Centaurea alba

{{Short description|Species of flowering plant}} {{Speciesbox | image = Centaurea alba.jpg | image_caption = | genus = Centaurea | species = alba | authority = L.<ref name=IPNI>{{Cite web |title=''Centaurea alba'' |url=https://www.ipni.org/n/189825-1 |website=International Plant Names Index |publisher=The Royal Botanic Gardens, Kew, Harvard University Herbaria & Libraries and Australian National Botanic Gardens |access-date=24 September 2020}}</ref> | synonyms = | synonyms_ref = }}

'''''Centaurea alba''''' is a species of ''Centaurea'' found in the Iberian Peninsula in southern and central Spain and in a small neighbouring area in the interior of Portugal. There are three recognised subspecies, and of one subspecies, the nominate, there are furthermore three varieties.

It has been called '''pale knapweed''' in English.<ref name=EurMed>{{cite web |title=Details for: ''Centaurea alba'' in Compositae (''pro parte majore'') |url=http://ww2.bgbm.org/EuroPlusMed/PTaxonDetail.asp?UUID=7D002A0D-9C0D-44B8-9B8F-3943D59DC864 |last=Greuter |first=Werner |author-link=Werner Greuter |editor-last=Greuter |editor-first=Werner |editor2-last=von Raab-Straube |editor2-first=E. |date=2006 |website=Euro+Med Plantbase |publisher=Botanic Garden and Botanical Museum Berlin-Dahlem |access-date=25 September 2020}}</ref> Vernacular names which have been recorded for this herb in Castilian Spanish are ''calcitrapa'', ''cardo estrellado'', ''centaura estrellada'', ''garbanzos del cura'',<ref name=EurMed/><ref name=ibérica>{{cite book |last1=Devesa Alcaraz |first1=Juan Antonio |last2=López Nieto |first2=Eusebio |date=4 December 2014 |chapter='''29'''. ''Centaurea'' |chapter-url=http://www.floraiberica.es/floraiberica/texto/pdfs/16_159_029_Centaurea.pdf#page=98 |title=Flora ibérica, Vol. XVI |url=http://www.floraiberica.es/index.php |language=es |location=Madrid |publisher=Real Jardín Botánico |pages=349-350, 439-444 |isbn=978-84-00-10273-9}}</ref><ref name=ANTHOS>{{cite web |url=http://www.anthos.es/ |title=Búsquedas: ''Centaurea alba'' |author= |date=2 March 2012 |website=ANTHOS |publisher=Fundación Biodiversidad, Ministerio de Agricultura, Alimentación y Medio Ambiente, & Real Jardín Botánico |language=es |access-date=25 September 2020}}</ref> ''siempre nueva'',<ref name=EurMed/><ref name=ibérica/> ''siempre-nueva'',<ref name=ANTHOS/> and ''trapacaballos''.<ref name=EurMed/><ref name=ibérica/><ref name=ANTHOS/> Other local recorded names in Spanish are ''abreojos'', ''abrepuños'', ''amargosa'', ''amargosilla'', ''amargoso'', ''ardolla'', ''arzolla'', ''cardo abrepuños'', ''cardo de la arzolla'', ''marbosilla'', ''margosilla'', ''piropo'', ''planta para hemorroides'' and ''raíz de la arzolla''.<ref name=ANTHOS/> In the Catalan language it is known as ''raspallera'' in the Valencian dialect.<ref name=EurMed/><ref name=ibérica/><ref name=ANTHOS/>

