Hybridization as a Stimulus for the Evolution of Invasiveness in Plants
Snow, Allison , Campbell, Lesley G. , Pilson, Diana , Alexander, Helen , Moody-Weis, Jennifer , Ridley, Caroline .
Crop-weed hybrids with enhanced fitness: causes and consequences for weed populations.
MANY cultivated plants hybridize with wild or weedy relatives, but the ecological effects of this process are not well documented. The evolutionary fitness of crop-weed hybrid progeny is influenced by many interacting factors, including 1) partial reproductive isolation, 2) outbreeding depression, 3) heterosis, 4) crop traits that enhance fitness, and 5) the amount and duration of gene flow from crops to weed populations. We present case studies illustrating several of these factors, some of which are expected to be transient (e.g., heterosis). Over time, natural selection may purge weed populations of deleterious crop traits and in some cases the persistence of advantageous crop traits could exacerbate problems with agricultural weeds. However, only a handful of studies clearly show that hybridization can cause weed populations to become more abundant and/or more difficult to manage, and much of the evidence for this hypothesis is circumstantial. Few researchers have quantified the relative survival and lifetime fecundity of hybrids under multiple field conditions, and few have investigated whether genotypes with enhanced fitness give rise to more “invasive” weed populations. Ideally, researchers should quantify the fitness of both early and advanced generations of naturally evolving hybrid swarms and determine whether observed fitness advantages, if present, are correlated with increased rates of population growth relative to non-hybrid populations. Realistically, this is seldom feasible. We present examples of these approaches as applied to wild radish (Raphanus raphanistrum) and wild sunflower (Helianthus annuus), and we show that the introgression of crop alleles is likely to enhance “weediness” under some conditions. When possible, studies of the ecological consequences of crop-weed hybridization should incorporate models of population and metapopulation dynamics using data from experimental field studies. This would allow more rigorous investigations of how gene flow from crops affects the abundance and distribution of weed populations.
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1 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Ave., Columbus, Ohio, 43210-1293, USA
2 - University of Nebraska, School of Biological Sciences, Lincoln, Nebraska, 68588, USA
3 - University of Kansas, Department of Ecology and Evolution, Lawrence, Kansas, 66045, USA
4 - University of California Riverside, Department of Botany & Plant Sciences, Riverside, California, 92521-0124, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 8:45 AM