Aiton is illustrated based on plants grown at the Royal Botanic Gardens, Kew. Its ecology; phylogenetic and taxonomic placement, and conservation status are discussed. Twenty‐nine species of Echium are endemic to the Macaronesian Islands and they represent one of the most spectacular and best known examples of adaptive radiation on oceanic islands.     

Comparative genomic analyses in Asparagus.

Garden asparagus (Asparagus officinalis L.) belongs to the monocot family Asparagaceae in the order Asparagales. Onion (Allium cepa L.) and Asparagus officinalis are 2 of the most economically important plants of the core Asparagales, a well supported monophyletic group within the Asparagales. Coding regions in onion have lower GC contents than the grasses. We compared the GC content of 3374 unique expressed sequence tags (ESTs) from A. officinalis with Lycoris longituba and onion (both members of the core Asparagales), Acorus americanus (sister to all other monocots), the grasses, and Arabidopsis. Although ESTs in A. officinalis and Acorus had a higher average GC content than Arabidopsis, Lycoris, and onion, all were clearly lower than the grasses. The Asparagaceae have the smallest nuclear genomes among all plants in the core Asparagales, which typically have huge genomes. Within the Asparagaceae, European Asparagus species have approximately twice the nuclear DNA of that of southern African Asparagus species. We cloned and sequenced 20 genomic amplicons from European A. officinalis and the southern African species Asparagus plumosus and observed no clear evidence for a recent genome doubling in A. officinalis relative to A. plumosus. These results indicate that members of the genus Asparagus with smaller genomes may be useful genomic models for plants in the core Asparagales.     

Light brown apple moth in California: a diversity of host plants and indigenous parasitoids

The light brown apple moth, Epiphyas postvittana (Walker), an Australia native tortricid, was found in California in 2006. A field survey of host plants used by E. postvittana was conducted in an urban region of the San Francisco Bay Area. An inspection of 152 plant species (66 families), within a 23-ha residential community, found E. postvittana on 75 species (36 families). Most (69 species) host plants were not Australian natives, but had a wide geographic origin; 34 species were new host records for E. postvittana. Heavily infested species were the ornamental shrubs Myrtus communis L., Pittosporum tobira (Thunb.) W.T. Aiton, Euonymus japonicus Thunb., and Sollya heterophylla Lindl. To survey for parasitoids, four urban locations were sampled, with E. postvittana collected from five commonly infested plants [M. communis, P. tobira, E. japonicus, Rosmarinus officinalis L., and Genista monspessulana (L.) L.A.S. Johnson]. Twelve primary parasitoid species and two hyperparasitoids were reared; the most common were the egg parasitoid Trichogramma fasciatum (Perkins), the larval parasitoids Meteorus ictericus Nees, and Enytus eureka (Ashmead), and the pupal parasitoid Pediobius ni Peck. Meteorus ictericus accounted for >80% of the larval parasitoids, and was recovered from larvae collected on 39 plant species. Across all samples, mean parasitism was 84.4% for eggs, 43.6% for larvae, and 57.5% for pupae. The results are discussed with respect to the potential for resident parasitoid species to suppress E. postvittana populations.     

Bird–flower interactions in the Macaronesian islands

Aims Several bird‐pollinated or ornithophilous flowers are present on the Macaronesian archipelagos, the Canary Islands and Madeira, but absent from nearby NW Africa and Europe. In Macaronesia, no specialist nectar‐feeding birds are found, but several generalist passerine bird species visit flowers for nectar. Two hypotheses attempt to explain the origin and evolution of ornithophily in the Macaronesian flora. According to ‘the island de novo hypothesis’, bird‐flowers evolved from mainland insect‐pollinated ancestors after island colonization. Alternatively, ancestors of the ornithophilous Macaronesian plant species evolved bird‐flowers before reaching the islands (‘the relict hypothesis’). In this study we first compile information of Macaronesian bird–flower interactions from the literature and our own field observations. Secondly, we discuss the two hypotheses of origin of ornithophily in the light of evidence from recent molecular plant phylogenies, palaeontology, historical biogeography of the African avifauna and flora, and present‐day ecological patterns. Location Madeira and Canary Islands. Results At least eleven endemic Macaronesian plant species from six genera have typical ornithophilous floral traits. These genera are: Canarina and Musschia (Campanulaceae), Isoplexis (Scrophulariaceae), Echium (Boraginaceae), Lotus (Fabaceae) and Lavatera (Malvaceae). These lineages have clear affinities to the Mediterranean region, except for Canarina whose closest relatives grow in East African mountains. Six generalist passerine bird species of Sylvia, Phylloscopus (Sylviidae), Serinus (Fringillidae) and Parus (Paridae) visit this flora for nectar. Main conclusion We suggest that the origin and evolution of ornithophilous traits in these plant species took place mostly in mainland areas prior to island colonization. In Canarina and Lavatera, it is well supported that ornithophily is a relict condition, which originated in mainland areas possibly in association with specialist nectar‐feeding birds. For the remaining plant species except Echium wildpretii bird floral traits probably also are a relict condition. These species may be derived from ancestors, which were visited by specialist nectar‐feeding birds during geological periods when the Mediterranean and the Ethiopian vegetation were intermingled in mainland Africa. Probably, these mainland ancestors went extinct due to severe climatic fluctuations, while their Macaronesian descendants survived in ‘refuge’ on the islands. Finally, the island de novo hypothesis may explain the evolution of a mixed bird/insect‐pollination system in the neo‐endemic red‐flowered Echium wildpretii.     

