Phylogeography and molecular phylogeny of Macaronesian island Tarphius (Coleoptera: Zopheridae): why are there so few species in the Azores?

Aim We used a phylogenetic framework to examine island colonization and predictions pertaining to differentiation within Macaronesian Tarphius (Insecta, Coleoptera, Zopheridae), and explain the paucity of endemics in the Azores compared with other Macaronesian archipelagos. Specifically, we test whether low diversity in the Azores could be due to recent colonization (phylogenetic lineage youth), cryptic speciation (distinct phylogenetic entities within species) or the young geological age of the archipelago. Location Macaronesian archipelagos (Azores, Madeira and the Canary Islands), northern Portugal and Morocco. Methods Phylogenetic analyses of mitochondrial and nuclear genes of Tarphius beetles of the Azores, other Macaronesian islands and neighbouring continental areas were used to investigate the origin of island biodiversity and to compare patterns of colonization and differentiation. A comparative nucleotide substitution rate test was used to select the appropriate substitution rate to infer clade divergence times. Results Madeiran and Canarian Tarphius species were found to be more closely related to each other, while Azorean taxa grouped separately. Azorean taxa showed concordance between species and phylogenetic clades, except for species that occur on multiple islands, which segregated by island of origin. Divergence time estimates revealed that Azorean Tarphius are an old group and that the most recent intra‐island speciation event on Santa Maria, the oldest island, occurred between 3.7 and 6.1 Ma. Main conclusions Our phylogenetic approach provides new evidence to understand the impoverishment of Azorean endemics: (1) Tarphius have had a long evolutionary history within the Azores, which does not support the hypothesis of fewer radiation events due to recent colonization; (2) the current taxonomy of Azorean Tarphius does not reflect common ancestry and cryptic speciation is responsible for the underestimation of endemics; (3) intra‐island differentiation in the Azores was found only in the oldest island, supporting the idea that young geological age of the archipelago limits the number of endemics; and (4) the lack of evidence for recent intra‐island diversification in Santa Maria could also explain the paucity of Azorean endemics. Phylogenetic reconstructions of other species‐rich taxa that occur on multiple Macaronesian archipelagos will reveal whether our conclusions are taxon specific, or of a more general nature.     

Phylogeography of the Macaronesian Lettuce Species <Emphasis Type="Italic">Lactuca watsoniana</Emphasis> and <Emphasis Type="Italic">L. palmensis</Emphasis> (Asteraceae)

The phylogenetic relationships and phylogeography of two relatively rare Macaronesian Lactuca species, Lactuca watsoniana (Azores) and L. palmensis (Canary Islands), were, until this date, unclear. Karyological information of the Azorean species was also unknown. For this study, a chromosome count was performed and L. watsoniana showed 2n = 34. A phylogenetic approach was used to clarify the relationships of the Azorean endemic L. watsoniana and the La Palma endemic L. palmensis within the subtribe Lactucinae. Maximum parsimony, Maximum likelihood and Bayesian analysis of a combined molecular dataset (ITS and four chloroplast DNA regions) and molecular clock analyses were performed with the Macaronesian Lactuca species, as well as a TCS haplotype network. The analyses revealed that L. watsoniana and L. palmensis belong to different subclades of the Lactuca clade. Lactuca watsoniana showed a strongly supported phylogenetic relationship with North American species, while L. palmensis was closely related to L. tenerrima and L. inermis, from Europe and Africa. Lactuca watsoniana showed four single-island haplotypes. A divergence time estimation of the Macaronesian lineages was used to examine island colonization pathways. Results obtained with BEAST suggest a divergence of L. palmensis and L. watsoniana clades c. 11 million years ago, L. watsoniana diverged from its North American sister species c. 3.8 million years ago and L. palmensis diverged from its sister L. tenerrima, c. 1.3 million years ago, probably originating from an African ancestral lineage which colonized the Canary Islands. Divergence analyses with *BEAST indicate a more recent divergence of the L. watsoniana crown, c. 0.9 million years ago. In the Azores colonization, in a stepping stone, east-to-west dispersal pattern, associated with geological events might explain the current distribution range of L. watsoniana.     

