Premium
THE ECOLOGICAL NICHE OF DAPHNIA MAGNA CHARACTERIZED USING POPULATION GROWTH RATE
Author(s) -
Hooper Helen L.,
Con Richard,
Callaghan Amanda,
Fryer Geoffrey,
Yarwood-Buchanan Sarah,
Biggs Jeremy,
Maund Steve J.,
Hutchinson Thomas H.,
Sibly Richard M.
Publication year - 2008
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/07-0559.1
Subject(s) - niche , ecology , population , ecological niche , biology , latitude , extinction (optical mineralogy) , geography , habitat , paleontology , demography , geodesy , sociology
The concept of an organism's niche is central to ecological theory, but an operational definition is needed that allows both its experimental delineation and interpretation of field distributions of the species. Here we use population growth rate (hereafter, pgr) to define the niche as the set of points in niche space where pgr > 0. If there are just two axes to the niche space, their relationship to pgr can be pictured as a contour map in which pgr varies along the axes in the same way that the height of land above sea level varies with latitude and longitude. In laboratory experiments we measured the pgr of Daphnia magna over a grid of values of pH and Ca 2+ , and so defined its “laboratory niche” in pH–Ca 2+ space. The position of the laboratory niche boundary suggests that population persistence is only possible above 0.5 mg Ca 2+ /L and between pH 5.75 and pH 9, though more Ca 2+ is needed at lower pH values. To see how well the measured niche predicts the field distribution of D. magna , we examined relevant field data from 422 sites in England and Wales. Of the 58 colonized water bodies, 56 lay within the laboratory niche. Very few of the sites near the niche boundary were colonized, probably because pgr there is so low that populations are vulnerable to extinction by other factors. Our study shows how the niche can be quantified and used to predict field distributions successfully.