The utilization of nitrogen from insect capture by different growth forms of Drosera from Southwest Australia.
Plants of Drosera species, neighbouring noncarnivorous plants, and arthropods on or near each Drosera sp. were collected at 11 contrasting habitat locations in SW Australia. At three of the sites clones of the rare glandless mutant form of D. erythrorhiza were collected alongside fully glandular counterparts. The δ15N value (15N/14N natural isotope composition) of insect-free leaf and stem fractions was measured, and the data then used to estimate proportional dependence on insect N (%NdI) for the respective species and growth forms of Drosera. The data indicated lower %NdIvalues for rosette than for self-supporting erect or for climbing vine species. The latter two groups showed an average %NdIvalue close to 50%. The %NdIincreased with length and biomass of climbing but not erect forms of Drosera. δ15N values of stems were positively correlated with corresponding values for leaves of Drosera. Leaf material was on average significantly more15N enriched than stems, possibly due to delayed transport of recent insect-derived N, or to discrimination against15N in transfer from leaf to the rest of the plant. The comparison of δ15N values of insects and arthropod prey, glandless and glandular plants of D. erythrorhiza indicated %NdIvalues of 14.3, 12.2 and 32.2 at the respective sites, while matching comparisons based on δ15N of insect, reference plants and glandular plants proved less definitive, with only one site recording a positive %NdI(value of 10.4%) despite evidence at all sites of feeding on insects by the glandular plants. The use of the δ15N technique for studying nutrition of carnivorous species and the ecological significance of insect feeding of different growth forms of Drosera growing in a large range of habitats is discussed.
Lehrstuhl Pflanzenökologie, Universität Bayreuth, Postfach 101251, W-8580, Bayreuth, Federal Republic of Germany.
E -D
E-
Schulze
Lehrstuhl Pflanzenökologie, Universität Bayreuth, Postfach 101251, W-8580, Bayreuth, Federal Republic of Germany.
G
G
Gebauer
Lehrstuhl Pflanzenökologie, Universität Bayreuth, Postfach 101251, W-8580, Bayreuth, Federal Republic of Germany.
W
W
Schulze
Department of Botany, University of Western Australia, 6009, Nedlands, WA, Australia.
J S
JS
Pate
Drosera; Insectivorous plants; Nitrogen isotope ratio; Nutrition