Timing and tempo of early and successive adaptive radiations in Macaronesia

The flora of Macaronesia, which encompasses five Atlantic archipelagos (Azores, Canaries, Madeira, Cape Verde, and Salvage), is exceptionally rich and diverse. Spectacular radiation of numerous endemic plant groups has made the Macaronesian islands an outstanding area for studies of evolution and speciation. Despite intensive investigation in the last 15 years, absolute age and rate of diversification are poorly known for the flora of Macaronesia. Here we report molecular divergence estimates and rates of diversification for five representative, putative rapid radiations of monophyletic endemic plant lineages across the core eudicot clade of flowering plants. Three discrete windows of colonization during the Miocene and early Pliocene are suggested for these lineages, all of which are inferred to have had a single colonization event followed by rapid radiation. Subsequent inter-archipelago dispersal events into Madeira and the Cape Verdes took place very recently during the late Pliocene and Pleistocene after initial diversification on the Canary Islands. The tempo of adaptive radiations differs among the groups, but is relatively rapid compared to continental and other island radiations. Our results demonstrate that opportunity for island colonization and successful radiation may have been constrained to discrete time periods of profound climatic and geological changes in northern African and the Mediterranean.     

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.     

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.     

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.     

Recent origin,active speciation and dispersal for the lichen genus Nephroma (Peltigerales) in Macaronesia

Aim We reconstructed the phylogeny of the lichen genus Nephroma (Peltigerales) to assess the relationships of species endemic to Macaronesia. We estimated dates of divergences to test the hypothesis that the species arose in Macaronesia (neo‐endemism) versus the oceanic archipelagos serving as refugia for formerly widespread taxa (palaeo‐endemism). Location Cosmopolitan with a special focus on the archipelagos of the Azores, Madeira and the Canary Islands. Methods DNA sequences were obtained from 18 species for three loci and analysed using maximum parsimony, maximum likelihood and Bayesian inferences. Divergence dates were estimated for the internal transcribed spacer (ITS)‐based phylogeny using a relaxed molecular clock. Reconstruction of the ancestral geographical range was conducted using the Bayesian 50% majority rule consensus tree under a parsimony method. Results The backbone phylogenetic tree was fully supported, with Nephroma plumbeum as sister to all other species. Four strongly supported clades were detected: the Nephroma helveticum, the N. bellum, the N. laevigatum and the N. parile clades. The latter two share a common ancestor and each includes a widespread Holarctic species (N. laevigatum and N. parile, respectively) and all species endemic to Macaronesia. The data suggest a neo‐endemic origin of Macaronesian taxa, a recent range expansion from Macaronesia of both widespread species, a range expansion limited to the Mediteranean Basin and south‐western Europe for another taxon, and a long dispersal event that resulted in a speciation event in the western parts of North America. Main conclusions The Macaronesian endemic species belong to two sister clades and originated from a most recent common ancestor (MRCA) shared with one widely distributed taxon, either N. parile or N. laevigatum. Estimates of the mean divergence dates suggest that the endemics originated in the archipelagos after the rise of the volcanic islands, along with the ancestor to the now widespread species, which probably expanded their range beyond Macaronesia via long‐distance dispersal. This study provides the first phylogenetic evidence of Macaronesian neo‐endemism in lichenized fungi and provides support for the hypothesis that oceanic islands may serve as a source for the colonization of continents. However, further data are needed to properly assess the alternative hypothesis, namely colonization from western North America.     

Resolving the Azorean knot: a response to Carine & Schaefer (2010)

Carine & Schaefer (Journal of Biogeography, 2010, 37 , 77–89) suggest that the lack of past climate oscillations in the Azores may have contributed to the low plant endemism in this archipelago compared to that of the Canary Islands, a pattern they term the Azorean diversity enigma. Here we challenge their hypothesis, and discuss how the particular characteristics of the Azores may have driven current diversification patterns in this archipelago. We argue that the restricted number of Azorean endemic species and their wide distribution is explicable by the geological, geographical and ecological attributes of the archipelago. That is, the Azores are too young, too small, and too environmentally homogeneous to have hosted many in situ diversification events, so they do not host as many endemic species as other Macaronesian archipelagos, such as Madeira and especially the Canary Islands.     

