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Biosystematic studies on Xathium : taxonomic appraisal and ecological status / Doris Löve in Canadian Journal of Botany, vol. 37 (Année 1959)

Public [article]  inCanadian Journal of Botany > vol. 37 (Année 1959) . - pp. 173-208 Titre : Biosystematic studies on Xathium : taxonomic appraisal and ecological status Type de document : texte imprimé Auteurs : Doris Löve, Auteur ; Pierre Dansereau, Auteur Année de publication : 1959 Article en page(s) : pp. 173-208 Langues : Anglais (eng) Catégories : [Espèces (in biblio)] Xanthium [Thèmes] Taxonomie Mots-clés : écologie  systématique  aire de répartition  biogéographie Résumé : "The following paper is an evaluation of the taxonomic and ecological status of the genus Xanthium L. A review of its systematics demonstrates that many so-called "species" described on material from Europe actually have their origin in America, except one, X. strumarium s. str., which seems to have a Mediterranean–European center of dispersal. Another conclusion drawn is that Xanthium consists of only two distinct species: X. spinosum L. and X. strumarium L. The former is a relatively stable species, the latter an enormously variable one readily subdivided into a number of minor taxonomic entities.Ecologically, in eastern North America at least, Xanthium is primarily a beach plant, which prefers open habitats and succumbs to crowding. The seeds are most often dispersed by water and wind. It enters easily into ruderal habitats, but only as long as these are open and unshaded.The generalized short-day flowering response in this genus supports our hypothesis that Xanthium has a tropical–subtropical origin, and we feel that it has its center in Central and/or South America, whence it has spread over the continents north and southward.There is no evidence for any sterility barriers separating the entities of X. strumarium, but we feel that an intense inbreeding with an occasional outbreeding is responsible for the enormous variation, often resulting in small, local, but unstable taxa." (source : auteurs) Type de publication : périodique Référence biblio : Löve D., Dansereau P., 1959 - Biosystematic studies on Xathium : taxonomic appraisal and ecological status. Canadian Journal of Botany, 37 : 173-208. ID PMB : 69398 Permalink : http://www.cbnbrest.fr/catalogue_en_ligne/index.php?lvl=notice_display&id=69398 [article]

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