Androdioecy is a reproductive system

Sexual reproduction

Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...

 found in species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 composed of a male

Male

Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...

 population

Population

A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

 and a distinct hermaphrodite

Hermaphrodite

In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

 population. Such species are rare.

The conditions required for androdioecy to arise and sustain itself are theoretically so improbable that it was long considered that such systems would never be found. However, androdioecy (and near-androdioecy) has now been documented in both phylogenetically

Phylogenetics

In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...

 distinct plant and animal species. Hence androdioecy has actually evolved independently several times.

Androdioecious species

• Caenorhabditis briggsae
  Caenorhabditis briggsae
  Caenorhabditis briggsae is a small nematode, closely related to Caenorhabditis elegans. The differences between the two species are subtle. The male tail in C. briggsae has a slightly different morphology than C. elegans. Other differences include changes in vulval precursor competence and the...
  
  
• Caenorhabditis elegans
  Caenorhabditis elegans
  Caenorhabditis elegans is a free-living, transparent nematode , about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner and it has since been used extensively as a model...
  
  
• Datisca glomerata
  Datisca glomerata
  Datisca glomerata is a species of plant native to California, Nevada, and Baja California known by the common name Durango root. It is one of only two to four species in the plant family Datiscaceae. It is an erect perennial herb with distinctive long, pointed, often sharply serrated leaves. It is...
  
  
• Eulimnadia texana
• Fraxinus lanuginosa
  Fraxinus lanuginosa
  Fraxinus lanuginosa is a species of ash native to Japan.It is a medium-sized deciduous tree growing to 10–15 m tall with a trunk up to 50 cm diameter. The bark is smooth, dark grey. The buds are pale pinkish-brown to grey-brown, with a dense covering of short grey hairs...
  
  
• Nephelium lappaceum
• Panax trifolius
• Rivulus marmoratus
• Triops cancriformis
  Triops cancriformis
  Triops cancriformis, or tadpole shrimp , is a species of tadpole shrimp found in Europe, the Middle East and Japan....
  
  
• Triops newberryi
  Triops newberryi
  Triops newberryi is a species of Triops found on the Western coast of North America, commonly in valleys throughout the states of Washington, Oregon, California, and small areas of Nevada and Mexico. They are found in vast numbers though in the Coachella Valley in California. T...
  
  

External links

• Kiyoshi Ishida and Tsutom Hiura. 'Pollen Fertility and Flowering Phenology in an Androdioecious Tree, Fraxinus lanuginosa (Oleaceae), in Hokkaido, Japan'. International Journal of Plant Sciences 159 (1998): 941–947.
• Elizabeth Pennisi. 'Sex and the Single Killifish'. Science 313 (2006)

Literature

• Bawa, 1980
• Charlesworth, B. 'The evolution of sex chromosomes'. Science 251 (1991): 1030-1033.
• Charlesworth, B. 'The nature and origin of mating types'. Curr. Biol. 4 (1994): 739-741.
• D. Charlesworth, 1985
• Darwin, 1877
• Lewis, 1942
• Lloyd, 1975
• Ross & Weir, 1976
• Wolf and Takebayashi, 2004