==Taxonomy== The species was first described in the modern Linnaean system by Linnaeus himself in the first edition of the Species Plantarum, published in 1753.<ref name=IPNI/><ref name=Tropicos>{{cite web|url=http://www.tropicos.org/Name/2702120 |title=''Centaurea alba'' |website=Tropicos |access-date=28 November 2014}}</ref> It is presently placed in Augustin Pyramus de Candolle's section or subsection ''Phalolepis'', along with ''Centaurea costae'' and the much more widely distributed ''C. deusta''.<ref name=López2011>{{cite journal |last1=López Nieto |first1=Eusebio |last2=Devesa Alcaraz |first2=Juan Antonio |date=December 2011 |title=Revisión taxonómica del complejo ''Centaurea alba'' L. (Asteraceae) en la Península Ibérica |url=https://www.researchgate.net/publication/233391950 |journal=Collectanea Botanica |volume=30 |pages=37–52 |language=es |issn=0010-0730 |doi=10.3989/collectbot.2011.004 |access-date=25 September 2020|doi-access=free |hdl=10396/7780 |hdl-access=free }}</ref><ref name=Garcia2019>{{cite journal |last1=Garcia-Jacas |first1=Núria |last2=López-Pujol |first2=Jordi |last3=López-Vinyallonga |first3=Sara |last4=Janaćković |first4=Pedja |last5=Susanna |first5=Alfonso |date=4 February 2019 |title=''Centaurea'' subsect. ''Phalolepis'' in Southern Italy: ongoing speciation or species overestimation? Genetic evidence based on SSRs analyses |journal=Systematics and Biodiversity |volume=17 |issue=2 |pages=93–109 |doi=10.1080/14772000.2018.1549617|s2cid=92405872 }}</ref> In 2014 Hilpold ''et al''. redefined the infrageneric taxa, classifying the traditional section ''Phalolepis'' in the subgenus ''Centaurea''.<ref name=Hilpold2014>{{cite journal |last1=Hilpold |first1=A. |last2=Garcia-Jacas |first2=Núria |last3=Vilatersana |first3=R. |last4=Susanna |first4=Alfonso |date=2014 |title=Taxonomical and nomenclatural notes on ''Centaurea'': A proposal of classification, a description of new sections and subsections, and a species list of the redefined section ''Centaurea'' |url=http://collectaneabotanica.revistas.csic.es/index.php/collectaneabotanica/article/view/218/238 |journal=Collectanea Botanica |volume=33 |pages=e001 |doi=10.3989/collectbot.2013.v33.001 |access-date=25 September 2020|doi-access=free |hdl=10261/112538 |hdl-access=free }}</ref> Formerly the genus ''Centaurea'' was paraphyletic, because it was based on a species, ''C. centaurium'' -the type species, which was less related to the vast majority of other ''Centaurea'' than to species which were classified as belonging to other genera. In 2001 Werner Greuter solved this by moving the ''C. centaurium'' to the old, resurrected genus ''Rhaponticoides'', conserving the name ''Centaurea'' for the majority of the other species, and electing ''C. paniculata'' to serve as the new type species.<ref name=ibérica/><ref name=López2011/><ref name=Hilpold2014/>

The infraspecific taxonomy has been rather volatile since the 1970s. A large number of former subspecies were recognised at one time or another.<ref name=PoWO>{{cite web |title=''Centaurea alba'' L. |date=2017 |work=Plants of the World Online |publisher=Royal Botanic Gardens, Kew |url=http://powo.science.kew.org/taxon/189825-1 |access-date=24 September 2020}}</ref> These were synonymised over the last century or so, or are now considered independent species. *''Centaurea alba'' subsp. ''albanica'' (Halácsy) Dostál - a taxon from Albania. *''Centaurea alba'' subsp. ''brunnea'' (Halácsy) Dostál *''Centaurea alba'' subsp. ''ciliata'' (Font Quer ex O.Bolòs & Vigo) Greuter *''Centaurea alba'' subsp. ''costae'' (Willk.) Dostál *''Centaurea alba'' subsp. ''formanekii'' (Halácsy) Dostál *''Centaurea alba'' subsp. ''latronum'' (Pau) Dostál *''Centaurea alba'' subsp. ''macrocephala'' (Pau) Talavera *''Centaurea alba'' subsp. ''maluqueri'' (Font Quer) Molero & Vigo *''Centaurea alba'' subsp. ''montsicciana'' (Pau & Font Quer) Romo *''Centaurea alba'' subsp. ''strepens'' (Hoffmanns. & Link) Rocha Afonso *''Centaurea alba'' subsp. ''subciliaris'' (Boiss. & Heldr.) Dostál *''Centaurea alba'' subsp. ''tartesiana'' Talavera

