Plastid DNA Regions Research Articles

Phylogeography and population genomics of the critically endangered aquatic plant Caldesia grandis in China

Caldesia grandis, a critically endangered aquatic species, is predominantly found in the mid-low mountainous swamps of subtropical China. This study assessed the genetic diversity and population structure of the species using RAD-seq data, explored its phylogeography across the extant nine populations based on five plastid DNA (ptDNA) regions, and conducted niche modeling analysis. We found low genetic diversity (HE = 0.180, Ho = 0.222, and π = 0.197) and genetic differentiation among populations (Fst = 0.089), which was likely due to genetic drift in small populations and frequent inter-population contact during the Quaternary period. Although RAD-seq analysis did not reveal a clear population structure, two distinct clades, comprising western and eastern populations, were identified using five ptDNA haplotypes. Molecular dating and niche modeling suggested that the uplift of the Luoxiao Mts may have contributed to the divergence of the eastern and western clades (ca. 1.51 Ma)during the Pleistocene, which also supports the hypothesis that the Nanling Mts acted as a refugium for C. grandis. Additionally, the repeated glacial periods of the Quaternary, accompanied by contraction and expansion of suitable habitats, likely facilitated gene exchange among populations, influencing the current distribution pattern in subtropical China. Our results suggested that each ptDNA haplotype should be treated as an independent unit for conservation purposes, and ex-situ efforts should be prioritized to conserve C. grandis in China.

Phylogenetic and phylogeographic evidence for the colonization success of the diplochorous Astydamia latifolia across the Canary Islands.

Astydamia latifolia is the only species of the genus Astydamia, which forms an early-diverging lineage of Apiaceae, subfamily Apioideae. This species is subendemic to the Canary Islands and one of the most representative species of the coastal environments of this archipelago. Astydamia displays diplochory, that is, diaspores with two long-distance dispersal (LDD) syndromes. In particular, A. latifolia has both anemochorous and thalassochorous fruit traits (corky and winged mericarps). Although we expect this species to have a high dispersal capacity, there is no genetic study addressing it. The divergence time of this species from its sister taxon is also unknown. In this study, we aimed (i) to unveil the phylogenetic relationships and divergence times of A. latifolia; (ii) to reconstruct its phylogeographic structure across the Canary Islands; and (iii) to estimate the number of inter-island colonization events. To these ends, we first sequenced the internal transcribed spacer (ITS) region for A. latifolia, reconstructed the phylogenetic relationships of Astydamia and Apiaceae relatives and estimated divergence times. Then, two plastid DNA regions (psaI-aacD and psbK-trnS) were sequenced for 158 individuals (from 36 Canarian population and one NW African population) to reconstruct a haplotype network. The recently developed method Phylogeographic Analysis of Island Colonization Events (PAICE) was used to estimate the number of inter-island colonization events. Results show that A. latifolia is a phylogenetically isolated lineage that diverged from the most closely related genus (Molopospermum) in the Eocene-Miocene. It displays a low plastid DNA diversity (only four haplotypes detected), which is accompanied by a high degree of haplotype sharing between islands and highly linear rarefaction curves of colonization obtained in PAICE. These findings suggest a high colonization ability for this species, most likely related to the availability of two LDD syndromes.

The polyphyletic Caucasus-centred Campanula subg. Scapiflorae (Campanulaceae) revisited with a newly circumscribed C. sect. Tridentatae for its core clade.

Campanula L. is among the genera with the highest number of endemics in the Caucasus ecoregion. A group of attractive alpine and subalpine perennial rosette plants with short single-flowered stems centred in the Caucasus has been treated as Campanulasubg.Scapiflorae or at other ranks, with considerably varying circumscription and classification. Molecular phylogenetic analysis of three plastid DNA regions (trnK/matK, petD, rpl16) of a strongly extended sampling, comprising 23 of the 27 commonly accepted taxa (85%) with 330 accessions built on and guided by the results of our previous study of the group, confirmed the polyphyly of C.subg.Scapiflorae in any of its circumscriptions. The core clade of the group comprises exclusively endemics and near-endemics of the Caucasus and is treated here as C.sect.Tridentatae in a revised circumscription. The phylogenetic relationships of the disparate other elements of the Scapiflorae group are outlined.

