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Articles 1 - 5 of 5
Full-Text Articles in Biology
Interspecific Competition For Pollination Lowers Seed Production And Outcrossing In Mimulus Ringens, John M. Bell, Jeffrey D. Karron, Randall J. Mitchell
Interspecific Competition For Pollination Lowers Seed Production And Outcrossing In Mimulus Ringens, John M. Bell, Jeffrey D. Karron, Randall J. Mitchell
Randall J. Mitchell
Sympatric plant species with similar flowering phenologies and floral morphologies may compete for pollination, and as a consequence potentially influence each other's reproductive success and mating system. Two likely competitors are Mimulus ringens and Lobelia siphilitica, which co-occur in wet meadows of central and eastern North America, produce blue zygomorphic flowers, and share several species of bumble bee pollinators. To test for effects of competition for pollination, we planted experimental arrays of Mimulus ringens, each consisting of genets with unique combinations of homozygous marker genotypes. In two arrays we planted mixtures of Mimulus and Lobelia. and in two additional arrays …
Competition For Pollination Between An Invasive Species (Purple Loosestrife) And A Native Congener, Beverly J. Brown, Randall J. Mitchell, Shirley A. Graham
Competition For Pollination Between An Invasive Species (Purple Loosestrife) And A Native Congener, Beverly J. Brown, Randall J. Mitchell, Shirley A. Graham
Randall J. Mitchell
Invasive species are frequently regarded as Superlative competitors that can vegetatively crowd Out natives, but little is known about whether invasives call compete for pollination services with native plants. We hypothesized that, when the showy invasive species Lythrum salicaria (purple loosestrife) was present, pollinator visitation and seed set would be reduced in a native congener, L. alatum (winged loosestrife). To test this hypothesis, we constructed mixed and monospecific plots of the two species. Over two years of study, we found that L. salicaria significantly reduced both pollinator visitation and seed set in L. alatum. Furthermore, pollinators moved frequently between the …
Heritability Of Nectar Traits: Why Do We Know So Little?, Randall J. Mitchell
Heritability Of Nectar Traits: Why Do We Know So Little?, Randall J. Mitchell
Randall J. Mitchell
Although floral and extrafloral nectar traits are important for plant reproduction and defense, we know little about their genetic basis. Only a handful of studies have quantified heritable variation for nectar traits, primarily in controlled environments that minimize environmental variation. Most such studies have reported strong genetic influences, with heritabilities often >0.35. However, because nectar traits are often very responsive to environmental variation, even substantial amounts of genetic variation may be swamped out in the,field. Environmental variation deserves to be studied in its own right, including exploration of genotype X environment interaction for nectar traits . Most genetic studies of …
Effects Of Population Size And Density On Pollinator Visitation, Pollinator Behavior, And Pollen Tube Abundance In Lupinus Perennis, Christopher Bernhardt, Randall Mitchell, Helen Michaels
Effects Of Population Size And Density On Pollinator Visitation, Pollinator Behavior, And Pollen Tube Abundance In Lupinus Perennis, Christopher Bernhardt, Randall Mitchell, Helen Michaels
Randall J. Mitchell
Both the number and the density of flowering plants in a population can be important determinants of pollinator abundance and behavior. We report the joint effects of population size and density on pollinator visitation and pollination success for Lupinus perennis (Fabaceae). Focusing on five pairs of populations, we matched one small population (125-800 flowering plants) with one distinctly larger population (1000-3000 flowering plants). In these pairs, population size did not affect pollinator communities or pollination success. All measures of pollination success increased significantly with density. Only bee behavior (number of flowers probed per inflorescence) exhibited a significant interaction of size …
Pollinator Selection, Quantitative Genetics, And Predicted Evolutionary Responses Of Floral Traits In Penstemon Centranthifolius (Scrophulariaceae), Randall J. Mitchell, Ruth G. Shaw, Nickolas M. Waser
Pollinator Selection, Quantitative Genetics, And Predicted Evolutionary Responses Of Floral Traits In Penstemon Centranthifolius (Scrophulariaceae), Randall J. Mitchell, Ruth G. Shaw, Nickolas M. Waser
Randall J. Mitchell
Much of the remarkable diversity of angiosperm flowers is thought to have evolved in response to selection by animal pollinators. Selection during pollination can readily be documented, but the extent to which it leads to evolutionary change depends on the genetic basis of floral traits. Here we combine estimates of genetic variance and covariance for several traits of flowers and inflorescences in a wild plant species, with estimates of natural selection by hummingbird pollinators. Analysis of phenotypic selection through two components of pollination success indicates direct selection of plants toward larger size and toward bearing shorter flowers that produce more …