Search

[Background and Aims] Changes in the amount of repetitive DNA (dispersed and tandem repeats) are considered the main contributors to genome size variation across plant species in the absence of polyploidy. However, the study of repeatome dynamism in groups showing contrasting genomic features and complex evolutionary histories is needed to determine whether other processes underlying genome size variation may have been overlooked. The main aim here was to elucidate which mechanism best explains genome size evolution in Anacyclus (Asteraceae). [Methods] Using data from Illumina sequencing, we analysed the repetitive DNA in all species of Anacyclus, a genus with a reticulate evolutionary history, which displays significant genome size and karyotype diversity albeit presenting a stable chromosome number. [Key Results] By reconstructing ancestral genome size values, we inferred independent episodes of genome size expansions and contractions during the evolution of the genus. However, analysis of the repeatome revealed a similar DNA repeat composition across species, both qualitative and quantitative. Using comparative methods to study repeatome dynamics in the genus, we found no evidence for repeat activity causing genome size variation among species. [Conclusions] Our results, combined with previous cytogenetic data, suggest that genome size differences in Anacyclus are probably related to chromosome rearrangements involving losses or gains of chromosome fragments, possibly associated with homoploid hybridization. These could represent balanced rearrangements that do not disrupt gene dosage in merged genomes, for example via chromosome segment exchanges., This work was supported by the Catalan government (grant number 2017SGR1116) and by the Spanish government [grant numbers CGL2010-18039, CGL2013-49097-C2-1-P, CGL2013-49097-C2-2-P, CGL2016-75694-P (AEI/FEDER, UE), RYC-2014–16608 to S.G. and RYC-2016–21176 to O.H.]

Premise of research. Interspecific hybridization was hypothesized to explain the remarkable floral phenotype variation found in overlapping areas of distribution for several Anacyclus species. We aimed to investigate genome size in natural populations of three diploid Anacyclus species with special emphasis in their contact areas to explore patterns of variation as additional evidence supporting current hybridization in these areas. Methodology. Flow cytometry was used to estimate the genome size of 564 individuals of the species complex of A. clavatus, A. homogamos, and A. valentinus from 30 sites. Additionally, genome size variation of 173 first-generation synthetic hybrids between these three species was also studied and compared with the estimates obtained in sympatric sites. Pivotal results. Differences in genome size between A. clavatus and A. valentinus were significant in non-overlapping areas of species distribution, whereas in overlapping areas, the variation increased, preventing a clear differentiation between species. In sympatric sites of A. clavatus and A. valentinus, individuals with intermediate genome sizes between them were also observed and were significantly similar to those obtained from the first-generation experimental hybrids between these species. Genome sizes of A. clavatus and A. homogamos did not differ enough to allow discrimination between these species. Conclusions. The patterns of genome size variation observed in sympatric populations of A. clavatus and A. valentinus support the occurrence of current gene flow between these species and the existence of contact areas in overlapping distribution areas where phenotypic and genomic variation increases.

Premise of the Study: Ray flowers commonly observed in daisies’ flowering heads are a well-known example of advertising structures for enhancing pollinator attraction. Despite this, ray loss has occurred in multiple lineages, which still rely on pollinators, suggesting that rayless phenotypes could also be adaptive for animal-pollination. Here, we investigate the benefits and costs of these specialized floral advertising structures by comparing rayed and rayless phenotypes in two hybridizing closely related species. Methods: We assessed the advantages and costs of ray production in terms of floral visitor's attraction, pollen limitation, and female reproductive success using the broad natural variation on ray size and number at the contact zone of A. clavatus (rayed) and A. valentinus (rayless). In addition, we experimentally explored the effect of rays under controlled neighborhoods and the effect of ray removal on fruit production. Key Results: In sympatry, rayed phenotypes attracted significantly more visitors than rayless plants, in which seed production was pollen limited. However, rayed phenotypes did not show higher fruit set or seed production than rayless phenotypes. Fruit set and seed production benefited from denser neighborhood displays and larger individual floral displays, respectively. The removal of ray florets did not appear to enable resource reallocation to fruit production. Conclusions: Rayless heads compensated their lower visitation rate by means of a higher number of flowers per head achieving similar fecundity levels to rayed plants. The larger size of rayless heads might thus indicate an inflorescence-level trade-off between attraction and fertility., This research was supported by the project “Evolution in Anacyclus L. (Anthemideae, Compositae): Analysis of the A. clavatus (Desf.) Pers. and A. valentinus L. contact zone,” cofunded by the Ministry of Science and Innovation, Spain (Plan Nacional de I+D+I, CGL2010‐18039) and the European Regional Development Fund. SC and AAf were supported by the Portuguese Foundation for Science and Technology (Starting Grant IF/01267/2013 and SFRH/BD/108451/2015, respectively), RT and AAg were supported by the Ministry of Education, Spain (BVA 2010‐0375 for R.T.; BES‐2011‐048197 for AAg).