Genetic Diversity and Phylogeography of the Relict Tree Fern Culcita macrocarpa: Influence of Clonality and Breeding System on Genetic Variation.

The tree fern Culcita macrocarpa, a threatened Iberian-Macaronesian endemism, represents the sole European species of the order Cyatheales. Considered a Tertiary relict of European Palaeotropical flora, its evolutionary history and genetic diversity, potentially influenced by presumed high clonal propagation, remain largely unknown. This study elucidates the phylogeographic history of C. macrocarpa, assessing the impact of vegetative reproduction on population dynamics and genetic variability. We provide genetic data from eight newly identified nuclear microsatellite loci and one plastid DNA region for 17 populations spanning the species' range, together with species distribution modeling data. Microsatellites reveal pervasive clonality in C. macrocarpa, which has varied among populations. We assess the impact of clonality on genetic diversity and evaluate how estimates of intra-population genetic diversity indices and genetic structuring are affected by the chosen definition of "individual" (focusing exclusively on genetically distinct individuals, genets, as opposed to considering all independent clonal replicates, ramets). We identify two main population groups, one in the northern Iberian Peninsula and the other in the Macaronesian archipelagos and southern Iberian Peninsula. Within each group, we found relict populations (in the Azores and the Cantabrian Cornice) as well as recent originated populations. This population structure suggests colonization dynamics in which recent populations originated from one or a few genets of relict populations and became established through intra-gametophytic self-fertilization and vegetative expansion. DAPC analysis facilitated the identification of alleles that most significantly contributed to the observed population structure. The current Andalusian populations appear to have originated from colonization events from the Azores and the Cantabrian Cornice. Our findings suggest that C. macrocarpa persisted through the Last Glacial Maximum in two refugia: the Azores and the Cantabrian Cornice. Colonization into new areas occurred presumably from these refuges, generating two large population groups with structured genetic diversity. This study underscores the significance of clonality in establishing new populations and shaping genetic structure.

Biphyly of the genus Wendlandia and establishment of a new tribe Clavistigmateae and a new genus Clavistigma of Rubiaceae from Asia

AbstractWendlandia, as currently circumscribed, is a genus of Rubiaceae comprising about 90 species mainly in tropical and subtropical Asia. By sampling species from all four series (Clavigerae, Euexsertae, Montigenae, Subinclusae) and all tribes in the subfamily Dialypetalanthoideae, we examined the monophyly of Wendlandia based on phylogenetic reconstruction using the nuclear ribosomal internal transcribed spacer and four plastid DNA regions. Wendlandia was resolved as biphyletic, consisting of two distantly related lineages that correspond to the monotypic series Clavigerae (Wendlandia pendula), sister to the Chinese endemic genus Trailliaedoxa, and a clade containing the remainder sampled members of Wendlandia. Based on the isolated phylogenetic position of W. pendula and its unique morphological characteristics compared to the recognized tribes of the Vanguerieae alliance, we herein erect a new monotypic genus, Clavistigma, and a new tribe, Clavistigmateae to accommodate the unique species. The secondary pollen presentation and the unique seed morphology were firstly described for the species. The divergence time between Clavistigma and Trailliaedoxa was dated back to 13.8 mya, coinciding with the climate change in northwestern Yunnan driven by the uplift Tibet Plateau and the river incision in the Hengduan Mountains during the Miocene and Late Pliocene.

