Guaianolides from Saussurea affinis

Cynaropicrin, 11βH-11,13-dihydrodesacylcynaropicrin, aguerins A and B, isoamberboin and the new guaianolides saussureolide and 11βH-11,13-dihydrodesacylcynaropicrin 8-β-d-glucoside were isolated from Saussurea affinis.     

Phylogeny and ecological radiation of New World thistles (Cirsium,Cardueae - Compositae) based on ITS and ETS rDNA sequence data

Sequence data from a portion of the external transcribed spacer (ETS) and internal transcribed spacers (ITS-1 and ITS-2) of 18S-26S nuclear ribosomal DNA were used to resolve historical biogeography and ecology of true thistles (Cirsium, Cardueae, Compositae) in the New World. The 650 base-pair, 3' portion of the ETS examined here showed a level of variation across taxa similar to that of the ITS sequences included. A maximum-likelihood tree based on combined ETS and ITS sequences leads us to suggest that the New World species of true thistles constitute a major lineage, which in turn comprises several smaller lineages. A western North American lineage shows weak quartet-puzzling support, but includes a well-supported lineage of species endemic to the California Floristic Province. Comparisons of this Californian lineage with other neoendemic angiosperm groups of the region show that the Californian Cirsium lineage exhibits unusually high ecological diversity for a group displaying such low levels of rDNA sequence divergence across taxa. Similarly low levels of sequence divergence were found throughout the New World Cirsium lineage. These results indicate either that Cirsium underwent a rapid ecological radiation in North America, or that rDNA evolution in North American Cirsium has been highly conservative.     

A new species of Centaurea (Asteraceae) from Sicily

A new species of Centaurea, Centaurea sicana , endemic to Sicily, is described. This new taxon is close to Centaurea parlatoris and Centaurea giardinae (Sect. Dissectae), the former occurring at Palermo and in the Madonie Mountains, while the latter occurs on the Etna volcano. The new species has so far been found only on the Sicani Mountains, a limestone mountain range in western Sicily, while the related species occur in the surrounding mountains. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 785–788.     

Hosts as habitats: faunal similarity of phytophagous insects between host plants

1. Published lists on the phytophages recorded on 86 cabbage plant species (Brassicaceae) and 30 thistle species (Cynaroideae) were used to investigate patterns in the faunal similarity of phytophages. This was done by calculating the Jaccard index and a standardised index of similarity between pairs of host species using presence/absence data. 2. The faunal similarity measured as Jaccard indices indicated that pairs of cabbage hosts share on average 36% of phytophagous species whereas pairs of thistle hosts share only 10%. 3. The faunal similarity between two host species increased with the taxonomic affinity of hosts. This increase was more pronounced in thistles than in cabbage plants. 4. Irrespective of the taxonomic affinity of hosts, in the cabbage plants the faunal similarity of endophages was lower than in ectophages. In contrast, in the thistles faunal similarity differed only between endophages and ectophages for hosts of the same genera. 5. Differences in the patterns of faunal similarity between the two host taxa may be due to idiosyncratic characteristics of the plant taxa, e.g. the unique chemical properties of the cabbage plants and the resource‐rich flower heads of thistles.     

Phylogenetic relationships of the enigmatic species Serratula chinensis and Serratula forrestii (Asteraceae - Cardueae)

The phylogenetic relationships of the Chinese species Serratula forrestii and S. chinensis within the subtribe Centaureinae (Asteraceae – Cardueae) were investigated based on nuclear ribosomal DNA external and internal transcribed spacer sequences. Results indicated that Serratula s. l. is clearly polyphyletic, none of the two species showing close affinities to either Serratula s. str. or Klasea, a genus traditionally included in Serratula. Serratula forrestii has a basal position within the subtribe and has retained most plesiomorphic character states. Serratula chinensis is related to the genera of the Rhaponticum group. Its chromosome number was determined as 2n = 26, and the relationship between this species and the Rhapon-ticum group is discussed from a morphological and karyological point of view.     

Endangered by laws: potential consequences of regulations against thistles on bumblebee conservation

Many bumblebee (Bombus) species are undergoing a strong decline in Europe due to, amongst other things, a decrease of food resources. While leguminous plants (Fabaceae) are considered to be one of the main pollen sources of bumblebees, thistles (Asteraceae tribe Cardueae) have been suggested to be important for male diet. Yet, several European countries apply strict regulations against thistles since they are considered to be one of the principal weeds in agricultural landscapes. Such regulations could impact bumblebee conservation through disruption of male diet and ecology. Here, we assess the male-depending importance of thistles for bumblebee species based on field observations across countries where a legal regulation against thistles is in effect. We ultimately aim to evaluate the potential consequences of these regulations on bumblebee conservation. Our results confirm that most floral visit observations of males occur on thistles (mainly Cirsium spp. and Carduus spp.) and some species are almost exclusively observed on them. Thistle removal is thus most likely a threat for bumblebees. Therefore, we advocate repealing the thistle removal acts to make way for alternative thistle regulations which reconcile biodiversity conservation and agricultural requirements.     