Reconstruction of the spatio-temporal diversification and ecological niche evolution of Helianthemum (Cistaceae) in the Canary Islands using genotyping-by-sequencing data

Background and AimsSeveral biogeographical models have been proposed to explain the colonization and diversification patterns of Macaronesian lineages. In this study, we calculated the diversification rates and explored what model best explains the current distribution of the 15 species endemic to the Canary Islands belonging to Helianthemum sect. Helianthemum (Cistaceae).MethodsWe performed robust phylogenetic reconstructions based on genotyping-by-sequencing data and analysed the timing, biogeographical history and ecological niche conservatism of this endemic Canarian clade.Key ResultsOur phylogenetic analyses provided strong support for the monophyly of this clade, and retrieved five lineages not currently restricted to a single island. The pristine colonization event took place in the Pleistocene (~1.82 Ma) via dispersal to Tenerife by a Mediterranean ancestor.ConclusionsThe rapid and abundant diversification (0.75–1.85 species per million years) undergone by this Canarian clade seems the result of complex inter-island dispersal events followed by allopatric speciation driven mostly by niche conservatism, i.e. inter-island dispersal towards niches featuring similar environmental conditions. Nevertheless, significant instances of ecological niche shifts have also been observed in some lineages, making an important contribution to the overall diversification history of this clade.     

Mitochondrial DNA phylogeny of Brimstone butterflies (genus Gonepteryx) from the Canary Islands and Madeira

Part of the mitochondrial Cytochrome Oxidase I gene was sequenced for seven species of Gonepteryx (Pieridac) butterflies. Four of the species are island endemics inhabiting the Canary Island archipelago and Madeira. The remaining three are European and African conspecifics. Sequence data were analysed phylogenetically by maximum parsimony and maximum likelihood methods. The resulting trees were used to deduce Canarian species' ancestry, sequential inter-island colonization and systematics. They suggest African ancestry for the Canary Island taxa and a colonization pattern, within the archipelago, compatible with the geological ages of the islands and other Canarian fauna: a colonization sequence from Africa to Tenerife and Gomera, followed by Tenerife to La Palma. The molecular phylogeny indicated that there are three Canarian endemics, G. cleobule, G. palmae and G. eversi from Tenerife, La Palma and Gomera, respectively.     

Genetic diversity of the Macaronesian leafy liverwort Porella canariensis inferred from RAPD markers

Plant colonization of the North Atlantic raises the intriguing question of the relationships between extant island species with their continental counterparts (European, African, and American), which may provide clues to past geographic distribution and colonization history. It has been suggested that during past glaciations, many plant species with typical Mediterranean distributions survived in the Atlantic islands that belong to what is today known as Macronesia. We used random amplified polymorphic DNA (RAPD) markers to study 12 populations of the liverwort Porella canariensis partly covering its present-day distribution (Azores, Madeira, Canary and Cape Verde Islands, and Iberian Peninsula). Unweighted pair-group (UPGMA) and principal component (PCO) analyses showed a similar geographical pattern that suggested a close relationship between Iberian populations and those from the Canaries and Cape Verde Islands. Populations from Madeira had more genetic variation than those from the Azores, a result from either a richer diversity of habitats in Madeira, which prompted more population diversification, successive colonization waves from different origins, or an older colonization of Madeira. The data show that continuous patches of liverworts are often comprised of more than one individual. Finally, RAPDs can be used to investigate intraspecific diversity within a comparatively large geographic area and, with utmost care, can be used to infer a historic context to explain the patterns observed.     

Origin and evolution of the endemic genera of Gonosperminae (Asteraceae: Anthemideae) from the Canary Islands: evidence from nucleotide sequences of the internal transcribed spacers of the nuclear ribosomal DNA

The Gonosperminae (Asteraceae) are composed of three genera endemic to the Canary Islands (GONOSPERMUM: Less., and LUGOA: DC.) and southern Africa (INULANTHERA: K?llersj?), and they are considered an example of a floristic link between these two regions. Phylogenetic analyses of ITS sequences reveal that the Canarian genera are not sister to INULANTHERA: and do not support the monophyly of the Gonosperminae. These results, coupled with previous phylogenetic studies of other groups, suggest that many of the putative biogeographic links between Macaronesia and southeast Africa need to be evaluated by rigorous phylogenetic analyses. INULANTHERA: forms part of the basal southern African radiation of the Anthemideae, and therefore it is closely related to other taxa from this region. Maximum likelihood and weighted parsimony analyses support a monophyletic group in the Canary Islands, that includes LUGOA:, Gonospermum, and three TANACETUM: species endemic to the island of Gran Canaria. Bootstrap support for the monophyly of this Canarian group is weak, and it collapses in the strict consensus tree based on unweighted parsimony. LUGOA: is nested within Gonospermum, and both interisland colonization among the western islands of La Gomera, El Hierro, La Palma and Tenerife, and radiation on the central island of Gran Canaria have been the major patterns of species diversification for these Canarian endemics.     