Using DNA barcoding markers, we inferred the phylogenetic relationships of the genus Anacyclus including for the first time the three Eastern Mediterranean species, A. anatolicus, A. latealatus and A. nigellifolius. Our results conclusively reveal the polyphyletic condition of this genus in its current circumscription. The molecular data show that A. anatolicus, A. latealatus and A. nigellifolius do not belong to Anacyclus. According to the current knowledge of the Anthemideae systematics, these three species should be placed within the genus Cota and thus the new combinations Cota anatolica, Cota latealata, and Cota nigellifolia are proposed. Such a taxonomic placement is congruent with the achene morphology and biogeography although the circumscription of Cota itself requires further studies., Projects 2014SGR514 (Catalan government) and CGL2013-49097-C2 (subprojects 1-P and 2-P, Spanish government) are also acknowledged.

BACKGROUND AND AIMS: Interstitial telomeric repeat (ITR) sites, consisting of tandem repeats of telomeric motifs localized at intrachromosomal sites, have been reported in a few unrelated organisms including plants. However, the causes for the occurrence of ITRs outside of the chromosomal termini are not fully understood. One possible explanation are the chromosomal rearrangements involving telomeric sites, which could also affect the location of other structural genome elements, such as the 45S rDNA. Taking advantage of the high dynamism in 45S rDNA loci previously found in Anacyclus (Asteraceae, Anthemideae), the occurrence and patterns of variation of ITRs were explored in this genus with the aim of finding common underlying causes. METHODS: In total, 132 individuals from 44 populations of nine species were analysed by fluorescence in situ hybridization using an Arabidopsis-type telomeric sequence as a probe. KEY RESULTS: Variable presence of ITR sites was detected in six out of nine species of Anacyclus, ranging from two to 45 sites and showing contrasting chromosomal locations and a differential presence of the ITR site on homologous chromosome pairs. At the intraspecific level, the ranges were as large as 0–12 ITR sites. Although only 26 % of the total observed ITR sites were localized in chromosomes bearing 45S rDNA loci, all cases of interstitial 45S rDNA reported in a previous work co-occurred with ITRs in close proximity in the same chromosome arms. CONCLUSIONS: High levels of ITR polymorphism within a single species have not been previously reported in plants and suggest that this pattern might have been overlooked due to insufficient sampling. Although ancient Robertsonian translocations or the amplification of terminal 45S rDNA sites cannot, on their own, explain all of the levels of variability in ITRs reported here, there are suggestions that they may have been involved in the evolutionary history of this genus or its ancestors in Anthemideae.

Homologs of the CYC/TB1 gene family have been independently recruited many times across the eudicots to control aspects of floral symmetry The family Asteraceae exhibits the largest known diversification in this gene paralog family accompanied by a parallel morphological floral richness in its specialized head-like inflorescence. In Asteraceae, whether or not CYC/TB1 gene floral symmetry function is preserved along organismic and gene lineages is unknown. In this study, we used phylogenetic, structural and expression analyses focused on the highly derived genus Anacyclus (tribe Anthemidae) to address this question. Phylogenetic reconstruction recovered eight main gene lineages present in Asteraceae: two from CYC1, four from CYC2 and two from CYC3-like genes. The species phylogeny was recovered in most of the gene lineages, allowing the delimitation of orthologous sets of CYC/TB1 genes in Asteraceae. Quantitative real-time PCR analysis indicated that in Anacyclus three of the four isolated CYC2 genes are more highly expressed in ray flowers. The expression of the four AcCYC2 genes overlaps in several organs including the ligule of ray flowers, as well as in anthers and ovules throughout development., This work was supported by grants from the Spanish Ministry of Economy and Competitivness, Plan Estatal de I+D+I and European Social Fund to JF, IA, and PC (CGL2007-66516, CGL2013-49097-C2-2-P and BIO2014-57011-R), “Juan de la Cierva” program co-financed by the European Social Fund to MB (JCI-2010-07374) and Proyecto Intramural CSIC 201430E023 to JF.

