The role of geography, ecology, and hybridization in the evolutionary history of Canary Island Descurainia.

PREMISE: Oceanic islands offer the opportunity to understand evolutionary processes underlying rapid diversification. Along with geographic isolation and ecological shifts, a growing body of genomic evidence has suggested that hybridization can play an important role in island evolution. Here we use genotyping-by-sequencing (GBS) to understand the roles of hybridization, ecology, and geographic isolation in the radiation of Canary Island Descurainia (Brassicaceae). METHODS: We carried out GBS for multiple individuals of all Canary Island species and two outgroups. Phylogenetic analyses of the GBS data were performed using both supermatrix and gene tree approaches and hybridization events were examined using D-statistics and Approximate Bayesian Computation. Climatic data were analyzed to examine the relationship between ecology and diversification. RESULTS: Analysis of the supermatrix data set resulted in a fully resolved phylogeny. Species networks suggest a hybridization event has occurred for D. gilva, with these results being supported by Approximate Bayesian Computation analysis. Strong phylogenetic signals for temperature and precipitation indicate one major ecological shift within Canary Island Descurainia. CONCLUSIONS: Inter-island dispersal played a significant role in the diversification of Descurainia, with evidence of only one major shift in climate preferences. Despite weak reproductive barriers and the occurrence of hybrids, hybridization appears to have played only a limited role in the diversification of the group with a single instance detected. The results highlight the need to use phylogenetic network approaches that can simultaneously accommodate incomplete lineage sorting and gene flow when studying groups prone to hybridization; patterns that might otherwise be obscured in species trees.

Geographical isolation, habitat shifts and hybridisation in the diversification of the Macaronesian endemic genus Argyranthemum (Asteraceae).

Inferring the processes responsible for the rich endemic diversity of oceanic island floras is important for our understanding of plant evolution and setting practical conservation priorities. This requires an accurate knowledge of phylogenetic relationships, which have often been difficult to resolve due to a lack of genetic variation. We employed genotyping-by-sequencing (GBS) to investigate how geographical isolation, habitat shifts, and hybridisation have contributed to the evolution of diversity observed in Argyranthemum Webb (Asteraceae), the largest genus of flowering plants endemic to the Macaronesian archipelagos. Species relationships were resolved, and biogeographical stochastic mapping identified intra-island speciation as the most frequent biogeographic process underlying diversification, contrary to the prevailing view in Argyranthemum and the Canary Islands. D-statistics revealed significant evidence of hybridisation between lineages co-occurring on the same island, however there was little support for the hypothesis that hybridisation may be responsible for the occurrence of nonmonophyletic multi-island endemic (MIE) species. Geographic isolation, habitat shifts and hybridisation have all contributed to the diversification of Argyranthemum, with intra-island speciation found to be more frequent than previously thought. Morphological convergence is also proposed to explain the occurrence of nonmonophyletic MIE species. This study reveals greater complexity in the evolutionary processes generating Macaronesian endemic diversity.

Independent homoploid hybrid speciation events in the Macaronesian endemic genus Argyranthemum.

Well-characterized examples of homoploid hybrid speciation (HHS) are rare in nature, yet they offer the potential to study a number of evolutionary processes. In this study, we investigate putative homoploid hybrid species in the genus Argyranthemum (Asteraceae), a group of plants endemic to the Macaronesian archipelagos of the North Atlantic Ocean. We specifically address a number of knowledge gaps surrounding the origin(s) of A. sundingii and A. lemsii, which are thought to be derived from the same parental cross. Comparisons of leaf morphology suggest that A. sundingii and A. lemsii are distinct from their parental progenitors and distinguishable from each other based on leaf area. Ecological niche modelling (ENM) demonstrated that the homoploid hybrid species occupy novel habitats that are intermediate relative to the parental species. Nuclear simple sequence repeat markers (SSRs) and single nucleotide polymorphism (SNP) data indicate that the homoploid hybrid species are distinct from the parental taxa, while population-level sampling of chloroplast SSRs and approximate Bayesian computation show that A. sundingii and A. lemsii are independently derived from the same parental cross. As such, Argyranthemum represents an example of independent homoploid hybrid speciation events with evidence of divergence in leaf morphology and adaptation to novel intermediate habitats. On oceanic islands, which are often typified by steep ecological gradients and inhabited by recently derived species with weak reproductive barriers, multiple HHS events from the same parental cross are not only possible but also likely to have played a more important role in oceanic island radiations than we currently think.

