It’s not a new species, it’s a hybrid!

In 1951 American ornithologist Rodolphe Meyer de Schauensee did what many dream about: he described a new bird species: the Argus Bare-eye (Phlegopsis barringeri). This new species of antbird was based on one specimen, collected on the Rio Rumiyaco in Colombia.

Later, Willis (1979) suggested that the specimen might be a hybrid between Black-spotted Bare-eye (P. nigromaculata) and Red-winged Bare-eye (P. erythroptera). These two species overlap from eastern Colombia to northern Bolivia.

This suggestion was tested by Graves (1992), who reexamined the original specimen and compared it to the two putative parental species. His conclusion: it’s a hybrid!

Black-spotted Bare-eye (from Wikimedia Commons)

References

Graves, G. (1992). Diagnosis of a hybrid antbird (Phlegopsis nigromaculata× Phlegopsis erythroptera) and the rarity of hybridization among suboscines. Proceedings of the Biological Society of Washington 105, 838-840.

Willis, E. O. (1979). Comportamento e ecologia da maede-taoca, Phlegopsis nigromaculata (d’Orbigny & Lafresnaye)(Aves, Formicariidae). Rev. Brasil Biol 39, 117-159.

These papers have been added to the Thamnophilidae page. A special thank you to Mort Isler for directing me to this case.

Conservation of the Mottled Duck: Multiple Populations and a Feral Threat

The Mottled duck (Anas fulvigula) is a North-American dabbling duck species. There are two main populations: one in Florida and one in Louisiana, Texas and Northern Mexico (known as the Western Gulf Coast population). In addition, a third population originated in 1976 and 1982 when about 1200 Western Gulf Coast and 26 Florida ducks were introduced in South Carolina.

A male Mottled duck (picture by Dick Daniels – http://carolinabirds.org/)

Whether the two main populations (Florida and Western Gulf Coast) can be considered discrete populations is unclear. If so, they should be recognized as separate conservation units. Although there is some genetic evidence that these populations are isolated, it remains to be determined if the genetic differences between these populations are simply a consequence of geographic distance (a pattern known as isolation-by-distance or IBD). To settle this issue, Peters et al. (2016) sequenced over 3000 genetic loci for 100 Mottled ducks from the three populations.

The multilocus data clearly separated the two main populations. In addition, kinship coefficients showed a sharp transition that coincides with the range gap between the populations. If these populations were still connected by gene flow, the transition would have been smoother. Finally, modelling of the demographic history of these populations indicated low levels of gene flow (about 1-3 individuals per generation).

These genetic results are backed up by ringing data: Mottled ducks ringed in Florida have never been recovered in Texas or Louisiana (2075 recoveries), and vice versa (8111 recoveries).

The authors conclude that ‘collectively, these results suggest that Florida and Western Gulf Coast Mottled ducks are on independent evolutionary trajectories and may be in the early stages of speciation. Therefore, they should be considered as distinct units for conservation and management.’

Apart from the 100 Mottled ducks, 17 Mallards (Anas platyrhynchos) were included in the analyses. Feral mallards are interbreeding with Mottled ducks and this genetic study confirms high levels of gene flow between these species. Hybridization with the Mallard, in combination with habitat loss, is a major conservation threat for the Mottled duck. Therefore, it is important for managers to confidently discriminate between Mottled ducks, Mallards, and their hybrids. For this purpose, Bielefeld et al. (2016) developed a genetically cross-validated phenotypic key.

 

References

Bielefeld, R. R., Engilis, A., Feddersen, J. C., Eadie, J. M., Tringali, M. D. & Benedict, R. J. (2016). Is it a mottled duck? The key is in the feathers. Wildlife Society Bulletin 40, 446-455.

Peters, J. L., Lavretsky, P., DaCosta, J. M., Bielefeld, R. R., Feddersen, J. C. & Sorenson, M. D. (2016). Population genomic data delineate conservation units in mottled ducks (Anas fulvigula). Biological Conservation 203, 272-281.

These two papers have been added to the Anseriformes page.

A New Year and some new papers

The end of 2016 has been quite hectic for me as I successfully defended my PhD thesis (read a report of that day here). So, I took some well-deserved holidays. But at the start of 2017, I felt the urge to update the Avian Hybrids Project. Here is an overview of some recent papers.

 

(House Sparrow x Spanish Sparrow)^2

In Northern Africa, House Sparrow and Spanish Sparrow also interbreed (Summers‐Smith & Vernon, 1972). In Algeria, House Sparrows and hybrids mainly reside in urban areas, while Spanish Sparrows live in cultivated areas. The latter also breed later and raise only two clutches (House Sparrows and hybrids raise three clutches). The mitogenome of the House Sparrow has almost completed introgressed into the Italian Sparrow (see above). In Algeria, however, a small percentage of the hybrids has a Spanish haplotype (Belkacem et al., 2016).

Belkacem, A. A., Gast, O., Stuckas, H., Canal, D., LoValvo, M., Giacalone, G. & Packert, M. (2016). North African hybrid sparrows (Passer domesticus, P. hispaniolensis) back from oblivion – ecological segregation and asymmetric mitochondrial introgression between parental species. Ecology and Evolution 6, 5190-5206.

Spanish Sparrow in Sardinia (picture by Francesco Canu)

 

Lord of the Rings

The Short-tailed Albatross (Phoebastria albatrus) is a vulnerable seabird that mainly breeds on Torishima and the Senkaku Islands in the Pacific Ocean. The two populations are genetically distinct and display assortative mating. However, a study based on mate choice of ringed (from Torishima) and unringed birds (from the Senkaku Islands) revealed some mixed pairings, indicating that pre-mating isolation is incomplete (Eda et al., 2016).

Eda, M., Izumi, H., Konno, S., Konno, M. & Sato, F. (2016). Assortative mating in two populations of Short‐tailed Albatross Phoebastria albatrus on Torishima. Ibis 158, 868-875.

Short-tailed Albatross (picture by James Lloyd Pace)

 

Mangrove Matings

The Mangrove Finch (Camarhynchus heliobates) is critically endangered and currently restricted to one small population on Isabela Island (Galapagos Islands). A genetic study found that a number of individuals have hybridized with the closely related Woodpecker Finch (C. pallidus). Possibly, there is a breakdown of reproductive isolation between these species because the Mangrove Finches cannot find a mate due to the low population size (Lawson et al., 2016).

Lawson, L. P., Fessl, B., Vargas, F. H., Farrington, H. L., Cunninghame, H. F., Mueller, J. C., Nemeth, E., Sevilla, P. C. & Petren, K. (2016). Slow motion extinction: inbreeding, introgression, and loss in the critically endangered mangrove finch (Camarhynchus heliobates). Conservation Genetics, 1-12.

Mangrove Finch (picture by Michael Dvorak)

 

Lonely Lineages

A genomic analysis of a contact zone between two divergence lineages of the Brown Creeper (Certhia americana) in the Madrean Archipelago sky islands (Arizona, USA) reported complete allopatry during the breeding season and no gene flow (Manthey, Robbins & Moyle, 2016).

Manthey, J. D., Robbins, M. B. & Moyle, R. G. (2016). A genomic investigation of the putative contact zone between divergent Brown Creeper (Certhia americana) lineages: chromosomal patterns of genetic differentiation. Genome 59, 115-25.

Brown Creeper

 

Keep an eye on the website, more updates will follow soon!