A revised tribal classification of Papaveraceae (poppy family) based on molecular and morphological data

AbstractPapaveraceae, commonly known as the poppy family, contains many species with horticultural and/or pharmaceutical importance and has been the subject of various molecular studies. However, a widely accepted tribal classification for Papaveraceae remains lacking. In this study, we used a sampling covering all 48 of the currently recognized genera of Papaveraceae. Our study is to employ broad morphological data in combination with sequence data from two nuclear and seven plastid DNA regions to reconstruct phylogenetic relationships within the family. Our analyses indicate that Pteridophylloideae is sister to the clade containing Hypecooideae and Fumarioideae, and these three lineages are in turn sister to Papaveroideae. The alternative topologies constraining Pteridophylloideae as sister to the other poppy species, to Papaveroideae or to Hypecooideae, as recovered in previous studies, are all rejected. Fumarioideae contains nine main clades, and Fumarieae is nested in traditional Corydaleae. Within Papaveroideae, three main clades are recovered and Platystemoneae is embedded within traditional Papavereae. Both topologies constraining traditional Corydaleae or Papavereae as monophyletic are significantly rejected. Within this phylogenetic framework, the evolution of selected characters is inferred and diagnostic morphological characters at different taxonomic levels are identified and discussed. Based on morphological and molecular evidence, a new tribal classification of Papaveraceae is presented, in which 4 subfamilies, 14 tribes (including 7 newly described tribes), and 43 genera are recognized.

Andean uplift, climatic events, and rainforest bridges determined the spatiotemporal evolution of the cumaru and tonka beans (Dipterygeae: Leguminosae)

Abstract Historical climatic and geological events are largely known to have impacted biome evolution across the Neotropics and their associated rich biodiversity. However, a clear understanding of dispersal and biome shifts between neotropical biomes over time is still lacking for many ecologically important plant clades. We investigated the timing and ancestral species movements within the early branching papilionoid legume Dipterygeae lineage of neotropical tree species, some of which are among the most ecologically dominant across Amazonian rainforests and Brazilian savannas, to understand how dispersal and evolutionary trajectories in biome predilection have led to their modern distribution. We also estimated the evolution of fruit types and discuss their potential roles in the colonization of non-Amazonian rainforest habitats. To address these questions, we used one nuclear (ITS/5.8S) and two plastid (matK and trnL intron) DNA regions of the Dipterygeae clade to estimate divergence times with a Bayesian relaxed-clock approach, ancestral area distribution, and evolutionary shifts in biome and morphological traits. All currently recognized species of this clade were sampled, covering its full geographical range. Dipterygeae originated in the Amazonia during the Middle Eocene, where it has undergone a long history of in situ diversification, particularly over the last 15 Myr. Dispersal events into the rainforests of the Brazilian Coastal Atlantic Forest and Chocó + Central America, the fire-prone savannas of the Cerrado, and the Caatinga seasonally dry tropical forest occurred independently. Most lineages ecologically associated with rainforests are dispersed by animals (zoochory), whereas shifts to open habitats generally coincide with wind dispersal (anemochory). Our study highlights the significance of geological events, climatic factors, and shifts in fruit type as crucial contributors to the diversification of Dipterygeae.

Evolutionary history of an Irano-Turanian cushion-forming legume (Onobrychis cornuta).

The Irano-Turanian region is one of the largest floristic regions in the world and harbors a high percentage of endemics, including cushion-like and dwarf-shrubby taxa. Onobrychis cornuta is an important cushion-forming element of the subalpine/alpine flora of the Irano-Turanian floristic region. To specify the genetic diversity among the populations of this species (including individuals of O. elymaitica), we employed nrDNA ITS and two noncoding regions of plastid DNA (rpl32-trnL(UAG) and trnT(UGU)-trnL(UAA)). The most striking feature of O. cornuta assemblages was the unexpectedly high nucleotide diversity in both the nDNA and cpDNA dataset. In the analyses of nuclear and plastid regions, 25 ribotypes and 42 haplotypes were found among 77 and 59 accessions, respectively, from Iran, Turkey, and Afghanistan. Network analysis of the datasets demonstrated geographic differentiation within the species. Phylogenetic analyses of all dataset retrieved O. cornuta as a non-monophyletic species due to the inclusion of O. elymaitica, comprising four distinct lineages. In addition, our analyses showed cytonuclear discordance between both nuclear and plastid topologies regarding the position of some O. cornuta individuals. The underlying causes of this inconsistency remain unclear. However, we speculate that chloroplast capture, incomplete lineage sorting, and introgression were the main reasons for this event. Furthermore, molecular dating analysis indicated that O. cornuta originated in the early Pliocene (around 4.8 Mya) and started to diversify throughout the Pliocene and in particular the Pleistocene. Moreover, O. elymaitica was reduced to a subspecific rank within the species.