Phylogeography of the Macaronesian Lettuce Species Lactuca watsoniana and L. palmensis (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.

How the temperate world was colonised by bindweeds: biogeography of the Convolvuleae (Convolvulaceae).

BACKGROUND: At a global scale, the temperate zone is highly fragmented both between and within hemispheres. This paper aims to investigate how the world's disjunct temperate zones have been colonised by the pan-temperate plant group Convolvuleae, sampling 148 of the c. 225 known species. We specifically determine the number and timing of amphitropical and transoceanic disjunctions, investigate the extent to which disjunctions in Convolvuleae are spatio-temporally congruent with those in other temperate plant groups and determine the impact of long-distance dispersal events on diversification rates. RESULTS: Eight major disjunctions are observed in Convolvuleae: two Northern Hemisphere, two Southern Hemisphere and four amphitropical. Diversity in the Southern Hemisphere is largely the result of a single colonisation of Africa 3.1-6.4 Ma, and subsequent dispersals from Africa to both Australasia and South America. Speciation rates within this monophyletic, largely Southern Hemisphere group (1.38 species Myr(-1)) are found to be over twice those of the tribe as a whole (0.64 species Myr(-1)). Increased speciation rates are also observed in Calystegia (1.65 species Myr(-1)). CONCLUSIONS: The Convolvuleae has colonised every continent of the world with a temperate biome in c. 18 Myr and eight major range disjunctions underlie this broad distribution. In keeping with other temperate lineages exhibiting disjunct distributions, long-distance dispersal is inferred as the main process explaining the patterns observed although for one American-Eurasian disjunction we cannot exclude vicariance. The colonisation of the temperate zones of the three southern continents within the last c. 4 Myr is likely to have stimulated high rates of diversification recovered in this group, with lineage accumulation rates comparable to those reported for adaptive radiations.

Approximate Bayesian Computation Reveals the Crucial Role of Oceanic Islands for the Assembly of Continental Biodiversity.

The perceived low levels of genetic diversity, poor interspecific competitive and defensive ability, and loss of dispersal capacities of insular lineages have driven the view that oceanic islands are evolutionary dead ends. Focusing on the Atlantic bryophyte flora distributed across the archipelagos of the Azores, Madeira, the Canary Islands, Western Europe, and northwestern Africa, we used an integrative approach with species distribution modeling and population genetic analyses based on approximate Bayesian computation to determine whether this view applies to organisms with inherent high dispersal capacities. Genetic diversity was found to be higher in island than in continental populations, contributing to mounting evidence that, contrary to theoretical expectations, island populations are not necessarily genetically depauperate. Patterns of genetic variation among island and continental populations consistently fitted those simulated under a scenario of de novo foundation of continental populations from insular ancestors better than those expected if islands would represent a sink or a refugium of continental biodiversity. We, suggest that the northeastern Atlantic archipelagos have played a key role as a stepping stone for transoceanic migrants. Our results challenge the traditional notion that oceanic islands are the end of the colonization road and illustrate the significant role of oceanic islands as reservoirs of novel biodiversity for the assembly of continental floras.

Cardamine hirsuta: a versatile genetic system for comparative studies.

A major goal in biology is to identify the genetic basis for phenotypic diversity. This goal underpins research in areas as diverse as evolutionary biology, plant breeding and human genetics. A limitation for this research is no longer the availability of sequence information but the development of functional genetic tools to understand the link between changes in sequence and phenotype. Here we describe Cardamine hirsuta, a close relative of the reference plant Arabidopsis thaliana, as an experimental system in which genetic and transgenic approaches can be deployed effectively for comparative studies. We present high-resolution genetic and cytogenetic maps for C. hirsuta and show that the genome structure of C. hirsuta closely resembles the eight chromosomes of the ancestral crucifer karyotype and provides a good reference point for comparative genome studies across the Brassicaceae. We compared morphological and physiological traits between C. hirsuta and A. thaliana and analysed natural variation in stamen number in which lateral stamen loss is a species characteristic of C. hirsuta. We constructed a set of recombinant inbred lines and detected eight quantitative trait loci that can explain stamen number variation in this population. We found clear phylogeographic structure to the genetic variation in C. hirsuta, thus providing a context within which to address questions about evolutionary changes that link genotype with phenotype and the environment.

