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[EN] Among the most intriguing mysteries in the evolutionary biology of photosynthetic organisms are the genesis and consequences of the dramatic increase in the mitochondrial and nuclear genome sizes, together with the concomitant evolution of the three genetic compartments, particularly during the transition from water to land. To clarify the evolutionary trends in the mitochondrial genome of Archaeplastida, we analyzed the sequences from 37 complete genomes. Therefore, we utilized mitochondrial, plastidial and nuclear ribosomal DNA molecular markers on 100 species of Streptophyta for each subunit. Hierarchical models of sequence evolution were fitted to test the heterogeneity in the base composition. The best resulting phylogenies were used for reconstructing the ancestral Guanine-Cytosine (GC) content and equilibrium GC frequency (GC*) using non-homogeneous and non-stationary models fitted with a maximum likelihood approach. The mitochondrial genome length was strongly related to repetitive sequences across Archaeplastida evolution; however, the length seemed not to be linked to the other studied variables, as different lineages showed diverse evolutionary patterns. In contrast, Streptophyta exhibited a powerful positive relationship between the GC content, non-coding DNA, and repetitive sequences, while the evolution of Chlorophyta reflected a strong positive linear relationship between the genome length and the number of genes., This research was funded by the European Commission (Environment - LIFE Programme) project for the Comunidad Valenciana (Spain), LIFE05 NAT/E/000060.

The genus Androcymbium (Colchicaceae) includes 57 species that are distributed in the extreme northern and southern portions of Africa, mainly in regions with a Mediterranean climate. We present the first phylogeographic analysis of the genus with species from all five of its distribution areas (North Africa, Horn of Africa, Namibia, western South Africa, and eastern South Africa). We used sequence data from six chloroplast regions and one nuclear region. Phylogeographic reconstructions were conducted using both parsimony and Bayesian inference methods. Molecular dating estimates using a Bayesian approach suggest a middle Miocene (13.4 ± 1.5 mya) origin of the genus; this approach also provides support for a late Miocene (9.6 ± 1.7 mya) diversification in the winter-rainfall area of western South Africa–south of Namibia and strongly influenced by the Benguela current. Three northward dispersion events have been reported in Androcymbium. The first dated to the end of the Miocene (7.0 ± 2.0 mya) and gave rise to the genus Colchicum. The second and the third dispersion events took place in the mid Pliocene, rising one from eastern South Africa and originating the only species found in the Horn of Africa (3.0 mya), and the other from Namibia to the Mediterranean basin (4.0 mya). The formation of a late Miocene–Pliocene arid track in the east of Africa is of a great importance to explain these northward dispersions in Androcymbium.

The inclusion of species of Colchicum within Androcymbium in a previous cpDNA phylogeny of the Colchicaceae, questioned the monophyly of Androcymbium, and it was proposed to unite the two genera in Colchicum. Here we expand the previous phylogenetic analyses of Androcymbium by increasing the taxon sampling and adding more data. The analysis include 29 of the 57 species of Androcymbium, more cpDNA (trnL intron, trnL-trnF IGS, trnY-trnD IGS, and trnH-psbA IGS), and nDNA (RNApol2 intron 23) regions, and morphological and life-history traits data. Both parsimony and Bayesian inference were used. According to our data there is no reason to expand Colchicum to include Androcymbium, but we support the inclusion of Bulbocodium and Merendera within Colchicum. Morphology and life history traits are the main arguments in favor of recognizing Androcymbium as a well-circumscribed genus. In the phylogeny two Androcymbium groups are clearly differentiated: (1) one including species from Western and Eastern South Africa, Namibia, and North Africa, and (2) one including species from the north west of South Africa and south of Namibia.

With the objective of clarifying some aspects of the biogeography, phylogeny, and taxonomy of the genus Androcymbium, we sequenced three chloroplastic DNA noncoding regions (trnL intron, trnL-trnF IGS, and trnY-trnD IGS). These data were analyzed with maximum parsimony and the ancestral areas methods following Bremer. Results show that Androcymbium is not monophyletic and that the origin of its distribution and speciation is situated in western South Africa. Later, it dispersed to North Africa, going first to eastern South Africa. Androcymbium austrocapense and A. roseum allow us to phylogenetically connect the species of western with eastern South Africa, and the southern species with the northern, respectively. The formation of an arid track in Africa at the end of the Miocene explains the colonization of Androcymbium in the Mediterranean basin. Androcymbium wyssianum is a key element in understanding colonization of the Canary Islands. The biogeographical pattern of distribution of Androcymbium fits with many other genera with similar disjunct distributions. This indicates the importance of the Miocene arid track in understanding the floristic connections between northern and southern Africa. Because of the close relationships of Bulbocodium, Colchicum, and Merendera, with Androcymbium inferred from the chloroplast data, restructuring the taxonomy and nomenclature of the tribe Colchiceae may be required.

