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''Niebla dissecta '' is a fruticose lichen that grows on rocks along the Pacific Coast of California, in San Mateo County and in the Channel Islands. The epithet, '' dissecta'' is in reference to the thallus repeatedly divided into branches.〔Spjut, R. W. 1996. ''Niebla'' and ''Vermilacinia'' (Ramalinaceae) from California and Baja California. Sida Bot. Misc. 14.〕 ==Distinguishing Features== ''Niebla dissecta'' is recognized by the thallus broader than tall—not more than 4 cm high, divided into many narrow partly subterete but mostly irregular 3-angled branches that arise from a common attachment area, blackened slightly around the base to a short distance above, the 3 longitudinal ridges spirally twisted 90° at frequent but irregular intervals, the primary branches often more compressed and broader where they divide more or less equally into secondary branches that ultimately divide again and spread as much as 180°.〔World Botanical Associates, ''Niebla dissecta'', retrieved 20 Dec 2014, http://www.worldbotanical.com/niebla_dissecta.htm#dissecta〕 Lichen substance are sekikaic acid, with accessory triterpenes, in contrast to divaricatic acid in ''Niebla testudinaria''. Determination of the secondary metabolites helps distinguish these species in the Channel Islands (Santa Cruz Island) and in the Santa Ynez Mountains where they appear morphologically intermediate.〔''Niebla testudinaria'', World Botanical Associates, web page, retrieved 20 Dec 2014; images of specimens collected by Charis Bratt, numbers 6451, 7202; http://www.worldbotanical.com/niebla_testudinaria.htm〕〔''Niebla siphonoloba'', World Botanical Associates, web page, retrieved 20 Dec 2014, http://www.worldbotanical.com/niebla_siphonoloba.htm〕 The branches of the intermediate or putative hybrid is not as clearly 3-ridged, twist more frequently, and have smaller and more frequent crater-like depressions between the longitudinal ridges (see also Photo 38.6 in Spjut 1996).〔 The type (biology) specimen of ''Niebla dissecta'' also appears to be a hybrid or intermediate form to ''Niebla disrupta''. It has the relatively broad thallus, the 3-angled branches, the dilated branching node-like areas (plant stem), and the wide spreading terminal branches that characterizes the species, but unlike the Channel Island specimens, its longitudinal ridges are more sharply angled, and the subterminal apothecia have extended branches as seen in ''N. disrupta''.〔 As in most species of ''Niebla'', there is a common set of morphological traits shared throughout the range of a species, while one or more of the individual character features may vary from one location to another; as a result the individual species have been referred to as shape shifters.〔''Niebla'' and ''Vermilacinia'' of Baja California, web page, retrieved 20 Dec 2014, http://www.worldbotanical.com/lichens.htm〕 The variation appears related to the associated species. ''Niebla dissecta'' is just one example that also includes a morph〔Morph: distinct variant of a species.〕 similar to ''Niebla cornea''(Photo 9.4 in Spjut 1996).〔 The association of ''Niebla'' species at each geographical location might be viewed as the ''Niebla'' collective in that each appears to have a unique set of morphological and chemical features not seen at other locations, the exceptions being the isidiate species and those that appear to be recent colonizers or occur at the extreme range of the genus (see p. 20–24 in Spjut 1996).〔 On San Nicolas Island, for example, are two distinct species of ''Niebla'' without intermediate morphological forms. ''Niebla ramosissima'' and ''Niebla dactylifera''; both contain despsites, one has sekikaic acid, the other divaricatic acid.〔 However, it should be noted that the morphological variation in ''Niebla'' is also viewed has highly “plastic.”〔Bowler, P. and J. Marsh. 2004. ''Niebla''. ‘Lichen Flora of the Greater Sonoran Desert 2’: 368–380.〕 The 42 species recognized in the genus〔 are treated as just three species. Two of the species,''Niebla homalea'' and ''Niebla josecuervoi'', are distinguished by chemistry, depsidones (''Niebla josecuervoi'') and depsides (''Niebla homalea''),〔 which also includes the acid deficient ''Niebla homaleoides'' considered to be more related to species with depsidones;〔Lichen Flora of the Greater Sonoran Desert: Book Review, Richard Spjut, web page, retrieved 20 Dec 2014; http://www.worldbotanical.com/lichen%20flora%20review.htm〕 ''N. dissecta'' is included in the depside group. This view implies that there are no geographical patterns to the morphological variation; i.e. , the morphological variation is purely random due to genetic and environmental factors. But it is not random; the California Nieblas with sekikaic acid, which are more common in the Channel Islands than on the mainland, exhibit an evolutionary pattern in the Channel Islands from sparingly branched thalli with prismatic branch forms (''Niebla siphonoloba''), to uniformly dissected thalli (''N. dissecta''), to thalli more densely branched near apex (''N. dactylifera'').〔''Niebla'' and ''Vermilacinia'' of Baja California, World Botanical Associates, web page, retrieved 20 Dec 2014; http://www.worldbotanical.com/lichens.htm〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Niebla dissecta」の詳細全文を読む スポンサード リンク
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