Romina Vidal-Russell

Phylogenetic inference in Rafflesiales: the influence of rate heterogeneity and horizontal gene transfer

BackgroundThe phylogenetic relationships among the holoparasites of Rafflesiales have remained enigmatic for over a century. Recent molecular phylogenetic studies using the mitochondrial matR gene placed Rafflesia, Rhizanthes and Sapria (Rafflesiaceae s. str.) in the angiosperm order Malpighiales and Mitrastema (Mitrastemonaceae) in Ericales. These phylogenetic studies did not, however, sample two additional groups traditionally classified within Rafflesiales (Apodantheaceae and Cytinaceae). Here we provide molecular phylogenetic evidence using DNA sequence data from mitochondrial and nuclear genes for representatives of all genera in Rafflesiales.ResultsOur analyses indicate that the phylogenetic affinities of the large-flowered clade and Mitrastema, ascertained using mitochondrial matR, are congruent with results from nuclear SSU rDNA when these data are analyzed using maximum likelihood and Bayesian methods. The relationship of Cytinaceae to Malvales was recovered in all analyses. Relationships between Apodanthaceae and photosynthetic angiosperms varied depending upon the data partition: Malvales (3-gene), Cucurbitales (matR) or Fabales (atp1). The latter incongruencies suggest that horizontal gene transfer (HGT) may be affecting the mitochondrial gene topologies. The lack of association between Mitrastema and Ericales using atp1 is suggestive of HGT, but greater sampling within eudicots is needed to test this hypothesis further.ConclusionsRafflesiales are not monophyletic but composed of three or four independent lineages (families): Rafflesiaceae, Mitrastemonaceae, Apodanthaceae and Cytinaceae. Long-branch attraction appears to be misleading parsimony analyses of nuclear small-subunit rDNA data, but model-based methods (maximum likelihood and Bayesian analyses) recover a topology that is congruent with the mitochondrial matR gene tree, thus providing compelling evidence for organismal relationships. Horizontal gene transfer appears to be influencing only some taxa and some mitochondrial genes, thus indicating that the process is acting at the single gene (not whole genome) level.

Evolutionary relationships in the showy mistletoe family (Loranthaceae).

Loranthaceae (73 genera and ca. 900 species) comprise mostly aerial hemiparasitic plants. Three monotypic genera considered relicts are root parasites. The family is diverse in tropical areas, but representatives are also found in temperate habitats. Previous classifications were based on floral and inflorescence morphology, karyological information, and biogeography. The family has been divided into three tribes: Nuytsiae, Elytrantheae (subtribes Elytranthinae and Gaiadendrinae), and Lorantheae (subtribes Loranthinae and Psittacanthinae). Nuytsiae and Elytrantheae are characterized by a base chromosome number of x = 12, whereas subtribes Loranthinae (x = 9) and Psittacanthinae (x = 8) numbers are derived via aneuploid reduction. To elucidate the phylogeny of the family, we analyzed sequences from five genes (nuclear small and large subunit rDNA and the chloroplast genes rbcL, matK, and trnL-F) representing most genera using parsimony, likelihood, and Bayesian inference. The three root parasites, Nuytsia, Atkinsonia, and Gaiadendron, are supported as successive sister taxa to the remaining genera, resulting in a monophyletic group of aerial parasites. Three major clades are resolved each corresponding to a subtribe. However, two South American genera (Tristerix and Notanthera) and the New Zealand genus Tupeia, which were previously classified in subtribe Elytranthinae, are weakly supported as part of a clade representing the South American subtribe Psittacanthinae.

Phylogenetic relationships and ecological speciation in the mistletoe Tristerix (Loranthaceae): the influence of pollinators, dispersers, and hosts.

