Chronospecies

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A chronospecies is a species which changes physically, morphologically, genetically, and/or behaviorally over time on an evolutionary scale such that the originating species and the species it becomes could not be classified as the same species had they existed at the same point in time. Throughout this change, there is only one species in the lineage living at any point in time, as opposed to cases where one species branches off into many through divergent evolution.

With a phyletic gradualism model of evolution, it can be difficult to separate chronospecies, since morphological changes accumulate over time and two very different organisms could be connected by a series of intermediaries. In practice, chronospecies are usually recognized because two species in the same lineage are named by palaeontologists without knowledge of any intermediate organisms. When organisms evolve by punctuated equilibrium, chronospecies can be readily seen in the fossil record when a lineage changes without splitting.

Prehistoric (but comparatively recent - usually Late Pleistocene) subspecies of extant taxa which evolved in a similar way as chronospecies are called pal(a)eosubspecies Most of those known have changed in size during adaptation to the climatic changes during the last ice age.

[edit] Examples

• Coragyps (chronospecies)
• Gymnogyps (palaeosubspecies)

[edit] References

• Stanley, S. M. (1978) "Chronospecies' longevities, the origin of genera, and the punctuational model of evolution," Paleobiology, 4, 26-40.
• Evolutionary species vs. chronospecies from Dr. Steven M. Carr, Memorial University of Newfoundland biology department

Speciation guide v • d • e
Basic concepts: species | chronospecies | speciation | cline
Modes of speciation: allopatric | peripatric | parapatric | sympatric | polyploidy
Auxiliary mechanisms: sexual selection | assortative mating | punctuated equilibrium
Intermediate stages: hybrid | Haldane's rule | ring species