Superoxide-scavenging and prolyl endopeptidase inhibitory activities of Bangladeshi indigenous medicinal plants

The superoxide-scavenging and prolyl endopeptidase (PEP) inhibitory activities of 15 different kinds of Bangladeshi medicinal plants were evaluated. Methanol extraction was performed for the screening tests. Swertia chirata, Emblica officinalis, Zingiber officinale and Myristica malabarica were screened as superoxide-scavenging samples. Similarly, E. officinalis was identified as one of the strongest PEP inhibitory samples. The 50% (O2-)-scavenging and PEP-inhibitory concentrations from E. officinalis methanol extracts were found to be 13.17 and 26.10 microg/ml, respectively.     

Distribution and forage use of exotic bumblebees in South Island, New Zealand

The rapid decline in bumblebee populations within Europe has been linked to habitat loss through agricultural intensification, and a consequential reduction in the availability of preferred forage plants. The successful introduction of four European Bombus species to the South Island of New Zealand from England (in 1885 and 1906) provides an opportunity to determine how important different forage plants (also introduced from the U.K.) are to two severely threatened European bumblebee species (Bombus ruderatus and B. subterraneus). In January 2003 we conducted a survey of bumblebee populations across 70 sites in the central and southern South Island, recording which plant species were being used as pollen and nectar sources for each Bombus species. All four bumblebee species showed a clear preference for plants of European origin. Only B. terrestris, the most polylectic species, was recorded feeding on native plant species. The longer-tongued bumblebees, B. hortorum, B. ruderatus, and B. subterraneus, foraged predominantly on just two plant species; Trifolium pratense for both nectar and pollen, and Echium vulgare for nectar. These plant species are now declining in abundance in the U.K. Our results provide support for the hypothesis that the loss of flower-rich meadows, particularly those containing populations of Fabaceae species with long corollae, is responsible for the decline of bumblebee species across Europe. Comparison with earlier bumblebee surveys suggests that long-tongued bumblebees may also be in decline in New Zealand, particularly B. subterraneus which is now very localised and scarce.     

Odour-mediated nectar foraging in the silver Y moth, Autographa gamma (Lepidoptera: Noctuidae): behavioural and electrophysiological responses to floral volatiles

Naive male and female silver Y moths, Autographa gamma (Lepidoptera: Noctuidae), were attracted in a flight tunnel assay to potted creeping thistle, Cirsium arvense (Asteraceae), butterfly-orchid, Platanthera bifolia (Orchidaceae), soapwort, Saponaria officinalis (Caryophyllaceae), greater knapweed, Centaurea scabiosa (Asteraceae), red clover, Trifolium pratense (Fabaceae), and catnip, Nepeta faasseni (Labiatae), plants with flowers. The most attractive plants were C. arvense , P. bifolia and S. officinalis that elicited 87, 78 and 65% source contacts, respectively. C. scabiosa was less attractive eliciting 43% response. T. pratense and N. faasseni showed the least attraction eliciting 28 and 26% source contacts, respectively. A cotton plant used as control, was not attractive. Floral volatiles from the investigated plant species were collected using headspace sampling technique. Samples were analysed using gas chromatography coupled with electroantennographic detection, and electrophysiologically active compounds were identified by coupled gas chromatography/mass spectrometry. Consistent electrophysiological responses were elicited by twelve compounds from headspace of C. arvense , thirteen compounds from P. bifolia , eleven compounds from S. officinalis , nine from C. scabiosa , ten from T. pratense and two from N. faasseni . Most of the active compounds were specific for one or two species, while benzyl benzoate was present in four and benzaldehyde and benzyl alcohol in three species. Floral scents of C. arvense , P. bifolia and S. officinalis , the most attractive flowers, were dominated by aromatic compounds that were not abundant in the scent of other flowers. To conclude, the results demonstrate the absence of a common denominator of odours present in flowers of different plants visited by A. gamma .     