Patterns of long-distance dispersal in Tiquilia subg. Tiquilia (Boraginaceae): implications for the origins of amphitropical disjuncts and Galapagos Islands endemics

Plant biogeographers have long argued whether plant disjunctions result from vicariance or dispersal. One of the classic patterns of plant disjunction involves New World amphitropical disjuncts, as exemplified by Tiquilia subg. Tiquilia (Boraginaceae). Subgenus Tiquilia forms a heterogeneous group of ~20 species that is amphitropically distributed in the deserts of North and South America, with four taxa endemic to the Galápagos Islands. The current study reconstructs the biogeographic history of subg. Tiquilia in order to explore the origins of New World amphitropical disjunction and of Galápagos endemism. A strongly supported phylogeny of the subgenus is estimated using sequence data from matK, ndhF, rps16, ITS, and waxy. Biogeographic analyses using combined and individual marker data sets reveal a complex history of long-distance dispersal in subg. Tiquilia. Biogeographic reconstructions imply a North American origin of the subgenus and its three major lineages and require at least four long-distance dispersal events to explain its current distribution. The South American taxa of subg. Tiquilia result from three independent and nonsimultaneous colonization events, while the monophyly and continental origins of the Galápagos endemics are unresolved. This study contributes to a growing body of evidence that intercontinental dispersal has been more common than previously realized.     

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.     

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.     

Sex and reproduction of the alfonsino Beryx splendens (Pisces, Berycidae) from the Macaronesian archipelagos

This paper provides comparative information on the reproductive biology of the alfonsino, Beryx splendens Lowe, 1834, species with commercial interest in the Azores, Madeira and the Canary Islands. A total of 846 individuals from Azores (14.0–42.0 cm fork length), 621 from Madeira (17.2–50.0 cm fork length) and 643 from the Canaries (18.2–38.9 cm fork length) were used for the study. The alfonsino is gonochoric with no evidence of sexual dimorphism. Females are more abundant than males; this dominance probably reflects certain differences in the spatial distribution and/or the catchability of males and females in the Macaronesian archipelagos. The spawning season was distinct for the three Macaronesian areas, with an observed North–South variation in the reproductive period: September–March in the Azores, March–June in Madeira and July–September in the Canary Islands. The size at sexual maturity estimated for Madeira and the Canary Islands is similar (32 and 30 cm fork length, respectively), while for the Azores it is reached at smaller length (23 cm fork length). The differences observed in the size at sexual maturity can be explained by the different exploitation levels in each archipelago. Life‐history parameters of the alfonsino suggest that this species has a specialistic life‐history strategy and fisheries based on this species are more susceptible to growth overfishing and population depletion.     

Drivers of diversity in Macaronesian spiders and the role of species extinctions

Aim To identify the biogeographical factors underlying spider species richness in the Macaronesian region and assess the importance of species extinctions in shaping the current diversity. Location The European archipelagos of Macaronesia with an emphasis on the Azores and Canary Islands. Methods Seven variables were tested as predictors of single‐island endemics (SIE), archipelago endemics and indigenous spider species richness in the Azores, Canary Islands and Macaronesia as a whole: island area; geological age; maximum elevation; distance from mainland; distance from the closest island; distance from an older island; and natural forest area remaining per island – a measure of deforestation (the latter only in the Azores). Different mathematical formulations of the general dynamic model of oceanic island biogeography (GDM) were also tested. Results Island area and the proportion of remaining natural forest were the best predictors of species richness in the Azores. In the Canary Islands, area alone did not explain the richness of spiders. However, a hump‐shaped relationship between richness and time was apparent in these islands. The island richness in Macaronesia was correlated with island area, geological age, maximum elevation and distance to mainland. Main conclusions In Macaronesia as a whole, area, island age, the large distance that separates the Azores from the mainland, and the recent disappearance of native habitats with subsequent unrecorded extinctions seem to be the most probable explanations for the current observed richness. In the Canary Islands, the GDM model is strongly supported by many genera that radiated early, reached a peak at intermediate island ages, and have gone extinct on older, eroded islands. In the Azores, the unrecorded extinctions of many species in the oldest, most disturbed islands seem to be one of the main drivers of the current richness patterns. Spiders, the most important terrestrial predators on these islands, may be acting as early indicators for the future disappearance of other insular taxa.     

