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Summary: Inferring the processes responsible for the rich endemic diversity of oceanic island floras is important for our understanding of plant evolution and setting practical conservation priorities. This requires an accurate knowledge of phylogenetic relationships, which have often been difficult to resolve due to a lack of genetic variation.We employed genotyping‐by‐sequencing (GBS) to investigate how geographical isolation, habitat shifts, and hybridisation have contributed to the evolution of diversity observed in Argyranthemum Webb (Asteraceae), the largest genus of flowering plants endemic to the Macaronesian archipelagos.Species relationships were resolved, and biogeographical stochastic mapping identified intra‐island speciation as the most frequent biogeographic process underlying diversification, contrary to the prevailing view in Argyranthemum and the Canary Islands. D‐statistics revealed significant evidence of hybridisation between lineages co‐occurring on the same island, however there was little support for the hypothesis that hybridisation may be responsible for the occurrence of nonmonophyletic multi‐island endemic (MIE) species.Geographic isolation, habitat shifts and hybridisation have all contributed to the diversification of Argyranthemum, with intra‐island speciation found to be more frequent than previously thought. Morphological convergence is also proposed to explain the occurrence of nonmonophyletic MIE species. This study reveals greater complexity in the evolutionary processes generating Macaronesian endemic diversity. [ABSTRACT FROM AUTHOR] more...

Well‐characterized examples of homoploid hybrid speciation (HHS) are rare in nature, yet they offer the potential to study a number of evolutionary processes. In this study, we investigate putative homoploid hybrid species in the genus Argyranthemum (Asteraceae), a group of plants endemic to the Macaronesian archipelagos of the North Atlantic Ocean. We specifically address a number of knowledge gaps surrounding the origin(s) of A. sundingii and A. lemsii, which are thought to be derived from the same parental cross. Comparisons of leaf morphology suggest that A. sundingii and A. lemsii are distinct from their parental progenitors and distinguishable from each other based on leaf area. Ecological niche modelling (ENM) demonstrated that the homoploid hybrid species occupy novel habitats that are intermediate relative to the parental species. Nuclear simple sequence repeat markers (SSRs) and single nucleotide polymorphism (SNP) data indicate that the homoploid hybrid species are distinct from the parental taxa, while population‐level sampling of chloroplast SSRs and approximate Bayesian computation show that A. sundingii and A. lemsii are independently derived from the same parental cross. As such, Argyranthemum represents an example of independent homoploid hybrid speciation events with evidence of divergence in leaf morphology and adaptation to novel intermediate habitats. On oceanic islands, which are often typified by steep ecological gradients and inhabited by recently derived species with weak reproductive barriers, multiple HHS events from the same parental cross are not only possible but also likely to have played a more important role in oceanic island radiations than we currently think. [ABSTRACT FROM AUTHOR] more...

Abstract: Insular woodiness refers to the evolutionary transition from herbaceousness towards derived woodiness on (sub)tropical islands and leads to island floras that have a higher proportion of woody species compared to floras of nearby continents. Several hypotheses have tried to explain insular woodiness since Darwin's original observations, but experimental evidence why plants became woody on islands is scarce at best. Here, we combine experimental measurements of hydraulic failure in stems (as a proxy for drought stress resistance) with stem anatomical observations in the daisy lineage (Asteraceae), including insular woody Argyranthemum species from the Canary Islands and their herbaceous continental relatives. Our results show that stems of insular woody daisies are more resistant to drought‐induced hydraulic failure than the stems of their herbaceous counterparts. The anatomical character that best predicts variation in embolism resistance is intervessel pit membrane thickness (TPM), which can be functionally linked with air bubble dynamics throughout the 3D vessel network. There is also a strong link between TPM vs. degree of woodiness and thickness of the xylem fibre wall vs. embolism resistance, resulting in an indirect link between lignification and resistance to embolism formation. Thicker intervessel pit membranes in Argyranthemum functionally explain why this insular woody genus is more embolism resistant to drought‐induced failure compared to the herbaceous relatives from which it has evolved, but additional data are needed to confirm that palaeoclimatic drought conditions have triggered wood formation in this daisy lineage. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR] more...

The pathogenicity of five isolates of Fusarium oxysporum obtained from infected gerbera ( Gerbera jamesonii), chrysanthemum ( Chrysanthemum morifolium), Paris daisy ( Argyranthemum frutescens) and African daisy ( Osteospermum sp.) plants was tested on some varieties of the following Compositae hosts: C. morifolium, G. jamesonii, Argyranthemum frutescens (Paris daisy) and Osteospermum sp. and compared with the host range and pathogenicity of an isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC collection. The results indicated that isolates of F. oxysporum from G. jamesonii as well as those from A. frutescens and Osteospermum sp. belong to the forma specialis chrysanthemi. The isolate from gerbera was virulent on all tested varieties of gerbera, C. morifolium, A. frutescens and Osteospermumsp. Similar results were obtained testing the isolates obtained from A. frutescens and Osteospermumsp. The strain from C. morifolium infected cultivar of gerbera, A. frutescens and Osteospermum sp. The pathogenicity of isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC showed a different cultivar range particularly in the case of chrysanthemum and gerbera. [ABSTRACT FROM AUTHOR] more...

Results of aimed patch testing with constituents of sesquiterpene lactone (SL) mix, Compositae mix (CM) and other Compositae extracts and allergens in 190 Compositae-allergic patients detected in an 8-year period are presented. Feverfew of CM elicited positive reactions most frequently, followed by tansy, wild chamomile, yarrow and arnica, whereas dehydrocostus lactone of SL was the most frequent elicitor of positive reactions, followed by alantolactone and costunolide. Chrysanthemum (Dendranthema) and marguerite (Argyranthemum frutescens) were the most important suspected sensitizers in both occupationally and nonoccupationally exposed, and cross-reactions between chrysanthemum and feverfew/tansy/chamomile may partly explain the high prevalence of positive reactions to the 3 last mentioned. In the nonoccupationally sensitized group, garden plants such as feverfew, blanket flower (Gaillardia), elecampane (Inula helenium), large yellow ox-eye (Telekia speciosa) and cosmea (Cosmos) were additional important allergenic plants. The 3 last mentioned were picked up by SL mix. Most of the lettuce-sensitized persons were CM-positive. 19% of the occupationally sensitized group were negative to both SL and CM, making very aimed patch testing necessary, notably when suspecting rare sensitizers such as Gerbera and star of the veldt (Osteospermum). The significance of the weeds dandelion, dog fennel and ox-eye daisy as sensitizers is not clarified, but they are probably less important than cultivated plants. [ABSTRACT FROM AUTHOR] more...

Presents a study on genera of Argyranthemum (Asteraceae) in the Mediterranean and Macaronesian regions. Information on the phylogenetic analysis of the internal transcribed spacers; Methodology used in the study; Results of the study. more...

Fusarium oxysporum isolates, pathogenic on Paris daisy ( Argyranthemum frutescens), were classified by vegetative compatibility grouping analysis. They were compared with isolates of the formae speciales chrysanthemi and tracheiphilum, and with f. sp. dianthi as a genetically distant control. The results show the uniformity of the pathogenic isolates from Paris daisy, except for one which was of a different geographic origin. They were classified as a new VC group (0052). We report also the efficacy of different media in obtaining nit mutants. [ABSTRACT FROM AUTHOR] more...