Ecological genomics of species invasions: Identifying adaptation, hybridization, and genetic tradeoffs in invading lineages

Background/Question/Methods

Invasive species are defined by their ability to establish populations in new locations, yet novel environments will often pose unique challenges in terms of the nature, pattern, or severity of stresses faced by the colonizers. The Sunflower (Compositae, or Asteraceae) family of plants includes many of the worlds most notorious invaders, and provides examples of aggressive, colonizing lineages arising from more benign native populations. We are using comparative and population genomic techniques to gain insight into the traits that facilitate the establishment and local adaptation of these species, with particular attention to the evolution of responses to environmental stresses. To do this, we are employing common garden, gene expression, transcriptome (EST) sequencing, and association mapping approaches.

Results/Conclusions

Results to date indicate that changes in stress response have been a significant feature of evolution in some weedy and invasive populations. Focusing in particular on yellow starthistle (Centaurea solstitialis, Compositae), a noxious invader of grasslands in Mediterranean climates, we report genomic evidence that loci afffecting growth and stress reponse pathways are evolving under novel selection pressures in invading populations, and that cryptic hybridization may be contributing to invasive phenotypes. We are currently mapping the genetic basis for increased growth rates observed among invading genotypes. We also report on several methodological issues for which we have released freely-available software, including the editing and assembly of 454 next-generation cDNA sequence data, and the comparison of genetic variation among individuals with incomplete genomic information.