Can an increased copper requirement in copper‐tolerant Mimulus guttatus explain the cost of tolerance?

Abstract

SUMMARYIf metal tolerant plants, by virtue of their tolerance mechanism, are less efficient at the uptake, distribution or utilization of metals then essential micronutrient deficiency may occur at the low levels of metal supply found on non-mine soils. This argument forms the basis of the metal requirement hypothesis put forward to explain the lower fitness of tolerant individuals on uncontaminated soil, the so called 'cost of tolerance'. In this paper, copper balance was investigated in Mimulus guttatus Fischer ex. DC (the yellow monkey fiower) for plants with or without the major tolerance gene which confers primary tolerance, and plants with few or many modifier genes which control degree of tolerance. No conclusive evidence to support an increased copper requirement in plants with the major tolerance gene, and/or many modifier genes was shown. Any differences in copper requirement found during vegetative growth were small, and were deemed insufficient to explain the apparent cost of tolerance.

Copper tolerance in the cuprophyte Haumaniastrum katangense (S. Moore) P.A. Duvign. & Plancke

“…On the contrary, copper tolerant and non-tolerant genotypes of Mimulus guttatus were similarly affected by decreasing copper supply, which is against the cost of living in the presence of copper excess. Mechanisms underlying a higher requirement of copper in cuprophytes need further study (Harper et al 1997(Harper et al , 1998. In Zn hyperaccumulators, the higher Zn requirement is proposed to be related to efficient sequestration mechanisms and deregulated Zn deficiency response (reviewed in Verbruggen et al 2009).…”

Life-history consequences of adaptation to pollution. “Daphnia longispina clones historically exposed to copper”

“…A detoxification mechanism might use energy and other resources that are then unavailable for other fitness traits such as growth and reproduction (Sibly and Calow 1989). Alternatively, resistant individuals might be less efficient at metal uptake, thus leading to micronutrient deficiency in unpolluted environments (Harper et al 1997). Field and laboratory studies suggest that metal tolerant plants have a selective disadvantage in low metal environments; however, it is possible that plants adapted to mine environments are also resistant to other mine stressors, such as low nutrient levels and increased susceptibility to drought (Harper et al 1997).…”

“…Alternatively, resistant individuals might be less efficient at metal uptake, thus leading to micronutrient deficiency in unpolluted environments (Harper et al 1997). Field and laboratory studies suggest that metal tolerant plants have a selective disadvantage in low metal environments; however, it is possible that plants adapted to mine environments are also resistant to other mine stressors, such as low nutrient levels and increased susceptibility to drought (Harper et al 1997). Evidence for evolution and fitness costs of metal tolerance in invertebrates is not as evident as in plants.…”

Productivity differences between dandelion (Taraxacum officinale; Asteraceae) clones from pollution impacted versus non-impacted soils

“…Although pollution tolerant plants may have a selective advantage in contaminated soils, they are often much smaller in size, produce fewer seeds (often of poorer quality), have a lower biomass production and have lower flowering potential compared with conspecifics from uncontaminated soils when both are grown in uncontaminated soil (Pollard 1980;Wilson 1988;Wu 1990;Harper et al 1997;Stanton et al 2000). It has also been shown that metal-tolerant plants in some instances can be inferior to intolerant plants when grown on uncontaminated ("normal") soil (Cook et al 1971;Hickey and McNeilly 1975).…”