In other species: Panuco swordtail , Perugia's limia

Categories: Reproductive system phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 155555 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal

Disease-related: no

Key variant known: yes

Year key variant first reported: 2015

Species-specific name: alternative reproductive tactics

Species-specific description: Lank et al. (1995) described two "morphs" in this species: independent males "have a territorial breeding strategy of defending lek mating courts against other independents" while satellites, which are non-territorial, "move among, are recruited to and share independents' courts". Jukema and Piersma (2006) added a third, namely "faeder": "Faeders are slightly larger than females and in late April have testes 2.5 time the size of testes of normal males. On leks in aviaries and in the wild they appear to combine feminine and masculine behaviours. Faeders may represent the ancestral, care-giving, male strategy, but their relatively large testes suggest that currently they behave as sneakers." A video demonstrating ruff male reproductive strategies at a lek in Karesuando, Sweden is viewable at http://www.scilifelab.se/research/scientific-highlights/ruff

Inheritance: From planned matings, Lank et al. (1995) concluded that the two "morphs" of mating strategy in this species (independent and satellite) are determined by the segregation of two alleles at an autosomal locus, with satellite allele (S) being dominant to the independent allele (s). Lank et al. (2013) attributed the "faeder" morph to a dominant allele, but were not sure whether it was part of the S locus.

Molecular basis: Two independent papers published simultaneously online in 2015 and as adjacent papers in 2016 (Lamichhaney et al., 2016; Küpper et al., 2016) showed that the two variant morphs (satellites and faeders) are associated with a 4.5Mb inversion on the ruff orthologue of chicken chromosome GGA11 which, due to the well-known lethality of recombinants within an inversion, has created a supergene determining male breeding behaviour, body size and plumage colour. The large sequence divergence between the wild-type and inverted variant (1.4%) indicates that the inversion happened about 4 million years ago. The inversion disrupts an essential gene (CENPN) and is therefore lethal in the homozygous condition, which means that it has been maintained as a balanced polymorphism for millions of years. Furthermore, some 500,000 years ago, the inverted supergene recombined with the wild-type allele creating a second version. Faeders possess one copy of the original inverted supergene, satellite males have one copy of the newer recombinant version, and independents lack either version. The inverted region contains about 90 genes, which include five genes (e.g. HSD17B2) affecting the metabolism of steroid hormones and the MC1R gene that is assumed to explain the white colour in satellites. (based on text kindly provided by Leif Andersson)

Associated genes: