Tidepool Copepod

Longterm hybrid

Interpopulation crosses in T. californicus typically result in F1 hybrid vigor and F2 hybrid breakdown. Fitness of hybrids in later generations is less well known. Fitness may continue to decrease as recombination further breaks up beneficial gene combinations, or fitness may increase as selection promotes those few hybrid gene combinations that are beneficial.

We conducted a pilot study of the genetic composition of hybridizing populations maintained over one year (Edmands et al. 2005). Results suggest that hybrid inferiority in early generations gave way to hybrid superiority in later generations.

Postdoc Vicky Pritchard is currently conducting a much larger hybridization study with morphology, fitness and genetic composition assessed at regular intervals. Ph.D. student Annie Hwang is looking specifically at how the long-term consequences of hybridization are impacted by environmental stress.

Understanding how the effects of hybridization change over many generations is critical to assessing the role of hybridization in generating novelty and the likelihood of speciation through hybridization. The work also has implications for the likely impact of introgression on threatened populations.