Skip to main content
. 2021 Nov 5;9:e12451. doi: 10.7717/peerj.12451

Figure 5. An evolutionary hypothesis describing the history of gene gain and loss among vertebrates.

Figure 5

The common ancestor of vertebrates had two Piwis (an ancestral Piwil1 and Piwil2). Piwil2 has not undergone any gain or loss during vertebrate evolution. Most likely, Piwil4 was derived from a tandem duplication of Piwil1 in the common ancestor of gnathostomes, but was independently lost in ray-finned fishes, birds, and monotreme mammals. Piwil3 was derived from a tandem duplication of Piwil1 in the common ancestor of therian mammals. Source credits: Lamprey/cyclostome, Gareth Monger, http://phylopic.org/image/f9313512-3ce4-4349-86bc-060d4faa013e/ (CC 3.0, http://creativecommons.org/licenses/by/3.0/); Lobe-finned fish, Maija Karala, http://phylopic.org/image/202c2ad3-48a7-471d-87ef-c6d8406640e8/ (CC NC 3.0, http://creativecommons.org/licenses/by-nc-sa/3.0/); Amphibian, Sarah Werning, http://phylopic.org/image/cd0f49a1-4adf-448e-859c-b703a73b9481/ (CC 3.0, http://creativecommons.org/licenses/by/3.0/) Monotreme, Sarah Werning, http://phylopic.org/image/cd0f49a1-4adf-448e-859c-b703a73b9481/ (CC 3.0, http://phylopic.org/image/b406c409-2735-4a3d-a7aa-8afe0b6e72dc/); Therian, Bogdan Bocianowski, http://phylopic.org/image/2d078b25-e6a0-4beb-a5d3-5d6f16be8ebf/) (CC 3.0, http://creativecommons.org/licenses/by/3.0/); Cartilaginous fish, Public Domain: http://phylopic.org/image/545d45f0-0dd1-4cfd-aad6-2b835223ea0d/; ray-finned fish, Public Domain: http://phylopic.org/image/6f4c653a-1da1-4e02-85ef-6344b2d8e02a/; Reptile, Public Domain: http://phylopic.org/image/dffda000-77cb-4251-b837-0cd2ab21ed5b/; Chicken, Public Domain: http://phylopic.org/image/aff847b0-ecbd-4d41-98ce-665921a6d96e/.