Abstract #02
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11/09/04
FW 315
McDowall, R.M. 2001. Diadromy, diversity and divergence: implications for speciation processes in fishes. Fish and Fisheries. 2:278-285.
Diadromy has the potential to greatly affect genetic diversity and speciation within fishes. Diadromous fish are often separated by large geographical ranges during part of their life cycle, but are still able to have gene flow occur while they are at sea due to mixing of fish between groups. If the homing instinct is low, gene flow among populations will be higher, thusly inhibiting local genetic diversity and speciation. However, since diadromy also facilitates dispersal and promotes expansion of species into new geographic ranges, there is the possibility for promotion of taxonomic diversity and speciation. Since some species are not obligatorily diadromous (anadromous), individuals, or even entire populations, sometimes do not migrate from fresh to salt water. This facultative ability allows for newly separated populations to evolve and diverge, and eventually become a new species of non-migratory freshwater fish. There has been research to show that some non-diadromous fresh water species of fish evolved from diadromous species. In conclusion, diadromy allows for seemingly mutually exclusive outcomes (speciation inhibition and speciation) to occur. Diadromy disperses fish into the ocean to mix with each other, allowing for gene flow to take place (when homing instinct is not high) and inhibition of speciation, while at the same time allowing for diadromous fishes to broaden their range, giving them a chance to establish new non-migratory species.
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