Is sexual reproduction outside the same biological family possible? Ever successfully occured?

Question

Is there an example of two species taxonomically classified in different biological families sucessfully sexually reproducing viable offspring? If not, is there an example of where reproduction occured with non-viable offspring?

To be clear, I mean regular sexual reproduction that could occur in the natural world outside a lab. Even so, I'd be curious to know if it could even occur in a lab without direct genetic manipulation.

For example, grolar bears which are ursid hybrids between different species in the Ursus genus are known to exist. Also ursid hybrids between bear species in different genuses have been produced in captivity (sloth bear Melursus ursinus x Malayan sun bear Ursus malayanus and sloth bear x Asiatic black bear Ursus thibetanus). Would an extra-familial hybridisation be possible? Would this be more likely in the plant kingdom?

This question is inspired by a separate question on the Gardening SE which hints at a general lack of understanding of the genetic similarity required for cross-pollination in plants. It made me wonder whether there are any exceptions to the general assumption that extra-familial hybridisation is impossible.

Answer 1

Interfamilial hybrids have never, to my knowledge, been recorded occurring naturally (without human intervention).

In plants, somatic inter-familial hybrids have been produced for a wide variety of species pairs in the lab (e.g. between carrot and barley; Kisaka et al. 1997).

In animals, there are some historical reports of hybrids between chickens (Mathis & MacDougald 1987) or peafowl (Serebrovsky 1929), both in Phasianidae, and guineafowl (in Numididae). The animal example meets your condition of being outside the lab, although they were produced by breeders.

Refs

• Kisaka, H., Kisaka, M., Kanno, A. & Kameya, T. (1997) Production and analysis of plants that are somatic hybrids of barley (Hordeum vulgare L.) and carrot (Daucus carota L.). TAG Theoretical and Applied Genetics. 94 (2), 221–226.
• Mathis, G.F. & McDougald, L.R. (1987) Evaluation of interspecific hybrids of the chicken, guinea fowl, and Japanese quail for innate resistance to coccidia. Avian Diseases. 31 (4), 740–745.
• Serebrovsky, A. (1929) Observations on interspecific hybrids of the fowl. Journal of Genetics. 21 (3), 327–340.