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- Title
SCALE DEPENDENCE OF REPRODUCTIVE FAILURE IN FRAGMENTED ECHINACEA POPULATIONS.
- Authors
Wagenius, Stuart
- Abstract
I investigated reproduction in a three-year study of Echinacea angustifoIia, purple coneflower, growing in a fragmented prairie landscape. I quantified the local abundance of flowering conspecifics at individual-based spatial scales and at a population-based spatial scale. Regression analyses revealed that pollen limitation increased while seed set and fecundity decreased with isolation of individual plants. Isolation, defined as the distance to the kth nearest flowering conspecific, was a good predictor of pollen limitation, for all nearest neighbors considered (k = 1-33), but the strength of the relationship, as quantified by R², peaked at intermediate scales (k = 2-18). The relationship of isolation to seed set and fecundity was similarly strongest at intermediate scales (k = 3-4). The scale dependence of individual density effects on reproduction (density of flowering plants within x meters) resembled that of isolation. Analyses at a population-based scale showed that pollen limitation declined significantly with population size. Seed set and fecundity also declined with population size, but significantly so only in 1998. Whether quantifying local abundance with population- or individual-based measures, reproductive failure due to pollen limitation is a consistent consequence of Echinacea scarcity. However, individual-based measures of local abundance predicted pollen limitation from a wider sample of plants with a simpler model than did population size. Specifically, the largest site, a nature preserve, is composed of plants with intermediate individual isolation and, as predicted, intermediate pollen limitation, but its large population size poorly predicted population mean pollen limitation.
- Subjects
ECHINACEA (Plants); PLANT reproduction; SEX in plants; ANGIOSPERMS; REGRESSION analysis; PLANT populations; FRAGMENTED landscapes; PLANT habitats; PLANT ecology
- Publication
Ecology, 2006, Vol 87, Issue 4, p931
- ISSN
0012-9658
- Publication type
Article
- DOI
10.1890/0012-9658(2006)87[931:SDORFI]2.0.CO;2