Phylogenies can provide valuable information on biotic and abiotic factors associated with speciation. We examined species relationships in Tristerix (Loranthaceae), a genus of 11 species with an Andean distribution from Colombia to Chile. A previous classification divided Tristerix into subgenera Tristerix (two species) and Metastachys (nine species). We tested this classification by generating a molecular phylogeny of the genus using nuclear ribosomal DNA ITS and chloroplast atpB-rbcL intergenic spacer and trnL-F regions. All partitions generally gave congruent trees, thus a combined analysis was conducted. Tristerix was composed of a northern clade (six species) and a southern clade (four species). Tristerix verticillatus and T. penduliflorus (Metastachys) were strongly supported as members of the (southern) subgenus Tristerix clade. Speciation appears to be correlated with the emergence of matorral and cloud forest biomes and is driven by interactions with pollinators and seed dispersers. Tristerix aphyllus is sister to T. corymbosus of the matorral, not to neighboring temperate forest populations, thus rendering the latter species paraphyletic. This ecological speciation event may have occurred in sympatry. Tristerix provides excellent examples of how, during the orography of the Andes, many dynamic and interacting ecological factors have influenced their speciation.

A Molecular Phylogeny of the Feathery Mistletoe Misodendrum

Abstract Misodendrum comprises eight species of aerial hemiparasites endemic to temperate forests of Chile and Argentina that parasitize Nothofagus. This mistletoe is unique in that it has feathery staminodes on its wind dispersed achenes. Previous classifications included two subgenera, Misodendrum (two sections) and Angelopogon (three sections). The present study tested this classification using two chloroplast genes (trnL-F and matK) and 31 morphological characters. Maximum parsimony, likelihood and Bayesian analyses were performed for individual and combined partitions. Results from analyses of the separate partitions differed only in the positions of M. linearifolium and M. quadriflorum; however, the 2-gene tree gave higher support for M. quadriflorum as sister to all other species. Misodendrum brachystachyum and M. oblongifolium form a well supported clade that is sister to one composed of M. punctulatum, M. gayanum, and M. angulatum. These phylogenetic relationships generally agree with previous taxonomic classifications. Subgenus Misodendrum, characterized by warty stems and two stamens, here resolves as a polytomy: M. punctulatum, M. gayanum, and M. angulatum. Subgenus Angelopogon, characterized by the plesiomorphies three stamens and foliacious bracts, is paraphyletic given our rooting. Misodendrum brachystachyum and M. oblongifolium (section Archiphyllum) differ morphologically only by the length of their fruiting staminodes.

Multiple Pleistocene refugia in the widespread Patagonian tree Embothrium coccineum (Proteaceae)

Embothrium coccineum J.R.Forst. & G.Forst is an endemic tree of the Patagonian temperate forest. The objective of this study is to evaluate the impact of last glaciation events on the genetic structure of this widespread and ecologically tolerant species, to postulate possible refugial areas. Phylogeographic analyses were performed using chloroplast DNA sequences (trnL-trnF spacer and ndhC-trnV spacer) from individuals collected in 34 populations along the total range of the species, and these results were compared with a similar study in Nothofagus. A total of 22 haplotypes were found, three of which were widely distributed while 13 were found at only one location. Historical demography suggests a long period of stable effective population size, decreasing gradually towards the Last Glacial Maximum (LGM), followed by an increase in population size that stabilised 2500 years ago. The phylogeographic analyses reflect recent events of colonisation after the LGM from multiple refugia. In the northern area of its distribution probably the species survived in several pockets within the Andes mountain range and in Cordillera de la Costa in Chile. In the south, it is suggested that Embothrium survived the glacial period at the edge of the glaciers. These findings are in agreement with the fossil pollen record that shows 10 000-year-old grains in the south, suggesting colonisation from nearby areas when ice retreated. Embothrium is a coloniser that naturally occurs as scattered individuals within mixed forests. Hence, the shallow phylogeographic structure reported here reflects a Pleistocene signature highly impacted by drift resulting in the randomly fixation of new variants reducing the cpDNA structure.

