Morph (zoology)
Encyclopedia : M : MO : MOR : Morph (zoology)
A Morph, meaning "form" (from the Latin morpha), is a zoological term that describes local populations or subpopulations of a single species of animal that may or may not be phenotypically distinct from the larger population as a whole. Morphs, whether or not phenotypically distinguishable, are most usually behaviourally distinct from each other.
For example, an anadromous subpopulation of brown trout (Salmo trutta morpha trutta) may occur sympatrically with a stream-resident subpopulation of brown trout (Salmo trutta morpha fario). The two subpopulations are a single species and may, in fact, interbreed [link]. Nonetheless, the tendency to anadromy or to remaining stream-resident is innate in each of the subpopulations. Frequently, the likelihood of interbreeding is reduced because the morphs also have distinct reproductive behaviours such as variance in timing or in the selection of sites for reproduction.
The segregation of a species into sympatric morphs often can be thought of as a mechanism for the partitioning of available resources. An example of this might be certain lacustrine Arctic char populations which segregate into planktivorous and piscivorous morphs within the same lake. The planktivores feed on zooplankton in the epilimnion or on other invertebrates in the profundal zone. The piscivores feed on available forage fish (or, perhaps, on the planktivorous morph), usually over shoals in the metalimnion or by launching forays into the epilimnion. The planktivorous fish are smaller, grow more slowly and mature at a smaller size than do the piscivorous fish.
The segregation of a population into morphs, especially if the morphs are, or become, reproductively isolated, could be thought of as a pre-cursor to sympatric speciation.
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