Are there any widespread endemic flowering plant species in Macaronesia? Phylogeography of Ranunculus cortusifolius.

PREMISE OF THE STUDY: Oceanic island endemics typically exhibit very restricted distributions. In Macaronesia, only one endemic angiosperm species, Ranunculus cortusifolius, has a distribution spanning the archipelagos of the Azores, Madeira, and Canaries. Earlier work suggested possible differences between archipelagos and the multiple origins of the species. This paper tests the hypothesis that R. cortusifolius is a single widespread Macaronesian endemic species with a single origin. METHODS: Chloroplast (matK-trnK, psbJ-petA) and ITS sequences were generated from across the distribution of R. cortusifolius. Relationships were investigated using Bayesian inference and divergence times estimated using BEAST. Infraspecific variation was investigated using statistical parsimony. The general mixed Yule-coalescent model (GMYC) was further used to identify putative species boundaries based on maternally inherited plastid data. KEY RESULTS: The hypothesis of multiple independent origins of R. cortusifolius is rejected. Divergence of the R. cortusifolius lineage from a western Mediterranean sister group in the late Miocene is inferred. Distinct genotypes were resolved within R. cortusifolius that are endemic to the Azores, Madeira, and the Canaries. Four to five putative species were delimited by different versions of the GMYC model. CONCLUSION: Ranunculus cortusifolius is the result of a single colonization of Macaronesia. The large distances between archipelagos have been effective barriers to dispersal, promoting allopatric diversification at the molecular level with diversification also evident within the Canaries. Isolation has not been accompanied by marked morphological diversification, which may be explained by the typical association of R. cortusifolius with stable and climatically buffered laurel forest communities.

The anagenetic world of spore-producing land plants.

A fundamental challenge to our understanding of biodiversity is to explain why some groups of species diversify, whereas others do not. On islands, the gradual evolution of a new species from a founder event has been called 'anagenetic speciation'. This process does not lead to rapid and extensive speciation within lineages and has received little attention. Based on a survey of the endemic bryophyte, pteridophyte and spermatophyte floras of nine oceanic archipelagos, we show that anagenesis, as measured by the proportion of genera with single endemic species within a genus, is much higher in bryophytes (73%) and pteridophytes (65%) than in spermatophytes (55%). Anagenesis contributed 49% of bryophyte and 40% of endemic pteridophyte species, but only 17% of spermatophytes. The vast majority of endemic bryophytes and pteridophytes are restricted to subtropical evergreen laurel forests and failed to diversify in more open environments, in contrast with the pattern exhibited by spermatophytes. We propose that the dominance of anagenesis in island bryophytes and pteridophytes is a result of a mixture of intrinsic factors, notably their strong preference for (sub)tropical forest environments, and extrinsic factors, including the long-term macro-ecological stability of these habitats and the associated strong phylogenetic niche conservatism of their floras.

Allopatric diversification, multiple habitat shifts, and hybridization in the evolution of Pericallis (Asteraceae), a Macaronesian endemic genus.

PREMISE OF THE STUDY: Geographic isolation, habitat shifts, and hybridization have contributed to the diversification of oceanic island floras. We investigated the contribution of these processes to the diversification of Pericallis, a genus endemic to Macaronesia. METHODS: Data from the chloroplast psaI-accD and trnV-ndhC regions and the nuclear ribosomal internal transcribed spacer region (ITS) were sampled for multiple accessions of all taxa and used to establish phylogenetic hypotheses. Habitat preferences were optimized to investigate habitat shifts, and divergence times were estimated. Species nonmonophyly was investigated using Bayes factors. KEY RESULTS: Much of the diversification in Pericallis has occurred recently, within the past 1.7 Ma. Three habitat shifts have occurred in the evolution of the genus. However, geographic isolation has played a greater role in its diversification. Novel allopatric patterns were revealed within some species, highlighting the significance of geographic isolation in the evolution of Pericallis. One species (P. appendiculata) that resolved as monophyletic in the ITS analysis was polyphyletic in the chloroplast analysis. Bayes factors provide strong support for the nonmonophyly of P. appendiculata haplotypes, and their phylogenetic placement suggests that ancient hybridization is responsible for the haplotype diversity observed. CONCLUSIONS: Multiple markers and extensive sampling provided new insights into the evolution of Pericallis. In contrast to previous studies, our results reveal a more significant role for allopatry than habitat shifts and new evidence for ancient hybridization in the evolution of Pericallis. Our study highlights the power of broad taxon sampling for unraveling diversity patterns and processes within oceanic island radiations.

Speciation via floral heterochrony and presumed mycorrhizal host switching of endemic butterfly orchids on the Azorean archipelago.

• Premise of the study: Most orchid species native to the Macaronesian islands reflect immigration from western Europe or North Africa followed by anagenesis. The only putative exception is the butterfly orchids (Platanthera) of the Azores, where three species apparently reflect at least one cladogenetic speciation event. This multidisciplinary study explores the origin, speciation, phenotypic, and genotypic cohesion of these Azorean species and their mainland relatives.• Methods: Plants of Platanthera from 30 localities spanning all nine Azorean islands were compared with those of four continental European relatives for 38 morphometric characters; substantial subsets were also analyzed for plastid microsatellites, and for nrITS of both the orchids and their mycorrhizae.• Key results: Although the three Azorean and four mainland species are all readily distinguished morphometrically using several floral characters, and hybridization appears rare, divergence in ITS and especially plastid sequences is small. Despite occupying similar laurisilva habitats, the Azorean species differ radically in the identities and diversity of their mycorrhizal partners; specialism apparently increases rarity.• Conclusions: Although morphological evidence suggests two invasions of the islands from NW Africa and/or SW Europe, ITS data imply only one. As the molecular data are unable to distinguish among the potential mainland ancestors, two scenarios of relationship are explored that imply different ancestors. Both scenarios require both anagenetic and cladogenetic speciation events, involving homoplastic shifts in overall flower size and (often substantial) changes in the relative dimensions of individual floral organs. Limited genotypic divergence among the three species compared with greater phenotypic divergence suggests comparatively recent speciation. Mycorrhizae may be the most critical factor dictating the respective ecological tolerances, and thus the relative frequencies, of these species. The recent IUCN Red-List amalgamation of Azorean Platanthera taxa into a single species urgently requires reappraisal, as P. micrantha is an excellent indicator species of seminatural laurisilva forest and P. azorica is arguably Europe's rarest orchid.

Genomics of ecological adaptation in Canary Island Descurainia (Brassicaceae) and comparisons with other Brassicaceae.

Oceanic archipelagos provide striking examples of lineages that have radiated over pronounced ecological gradients. Accompanying this diversification, lineages have evolved adaptations allowing survival in extreme environments. Here, we investigate the genomic basis of ecological adaptation in Canary Island Descurainia (Brassicaceae), an island relative of Arabidopsis. The seven endemic species have diversified in situ along an elevational and ecological gradient, from low-elevation scrub to high-elevation sub-alpine desert. We first generated a reference genome for Descurainia millefolia, phylogenetic analysis of which placed it as sister to D. sophioides. Ninety-six gene families were found to be specific to D. millefolia and a further 1087 and 1469 gene families have expanded or contracted in size, respectively, along the D. millefolia branch. We then employed genome re-sequencing to sample 14 genomes across the seven species of Canary Island Descurainia and an outgroup. Phylogenomic analyses were consistent with previous reconstructions of Canary Island Descurainia in resolving low- and high-elevation clades. Using the branch-site dN/dS method, we detected positive selection for 275 genes on the branch separating the low- and high-elevation species and these positively selected genes (PSGs) were significantly enriched for functions related to reproduction and stress tolerance. Comparing PSGs to those in analyses of adaptation to elevation and/or latitude in other Brassicaceae, we found little evidence of widespread convergence and gene reuse, except for two examples, one of which was a significant overlap between Descurainia and Draba nivalis, a species restricted to high latitudes. The study of Canary Island Descurainia suggests that the transition to high-elevation environments such as that found in the high mountains of the Canary Islands involves selection on genes related to reproduction and stress tolerance but that repeated evolution across different lineages that have evolved into similar habitats is limited, indicating substantially different molecular trajectories to adaptation.

