Androdioecy

From Infogalactic: the planetary knowledge core
Jump to: navigation, search

Lua error in package.lua at line 80: module 'strict' not found. Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison to the other major reproductive systems dioecy and hermaphroditism.[1] In animals, androdioecy has been considered an important stepping stone in the transition from dioecy to hermaphroditism, and vice versa.[2]

Evolution of androdioecy

The fitness requirements for androdioecy to arise and sustain itself are theoretically so improbable that it was long considered that such systems do not exist.[3][4] Particularly, males and hermaphrodites have to have the same fitness, in other words the same number of offspring, in order to be maintained. However, males only have offspring by fertilizing eggs or ovules of hermaphrodites, while hermaphrodites have offspring both through fertilizing eggs or ovules of other hermaphrodites and their own ovules. This means that all else being equal, males have to fertilize twice as many eggs or ovules as hermaphrodites to make up for the lack of female reproduction.[5][6]

Androdioecy can evolve either from dioecious ancestors through the invasion of hermaphrodites or from hermaphroditic ancestors through the invasion of males. The ancestral state is important because conditions under which androdioecy can evolve differ significantly.

Androdioecy with dioecious ancestry

In roundworms, clam, tadpole and cancrid shrimps, androdioecy has evolved from dioecy. In these systems, hermaphrodites can only fertilize their own eggs (self-fertilize) and do not mate with other hermaphrodites. Males are the only means of outcrossing. Hermaphrodites may be beneficial in colonizing new habitats, because a single hermaphrodite can generate many other individuals.[7] In the well-studied roundworm Caenorhabditis elegans, males are very rare and only occur in populations that are in bad condition or stressed.[8]

Androdioecy with hermaphroditic ancestry

In plants, corals and barnacles, androdioecy has evolved from hermaphroditism. Many plants self-fertilize, and males may be sustained in a population when inbreeding depression is severe because males guarantee outcrossing.

Androdioecious species

Despite their unlikely evolution, 115 androdioecious animal and about 50 androdioecious plant species are known.[2][9] These species include

Anthozoa (Corals)

Nematoda (Roundworms)

Rhabditidae (Order Rhabditida)

Diplogastridae (Order Rhabditida)

Steinernematidae (Order Rhabditida)

Allanotnematidae (Order Rhabditida)

Dorylaimida

Nemertea (Ribbon worms)

Arthropoda

Clam shrimp

Tadpole shrimp

Barnacles

Lysmata

Insects

Annelida (Ringed worms)

Chordata

Plants

External links

See also

References

  1. Lua error in package.lua at line 80: module 'strict' not found.
  2. 2.0 2.1 Lua error in package.lua at line 80: module 'strict' not found.
  3. Lua error in package.lua at line 80: module 'strict' not found.
  4. Darwin C. 1877. The different forms of flowers and plants of the same species. New York: Appleton.
  5. Lua error in package.lua at line 80: module 'strict' not found.
  6. Lua error in package.lua at line 80: module 'strict' not found.
  7. Lua error in package.lua at line 80: module 'strict' not found.
  8. 8.0 8.1 Lua error in package.lua at line 80: module 'strict' not found.
  9. Lua error in package.lua at line 80: module 'strict' not found.
  10. Lua error in package.lua at line 80: module 'strict' not found.
  11. Lua error in package.lua at line 80: module 'strict' not found.
  12. Lua error in package.lua at line 80: module 'strict' not found.
  13. 13.0 13.1 Lua error in package.lua at line 80: module 'strict' not found.
  14. Lua error in package.lua at line 80: module 'strict' not found.
  15. Lua error in package.lua at line 80: module 'strict' not found.
  16. Lua error in package.lua at line 80: module 'strict' not found.
  17. 17.0 17.1 Lua error in package.lua at line 80: module 'strict' not found.
  18. Lua error in package.lua at line 80: module 'strict' not found.
  19. Lua error in package.lua at line 80: module 'strict' not found.
  20. Lua error in package.lua at line 80: module 'strict' not found.
  21. Lua error in package.lua at line 80: module 'strict' not found.
  22. Lua error in package.lua at line 80: module 'strict' not found.
  23. 23.0 23.1 23.2 Lua error in package.lua at line 80: module 'strict' not found.
  24. Lua error in package.lua at line 80: module 'strict' not found.
  25. Lua error in package.lua at line 80: module 'strict' not found.
  26. Lua error in package.lua at line 80: module 'strict' not found.
  27. Gleiser G, Verdú M. 2005. Repeated evolution of dioecy from androdioecy in Acer" New Phytologist 165(2):633-640. doi=10.1111/j.1469-8137.2004.01242.x
  28. Lua error in package.lua at line 80: module 'strict' not found.
  29. Lua error in package.lua at line 80: module 'strict' not found.
  30. Lua error in package.lua at line 80: module 'strict' not found.
  31. Thomson JD,Shivanna KR, Kenrick J and Knox RB. 1989" American Journal of Botany 76 (7):1048-1059
  32. Lua error in package.lua at line 80: module 'strict' not found.
  33. Lua error in package.lua at line 80: module 'strict' not found.