Recent anthropogenic habitat perturbationsrelated to the unsustainable development of thetwo areas of distribution of Androcymbiumgramineum in Almeria (South of Spain) andthe Atlantic coast of Morocco are outweighingthe intrinsic biological survival assets ofthis narrow Ibero-Moroccan endemic. We usedpopulation genetic data on 18 isozyme loci for13 populations to design a comprehensivesampling strategy for ex-situ conservation thatstraddles the results of independenttheoretical developments and the indications ofseveral genetic polymorphism parameters.Regressions based on the probabilities of lossestimate that sampling one population would beinsufficient to represent the variationattributable to the rare alleles found in thepopulations surveyed from Almeria orMorocco and suggest that the relationshipbetween the number of populations sampled ineither area should conform to the proportion0.6:0.4, respectively. The estimate of thenumber of populations that need be targeted torepresent 99% of the genetic variationdetected indicates that it would be necessaryto sample eight populations intensively. Fivepopulations from Almeria and three fromMorocco were selected through the ranked valuesof the average number of alleles per locus andthe expected heterozygosity on the grounds thatthese parameters provide unambiguousindications of polymorphism that, in the caseof heterozygosity, are less likely to beinfluenced by sampling error. Spatialautocorrelation surveys in the largestpopulation known indicate that seeds should becollected at a minimum separation of 15 m toavoid the sampling of close relatives.

International audience; Premise of research. Riparian plants are highly dependent on water sources; consequently, general climatic conditions are less important to these taxa relative to woodland and shrubland species. This leads to interesting research questions regarding riparian plant taxa. Research on phylogeography of Mediterranean riparian tree and shrub species is scarce. In this article, we investigated the plastidial genetic diversity in Celtis australis L. (hackberry) and Nerium oleander L. (oleander) throughout the Mediterranean Basin. Both species are distributed in gullies, rivers, and stream banks under warm temperate climates. Methodology. Eighteen cpSSR loci and three noncoding cpDNA regions (rps16, rpl32-trnL, and trnQ-5′-rps16) were examined to assess the levels and geographic distribution of sequence variation in 41 hackberry and 56 oleander populations. The rpl32-trnL intergenic region was used for molecular dating analysis. Pivotal results. The respective 2762- and 3134-bp noncoding cpDNA regions sequenced in C. australis and N. oleander, as well as the 22 cpSSR analyzed fragments, exhibited the absence of variability in natural populations throughout the Mediterranean Basin. In N. oleander, two regions (rps16, rpl32-trnL) exhibited variability in three positions, and four cpSSR microsatellite motifs were polymorphic. The polymorphisms were geographically structured, and three haplotypes were characterized, two from Saharan populations and one from Mediterranean populations. Phylogeny and molecular dating analyses resulted in a tree with high consistency values of posteriori probability (PP p 1) and bootstrap support (98%) from the ingroup (N. oleander). The relaxed molecular clock model applied to the calibration of the tree estimates that the diversification of these haplotypes occurred in a range of 7.2–1.2 Ma. Conclusions. The absence of plastid variability in both hackberry and oleander is explained by a low mutation rate and/or recent recolonization of the Mediterranean Basin. Low temperatures during the Last Glacial Maximum produced freezing water along riparian corridors, with the consequent drastic contraction or even disappearance of both species in the Mediterranean Basin

Pollen characters in 16 southern African type specimens of Androcymbium Willd. that represent the three sections into which the genus is presently divided (Androcymbium, Dregeocymbium and Erythrostictus), were examined to assess the possibility of sectional characterization based on pollen traits and to explore the relationship between pollen traits and geo­graphic species distribution. Differences in pollen grain size, shape, number of apertures and exine pattern, were observed. Principal Component Analysis, using both qualitative and biometric pollen characters, distinguished four groups of species with four different pollen types. Most of the species have a microreticulate exine pattern with either diaperturate or tria- perturate grains. The remaining species have either a rugulate exine pattern with diaperturate grains, or a rugulate-reticu- late exine pattern with thickened (hypertrophied) muri with diaperturate grains. While section Dregeocymbium can be well delimited by the unique thickened muri. and by a significantly larger grain size, no diagnostic pollen traits were found for sections Androcymbium and Erythrostictus. Similarly, although the six northern African species exhibit a microreticulate exine pattern, the high variability observed for this trait in their southern African counterparts, does not follow a geographic pattern.