Molecular phylogenetics and morphological evolution of St. John's wort (Hypericum; Hypericaceae).

Phylogenetic hypotheses for the large cosmopolitan genus Hypericum (St. John's wort) have previously been based on morphology, and molecular studies have thus far included only a few species. In this study, we used 360 sequences of the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) for 206 species representing Hypericum (incl. Triadenum and Thornea) and three other genera of Hypericaceae to generate an explicit phylogenetic hypothesis for the genus using parsimony and model-based methods. The results indicate that the small genus Triadenum is nested in a clade within Hypericum containing most of the New World species. Sister to Hypericum is Thornea from Central America. Within Hypericum, three large clades and two smaller grades were found; these are based on their general morphology, especially characters used previously in taxonomy of the genus. Relative to the most recent classification, around 60% of the sections of Hypericum were monophyletic. We used a Bayesian approach to reconstruct ancestral states of selected morphological characters, which resulted in recognition of characters that support major clades within the genus and a revised interpretation of morphological evolution in Hypericum. The shrubby habit represents the plesiomorphic state from which herbs evolved several times. Arborescent species have radiated convergently in high-elevation habitats in tropical Africa and South America.

Herbaria are a major frontier for species discovery.

Despite the importance of species discovery, the processes including collecting, recognizing, and describing new species are poorly understood. Data are presented for flowering plants, measuring quantitatively the lag between the date a specimen of a new species was collected for the first time and when it was subsequently described and published. The data from our sample of new species published between 1970 and 2010 show that only 16% were described within five years of being collected for the first time. The description of the remaining 84% involved much older specimens, with nearly one-quarter of new species descriptions involving specimens >50 y old. Extrapolation of these results suggest that, of the estimated 70,000 species still to be described, more than half already have been collected and are stored in herbaria. Effort, funding, and research focus should, therefore, be directed as much to examining extant herbarium material as collecting new material in the field.

Detection of locally adapted genomic regions in wild rice (Oryza rufipogon) using environmental association analysis.

Oryza rufipogon is the wild progenitor of cultivated rice Oryza sativa and exhibits high levels of genetic diversity across its distribution, making it a useful resource for the identification of abiotic stress-tolerant varieties and genes that could limit future climate-changed-induced yield losses. To investigate local adaptation in O. rufipogon, we analyzed single nucleotide polymorphism (SNP) data from a panel of 286 samples located across a diverse range of climates. Environmental association analysis (EAA), a genome-wide association study (GWAS)-based method, was used and revealed 15 regions of the genome significantly associated with various climate factors. Genes within these environmentally associated regions have putative functions in abiotic stress response, phytohormone signaling, and the control of flowering time. This provides an insight into potential local adaptation in O. rufipogon and reveals possible locally adaptive genes that may provide opportunities for breeding novel rice varieties with climate change-resilient phenotypes.

Comparative transcriptomics and gene expression divergence associated with homoploid hybrid speciation in Argyranthemum.

Ecological isolation is increasingly thought to play an important role in speciation, especially for the origin and reproductive isolation of homoploid hybrid species. However, the extent to which divergent and/or transgressive gene expression changes are involved in speciation is not well studied. In this study, we employ comparative transcriptomics to investigate gene expression changes associated with the origin and evolution of two homoploid hybrid plant species, Argyranthemum sundingii and A. lemsii (Asteraceae). As there is no standard methodology for comparative transcriptomics, we examined five different pipelines for data assembly and analysing gene expression across the four species (two hybrid and two parental). We note biases and problems with all pipelines, and the approach used affected the biological interpretation of the data. Using the approach that we found to be optimal, we identify transcripts showing DE between the parental taxa and between the homoploid hybrid species and their parents; in several cases, putative functions of these DE transcripts have a plausible role in ecological adaptation and could be the cause or consequence of ecological speciation. Although independently derived, the homoploid hybrid species have converged on similar expression phenotypes, likely due to adaptation to similar habitats.