A New Species of Brachystele (Spiranthinae, Orchidaceae) with Nonresupinate Flowers from Central East Argentina

Abstract— Brachystele morronei, a new orchid species recently discovered in the central-eastern region of Argentina, is described and illustrated. It is the first known species with nonresupinate flowers of the Pelexia clade, constituting a very distinctive member of the group. The phylogenetic position of the new taxon was inferred from nuclear ribosomal DNA (ITS) and two plastid DNA regions (matK and trnLF). The combined nuclear and plastid data analyses using Bayesian and parsimony-based methods revealed that B. morronei is closely related to B. camporum. The geographic distribution and a conservation assessment of the new species are presented. Morphological differences among sympatric Brachystele species are described.

Ixeridiumsagittarioides (Asteraceae-Cichorieae) revisited: range extension and molecular evidence for its systematic position in the Lactuca alliance.

Our first record of the rare and scatteredly distributed Ixeridiumsagittarioides for Guizhou, China, triggered a study to assess its systematic position. The species was placed in four different genera in the course of its taxonomic history and was recently treated with doubts as a member of Ixeridium in the Flora of China. Comparative morphological investigation and phylogenetic analyses based on the nuclear ribosomal DNA internal transcribed spacer (nrITS) and five non-coding plastid DNA regions (petD region, psbA-trnH, trnL-trnF, rpl32-trnL (UAG) and 5´rps16-trnQ (UUG) spacers) provided evidence that the species is not a member of Ixeridium and the Crepidinae but has evolved by ancient hybridisation of members of the Lactuca alliance (Lactucinae). It is reinstated as Lactucasagittarioides and a comprehensive morphological description is provided, based on material from its entire range of distribution.

Phylogenetic, cytogenetic and morphological evidences are critical for recognizing a new genus: Valdesiana, an Iberian intergeneric allopolyploid between Schenkia and Exaculum

The present taxonomic status of Schenkia elegans, endemism recently described in the Iberian Peninsula, and its relationship with the sympatric and the nearest morphological species Schenkia spicata and Exaculum pusillum is revaluated. Different kinds of evidence based on plant morphology, ploidy estimation by flow cytometry, karyotype characterisation, and phylogenetic data have been analysed. Two maternally inherited plastid DNA regions (trnL intron and trnL-F spacer) and biparentally inherited nuclear ribosomal DNA sequence region (nrDNA ITS) have been used. Comparative multivariate analyses show an intermediate morphology of the S. elegans plants between the other two species studied. Flow cytometry and karyotype analyses in S. elegans point to an allopolyploid origin, with the latter constituted by a mixture of those of the diploids S. spicata and E. pusillum. Phylogenetic analyses based on plastid and nuclear DNA regions cluster S. elegans in two different clades, those of S. spicata and E. pusillum, suggesting a possible hybrid origin of S. elegans between both species, acting as maternal or paternal progenitors. In consequence, taking in consideration the taxonomic relationships among genera (Exaculum, Schenkia and the closely related genus Zeltnera found in America), a monotypic genus Valdesiana gen. nov. is proposed to accommodate the allopolyploid species, combined as V. elegans, for which immediate conservation measures must be evaluated.