Torices, R., Agudo, A. & Alvarez, I. 2013. Not only size matters: achene morphology affects time of seedling emergence in three heterocarpic species of Anacyclus (Anthemideae, Asteraceae). Anales Jard. Bot. Madrid 70(1): 48-55. The production of two or more distinct fruit types by an individual, i.e. hete rocarpy, is considered as a mixed dispersal strategy in which a proportion of the offspring is able to colonize new sites, whilst others remain near the maternal location. Here, we aimed to explore the effects of achene morphology (winged vs. unwinged achenes) and achene size –measured here as achene mass– on post-dispersal life-history traits (probability and time of seedling emergence) in three heterocarpic Anacyclus species (Anthemideae, Asteraceae). Morphology, size and germination performance were studied in achenes from six populations of Anacyclus clavatus (Desf.) Pers., A. homogamos (Maire) Humphries, and A. valentinus L. Our results show that achene morphology and size were related to their position within the capitulum, such that outer, winged achenes were significantly heavier than the inner, unwinged ones. Additionally, winged achenes germinated faster than unwinged ones. This pattern may be related to the sequential achene time of release displayed by these species. Finally, our findings cast doubt on the role of wings as structures that favor dispersal by wind in these three species of Anacyclus.

Background and aims Most of the diversity in the pseudanthia of Asteraceae is based on the differential symmetry and sexuality of its flowers. In Anacyclus, where there are (1) homogamous capitula, with bisexual, mainly actinomorphic and pentamerous flowers; and (2) heterogamous capitula, with peripheral zygomorphic, trimerous and long-/short-rayed female flowers, the floral ontogeny was investigated to infer their origin. Methods Floral morphology and ontogeny were studied using scanning electron microscope and light microscope techniques. Key results Disc flowers, subtended by paleae, initiate acropetally. Perianth and androecium initiation is unidirectional/simultaneous. Late zygomorphy occurs by enlargement of the adaxial perianth lobes. In contrast, ray flowers, subtended by involucral bracts, initiate after the proximal disc buds, breaking the inflorescence acropetal pattern. Early zygomorphy is manifested through the fusion of the lateral and abaxial perianth lobes and the arrest of the adaxials. We report atypical phenotypes with peripheral 'trumpet' flowers from natural populations. The peripheral 'trumpet' buds initiate after disc flowers, but maintain an actinomorphic perianth. All phenotypes are compared and interpreted in the context of alternative scenarios for the origin of the capitulum and the perianth identity. Conclusions Homogamous inflorescences display a uniform floral morphology and development, whereas the peripheral buds in heterogamous capitula display remarkable plasticity. Disc and ray flowers follow different floral developmental pathways. Peripheral zygomorphic flowers initiate after the proximal actinomorphic disc flowers, behaving as lateral independent units of the pseudanthial disc from inception. The perianth and the androecium are the most variable whorls across the different types of flowers, but their changes are not correlated. Lack of homology between hypanthial appendages and a calyx, and the perianth double-sided structure are discussed for Anacyclus together with potential causes of its ray flower plasticity.

Erratum., Using DNA barcoding markers, we inferred the phylogenetic relationships of the genus Anacyclus including for the first time the three Eastern Mediterranean species, A. anatolicus, A. latealatus and A. nigellifolius. Our results conclusively reveal the polyphyletic condition of this genus in its current circumscription. The molecular data show that A. anatolicus, A. latealatus and A. nigellifolius do not belong to Anacyclus. According to the current knowledge of the Anthemideae systematics, these three species should be placed within the genus Cota and thus the new combinations Cota anatolica, Cota latealata, and Cota nigellifolia are proposed. Such a taxonomic placement is congruent with the achene morphology and biogeography although the circumscription of Cota itself requires further studies., Projects 2014SGR514 (Catalan government) and CGL2013-49097-C2 (subprojects 1-P and 2-P, Spanish government) are also acknowledged.

