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EVOLUTIONARY MORPHOLOGY: DISTINGUISHING ANCESTRAL STRUCTURE FROM DERIVED STRUCTURE IN FLOWERING PLANTS
Author(s) -
Eyde Richard H.
Publication year - 1971
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.2307/1218535
Subject(s) - biology , morphology (biology) , character evolution , pollen , taxon , plant evolution , systematics , fossil record , evolutionary biology , xylem , character (mathematics) , ecology , phylogenetics , botany , zoology , taxonomy (biology) , clade , biochemistry , geometry , mathematics , genome , gene
Summary Certain structural changes have occurred repeatedly in the evolution of flowering plants. Evidence for these evolutionary trends is often in the form of character gradients or morphoclines, within which the direction of change can be inferred from paleobotanical, geographical, or ecological circumstances. No trends are more firmly established than those involving microscopic characters of the secondary xylem, trends for which the ancestral condition is known from fossil evidence. Recently, trends in the evolution of angiospermous pollen grains have also been convincingly demonstrated from the fossil record. Since postulated evolutionary trends in floral structure cannot be verified in the same manner, floral anatomy has always been a controversial subject. Despite the controversy, the anatomical investigation of flowers benefits systematics in at least two ways: by revealing characters of potential taxonomic value and, when floral vascular bundles of related taxa are united in varying degree, by indicating the direction of evolutionary change.