Coexistence within a polymorphic species complex: the roles of predation and competition

Understanding the mechanisms that allow for coexistence between distinct morphs within a population or within a species complex poses a special challenge to ecologists, but also can provide considerable insight into the ecological and evolutionary relationships between the morphs, as well as the general features that shape populations in the environments in which they live. 

Two very similar, yet physically distinct (see Figure), morphotypes of the freshwater cladoceran Bosmina longirostris (var. typica and var. cornuta) co-occur in the zooplankton community of Lake Kinneret, Israel.  Exploration of this system offers a unique opportunity to address central topics in ecology, such as competition, predation and the maintenance of species diversity. The objective of this project is to discern the underlying mechanisms leading to the co-existence of the typica and cornuta morphs of Bosmina longirostris in Lake Kinneret. 

It is hypothesized that the typica morph is better defended against predation by raptorial invertebrate predators while the cornuta morph is better adapted for higher feeding efficiency.  As such, the typica morph is less efficient in food gathering, while the cornuta morph experiences greater vulnerability to predators.

During the coming years, I plan to test these hypotheses by 1) a detailed analysis of seasonal variability in the two Bosmina morphs in Lake Kinneret; 2) estimation of the relative proximate costs associated with each morphotype, and 3) estimation of the fitness of each morph under naturally-occurring environmental conditions.

B. I. var typica
B. I. var cornuta
Variation at the GPI locus