Systematics, biogeography, and character evolution of the legume tribe Fabeae with special focus on the middle-Atlantic island lineages.

BACKGROUND: Tribe Fabeae comprises about 380 legume species, including some of the most ancient and important crops like lentil, pea, and broad bean. Breeding efforts in legume crops rely on a detailed knowledge of closest wild relatives and geographic origin. Relationships within the tribe, however, are incompletely known and previous molecular results conflicted with the traditional morphology-based classification. Here we analyse the systematics, biogeography, and character evolution in the tribe based on plastid and nuclear DNA sequences. RESULTS: Phylogenetic analyses including c. 70% of the species in the tribe show that the genera Vicia and Lathyrus in their current circumscription are not monophyletic: Pisum and Vavilovia are nested in Lathyrus, the genus Lens is nested in Vicia. A small, well-supported clade including Vicia hirsuta, V. sylvatica, and some Mediterranean endemics, is the sister group to all remaining species in the tribe. Fabeae originated in the East Mediterranean region in the Miocene (23-16 million years ago (Ma)) and spread at least 39 times into Eurasia, seven times to the Americas, twice to tropical Africa and four times to Macaronesia. Broad bean (V. faba) and its sister V. paucijuga originated in Asia and might be sister to V. oroboides. Lentil (Lens culinaris ssp. culinaris) is of Mediterranean origin and together with eight very close relatives forms a clade that is nested in the core Vicia, where it evolved c. 14 Ma. The Pisum clade is nested in Lathyrus in a grade with the Mediterranean L. gloeosperma, L. neurolobus, and L. nissolia. The extinct Azorean endemic V. dennesiana belongs in section Cracca and is nested among Mediterranean species. According to our ancestral character state reconstruction results, ancestors of Fabeae had a basic chromosome number of 2n=14, an annual life form, and evenly hairy, dorsiventrally compressed styles. CONCLUSIONS: Fabeae evolved in the Eastern Mediterranean in the middle Miocene and spread from there across Eurasia, into Tropical Africa, and at least seven times to the Americas. The middle-Atlantic islands were colonized four times but apparently did not serve as stepping-stones for Atlantic crossings. Long-distance dispersal events are relatively common in Fabeae (seven per ten million years). Current generic and infrageneric circumscriptions in Fabeae do not reflect monophyletic groups and should be revised. Suggestions for generic level delimitation are offered.

Big hitting collectors make massive and disproportionate contribution to the discovery of plant species.

Discovering biological diversity is a fundamental goal--made urgent by the alarmingly high rate of extinction. We have compiled information from more than 100,000 type specimens to quantify the role of collectors in the discovery of plant diversity. Our results show that more than half of all type specimens were collected by less than 2 per cent of collectors. This highly skewed pattern has persisted through time. We demonstrate that a number of attributes are associated with prolific plant collectors: a long career with increasing productivity and experience in several countries and plant families. These results imply that funding a small number of expert plant collectors in the right geographical locations should be an important element in any effective strategy to find undiscovered plant species and complete the inventory of the world flora.

Bayesian Methods to Analyze Historical Collections in Time and Space: A Case Study Using Cabo Verde Endemic Flora.

Biological collections, including herbarium specimens, are unique sources of biodiversity data presenting a window on the history of the development and accumulation of knowledge of a specific geographical region. Understanding how the process of discovery impacts that knowledge is particularly important for oceanic islands which are often characterized by both high levels of endemic diversity and high proportions of threatened taxa. The archipelagos of the Macaronesian region (i.e. Azores, Canaries, Savages, Madeira, and Cabo Verde) have been the focus of attention for scientific expeditions since the end of the 17th century. However, there is no integrated study describing the historical process of collecting, discovery and description of its flora. Using as a case study the Cabo Verde endemic angiosperm flora, we review the history of collecting in the flora and apply a Bayesian approach to assess the accumulation of species discovery, through time and space across the nine islands of the archipelago. Our results highlight the central role not only of natural characteristics (e.g. area, age, maximum altitude and average value of the terrain ruggedness index) but also historical factors (i.e. the location of major harbors) for the development of knowledge of the flora. The main factors that have determined the process of species description in the archipelago and how this impact our understanding of diversity patterns across archipelagos are discussed.