Origin of Macaronesian Sideritis L. (Lamioideae: Lamiaceae) inferred from nuclear and chloroplast sequence datasets

Sideritis L. (Lamiaceae) comprises approximately 150 species of annuals and perennials distributed chiefly in the Mediterranean region. The majority of the species belong to the continental subgenus Sideritis which is divided into two perennial (Sideritis and Empedoclea) and two annual (Hesiodia and Burgsdorfia) sections. Twenty-three species are woody perennials endemic to the Macaronesian archipelagos of Madeira and the Canary Islands. In an effort to determine the continental origin of the insular group, we constructed independent phylogenies comprising sequence data from both chloroplast and nuclear markers. Sampling included 7 island taxa drawn from the Macaronesian subgenus Marrubiastrum and 25 continental taxa representing all four sections of subgenus Sideritis. Subgenus Marrubiastrum and the two continental perennial sections form well-supported monophyletic groups in both individual and combined analyses. The annual sections are not monophyletic in any analysis; further sampling of annual taxa is needed to resolve these relationships. All analyses identified Sideritis cossoniana, an annual species from Morocco, as the closest continental relative of the Macaronesian group. This contrasts with the hypothesis of earlier workers who suggested that the insular taxa were most closely related to eastern Mediterranean species of the genus. The phylogenies also demonstrate a distinct increase in woodiness among the Macaronesian species relative to their continental congeners, providing further support for the secondary nature of woodiness in island plants.     

Using taxonomically unbiased criteria to prioritize resource allocation for oceanic island species conservation

Oceanic islands have been the grand stage of documented extinctions. In view of limited resources, efficient prioritization is crucial to avoid the extinction of taxa. This work lists the top 100 management priority species for the European archipelagos of the Macaronesian region (Azores, Madeira and the Canary Islands), taking into account both their protection priority and their management feasibility. Bryophytes, vascular plants, molluscs, arthropods and vertebrates were scored by species experts following two sets of criteria: (i) protection priority, including ecological value, singularity, public institutions’ management responsibilities and social value; (ii) management feasibility, including threats knowledge and control feasibility, external socio-economical support for management and biological recovery potential. Environmental managers weighted the same criteria according to their management importance. Final species scores were determined by the combination of both species valuation and criteria weighting. Vascular plants dominate the Top 100 list, followed by arthropods and vertebrates. The majority of listed taxa are endemic to one archipelago or even to a single island. The management feasibility criteria did not dictate that all taxa must be eminently endangered, as for most of the species it should be relatively easy to control threats. The main advantages of this process are the independent participation of scientists and conservation managers, the inclusion of criteria on both protection priority and management feasibility and the taxonomically unbiased nature of the process. This study provides a potentially useful biodiversity conservation tool for the Macaronesian archipelagos that could be readily implemented by the respective regional governments in future legislation.     

Rosmarinic acid

Rosmarinic acid is an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid. It is commonly found in species of the Boraginaceae and the subfamily Nepetoideae of the Lamiaceae. However, it is also found in species of other higher plant families and in some fern and hornwort species. Rosmarinic acid has a number of interesting biological activities, e.g. antiviral, antibacterial, antiinflammatory and antioxidant. The presence of rosmarinic acid in medicinal plants, herbs and spices has beneficial and health promoting effects. In plants, rosmarinic acid is supposed to act as a preformed constitutively accumulated defence compound. The biosynthesis of rosmarinic acid starts with the amino acids L-phenylalanine and L-tyrosine. All eight enzymes involved in the biosynthesis are known and characterised and cDNAs of several of the involved genes have been isolated. Plant cell cultures, e.g. from Coleus blumei or Salvia officinalis, accumulate rosmarinic acid in amounts much higher than in the plant itself (up to 36% of the cell dry weight). For this reason a biotechnological production of rosmarinic acid with plant cell cultures has been proposed.     