Oberprieler, C.: On the taxonomic status and the phylogenetic relationships of some unispecific Mediterranean genera of Compositae-Anthemideae II. Daveaua, Leucocyclus and Nananthea. — Willde nowia 34: 341–350. — ISSN 0511-9618; © 2004 BGBM Berlin-Dahlem. Sequences of the nrDNA internal transcribed spacer (ITS) region were analysed for 113 representative species of 59 genera of Compositae-Anthemideae to ascertain the systematic position of the three unispecific Mediterranean genera Daveaua, Leucocyclus and Nananthea. Daveaua anthemoides is found to be a member of a well supported clade of genera around the closely-knit Leucanthemum group, being a candidate (together with Heteromera and Otospermum) for a sister-group of this assemblage. For Leucocyclus formosus, which was considered to be closely related to Anacyclus due to its dorsiventrally flattened achenes, a position close to or even among representatives of Achillea is demonstrated, corroborating alleged relationships suggested by the flavon...

The N Hemisphere genus Achillea includes about 130 perennial and allogamous species, is centered in SE Europe/SW Asia, and exhibits a complex phyletic structure due to excessive hybridization and polyploidy. About half ofthe species and five of the six traditional sections together with several outgroup genera were studied using nrITS and plastid trnL-F DNA sequences. In spite of some discordance, these markers were shown by Maximum Parsimony and Bayesian Inference to be suitable for revealing relationships with generic allies and for distinguishing the main lineages within Achillea. With the inclusion of Otanthus (and possibly Leucocyclus) Achillea s.1. becomes monophyletic and appears as sister to Anacyclus. A basal clade is formed by the xerophytes of Achillea sections Babounya and Santolinoideae in SW Asia together with the Mediterranean coastal Otanthus. Achillea sect. Ptarmica s.l. has to be divided into the meso- to hygrophytic herbs of A. sect. Ptarmica s.s. in the N Hemisphere and the mountain species of A. sect. Anthemoideae. The latter differentiated in the mountains from NW Anatolia to the Pyrenees, possibly originating from ancestors related to the extant A. ligustica. Finally, taxa of sect. Achillea s.l. (to be merged with A. sect. Filipendulinae) radiated from a center in SE Europe, occupied very different open habitats, and reached an extensive distribution with the very polymorphic polyploid and reticulate complex A. millefolium agg. Here and in other groups of Achillea, various instances of conflicting evidence from nrITS, plastid trnL-F, and morphology point to hybridization and lineage sorting. This means that reticulate evolution is not only involved in recent radiations but must have been active already in the early diversification of the genus.

The details of a cytogenetic study on 8 taxa of the mediterranean genus Anacyclus are presented. The results include information of the gross morphology, pollen fertilities and meiotic pairing behaviour of F1 hybrids supplemented by data on the karyotype morphology and DNA contents of parenthal plants. The results indicate that evolution in the genus has been accompanied by chromosomal repatterning. There are three distinctive groups within the experimental taxa, a pair of closely related perennials and two groups of annuals. There is considerable genome homology within each group but major differences between them. The groups are discussed in terms of their systematic relationships with other members of the genus in an effort to provide an explicit evolutionary model for the origin of different taxa. The understanding of the relationships of the annual taxa is complicated by sympatry and the occurrence of natural hybrids.

Giemsa C-banding allows the differentiation of six, otherwise very similar karyotypes from the small genusAnacyclus. “Banding style”—with stable centromeric and nucleolar bands, and diverse specific banding patterns in distal chromosome segments—contributes significantly to generic demarcation and systematic grouping. The amount of banding corresponds to heterochromatic chromocentres and increases from perennials to annuals. Relationships with other nucleotype parameters and evolutionary mechanisms are discussed.