Deduke, Chris , Piercey-Normore, Michele D. .
Trade-off between sexual fecundity and secondary compounds in three Shield lichens.
In pioneer species energy is typically allocated to sexual reproduction for rapid colonization of a disturbed habitat such as exposed soil or rock substrata. The exposed bedrock of the Precambrian Shield is subjected to intense solar radiation and desiccation for its lichen inhabitants. These conditions may trigger production of secondary metabolites that help the lichens tolerate abiotic stresses. An increase in number of apothecia and spores with a reduction in the quantity of secondary metabolites might reflect a trade-off between fecundity and secondary metabolite production in lichens. The goal of this study was to investigate the biological trade-off in three Shield lichens Arctoparmelia centrifuga, Xanthoparmelia viriduloumbrina and X. cumberlandia. Field collections were made from thirty-nine transects across Manitoba and northern Ontario. More than 300 apothecia were collected and monitored for spore numbers and germination over a 20-week period (A. centrifuga (54), X. viriduloumbrina (122) and X. cumberlandia (131)). Presence and quantity of secondary metabolites was determined from quantified thin layer chromatography, with thallus samples standardized at 5.0 mg. Pairwise regression between sexual reproduction and secondary metabolites, and between different secondary metabolites, tested whether significant trade-offs were present. Principal component analysis explored the data for other relationships among the variables measured. Preliminary analysis shows species-specific relationships between sexual reproduction and secondary metabolites. X. cumberlandia showed an increase in a medullary compound at the expense of apothecia production and maximum spore count. There is a significant relationship between a cortical compound and maximum number of spores produced in A. centrifuga. A significant relationship was found between maximum spore count and number of apothecia produced by X. viriduloumbrina and X. cumberlandia. Finally, there were positive relationships between different secondary compounds in all three species. The apparent independence of medullary and cortical compounds in A. centrifuga could reflect a genus-specific adaptation towards the interception of solar radiation not present in Xanthoparmelia. The findings are significant because they suggest that a trade-off does exist between sexual reproduction and secondary metabolite production in Shield lichens. Further studies on substrate nutrients, photobiont availability, and community composition will contribute to a better understanding of the biology of Shield lichens.
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1 - University of Manitoba, Department of Biological Sciences, Winnipeg, MB, r3t2n2, Canada
Presentation Type: Poster:Posters for Sections
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM