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Life History Studies on the Genus Trillium (Liliaceae) VI. Life History Characteristics of Three Western North American Species and Their Evolutionary‐Ecological Implications
Author(s) -
KAWANO SHOICHI,
OHARA MASASHI,
UTECH FREDERICK H.
Publication year - 1992
Publication title -
plant species biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 36
eISSN - 1442-1984
pISSN - 0913-557X
DOI - 10.1111/j.1442-1984.1992.tb00239.x
Subject(s) - biology , ecology , habitat , genus , shrub , deciduous , juvenile
Life history characteristics of three western North American Trillium species, i. e., T. ovatum (Pedicellate‐group), T. albidum and T. petiolatum (both Sessile‐group), were critically investigated and compared. The stage‐class structure, based upon leaf area, of populations of the three species all were indicative of stable populations, even though the species occurred in contrastingly different habitat conditions. Trillium ovatum occurred in the deep shade of mesic coniferous forests on mountain ridges or slopes. Trillium albidum was found in exceedingly damp sandy‐loam soils in deciduous forests developed on the lowland flood plains. Trillium petiolatum occurred on dry rocky or gravelly shrub‐dominant areas. There was a gradual but conspicuous decrease in the number of individuals in the early juvenile stages, followed by similar numbers of plants in the intermediate stages and mature flowering stages. Recruitment of offspring appears to be exclusively dependent upon sexual reproduction in all three species, since none of the species formed vegetative offshoots as found in some sessile group species occurring in eastern as well as western North America. Analysis of spatial distributions within the populations of T. ovatum and T. petiolatum revealed successive changes from aggregated (juveniles) to random (intermediate stages), and overdis‐persed (flowering plants) distributions. The evolutionary‐ecological relationships of these three species are compared with those of 27 other Trillium species.