The effects of ozone pollution on the perennial grass species Anthoxanthum odoratum L. were investigated in terms of ozone sensitivity to contrasting ozone pollution scenarios and intraspecific variation in relation to population genetic diversity. Four populations from North Wales, UK, were exposed to three ozone exposure profiles representing acute exposure and simulated current and future scenarios for both rural and upland areas. Population genetic diversity and differentiation were estimated for the nuclear genome using Amplified Fragment Length Polymorphism (AFLP) and microsatellite loci developed in this study using a streptavidin-biotin enrichment technique. Genetic variation within the chloroplast genome was assessed using Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP) and chloroplast microsatellite loci.
A. odoratum was sensitive to ozone exposure in terms of premature senescence
exhibiting a relatively fast response under all ozone profiles investigated. Exposure to chronic rural and upland ozone profiles demonstrated that elevated background concentrations may result in a similar or greater senescence response to increased ambient peak episodes. The development of premature senescence was only accompanied by significant reductions in above ground biomass under acute exposure. However, a trend for greater reduction in root biomass was also observed indicating a shift in resource allocation. The maintenance of shoot growth observed under chronic exposure may have also resulted from a reduction in resource allocation to root growth.
Intraspecific variation in response was observed with the four populations differing in response to elevated ozone dependant on the assessment criteria applied and the timing of exposure in relation to the growing season and phenological stage.
AFLP and microsatellite markers revealed high levels of intrapopulation genetic
diversity with low levels of population genetic differentiation maintained by high levels of pollen-mediated gene flow. Chloroplast markers also revealed high levels of intrapopulation genetic diversity although population differentiation was substantially greater indicating greater restrictions to seed-mediated gene flow between populations.