In his 1976 contribution in the ''Flora Europaea'', Josef Dostál recognised subsp. ''albanica'', subsp. ''brunnea'', subsp. ''costae'', subsp. ''deusta'', subsp. ''formanekii'', subsp. ''latronum'' and subsp. ''subciliaris''.<ref name=López2011/>

A lectotype was assigned by Salvador Talavera Lozano in 1984.<ref name=López2011/>

The 2006 entry by Greuter in the Euro+Med Plantbase, based on a critical evaluation of the information from the ''Flora Europaea'' and the ''Med-Checklist'', recognised the following infraspecific taxa:<ref name=EurMed/> *''Centaurea alba'' subsp. ''ciliata'' (O. Bolòs & Vigo) Greuter *''Centaurea alba'' subsp. ''costae'' (Willk.) Dostál *''Centaurea alba'' subsp. ''latronum'' (Pau) Dostál *''Centaurea alba'' subsp. ''macrocephala'' (Pau) Talavera *''Centaurea alba'' subsp. ''maluqueri'' (Font Quer) Molero & Vigo *''Centaurea alba'' subsp. ''montsicciana'' (Pau & Font Quer) Romo *''Centaurea alba'' subsp. ''strepens'' (Hoffmanns. & Link) Rocha Afonso *''Centaurea alba'' subsp. ''tartesiana'' Talavera

In 2008 the chromosomes of the different infraspecific taxa were investigated (karyotypy). All forms are 2''n''=18, but some differences between the taxa is seen in the chromosome morphology. The species was revised again in 2011.<ref name=López2011/> The 2014 entry in the ''Flora Ibérica'' follows this interpretation, although it only briefly mentions the three varieties.<ref name=ibérica/> *''Centaurea alba'' subsp. ''alba'' var. ''alba'' *''Centaurea alba'' subsp. ''alba'' var. ''latronum'' (Pau) E.López & Devesa *''Centaurea alba'' subsp. ''alba'' var. ''macrocephala'' Pau *''Centaurea alba'' subsp. ''aristifera'' (Pau ex Vicioso) E.López & Devesa *''Centaurea alba'' subsp. ''tartesiana'' Talavera

The name ''C. deusta'', a species more widely distributed in southern Italy, Greece and Turkey,<ref name=Garcia2019/> has also historically been mistakenly said to occur in Spain, for example by Augustin Pyramus de Candolle in 1838 in the ''Prodromus'', in the 1865 issue of the ''Prodromus Florae Hispanicae'' of Heinrich Moritz Willkomm and Johan Lange, or by Carl Fredrik Nyman in his ''Conspectus Florae Europaeae'' (1878-1884).<ref name=EurMed/><ref name=López2011/> Dostál subsumed ''C. deusta'' in the ''Flora Europaea'' as ''C. alba'' subsp. ''deusta'',<ref name=López2011/> and this taxon continued to be recognised as occurring in Spain in the 2001 entry in the ''Atlas de la flora del Pirineo Aragonés''.<ref name=EurMed/>

===Hybrids=== All of the species in the subgenus ''Centaurea'' appear to be able to hybridise freely with each other,<ref name=López2011/> and ''C. alba'' is no exception.<ref name=ibérica/><ref name=López2011/> In some, but not all, of the zones where the following taxa are in contact with ''C. alba'', the following natural hybrids have been described as occurring. A cross of the nominate form with ''C. langei'' subsp. ''kheilii'' creates the hybrid ''C.'' ×''bigerrensis'', and with ''C. aristata'', ''C.'' ×''matritensis'' is created. The variety ''latronum'' is also known to cross with ''C. calcitra'', creating ''C.'' ×''eliasii'', recognisable by having its involucral bracts being tipped by a large and sharp spine.<ref name=ibérica/> Another hybrid of the species has also recently (2009) been described from a 1988 collection in an industrial zone in the Province of Soria: ''Centaurea'' ×''soriana'' A.Segura ex Mateo & M.B.Crespo.<ref name=IPNI/><ref name=IPNI2>{{Cite web |title=''Centaurea'' × ''soriana'' |url=https://www.ipni.org/n/77095468-1 |website=International Plant Names Index |publisher=The Royal Botanic Gardens, Kew, Harvard University Herbaria & Libraries and Australian National Botanic Gardens |access-date=24 September 2020}}</ref> The other parent of the hybrid is ''C. paniculata'' subsp. ''castellana''.<ref name=IPNI2/> Lastly, in the Province of Soria relatively frequently transitional forms between the nominate variety ''alba'' with ''C. alba'' subsp. ''aristifera'' can be encountered.<ref name=ibérica/>

