Mortality dynamics of Daphnia in contrasting habitats and their role in ecological divergence
Article first published online: 16 APR 2004
Volume 49, Issue 5, pages 505–514, May 2004
How to Cite
Dudycha, J. L. (2004), Mortality dynamics of Daphnia in contrasting habitats and their role in ecological divergence. Freshwater Biology, 49: 505–514. doi: 10.1111/j.1365-2427.2004.01201.x
- Issue published online: 16 APR 2004
- Article first published online: 16 APR 2004
- (Manuscript accepted 30 January 2004)
- birth rate;
- death rate;
- ecological speciation;
1. The Daphnia pulex-pulicaria species complex has been proposed as an example of rapid ecological speciation, associated with divergence along the gradient of waterbody size from temporary ponds to deep, stratified lakes. However, this divergence is incomplete, and thus represents an opportunity to study ecological divergence as it is occurring.
2. Dynamics of twelve populations of Daphnia in the pulex-pulicaria species complex were monitored over 1 year. Six temporary pond populations and six permanent lake populations were compared to evaluate demographic differences that may contribute to ecological divergence in this complex.
3. Pond populations experienced greater changes in density, which were reflected in more extreme growth rates, higher birth rates and higher mortality rates than those of lake populations.
4. Mitochondrial DNA was isolated from up to three clones from each population, the D-loop of the control region was sequenced, and a phylogenetic tree was constructed. This tree revealed two strongly supported clades. The clades were not congruent with habitat type and nominal status, indicating that interhabitat gene flow occurs easily and that the nominal taxa are incompletely diverged.
5. Published reports of genetic life history differences in the D. pulex-pulicaria complex are consistent with the demographic differences reported here. This suggests that ecological differences between the habitats are selectively maintaining trait differences despite the possibility for genetic exchange. Thus, these taxa may be at the inception of ecological speciation.