Delta-6 desaturase makes a different fatty acid profile of seed oil in Iranian borage (Echium amoenum Fisch. and Mey.)

Iranian borage (Echium amoenum) from Boraginaceae is a valuable medicinal plant native to Iran and Syria. We determined fatty acid profile and individual fatty acid contents in E. amoenum seed oil using gas chromatography. Nevertheless, the cumulative amount of ω-6 and ω-3 fatty acids in E. amoenum (78.5 %) was in great accordance with those of other species of Echium, Stearidonic acid (SDA, C18:4ω3) and gamma-linolenic acid (GLA, C18:3ω6) constituted only 9.7 % of seed oil in this plant. This observation elucidated the weak activity of delta-6 desaturase (D6DES) in E. amoenum compared with D6DESs of other species. As D6DES enzyme is responsible for converting linoleic acid (LA, C18:2ω6) and alpha-linolenic acid (ALA, C18:3ω3) to GLA and SDA, we isolated coding sequence of D6DES gene and characterized primary structure of the translated protein to probably find some evidences explaining the weak activity of D6DES enzyme in E. amoenum. Gene sequence from E. amoenum showed a high identity of 94–96 % with the other Echium species and the amino acid homology increased by 98 %. All the expected signatures including cytochrome b5 domain and three conserved histidine-rich motifs were found in the translated amino acid sequence. Protein alignment revealed that all the conserved motifs in D6DES sequence from E. amoenum are coincident with its counterparts from other Echium species. However, secondary structure of the enzyme deduced from its primary structure using computational simulation represented obvious differences with D6DES proteins of the other species.     

The synthesis and accumulation of stearidonic acid in transgenic plants: a novel source of 'heart-healthy' omega-3 fatty acids

Dietary omega-3 polyunsaturated fatty acids have a proven role in reducing the risk of cardiovascular disease and precursor disease states such as metabolic syndrome. Although most studies have focussed on the predominant omega-3 fatty acids found in fish oils (eicosapentaenoic acid and docosahexaenoic acid), recent evidence suggests similar health benefits from their common precursor, stearidonic acid. Stearidonic acid is a Δ6-unsaturated C18 omega-3 fatty acid present in a few plant species (mainly the Boraginaceae and Primulaceae ) reflecting the general absence of Δ6-desaturation from higher plants. Using a Δ6-desaturase from Primula vialii , we generated transgenic Arabidopsis and linseed lines accumulating stearidonic acid in their seed lipids. Significantly, the P. vialii Δ6-desaturase specifically only utilises α-linolenic acid as a substrate, resulting in the accumulation of stearidonic acid but not omega-6 γ-linolenic acid. Detailed lipid analysis revealed the accumulation of stearidonic acid in neutral lipids such as triacylglycerol but an absence from the acyl-CoA pool. In the case of linseed, the achieved levels of stearidonic acid (13.4% of triacylglycerols) are very similar to those found in the sole natural commercial plant source ( Echium spp.) or transgenic soybean oil. However, both those latter oils contain γ-linolenic acid, which is not normally present in fish oils and considered undesirable for heart-healthy applications. By contrast, the stearidonic acid-enriched linseed oil is essentially devoid of this fatty acid. Moreover, the overall omega-3/omega-6 ratio for this modified linseed oil is also significantly higher. Thus, this nutritionally enhanced linseed oil may have superior health-beneficial properties.     

Effects of Rosmarinus officinalis neighbors on resprouting of Erica multiflora individuals

To study the effects of competition in Mediterranean shrubland regeneration following disturbance, we used a neighborhood approach to assess the influence of mature Rosmarinus officinalis neighbors on the resprouting of Erica multiflora individuals after clipping. Sprout biomass of target plants 2 years after clipping was regressed against various measures of neighbor abundance within a 2 m radius around target E. multiflora individuals in which all vegetation except R. officinalis had been removed. The largest single influence on the biomass of sprouts produced was the previous biomass of the resprouting plant. The abundance of R. officinalis neighbors had a weak but detectable effect on resprouting of E. multiflora. Abundance of neighbors within 60 cm from target plants was the best predictor of regrowth. At this distance, two simple measures of neighbor abundance within the neighborhood, the number of neighbors and the sum of their heights, were significant in accounting for variation in resprouted biomass. None of the combinations of neighbor variables performed significantly better than single variables. The best models accounted for around 24 percent of the variation in resprout biomass. As in other studies, angular dispersion of neighbors never had a significant effect on performance of target plants. The weak but significant response of resprouting to variation in R. officinalis abundance suggests that the intensity of competition in the experiment was low because of the removal of other species.     

