Variation in growth rates between populations of Scorpidium scorpioides with different habitats

Abstract

Growth rates of five populations of the rich-fen bryophyte species Scorpidium scorpioides were measured under field conditions and in a ‘common garden’ experiment in Ireland to investigate the importance of inherent population differences and habitat factors in natural differences in growth capacity.

In the field, growth in length and dry weight ranged from 1.8 to 8.1 em and 3.6 to 19.5 mg per plant per year. The differences between plants from different populations cultivated in the laboratory were much smaller, ranging from 3.5 to 4.9 em and 6.5 to 11.7 mg per plant in nine months and they differed in detail from the field assessments. The large differences in growth rates in the field are probably mainly attributable to habitat factors, rather than to genetically based differences in growth capacity.

High growth rates in S. scorpioides seem to be associated with high water levels, a relatively high mineral status (Ionic Ratio) and possibly an (moderately) increased supply of nutrients. Lower rates of growth may be found in places with large amounts of Fe, a low Ionic Ratio and/or regularly low water levels.