We examined patterns of cpDNA RFLP variability using 21 restriction endonucleases in 21 populations of Androcymbium that represent 12 endemic species distributed in the winter rainfall areas of South Africa to explore the diversification of the genus in its area of maximum species diversity. Our results are supportive of a diversification landscape characterized by continued opportunistic short-range invasion, naturalization, and rapid speciation, in which the selective action of the different environments where Androcymbium species occur determined their colonization success and subsequent short-range geographic expansion. The historical presence of fire, the constraint imposed by the low concentration of nutrients throughout southwestern South Africa and the different reproductive capabilities of Androcymbium species have also likely stimulated species' diversification. Our divergence time estimates bolster the view that speciation of South African Androcymbium initiated in the late Eocene, intensified in the Oligocene and proceeded more sporadically during the Miocene. These chronological estimates also substantiate the previous hypothesis that most lineages of Androcymbium in South Africa are much more ancient than their North African relatives, whose diversification began in the late Miocene-early Pliocene.

The cpDNA restriction variation in 39 populations representing a geographical sampling of 18 species ofAndrocymbium in southwestern and northern Africa was examined to assess the historical biogeography of the genus. The cpDNA phylogeny indicates that the disjunction between South and North Africa is best explained by the dispersal of southern African ancestors into North Africa. Divergence time estimates suggest that the geographic range of the genus may have extended considerably north (perhaps to Tanzania and Kenya) prior to the global desiccation of Africa in the Miocene. Further expansion of the genus northward was probably stalled until climatic changes in the late Miocene brought about the gradual replacement of a subtropical woodland savanna with the arid landscape that gave rise to the Sahara. Aridification of the northern quarter of the continent provided the ecological conditions for fostering the expansion of Androcymbium along the Mediterranean fringe (probably east to west) and its introduction into the Canary Islands. Unlike their South African congeners, the northern species have experienced expansions, fragmentations, and local extinctions in response to the severe climatic shifts in this area during the Pliocene-Pleistocene. According to our divergence time estimates, the arid track may have already existed as a continuous area connecting southern and northern Africa in the late Miocene.

Spatial autocorrelation analyses on genetic variability from three isozymic loci was used to explore the presence of possible patterns of genetic structure in four populations representing the South African species Androcymbium bellum, A. guttatum and A. pulchrum. Consistent profiles of short-distance genetic structure are only detected in patchy populations (A. bellum and A. guttatum), regardless of the sharp ecological differences between them. In the absence of microhabitat heterogeneity, our result strongly suggests that the predominant action of assortive mating (in A. bellum) and of vegetative reproduction (in A. guttatum) fostered the creation and enhancement of physical clumps that correspond to genetically related plants. A much lower incidence of both clonal propagation and outcrossing in the two continuous populations of A. pulchrum examined explains why isozymic variability is not spatially structured in this species.

The history, taxonomy, biology and cultivation of the Canary Islands endemics Androcymbium hierrense A. Santos and Androcymbium psammophilum Svent. (Colchicaceae) are discussed, together with hypotheses about their mainland origin; full botanical descriptions and illustrations are provided.

Space-time patterns of genetic structure within a stand of Androcymbium gramineum (Cav.) McBride (Colchicaceae)

Narrow endemism is a poor predictor of genetic potential in the six taxa that conform theAndrocymbium gramineum complex, as shown by the unexpectedly high values of variability associated with ten allozymic loci and 13 biometrical variables. Although both levels are shown not to be correlated, variability is always concentrated within populations. This result, together with environmental, reproductive and historical data strongly suggests differentiation in local isolates, where changes can be quickly assimilated by stochastic processes. A key implication for conservation is that sampling within the largest population will save effort while neglecting only very low frequency alleles.

Completely sequenced plastomes provide a valuable source of information about the duplication, loss, and transfer events of chloroplast genes and phylogenetic data for resolving relationships among major groups of plants. Moreover, they can also be useful for exploiting chloroplast genetic engineering technology. Ericales account for approximately six per cent of eudicot diversity with 11,545 species from which only three complete plastome sequences are currently available. With the aim of increasing the number of ericalean complete plastome sequences, and to open new perspectives in understanding Mediterranean plant adaptations, a genomic study on the basis of the complete chloroplast genome sequencing of Arbutus unedo and an updated phylogenomic analysis of Asteridae was implemented. The chloroplast genome of A. unedo shows extensive rearrangements but a medium size (150,897 nt) in comparison to most of angiosperms. A number of remarkable distinct features characterize the plastome of A. unedo: five-fold dismissing of the SSC region in relation to most angiosperms; complete loss or pseudogenization of a number of essential genes; duplication of the ndhH-D operon and its location within the two IRs; presence of large tandem repeats located near highly re-arranged regions and pseudogenes. All these features outline the primary evolutionary split between Ericaceae and other ericalean families. The newly sequenced plastome of A. unedo with the available asterid sequences allowed the resolution of some uncertainties in previous phylogenies of Asteridae.

