Cirsium eatonii

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Cirsium eatonii is a polymorphic species widely distributed in a high elevation archipelago across the central Rocky Mountains and the Intermountain Region. During Pleistocene glacial episodes, the progenitors of this species complex undoubtedly occupied lower elevation sites and likely had more contiguous populations. Post-glacial isolation of these populations in allopatric high elevation sites has allowed them to differentiate to a greater or lesser extent. Prehistoric or recent introgressive hybridization with other thistle species probably has contributed to the diversification of the complex (R. J. Moore and C. Frankton 1965). Several of the races recognized here as varieties have been treated in the past as species (e.g., C. clokeyi, C. peckii). Their current geographic isolation and more or less distinctive features might support such recognition, but application of this approach across the complex would result in a proliferation of microspecies.

Facts about "Cirsium eatonii"
apex architecture or shapespiny +
apex orientationascending + and spreading +
apex positionouter +
apex shapelinear-acicular +, entire +, plane + and spine-tipped +
array architecturesubcapitate +, spiciform +, racemiform + and branched +
base orientationshort-appressed +
blade shapeoblong +
bract shapespiny-fringed +
branch orientationascending +
caudex architecturetaprooted +
collar colorationstramineous +
collar variabilitydifferentiated +
corolla colorationochroleucous +, yellow +, lavender +, pink + and purple +
cypsela colorationbrown +
face architecturewinged-petiolate + and sessile +
face arrangementdistributed +
face countpresent + and many +
face external textureglabrous + and villous +
face otherprincipal +
face positionadaxial +, basal +, cauline + and distal +
face sizereduced +
head architecturesessile + and short-pedunculate +
head arrangementcrowded +
head orientationerect + and nodding +
involucre colorationgreen +, suffused with dark-c-purple + and purple +
involucre external texturevillous + and tomentose +
involucre shapeovoid + and campanulate +
involucre widthwider +
lobe arrangementspaced +
lobe arrangement or shapelinear +
margin arrangementoverlapping +
margin shapeundulate +, unlobed +, spiny-dentate +, pinnatifid +, lance-oblong +, triangular + and 3-lobed +
midvein external texturearachnoid-tomentose +
phyllary sizesubequal +
ridge widthnarrow +
stem architecturesimple + and branched +
stem external textureglabrous +, villous +, tomentose + and glabrate +
stem internal texturefleshy +
stem orientationerect + and ascending +
tip positionexserted +
tooth arrangementspaced +
trichome architectureseptate + and non-septate +
trichome external texturearachnoid-tomentose +
whole organism life styleperennial +