Lessons from Plectocephalus (Compositae, Cardueae-Centaureinae): ITS disorientation in annuals and Beringian dispersal as revealed by molecular analyses

Background and Aims

The geographic distribution of the genus Plectocephalus comprises a single species in Ethiopia, two in North America and possibly four more in South America, in a striking disjunction that is exceptional for genera of the tribe Cardueae. The enormity of this disjunction cast doubts on the precise taxonomic delineation of the genus, which is not unanimously recognized as a natural entity. The aims of this study were to define the generic boundaries of Plectocephalus and to formulate a hypothesis that would explain its natural range.

Methods

A combined molecular approach, using nuclear internal transcribed spacers (ITS) and external transcribed spacers (ETS), and plastid trnL-trnL-F, rpl32-trnL^UAG and ndhF markers, was chosen for phylogenetic reconstruction by maximum parsimony and Bayesian inference.

Key Results

Phylogenetic analysis shows that Plectocephalus is a natural genus that includes the African species P. varians, together with all the native South American species, currently classified as Centaurea, C. cachinalensis, C. floccosa and C. tweediei. The recognition of Centaurodendron as an independent genus, which we consider appropriate, would make Plectocephalus paraphyletic. Affinities of Plectocephalus should lie with eastern representatives of Centaureinae. Geographic disjunction is explained as a consequence of dispersal via the Bering Land Bridge during the Miocene–Pliocene. The phylogeny of the basal grade of Centaureinae differs from previous phylogenies, and artefacts resulting from differences in mutation rates of annual and perennial taxa are confirmed. Sensitivity of ITS to these differences was the highest observed for all DNA regions used in this study.

Conclusions

The natural status of the genus Plectocephalus is confirmed and several nomenclatural combinations are proposed. New evidence contributes to the debate concerning problems posed by the use of ITS in the phylogenetic reconstruction of groups that differ in terms of their life cycles. Dispersal from Caucasus and Anatolia along the Siberian route and then across the Bering Land Bridge follows a route previously proposed for other taxonomic groups.     

Taxonomic problems in Carthamus (Asteraceae): RAPD markers and sectional classification

Recent molecular studies have clarified the problem of the generic limits of Carthamus . However, taxonomic problems remain in the sectional classification: section Carthamus was confirmed as a natural group, but molecular phylogenies based on DNA sequences did not resolve the other sections, resulting in a confusing conglomerate. A survey based on RAPD markers has been carried out in this conflicting group of sections, with the aim of evaluating the usefulness of these markers at the section and species levels. On the basis of the results, correlated with morphological and karyological characters, some recommendations are made in relation to the taxonomy of Carthamus . The number of sections is reduced from five to two: section Thamnacanthus is currently classified as a different genus, Phonus ; section Carthamus s.s. is retained in its present delimitation, and section Atractylis is redefined, including current sections Atractylis , Lepidopappus and Odontagnathius . The commonly accepted treatment of some taxa as subspecies is not well founded, and C. alexandrinus , C. creticus , C. tenuis and C. turkestanicus should be considered as independent species. Our results confirm that methodological problems posed by RAPD markers can be avoided by careful laboratory procedures and appropriate data analyses; they also suggest that this kind of marker is useful at low taxonomic levels and is, furthermore, complementary to DNA sequence analysis.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 375–383.     

Why close relatives make bad neighbours: phylogenetic conservatism in niche preferences and dispersal disproves Darwin's naturalization hypothesis in the thistle tribe

The number of exotic plant species that have been introduced into the United States far exceeds that of other groups of organisms, and many of these have become invasive. As in many regions of the globe, invasive members of the thistle tribe, Cardueae, are highly problematic in the California Floristic Province, an established biodiversity hotspot. While Darwin's naturalization hypothesis posits that plant invaders closely related to native species would be at a disadvantage, evidence has been found that introduced thistles more closely related to native species are more likely to become invasive. To elucidate the mechanisms behind this pattern, we modelled the ecological niches of thistle species present in the province and compared niche similarity between taxa and their evolutionary relatedness, using fossil‐calibrated molecular phylogenies of the tribe. The predicted niches of invasive species were found to have higher degrees of overlap with native species than noninvasive introduced species do, and pairwise niche distance was significantly correlated with phylogenetic distance, suggesting phylogenetic niche conservatism. Invasive thistles also displayed superior dispersal capabilities compared to noninvasive introduced species, and these capabilities exhibited a phylogenetic signal. By analysing the modelled ecological niches and dispersal capabilities of over a hundred thistle species, we demonstrate that exapted preferences to the invaded environment may explain why close exotic relatives may make bad neighbours in the thistle tribe.