How Many Loci Does it Take to DNA Barcode a Crocus?

BACKGROUND: DNA barcoding promises to revolutionize the way taxonomists work, facilitating species identification by using small, standardized portions of the genome as substitutes for morphology. The concept has gained considerable momentum in many animal groups, but the higher plant world has been largely recalcitrant to the effort. In plants, efforts are concentrated on various regions of the plastid genome, but no agreement exists as to what kinds of regions are ideal, though most researchers agree that more than one region is necessary. One reason for this discrepancy is differences in the tests that are used to evaluate the performance of the proposed regions. Most tests have been made in a floristic setting, where the genetic distance and therefore the level of variation of the regions between taxa is large, or in a limited set of congeneric species. METHODOLOGY AND PRINCIPAL FINDINGS: Here we present the first in-depth coverage of a large taxonomic group, all 86 known species (except two doubtful ones) of crocus. Even six average-sized barcode regions do not identify all crocus species. This is currently an unrealistic burden in a barcode context. Whereas most proposed regions work well in a floristic context, the majority will--as is the case in crocus--undoubtedly be less efficient in a taxonomic setting. However, a reasonable but less than perfect level of identification may be reached--even in a taxonomic context. CONCLUSIONS/SIGNIFICANCE: The time is ripe for selecting barcode regions in plants, and for prudent examination of their utility. Thus, there is no reason for the plant community to hold back the barcoding effort by continued search for the Holy Grail. We must acknowledge that an emerging system will be far from perfect, fraught with problems and work best in a floristic setting

Phylogeny of Triticeae (Poaceae) Based on Three Organelle Genes, Two Single-Copy Nuclear Genes, and Morphology

Triticeae are renowned for their complicated taxonomy, but their phylogeny is equally intricate and perplexing, and remains largely unresolved. Based on morphology and nucleotide sequences from two plastid genes (rbcL, rpoA), one mitochondrial gene (coxII), and two single-copy nuclear genes (DMC1, EF-G), the most comprehensive hypothesis (both with respect to taxa and data points) of the phylogeny of diploid Triticeae to date is presented. The incongruence length difference tests clearly indicate that the four logical data partitions (morphology and the three genome compartments) are mutually incongruent, except the mitochondrial and nuclear sequences. Nonetheless, a total evidence approach results in a highly resolved, strongly supported consensus tree, though partitioned Bremer support points to a high level of conflict among the individual data sets

Genomes, Chromosomes, and Genes and the Concept of Homology

The traditional application of genome analysis in phylogenetic inference is questionable. Hypotheses about phylogeny are based upon the analysis of homologous characters, existing as a consequence of common descent. The concept of homology in morphology and molecular biology is well-defined: To count as an homology any character must pass the similarity, congruence, and conjunction tests. In genome analysis homology is related to the behaviour of chromosomes during meiosis: homologous chromosomes pair, nonhomologous chromosomes do not. Thus, in genome analysis homology becomes a purely operational concept. How well does this operational concept work? And what are the relationships, if any, between this operational concept of homology and the homology concept of morphology and molecular biology

Plastome evolution in hemiparasitic mistletoes

Santalales is an order of plants consisting almost entirely of parasites. Some, such as Osyris, are facultative root parasites whereas others, such as Viscum, are obligate stem parasitic mistletoes. Here, we report the complete plastome sequences of one species of Osyris and three species of Viscum, and we investigate the evolutionary aspects of structural changes and changes in gene content in relation to parasitism. Compared with typical angiosperms plastomes, the four Santalales plastomes are all reduced in size (10–22% compared with Vitis), and they have experienced rearrangements, mostly but not exclusively in the border areas of the inverted repeats. Additionally, a number of protein-coding genes (matK, infA, ccsA, rpl33, and all 11 ndh genes) as well as two transfer RNA genes (trnG-UCC and trnV-UAC) have been pseudogenized or completely lost. Most of the remaining plastid genes have a significantly changed selection pattern compared with other dicots, and the relaxed selection of photosynthesis genes is noteworthy. Although gene loss obviously reduces plastome size, intergenic regions were also shortened. As plastome modifications are generally most prominent in Viscum, they are most likely correlated with the increased nutritional dependence on the host compared with Osyris

Massive gene loss in mistletoe (<em>Viscum</em>, Viscaceae) mitochondria

Parasitism is a successful survival strategy across all kingdoms and has evolved repeatedly in angiosperms. Parasitic plants obtain nutrients from other plants and some are agricultural pests. Obligate parasites, which cannot complete their lifecycle without a host, may lack functional photosystems (holoparasites), or have retained photosynthesis (hemiparasites). Plastid genomes are often reduced in parasites, but complete mitochondrial genomes have not been sequenced and their mitochondrial respiratory capacities are largely unknown. The hemiparasitic European mistletoe (Viscum album), known from folklore and postulated therapeutic properties, is a pest in plantations and forestry. We compare the mitochondrial genomes of three Viscum species based on the complete mitochondrial genome of V. album, the first from a parasitic plant. We show that mitochondrial genes encoding proteins of all respiratory complexes are lacking or pseudogenized raising several questions relevant to all parasitic plants: Are any mitochondrial gene functions essential? Do any genes need to be located in the mitochondrial genome or can they all be transferred to the nucleus? Can parasitic plants survive without oxidative phosphorylation by using alternative respiratory pathways? More generally, our study is a step towards understanding how host- and self-perception, host integration and nucleic acid transfer has modified ancestral mitochondrial genomes

Fleshy Fruits in Liliflorous Monocots

Fleshy fruits occur in several monocot orders and families, and it is generally assumed that they have been derived from capsular fruits many times during the evolution of monocot lineages. Huber hypothesized in 1969 that most capsules in Asparagales are derived secondarily from berries and that this transformation was correlated with the evolution of phytomelan-coated seeds, a pivotal character in his circumscription of Asparagales as part of reclassifying Liliaceae s.l. Dahlgren and co-workers suggested several parallel derivations and reversals in this character, e.g., the transformation sequence trifollicular fruits → capsules → berries→ capsules→ berries. Mapping of fleshy fruits on a phylogeny based on molecular characters indicates that Asparagales do not have fleshy fruits as a basal character. Dahlgren\u27s cyclic character evolution hypothesis is not supported by the distribution of dry and fleshy fruits, and there is no obvious correlation between baccate fruits and phytomelaniferous seeds in Asparagales. Phytomelaniferous seeds are not an evident synapomorphy of Asparagales as presently circumscribed. The anatomy and development of different capsular and baccate fruits in selected genera are studied in an ongoing project to reveal homologies and establish an adequate fruit typology. Some observations of texture and dehiscence structures in dry and fleshy capsules and in typical berries from hypogynous and epigynous flowers are reported in this paper

Assembling the Tree of Life in Europe (AToLE)

A network of scientists under the umbrella of &#x27;Assembling the Tree of Life in Europe (AToLE)&#x27; seeks funding under the FP7-Theme: Cooperation - Environment (including Climate Change and Biodiversity Conservation) programme of the European Commission.&#xd;&#xa