The Native Dialectica aemula (Meyrick) and the Introduced Dialectica scalariella (Zeller) (Lepidoptera: Gracillariidae) in Australia: Characterisation of Two Closely Related Species on Boraginaceae

Two gracillariid leaf miners of the genus Dialectica Walsingham are present in Australia on plants belonging to the family Boraginaceae, one a native species here identified as Dialectica aemula (Meyrick) which was originally described from India, and the Palaearctic Dialectica scalariella (Zeller) or Echium leaf miner, deliberately introduced as a biological control agent for Echium plantagineum L. or Paterson's Curse. Differential diagnoses are given for the two species, and they are comprehensively illustrated to enable identification. In contrast to the externally indistinguishable adults, the cocoons of the two species differ significantly in shape and colour and a colour plate allows easy identification.     

Multiple colonizations, in situ speciation, and volcanism-associated stepping-stone dispersals shaped the phylogeography of the Macaronesian red fescues (Festuca L., Gramineae)

Whereas examples of insular speciation within the endemic-rich Macaronesian hotspot flora have been documented, the phylogeography of recently evolved plants in the region has received little attention. The Macaronesian red fescues constitute a narrow and recent radiation of four closely related diploid species distributed in the Canary Islands (F. agustinii), Madeira (F. jubata), and the Azores (F. francoi and F. petraea), with a single extant relative distributed in mainland southwest Europe (F. rivularis). Bayesian structure and priority consensus tree approaches and population spatial correlations between genetic, geographical, and dispersal distances were used to elucidate the phylogeographical patterns of these grasses. Independent versus related origins and dispersal versus isolation by distance (IBD) hypotheses were tested to explain the genetic differentiation of species and populations, respectively. Genetic structure was found to be geographically distributed among the archipelagos and the islands endemics. The high number of shared AFLP fragments in all four species suggests a recent single origin from a continental Pliocene ancestor. However, the strong allelic structure detected among the Canarian, Madeiran, and Azorean endemics and the significant standardized residual values obtained from structured Bayesian analysis for pairwise related origin hypotheses strongly supported the existence of three independent continental-oceanic colonization events. The Canarian F. agustinii, the Madeiran F. jubata, and the two sister F. francoi and F. petraea Azorean species likely evolved from different continental founders in their respective archipelagos. Despite the short span of time elapsed since colonization, the two sympatric Azorean species probably diverged in situ, following ecological adaptation, from a common ancestor that arrived from the near mainland. Simple dispersal hypotheses explained most of the genetic variation at the species level better than IBD models. The optimal dispersal model for F. agustinii was a bidirectional centripetal stepping-stone colonization pattern, an eastern-to-western volcanism-associated dispersion was favored for F. francoi, whereas for the recently derived F. petraea a counterintuitive direction of colonization (west-to-east) was suggested. The population-based phylogeographical trends deduced from our study could be used as predictive models for other Macaronesian plant endemics with similar distribution areas and dispersal abilities.     

AND IF ENGLER WAS NOT COMPLETELY WRONG? EVIDENCE FOR MULTIPLE EVOLUTIONARY ORIGINS IN THE MOSS FLORA OF MACARONESIA

The Macaronesian endemic flora has traditionally been interpreted as a relict of a subtropical element that spanned across Europe in the Tertiary. This hypothesis is revisited in the moss subfamily Helicodontioideae based on molecular divergence estimates derived from two independent calibration techniques either employing fossil evidence or using an Monte Carlo Markov Chain (MCMC) to sample absolute rates of nucleotide substitution from a prior distribution encompassing a wide range of rates documented across land plants. Both analyses suggest that the monotypic Madeiran endemic genus Hedenasiastrum diverged of other Helicodontioideae about 40 million years, that is, well before Macaronesian archipelagos actually emerged, in agreement with the relict hypothesis. Hedenasiastrum is characterized by a plesiomorphic morphology, which is suggestive of a complete morphological stasis over 40 million years. Macaronesian endemic Rhynchostegiella species, whose polyphyletic origin involves multiple colonization events, evolved much more recently, and yet accumulated many more morphological novelties than H. percurrens. The Macaronesian moss flora thus appears as a complex mix of ancient relicts and more recently dispersed, fast‐evolving taxa.