Southgate, Andrea , Wagenius, Stuart .
How population size influences the effect of inbreeding and outbreeding on early plant traits in the prairie native Echinacea angustifolia (Asteraceae).
Fragmentation of historically continuous landscapes, such as the tallgrass prairie, into smaller patches often reduces population fitness due to inbreeding. Habitat restoration efforts often increase interpopulation gene flow, which may increase fitness (genetic rescue, hybrid vigor) or decrease fitness (outbreeding depression). To investigate the role of remnant population size on the fitness expression of inbreeding and outbreeding, we established a common garden of Echinacea angustifolia plants from seven prairie remnants ranging in size from thirteen to over two thousand flowering plants. We hand- pollinated parental plants to produce progeny of three cross-types: the same family (inbred), the same population (random), and different populations (outbred). We weighed and germinated 1542 seeds, grew the seedlings in a greenhouse, and then in a common garden in western Minnesota. When the seedlings were 14, 21, 28, 35, and 133 days old, we assessed survival and measured every leaf. We found the tallest leaf of inbred plants was significantly shorter than in outbred plants by up to 15%. Inbred mortality was 37% and 44% higher on days 28 and 35, respectively, compared to outbred mortality. However, our generalized linear models revealed that this pattern was not consistent among populations, nor was it related to population size. For example, for total leaf height on day 14, outbred plants were only significantly taller than inbred plants for three of the seven populations, the second and third largest and the smallest populations. Neither achene masses nor abnormal cotyledons were significantly related to cross-type. Our study shows that the expression of inbreeding depression varies among traits, seedling ages, and populations. In most populations where inbreeding depression is significant, outcrossing can ameliorate the reduced fitness in the first generation of offspring.
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1 - Chicago Botanic Garden, The Institute for Plant Conservation Biology, 1000 Lake Cook Rd, Glencoe, IL, 60022, USA
2 - Chicago Botanic Garden, Cons Sci Department, 1000 Lake Cook Rd, Glencoe, Illinois, 60022, USA
Presentation Type: Oral Paper:Papers for Topics
Location: PDR 4/Hilton
Date: Monday, July 9th, 2007
Time: 11:00 AM