==Description== It is most similar to ''Centaurea costae'', being mainly distinguished by the shape of the involucral bracts. ''C. costae'' has bilobed bracts.<ref name=ibérica/><ref name=López2011/> *''Centaurea alba'' subsp. ''alba'' - *''Centaurea alba'' subsp. ''aristifera'' - *''Centaurea alba'' subsp. ''tartesiana'' -

==Distribution== It only occurs on the Iberian Peninsula, being found at generally inland sites in central, central-north, central-western y southwestern parts of the Peninsula. In Spain it is found in the provinces of Ávila, Badajoz, Burgos, Cádiz, Cáceres, Ciudad Real, Cuenca, Guadalajara, Huelva, León, Madrid, Salamanca, Sevilla, Segovia, Soria, Toledo, Valladolid, Zaragoza and Zamora. In Portugal it occurs in Beira Baixa and Ribatejo Province.<ref name=ibérica/><ref name=López2011/> The different subspecies and varieties now recognised are largely not sympatric and have discreet geographical distributions. Two taxa have disjunct distributions, subsp. ''tartesiana'' to the south of the main distribution, and var. ''macrocephala'' further to the south of that, at the southernmost tip of continental Spain.<ref name=López2011/>

For a long time it was believed to grow in northeast Algeria. According to López this was originally based on a single sheet of a specimen in the personal herbarium of Georges Rouy, collected in Segovia in 1905, but apparently accidentally included in the section ''Plantes d’Algérie'' of the herbarium. It is one of five duplicates, one of which is the lectotype of the subspecies ''alba'' synonym ''Centaurea segoviensis''.<ref name=López2011/><ref name=APD>{{cite web |url=http://www.ville-ge.ch/musinfo/bd/cjb/africa/details.php?langue=an&id=197403 |title=''Centaurea alba'' L. |author= |date=27 December 2008 |website=African Plants Database |publisher=Conservatoire et Jardin botaniques & South African National Biodiversity Institute |access-date=25 September 2020}}</ref><ref name=FlMaghreb>{{cite web |url=https://efloramaghreb.org/specie/197403 |title=''Centaurea alba'' L. |author= |website=eflore Maghreb |language=fr |access-date=25 September 2020}}</ref> However, ''C. alba'' var. ''mauritanica'' had already been described by Jules Aimé Battandier in his 1889 ''Flore de l'Algérie'' as growing in Algeria, and an Algerian population of ''Centaurea'' was called as ''C. alba'' in the local flora until the 2000s, for example in the 1963 ''Nouvelle flore d'Algérie'',<ref name=APD2>{{cite web |url=http://www.ville-ge.ch/musinfo/bd/cjb/africa/details.php?langue=an&id=197403 |title=''Centaurea alba'' var. ''mauritanica'' Batt. |author= |date=2012 |website=African Plants Database |publisher=Conservatoire et Jardin botaniques & South African National Biodiversity Institute |access-date=25 September 2020}}</ref><ref name=Quézel1963>{{cite web |url=https://www.ville-ge.ch/cjb/flore/html/QSv2-ASTERACEAE.htm#Centaurea |title=''Centaurea'' |author= |date=September 2018 |website=Flore du Maghreb - basé sur la "Nouvelle flore d'Algérie et des régions désertiques méridionales" de Pierre Quézel et S. Santa 1963, version 2.2 |publisher=Conservatoire et Jardin botaniques |language=fr |access-date=25 September 2020}}</ref> or the 1985 French collection on the Djebel Ich Ali near Tazoult in Batna wilaya.<ref name=FlMaghreb/> This population is now seen as a synonym of ''C. djebel-amouri'', which was only recently described as a new species by Greuter in 2003; the previous name ''C. alba'' for the population is now attributed as "auct. Afr. N. non L.".<ref name=FlMaghreb/><ref name=APD2/>