Evolutionary History of the South American Mistletoe Tripodanthus (Loranthaceae) using Nuclear and Plastid Markers

Abstract Tripodanthus consists of three species that are endemic to South America. While T. acutifolius and T. flagellaris have east-west distributions in tropical and subtropical South America, T. belmirensis is restricted to its type locality in the region of Belmira, Colombia. The objective of the present study was to reconstruct the phylogeny of the genus using molecular markers (nrDNA ITS and plastid atpB-rbcL and trnL-F regions) and to examine morphological characters in the variable species T. acutifolius. A total of 23 individuals of Tripodanthus, representing all species currently recognized in the genus, were sampled in the molecular phylogeny, while 73 individuals were measured for the morphological component of this study. Phylogenetic analyses of the combined ITS and plastid markers reconstructed two main clades within T. acutifolius that correspond to two geographic areas: the Andes and the eastern region of southern South America. This analysis also yielded a monophyletic T. flagellaris, although no geographic structure was obtained within this clade. Tripodanthus belmirensis and T. acutifolius together formed a clade that was sister to T. flagellaris. A principal component analysis of 70 individuals of T. acutifolius showed great variability in leaf morphological characters, leading to overlapping clusters for Andean and eastern mistletoes. The morphologically variable T. acutifolius was not well supported as monophyletic and possessed overlapping morphological features with T. belmirensis, calling into question whether T. belmirensis should be recognized as a distinct species.

Identifying Genetic Hotspots by Mapping Molecular Diversity of Widespread Trees: When Commonness Matters

Conservation planning requires setting priorities at the same spatial scale at which decision-making processes are undertaken considering all levels of biodiversity, but current methods for identifying biodiversity hotspots ignore its genetic component. We developed a fine-scale approach based on the definition of genetic hotspots, which have high genetic diversity and unique variants that represent their evolutionary potential and evolutionary novelties. Our hypothesis is that wide-ranging taxa with similar ecological tolerances, yet of phylogenetically independent lineages, have been and currently are shaped by ecological and evolutionary forces that result in geographically concordant genetic patterns. We mapped previously published genetic diversity and unique variants of biparentally inherited markers and chloroplast sequences for 9 species from 188 and 275 populations, respectively, of the 4 woody dominant families of the austral temperate forest, an area considered a biodiversity hotspot. Spatial distribution patterns of genetic polymorphisms differed among taxa according to their ecological tolerances. Eight genetic hotspots were detected and we recommend conservation actions for some in the southern Coastal Range in Chile. Existing spatially explicit genetic data from multiple populations and species can help to identify biodiversity hotspots and guide conservation actions to establish science-based protected areas that will preserve the evolutionary potential of key habitats and species.

The species pair Pseudocyphellaria pilosella-piloselloides (lichenized Ascomycota: Lobariaceae ) is a single species

Fil: Messuti, Maria Ines. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

Morphological Variation in Quinchamalium (Schoepfiaceae) is Associated with Climatic Patterns along Its Andean Distribution

Abstract Quinchamalium (Schoepfiaceae) is a root hemiparasite with a broad geographic range throughout the Andes. Regional studies have used various vegetative and floral traits to describe and identify species, but there has been no detailed analysis of the continuum of morphological variation across the entire geographic range of this genus. Currently 21 species names are being used in the genus but their taxonomic distinctiveness is unclear. The aim of this study was to use multivariate analyses to identify patterns of morphological variation, assess the existence of morpho-species, and correlate variation with climatic and geographic factors. Two putative species were initially circumscribed based on corolla length, and this hypothesis was tested using principal component and discriminant analyses of 17 vegetative and floral characters obtained from 117 herbarium specimens. No statistically significant support was obtained through multivariate analyses for the existence of the two morpho-species, thus, only one species is recognized, a widespread and variable Q. chilense. Patterns of co-variation between several morphological traits and climate were identified. Taller plants with larger flowers were associated with sites with higher precipitation, and narrower leaves with higher temperatures. The presence of thrum flowers (floral morphs with relatively short styles) was correlated with higher latitudes and lower temperatures. Nevertheless, we have not determined whether these variations are genetically fixed ecotypes or are a consequence of phenotypic plasticity.

Chaenothecopsis quintralis, a new species of calicioid fungus

Chaenothecopsis quintralis from southwestern Argentina is described and illustrated as a new species in the family Mycocaliciaceae. It has been found in three localities in the Andean Patagonian temperate forests, growing strictly on dung of an endemic marsupial Dromiciops gliroides. The new species is distinguished by the hemispherical, black capitulum of ascoma, the presence of asci with croziers, one-celled brown ascospores, and its fimicolous habitat. Analysis of partial nuclear large subunit rDNA (LSU) sequences showed that this taxon is within Mycocaliciales.