Molecular phylogenetic and morphological support for the recognition of Friesodielsia lalisae (Annonaceae), a new species from S Thailand

Thirteen species of Friesodielsia Steenis (Annonaceae) and 11 representatives of related genera were included in molecular phylogenetic analyses using up to six plastid DNA regions (psbA-trnH, trnL-trnF intergenic spacers; trnL intron; matK, ndhF, rbcL exons). The results support the recognition of a new species, F. lalisae Damth., Baka & Chaowasku from Narathiwat, S Thailand, as belonging to one of the two major clades of Friesodielsia. The members of this clade show outer petals that separate at anthesis and have a concave basal portion, while members in the other major clade exhibit outer petals that separate early during developmental stages and have a flat base. Friesodielsia lalisae is described and illustrated. It is most morphologically similar to F. argentea (J. Sinclair) Steenis and F. glauca (Hook. f. & Thomson) Steenis but differs from the two by having dissimilar sepal shape, higher proportion of inner petal to outer petal length and longer inner petals. The new species additionally differs from the former by having different leaf base and from the latter by having denser indumentum on young twigs and shorter flowering pedicels. Narathiwat, a province to which the new species is endemic, seems to be one of the most underexplored areas in Thailand as evidenced by a number of species described based on recent material. The conservation status of the new species is provisionally assessed as Critically Endangered. Citation: Damthongdee A., Khunarak N., Kaeokula S., Saengpho C., Wiya C., Ue-aree P., Baka A., Aongyong K. & Chaowasku T. 2023: Molecular phylogenetic and morphological support for the recognition of Friesodielsia lalisae (Annonaceae) a new species from S Thailand. – Willdenowia 53: 45–55. Version of record first published online on 10 April 2023 ahead of inclusion in April 2023 issue.

Carexquixotiana (Cyperaceae), a new Iberian endemic from Don Quixote's land (La Mancha, S Spain).

Despite centuries of work, the basic taxonomic knowledge of the flora of the Iberian Peninsula is still incomplete, especially for highly diverse and/or difficult genera such as Carex. In this study, we conducted an integrative systematic study based on molecular, morphological and cytogenetic data to elucidate the taxonomic status of several problematic Carex populations from La Mancha region (S Spain) belonging to Carexsect.Phacocystis. These populations have been traditionally considered of uncertain taxonomic adscription, but close to C.reuteriana due to their morphological appearance and ecological preferences. A detailed morphological and cytogenetic study was performed on 16 La Mancha's problematic populations (Sierra Madrona and Montes de Toledo) to compare them with the other Iberian sect. Phacocystis species. In addition, a phylogenetic analysis was conducted using two nuclear (ITS, ETS) and two plastid (rpl32-trnLUAG, ycf6-psbM) DNA regions, including representatives from all species of sect. Phacocystis. We found a significant degree of molecular and morphological differentiation that supports the recognition of La Mancha's problematic populations as a new Iberian endemic species, described here as Carexquixotiana Ben.Benítez, Martín-Bravo, Luceño & Jim.Mejías. Our results reveal that C.quixotiana, unexpectedly, is more closely related to C.nigra than to C.reuteriana on the basis of phylogenetic relationships and chromosome number. These contrasting patterns reflect the taxonomic complexity in sect. Phacocystis and highlight the need for integrative systematic approaches to disentangle such complicated evolutionary scenarios.

Paraphlomisyingdeensis (Lamiaceae), a new species from Guangdong (China).

Paraphlomisyingdeensis (Lamiaceae), a new species from the limestone area in northern Guangdong Province, China, is described and illustrated. Phylogenetic analyses, based on two nuclear DNA regions (ITS and ETS) and three plastid DNA regions (rpl32-trnL, rps16 and trnL-trnF), suggest that P.yingdeensis represents a distinct species in Paraphlomis. Morphologically, P.yingdeensis is similar to P.foliatasubsp.montigena and P.nana, but can be distinguished from the former by its densely villous lamina and calyx, not decurrent base of lamina and bristle-like-acuminate apex of calyx teeth, and distinguished from the latter by its significantly taller plant (15-20 cm vs. 1-5 cm) and larger lamina (6.2-16.5 × 4-11.5 vs. 2-7 × 1.5-4 cm), densely villous stem, lamina and calyx and yellow corolla.

A phylogenomic study of Iridaceae Juss. based on complete plastid genome sequences.

