Polygynandry: many-to-many marriage or relationship

The term polygynandry refers to a relationship between a group of females with a group of males. Group marriages are only found within a few vertebrate species. For example, in clans of acorn woodpeckers (Melanerpes formicivorus), which form reproductive arrangements of breeding females, breeding males and a few non-breeding adult off-spring helping their parents for up to five years (inspite of reaching sexual maturity at one year of age). Each breeding bird attempts to mate with all opposite-gender breeders in the clan [1,2].

Combined polyandrous (having two or more male partners, husbands) and polygynous (having two or more female partners, wives) patterns of mating have also been observed in populations of red foxes (Vulpes vulpes) [3], the Neotropical frog Allobates femoralis [4], the dusky pipefish (Syngnathus floridae) [5] and the sea spider (Ammothea hilgendorfi) [6]; just to name a few other species exhibiting polygynandrous “life style.”

Keywords: biology, sex, reproduction, breeding, marital community

References and more to explore
[1] Kate Marianchild: Acorn Woodpeckers, So Happy Together. Bay Nature October-December 2011, 11, (4), page 7 [baynature.org/articles/oct-dec-2011/acorn-woodpeckers-so-happy-together].
[2] Joseph Haydock and Walter D. Koenig: Reproductive skew in the polygynandrous acorn woodpecker. Proc. Natl. Acad. Sci. USA May 14, 2002, 99 (10), pp. 7178-7183 [www.pnas.org/content/99/10/7178.full].
[3] Philip J. Baker, Stephan M. Funk, Michael W. Bruford and Stephen Harris: Polygynandry in a red fox population: implications for the evolution of group living in canids? Behavioral Ecology 2004, 15 (5), pp. 766-778. 
doi: 10.1093/beheco/arh077.
[4] Eva Ursprung, Max Ringler, Robert Jehle and Walter Hödl: Strong male/male competition allows nonchoosy females: high levels of polygynandry in territorial frog with paternal care. Mol. Ecol. 2011, 20 (8), pp. 1759-1771 [onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2011.05056.x/abstract].
[5] Adam G. Jones and John C. Avise: Polygynandry in the dusky pipefish (Syngnathus floridae) revealed by microsatellite DNA markers. Evolution 1997, 51 (5), pp. 1611-1622 [www.jstor.org/pss/2411213].
[6] F. S. Barreto and J. C. Avise: Polygynandry and sexual size dimorphism in the sea spider Ammothea hilgendorfi (Pycnogonida: Ammotheidae), a marine arthropod with brood-carrying meals. Mol. Ecol. 2008, 17 (18), pp. 4164-4175 [www.ncbi.nlm.nih.gov/pubmed/18684134].