Levels of allozymic and morphological diversity amongAndrocymbium gramineum, A. europaeum, andA. psammophilum have been assessed using data on 17 allozyme loci and 18 morphological characters. No apparent pattern of geographic or ecological variation was found. Our results also suggest thatA. gramineum andA. europaeum should be considered members of a single species and that the insular speciesA. psammophilum can no longer be thought of as the result of a founder effect fromA. gramineum. Intrapopulational variability was greater than inter-populational variability at both levels studied, which is of strategic interest for the “ex-situ” conservation of these threatened endemic species.

Hoyo A. del & Pedrola-Monfort J.: Taxonomic clarification in W Mediterranean Androcymbium (Colchicaceae): A. wyssianum sunk in the synonymy of A. gramineum and A. europaeum restored. — Willdenowia 40: 47–53. — Online ISSN 1868-6397. — © 2010 BGBM Berlin-Dahlem. doi:10.3372/wi.40.40103 (available via http://dx.doi.org/) Capsule dehiscence has been used as a diagnostic character for W Mediterranean species of Androcymbium. Depending on the state of capsule maturity, the character, however, can be ambiguous in herbarium material. Based on morphological, phenological and cpDNA characters it is shown that misinterpretation of the capsule as indehiscent in the type material of A. gramineum has led to serious taxonomic confusion. The combined analyses produced evidence that A. gramineum of the population from the type locality at Essaouira, Morocco, is conspecific with A. wyssianum. A. gramineum is therefore the correct name for the species with dehiscent capsules, whereas the populations with indehisce...

We examined phylogenetic relationships among 51 populations representing 18 of the ap- proximately 40 currently recognized species in the genus Androcymbium using 559 parsimony informative cpDNA restriction site changes. Our results indicate that the genus is monophyletic and had a southern African origin. According to our estimates of divergence times, species distributed in North Africa arose in the early Miocene from an ancestor related to A. eucomoides. The two Canary Island endemics originated from an ancestor related to the North African A. wyssianum in the early Pliocene. Strong support for the monophyly of all the species represented by more than one population casts doubt on the inclusion of the six North African species into a Androcymbium gramineum complex and provides strong evidence against the possibility of reticulation in these species. Lack of support for the monophyly of the two currently recognized sections (Androcymbium and Erythrostictus) suggests that the presence of wing-like appendages on the tepals is not a reliable taxonomic character for sectional circumscription. Molecular clock estimates emphasize the importance of ecological diversity in the differentiation of South African species. In sharp contrast, the much less pronounced pattern of change among north African species seems to have been fostered by their relatively recent origin and by the uniform ecological conditions that prevail in their areas of geographic distribution. Androcymbium Willd. (Colchicaceae) consists of about 40 species of hermaphroditic, cormose mono- cots with androecial nectaries that pioneer open arid or semi-arid habitats in Africa. Although some populations of the genus have been documented in zones of central eastern Africa (Tanzania, Kenya, and Ethiopia), most species are restricted to north- ern and southern Africa. The six species in northern Africa are currently considered part of the Andro- cymbium gramineum complex (Greuter 1967). Four of them occur in the Mediterranean region: A. gra- mineum (widespread in southern Spain and the At- lantic coast of Morocco), A. palaestinum (with two known populations in the Middle East), A. rechin- gerii (widespread in the coastal fringe of Lybia and with one population in the Greek islet of Elafoni- sos), and A. wyssianum (widespread in interior Tu- nisia, Algeria and Morocco, and along the Atlantic coast of Mauritania). The other two north African species occur in the Canary Islands. Androcymbium hierrense has been described in three localities in the

A karyological study was carried out in the genusAndrocymbium Willd. The karyotypes of 26 populationsbelonging to six species of the section Erythrostictus(Schldtl.) Benth. in Benth. & Hook.f. (included intheA. gramineum (Cav.) T.Macbr. group) and of onepopulation of a species of the section Androcymbium are established and themean results for each taxon are given. Chromosome counts from severalpopulations of all the species, the chromosome number ofA. eucomoides Willd., and most of the karyotypes arepresented here for the first time. A new basic number, x= 10, is also reported for the genus. On the basis of the dataobtained, a descendent dysploidy process in the evolution of the genus issuggested and the members of the A. gramineum group areconsidered to be schizoendemics.