Plants from Italy, France and possibly Albania have also historically been misidentified as ''C. alba''.<ref name=EurMed/>

*''Centaurea alba'' subsp. ''alba'' **''C. alba'' subsp. ''alba'' var. ''alba'' - **''C. alba'' subsp. ''alba'' var. ''latronum'' - **''C. alba'' subsp. ''alba'' var. ''macrocephala'' - A disjunct population restricted to the southernmost tip of Spain, from the mouth of the Guadalquivir emptying in the Gulf of Cádiz northeastwards into the Baetic Depression, entirely within the Province of Cádiz.<ref name=RedListAnda>{{cite book |last1=Cabezudo |first1=B. |last2=Talavera |first2=S. |last3=Blanca |first3=G. |last4=Salazar |first4=C. |last5=Cueto |first5=M.J. |last6=Valdés |first6=B. |last7=Hernández Bermejo |first7=J.E. |last8=Herrera |first8=C. |last9=Rodríguez Hiraldo |first9=C. |last10=Navas |first10=D. |date=2005 |title=Lista roja de la flora vascular de Andalucía |url=http://www.anthos.es/docs/Phyteia/LYL_AND_02.pdf |location=Sevilla |publisher=Consejería de Medio Ambiente, Junta de Andalucía |pages=94, 95 |language=es |isbn=84-96329-62-3}}</ref> *''Centaurea alba'' subsp. ''aristifera'' - *''Centaurea alba'' subsp. ''tartesiana'' - An endemic of the northwest corner of Andalusia. It occurs in the western part of the Sierra Morena mountain range, in the provinces of Huelva and Sevilla.<ref name=RedListAnda/>

==Ecology== It blooms from April to October. This species inhabits woodland clearings and the fringes of forests,<ref name=ibérica/><ref name=López2011/> especially pine forests, oak forests and ''melojares'' (''Quercus pyrenaica'' forests),<ref name=López2011/> as well as growing in matorral, wasteland and gutters, slopes and wayside verge habitat along roads. It has been recorded growing at 3 to 2,000 metres in altitude.<ref name=ibérica/><ref name=López2011/> It prefers somewhat fertile soils,<ref name=ibérica/> or not excessively fertilised,<ref name=López2011/> which can be acidic to alkaline.<ref name=ibérica/> It is usually found growing in rocky, large-grained soil, very often calcareous mixed with silicates.<ref name=López2011/> The ''macrocephala'' variety occurs in matorral habitats on substrates derived from calcarenite and limestone. The ''tartesiana'' subspecies occurs in slate-based soils and marl.<ref name=RedListAnda/>

==Conservation== In 1992 two subspecies, subsp. ''heldreichii'' and subsp. ''princeps'', were designated as 'priority species' under Annex II of the Habitats Directive of the European Community (which was reformed as the European Union the following year). This designation was meant to serve as the basis for Spain to declare which areas in which it occurs were 'Special Areas of Conservation' -which were to form the backbone of the Natura 2000 network, but only if these areas include one of the number of habitats listed in Annex I of the directive.<ref name=EurLex1992>{{Cite web|url=https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:31992L0043&from=EN|title=Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora |website=Eur-Lex |access-date=24 September 2020}}</ref> Neither subspecies are still recognised.

In 2005 the flora of Andalusia was assessed for the ''Lista roja de la flora vascular de Andalucía'', with two subspecies, subsp. ''tartesiana'' and subsp. ''macrocephala'', being included in the list. These two taxa were assessed as 'data deficient', but were included because they have restricted distributions and the authors thought that they might be threatened, or at least impacted, by changes in agriculture.<ref name=RedListAnda/>

==References== {{Reflist}}

==External links== *{{Commons-inline|2=''Centaurea alba''}} *{{Wikispecies-inline|Centaurea alba|''Centaurea alba''}}

alba Category:Plants described in 1753 Category:Botanical taxa named by Carl Linnaeus