Redicting resource partitioning and community organization of filter-feeding dabbling ducks from functional morphology. 2007. D. Brent Gurd. American Naturalist 169:334-343.
From the press release:
Ecologists continue to debate how different species manage to coexist. If two species use identical resources, such as food, invariably one will be more efficient and out-compete the other. The classical explanation is that each species has evolved morphological or physiological traits that allow it to exploit some resources more efficiently than all other species.
Such partitioning of resources essentially provides each species with exclusive access to resources necessary for its survival. Although coexistence is often attributed to interspecific differences in morphology, direct evidence is relatively rare.
Dabbling ducks, which include the ubiquitous mallard, are a good example. Dabbling ducks are primarily filter-feeders. They use lamellae, which are comb-like projections on the bill, to sieve food particles from pond water. Many ecologists, including Darwin, suggested that ducks coexist because interspecific differences in the spacing of bill lamellae allow each species to consume food particles of different sizes. New Research by Brent Gurd has demonstrated that interspecific differences in lamellar length, not spacing, allow ducks to partition food by size.
To test his idea, Gurd created virtual bills using computer software typically used by engineers to design complex machinery. "The software allowed me to create exact, three-dimensional replicas of duck bills complete with articulating joints" said Gurd. "The replicas allowed me to determine the particle sizes each duck could ingest and the rate at which they could ingest them."
I'm always intersted in research that helps shed light on why multiple morphologically similar species can co-exist in a small region.
Daffy and The Dinosaur: