A phylogenetic study of Echidnopsis Hook. f. (Apocynaceae-Asclepiadoideae) - taxonomic implications and the colonization of the Socotran archipelago

We investigated the phylogeny, taxonomy and biogeography of the Eritreo-Arabian genus Echidnopsis Hook. f. (Apocynaceae-Asclepiadoideae). Phylogenetic reconstructions based on nrITS sequence data were obtained using maximum likelihood and parsimony analyses. The results reveal two weakly supported clades, each with a mix of African and Arabian taxa, including the genus Rhytidocaulon, and with four Socotran species forming a subclade of their own. Rather than a vicariance origin of these island elements, our data suggest a single dispersal event from eastern Africa. Echidnopsis thus parallels biogeographic patterns found for other Socotran endemic plants. Our revised taxonomy recognizes 28 species and 4 subspecies in the genus. Two new combinations, E. planiflora subsp. chrysantha and E. sharpei subsp. bavazzani are propose

The evolution of the Aristolochia pallida complex (Aristolochiaceae) challenges traditional taxonomy and reflects large-scale glacial refugia in the Mediterranean

The taxonomy of the Mediterranean Aristolochia pallida complex has been under debate since several decades with the following species currently recognized: A. pallida, A. lutea, A. nardiana, A. microstoma, A. merxmuelleri, A. croatica, and A. castellana. These taxa are distributed from Iberia to Turkey. To reconstruct phylogenetic and biogeographic patterns, we employed cpDNA sequence variation using both noncoding (intron and spacer) and protein-coding regions (i.e., trnK intron, matK gene, and trnK-psbA spacer). Our results show that the morphology-based traditional taxonomy was not corroborated by our phylogenetic analyses. Aristolochia pallida, A. lutea, A. nardiana, and A. microstoma were not monophyletic. Instead, strong geographic signals were detected. Two major clades, one exclusively occurring in Greece and a second one of pan-Mediterranean distribution, were found. Several subclades distributed in Greece, NW Turkey, Italy, as well as amphi-Adriatic subclades, and a subgroup of southern France and Spain, were revealed. The distribution areas of these groups are in close vicinity to hypothesized glacial refugia areas in the Mediterranean. According to molecular clock analyses the diversification of this complex started around 3–3.3 my, before the onset of glaciation cycles, and the further evolution of and within major lineages falls into the Pleistocene. Based on these data, we conclude that the Aristolochia pallida alliance survived in different Mediterranean refugia rarely with low, but often with a high potential for range extension, and a high degree of morphological diversity.Turkish Science Foundatio

Historical Isolation versus Recent Long-Distance Connections between Europe and Africa in Bifid Toadflaxes (Linaria sect. Versicolores)

Background: Due to its complex, dynamic and well-known paleogeography, the Mediterranean region provides an ideal framework to study the colonization history of plant lineages. The genus Linaria has its diversity centre in the Mediterranean region, both in Europe and Africa. The last land connection between both continental plates occurred during the Messinian Salinity Crisis, in the late Miocene (5.96 to 5.33 Ma). Methodology/Principal Findings: We analyzed the colonization history of Linaria sect. Versicolores (bifid toadflaxes), which includes c. 22 species distributed across the Mediterranean, including Europe and Africa. Two cpDNA regions (rpl32-trnL UAG and trnK-matK) were sequenced from 66 samples of Linaria. We conducted phylogenetic, dating, biogeographic and phylogeographic analyses to reconstruct colonization patterns in space and time. Four major clades were found: two of them exclusively contain Iberian samples, while the other two include northern African samples together with some European samples. The bifid toadflaxes have been split in African and European clades since the late Miocene, and most lineage and speciation differentiation occurred during the Pliocene and Quaternary. We have strongly inferred four events of post-Messinian colonization following long-distance dispersal from northern Africa to the Iberian Peninsula, Sicily and Greece. Conclusions/Significance: The current distribution of Linaria sect. Versicolores lineages is explained by both ancien

A taxonomic backbone for the global synthesis of species diversity in the angiosperm order Caryophyllales

The Caryophyllales constitute a major lineage of flowering plants with approximately 12500 species in 39 families. A taxonomic backbone at the genus level is provided that reflects the current state of knowledge and accepts 749 genera for the order. A detailed review of the literature of the past two decades shows that enormous progress has been made in understanding overall phylogenetic relationships in Caryophyllales. The process of re-circumscribing families in order to be monophyletic appears to be largely complete and has led to the recognition of eight new families (Anacampserotaceae, Kewaceae, Limeaceae, Lophiocarpaceae, Macarthuriaceae, Microteaceae, Montiaceae and Talinaceae), while the phylogenetic evaluation of generic concepts is still well underway. As a result of this, the number of genera has increased by more than ten percent in comparison to the last complete treatments in the Families and genera of vascular plants” series. A checklist with all currently accepted genus names in Caryophyllales, as well as nomenclatural references, type names and synonymy is presented. Notes indicate how extensively the respective genera have been studied in a phylogenetic context. The most diverse families at the generic level are Cactaceae and Aizoaceae, but 28 families comprise only one to six genera. This synopsis represents a first step towards the aim of creating a global synthesis of the species diversity in the angiosperm order Caryophyllales integrating the work of numerous specialists around the world

A phylogenetic study of Echidnopsis Hook. f. (Apocynaceae-Asclepiadoideae) - taxonomic implications and the colonization of the Socotran archipelago

We investigated the phylogeny, taxonomy and biogeography of the Eritreo-Arabian genus Echidnopsis Hook. f. (Apocynaceae-Asclepiadoideae). Phylogenetic reconstructions based on nrITS sequence data were obtained using maximum likelihood and parsimony analyses. The results reveal two weakly supported clades, each with a mix of African and Arabian taxa, including the genus Rhytidocaulon, and with four Socotran species forming a subclade of their own. Rather than a vicariance origin of these island elements, our data suggest a single dispersal event from eastern Africa. Echidnopsis thus parallels biogeographic patterns found for other Socotran endemic plants. Our revised taxonomy recognizes 28 species and 4 subspecies in the genus. Two new combinations, E. planiflora subsp. chrysantha and E. sharpei subsp. bavazzani are propose

Old-new world and trans-African disjunctions of Thamnosma (Rutaceae): Intercontinental long-distance dispersal and local differentiation in the succulent biome

Premise of the study: The succulent biome is highly fragmented throughout the Old and New World. The resulting disjunctions on global and regional scales have been explained by various hypotheses. To evaluate these, we used Thamnosma, which is restricted to the succulent biome and has trans-Atlantic and trans-African disjunctions. Its three main distribution centers are in southern North America, southern and eastern Africa including Socotra. Methods: We conducted parsimony, maximum likelihood, and Bayesian phylogenetic analyses based on chloroplast and nuclear sequence data. We applied molecular clock calculations using the programs BEAST and MULTIDIVTIME and biogeographic reconstructions using S-DIVA and Lagrange. Key results: Our data indicate a weakly supported paraphyly of the New World species with respect to a palaeotropical lineage, which is further subdivided into a southern African and a Horn of Africa group. The disjunctions in Thamnosma are mostly dated to the Miocene. Conclusions: We conclude that the Old–New World disjunction of Thamnosma is likely the result of long-distance dispersal. The Miocene closure of the arid corridor between southern and eastern Africa may have caused the split within the Old World lineage, thus making a vicariance explanation feasible. The colonization of Socotra is also due to long-distance dispersal. All recent Thamnosma species are part of the succulent biome, and the North American species may have been members of the arid Neogene Madro-Tertiary Geoflora. Phylogenetic niche conservatism, rare long-distance dispersal, and local differentiation account for the diversity among species of Thamnosma

Evidence for a vicariant origin of Macaronesian-Eritreo/Arabian disjunctions in Campylanthus Roth (Plantaginaceae)

The numerous disjunct plant distributions between Macaronesia and eastern Africa-Arabia suggest that these could be the relicts of a once continuous vegetation belt along the southern Tethys, which has been fragmented by Upper Miocene-Pliocene aridification. We tested this vicariance hypothesis with a phylogenetic analysis of Campylanthus (Plantaginaceae), based on nuclear and plastid DNA sequence data. Our results indicate a basal split within Campylanthus giving rise to Macaronesian and Eritreo-Arabian lineages in the Pliocene/Upper Miocene. This is consistent with the vicariance hypothesis, thus obviating the need to postulate trans-Saharan long-distance dispersal. The biogeography of Campylanthus may parallel patterns in other plant groups and the implications for our understanding of the biogeography of northern and eastern Africa, and Arabia are discussed

Molecular phylogenetic analyses identify Alpine differentiation and dysploid chromosome number changes as major forces for the evolution of the European endemic Phyteuma (Campanulaceae)

Phyteuma is a chromosomally and ecologically diverse vascular plant genus and constitutes an excellent system for studying both the role of chromosomal change for species diversification and the evolution of high-mountain biota. This kind of research is, however, hampered by the lack of a sound phylogenetic framework exacerbated by the notoriously low predictive power of traditional taxonomy with respect to phylogenetic relationships in Campanulaceae. Based on a comprehensive taxon sampling and analyses of nuclear and plastid sequence and AFLP fingerprint data, Phyteuma is confirmed as a monophyletic group sister to the monotypic Physoplexis, which is in line with their peculiar flower morphologies. Within Phyteuma two clades, largely corresponding to previously recognized sections, are consistently found. The traditional circumscription of taxonomic series is largely rejected. Whereas distinctness of the currently recognized species is mostly corroborated, some interspecific relationships remain ambiguous due to incongruences between nuclear and plastid data. Major forces for diversification and evolution of Phyteuma are descending dysploidy (i.e., a decrease in chromosome base number) as well as allopatric and ecological differentiation within the Alps, the genus' center of species diversity. (C) 2013 Elsevier Inc. All rights reserved