Phylogenetic biogeography of the leafy liverwort Herbertus (Jungermanniales, Herbertaceae) based on nuclear and chloroplast DNA sequence data: correlation between genetic variation and geographical distribution

Aim The cosmopolitan genus Herbertus is notorious for having a difficult taxonomy and for the fact that there is limited knowledge of species ranges and relationships. Topologies generated from variable molecular markers are used to discuss biogeographical patterns in Herbertus and to compare them with the geological history of continents and outcomes reported for other land plants. Location Africa, Asia, Azores, Europe, southern South America, northern South America, North America, New Zealand. Methods Phylogenetic analyses of nuclear ribosomal internal transcribed spacer and chloroplast (cp) trnL–trnF sequences of 66 accessions of Herbertus and the outgroup species Triandrophyllum subtrifidum and Mastigophora diclados were used to investigate biogeographical patterns in Herbertus. Areas of putative endemism were defined based on the distribution of species included in the analyses. Maximum parsimony analyses were undertaken to reconstruct ancestral areas and intraspecies migration routes. Results The analyses reveal species‐level cladograms with a correlation between genetic variation and the geographical distribution of the related accessions. The southern South American Herbertus runcinatus is sister to the remainder of the genus, which is split into two main clades. One contains the Neotropical–African Herbertus juniperoideus and the New Zealand/Tasmanian Herbertus oldfieldianus. An African accession of H. juniperoideus is nested within Neotropical accessions. The second main clade includes species that inhabit Asia, the Holarctic, Africa, and northern South America. Maximum parsimony analyses indicate that this clade arose in Asia. Herbertus sendtneri originated in Asia and subsequently colonized the Holarctic and northern South America. An Asian origin and colonization into Africa is indicated for H. dicranus. Main conclusions The current distribution of Herbertus cannot be explained by Gondwanan vicariance. A more feasible explanation of the range is a combination of short‐distance dispersal, rare long‐distance dispersal events (especially into regions that faced floral displacements as a result of climatic changes) extinction, recolonization, and diversification. The African Herbertus flora is a mixture of Asian and Neotropical elements. Southern South America harbours an isolated species. The molecular data indicate partial decoupling of molecular and morphological variation in Herbertus. Biogeographical patterns in Herbertus are not dissimilar to those of other groups of bryophytes, but elucidation of the geographical ranges requires a molecular approach. Some patterns could be the result of maintenance of Herbertus in the inner Tropics during glacial maxima, and dispersal into temperate regions in warm phases.     

Geographical,Temporal and Environmental Determinants of Bryophyte Species Richness in the Macaronesian Islands

Species richness on oceanic islands has been related to a series of ecological factors including island size and isolation (i.e. the Equilibrium Model of Island Biogeography, EMIB), habitat diversity, climate (i.e., temperature and precipitation) and more recently island ontogeny (i.e. the General Dynamic Model of oceanic island biogeography, GDM). Here we evaluate the relationship of these factors with the diversity of bryophytes in the Macaronesian region (Azores, Madeira, Canary Islands and Cape Verde). The predictive power of EMIB, habitat diversity, climate and the GDM on total bryophyte richness, as well as moss and liverwort richness (the two dominant bryophyte groups), was evaluated through ordinary least squares regressions. After choosing the best subset of variables using inference statistics, we used partial regression analyses to identify the independent and shared effects of each model. The variables included within each model were similar for mosses and liverworts, with orographic mist layer being one of the most important predictors of richness. Models combining climate with either the GDM or habitat diversity explained most of richness variation (up to 91%). There was a high portion of shared variance between all pairwise combinations of factors in mosses, while in liverworts around half of the variability in species richness was accounted for exclusively by climate. Our results suggest that the effects of climate and habitat are strong and prevalent in this region, while geographical factors have limited influence on Macaronesian bryophyte diversity. Although climate is of great importance for liverwort richness, in mosses its effect is similar to or, at least, indiscernible from the effect of habitat diversity and, strikingly, the effect of island ontogeny. These results indicate that for highly vagile taxa on oceanic islands, the dispersal process may be less important for successful colonization than the availability of suitable ecological conditions during the establishment phase.