The plastid genome has proven to be an effective tool for examining deep correlations in plant phylogenetics, owing to its highly conserved structure, uniparental inheritance, and limited variation in evolutionary rates. Iridaceae, comprising more than 2,000 species, includes numerous economically significant taxa that are frequently utilized in food industries and medicines and for ornamental and horticulture purposes. Molecular studies on chloroplast DNA have confirmed the position of this family in the order Asparagales with non-asparagoids. The current subfamilial classification of Iridaceae recognizes seven subfamilies-Isophysioideae, Nivenioideae, Iridoideae, Crocoideae, Geosiridaceae, Aristeoideae, and Patersonioideae-which are supported by limited plastid DNA regions. To date, no comparative phylogenomic studies have been conducted on the family Iridaceae. We assembled and annotated (de novo) the plastid genomes of 24 taxa together with seven published species representing all the seven subfamilies of Iridaceae and performed comparative genomics using the Illumina MiSeq platform. The plastomes of the autotrophic Iridaceae represent 79 protein-coding, 30 tRNA, and four rRNA genes, with lengths ranging from 150,062 to 164,622 bp. The phylogenetic analysis of the plastome sequences based on maximum parsimony, maximum likelihood, and Bayesian inference analyses suggested that Watsonia and Gladiolus were closely related, supported by strong support values, which differed considerably from recent phylogenetic studies. In addition, we identified genomic events, such as sequence inversions, deletions, mutations, and pseudogenization, in some species. Furthermore, the largest nucleotide variability was found in the seven plastome regions, which can be used in future phylogenetic studies. Notably, three subfamilies-Crocoideae, Nivenioideae, and Aristeoideae-shared a common ycf2 gene locus deletion. Our study is a preliminary report of a comparative study of the complete plastid genomes of 7/7 subfamilies and 9/10 tribes, elucidating the structural characteristics and shedding light on plastome evolution and phylogenetic relationships within Iridaceae. Additionally, further research is required to update the relative position of Watsonia within the tribal classification of the subfamily Crocoideae.

Phylogenetics of the Andean tree genusRuagea(Meliaceae): implications for taxonomy

AbstractRuagea (Meliaceae) comprises c. 15 species of small or medium-sized trees distributed in Central and South America, predominantly in montane rain forest and cloud forest of the Andes. The taxonomic position of Ruagea has changed several times in the past, and it was previously included in Guarea. Ruagea is currently accepted as a separate genus based on morphology and molecular phylogenetic analyses at the family level. However, its monophyly has not been accurately tested, and phylogenetic relationships among species are still largely unknown. In addition, delimitation of species boundaries is not straightforward due to morphological diversity within species. Here, we present the first phylogenetic reconstruction of Ruagea based on two nuclear ribosomal (ITS, ETS) and two plastid DNA regions (rps4-trnT, psbA-trnH). Our results show that Ruagea is monophyletic and composed of four main clades (A, B, C and D). Clade D, comprising the Ecuadorian endemic R. membranacea and a potentially new species from Colombia, is sister to the rest of the genus. Our results demonstrate that R. membranacea and R. insignis are monophyletic and provide support for the recognition of two new species with divergent morphologies. The delimitation of the remaining species remains unresolved as they are recovered as either poly- or paraphyletic. Our results highlight the complexity of the taxonomy of Ruagea, as found in other rainforest taxa, and the need for further detailed analyses to delimit these taxa. This study provides the first and most extensive phylogenetic analysis of the genus so far, representing a contribution towards understanding the evolutionary history of Ruagea.

ROWANS, WHITEBEAMS AND SERVICE TREES

ROWANS, WHITEBEAMS AND SERVICE TREES

Carex camposii subsp. tejedensis (Cyperaceae), a new taxon for Southern Iberian Peninsula based on molecular, morphological and ecological differentiation.

Carex camposii Boiss. & Reut., endemic to high mountain ranges in Southern Iberian Peninsula (Sierra Nevada, Sierra de los Filabres and Sierra de Baza), is a morphologically and molecularly well-defined species included in Carex gr. laevigata (subg. Carex, sect. Spirostachyae). We have discovered a population of a morphologically similar species to C. camposii in a different mountain range (Sierra de Tejeda), that displayed some deviant morphological characters and was found in a different habitat from that typical of the species. In order to disentangle the taxonomic status of this population, we have conducted a phylogenetic analysis using five nuclear (ITS, ETS, G3PDH, CATP and GZF) and three plastid (matK, rpS16 and 5’trnK intron) DNA regions. In addition, a morphological analysis including the population from Sierra de Tejeda was carried out. The resulting phylogenetic trees show that the samples of the problematic population are closely related to C. camposii, while the morphological study revealed that a total of nine morphological features did not match those of typical C. camposii. Even though the samples from Sierra de Tejeda are genetically not well differentiated from C. camposii, the morphological and ecological differentiation supports its recognition as a new subspecies, C. camposii subsp. tejedensis. An assessment of its conservation status using IUCN categories and criteria suggests that it could be critically endangered (CR).

New molecular evidence for Canarian endemicRuta(Rutaceae: Ruteae) reveals a complex evolutionary history and overlooked diversification processes

AbstractWe studied four currently recognized endemics of Ruta (Rutaceae) from the Canary Islands, an oceanic biodiversity hotspot, to identify genetic variation, reconstruct evolutionary relationships and clarify the taxonomic delimitation of several recently discovered populations. We analysed four plastid DNA regions for a thorough population sampling of Ruta oreojasme on Gran Canaria, R. pinnata on Tenerife and La Palma and R. microcarpa and the only known population of the recently described R. nanocarpa on La Gomera. Bayesian clock dating analysis, haplotype network and ancestral area reconstructions were carried out. Our results reveal a complex, extremely dynamic and largely overlooked pattern of colonization and evolutionary history of Ruta in the archipelago. Thirty haplotypes were found, but only one of them was shared across more than one island. Species divergence and all colonization events in the Canary Islands were dated from the late Pliocene to the Pleistocene, and R. oreojasme has an earlier origin than its Canarian congeners. Multiple secondary colonization events between and within islands account for the diversification of R. pinnata and R. microcarpa. Our data cannot discard a possible independent origin of R. oreojasme and do not support the currently accepted circumscription of R. pinnata and R. microcarpa. Rather, the high levels of genetic differentiation detected suggest the existence of ongoing diversification processes and of new taxa. Urgent population-level conservation efforts should be undertaken, especially focused on the single population on La Gomera that can be attributed to R. microcarpa, R. nanocarpa and genetically distinct populations from La Palma and the palaeo-islands of Tenerife.

A western representative of an eastern clade: Phylogeographic history of the gypsum-associated plant Nepeta hispanica

The preference of certain plant species for gypsum soils with a patchy distribution leads to disjunct population structures that are thought to generate island-like dynamics potentially influencing biogeographic patterns at multiple evolutionary scales. Here, we study the evolutionary and biogeographic history of Nepeta hispanica, a western Mediterranean plant associated with gypsum soils and displaying a patchy distribution with populations very distant from each other. Three approaches were used: (a) interspecific phylogenetic analyses based on nuclear DNA sequences of the ITS region to unveil the relationships and times of divergence between N. hispanica and its closest relatives; (b) phylogeographic analyses using plastid DNA regions trnS-trnG and psbJ-petA to evaluate the degree of genetic isolation between populations of N. hispanica, their relationships and their genetic diversity; and (c) ecological niche modelling to evaluate historical distributional changes. Results reveal that N. hispanica belongs to an eastern Mediterranean and Asian (Irano-Turanian) clade diversified in arid environments since the Miocene-Pliocene. This species represents the only lineage of this clade that colonised the western Mediterranean, probably through the northern Mediterranean coast (southern Europe). Present Iberian populations display a high plastid genetic diversity and, even if geographically distant from each other, they are highly connected according to the distribution of plastid haplotypes and lineages. This can be explained by a scenario involving a complex history of back-and-forth colonisation events, facilitated by a relative stability of suitable conditions for the species across the western Mediterranean throughout the Quaternary.