This order holds the parrots of the world, divided over three superfamilies: “True” Parrots (Psittacoidea), Cockatoos (Cacatuoidea) and New Zealand Parrots (Strigopoidea).
A new species, Aratinga pintoi, was previously regarded as a hybrid between A. solstitialis and A. jandaya (Silveira, De Lima & Hofling, 2005).
The Ring-necked Parrot (B. zonarius), which is sometimes included in the genus Platycercus, consists of four subspecies across Australia, namely barnardi, zonarius, semitorquatus and macgillivray. A phylogenetic analysis found a clear distinction between B. z. barnardi and the other three populations, probably due to a vicariant event. However, some subspecies are in secondary contact and gene flow occurs (Joseph & Wilke, 2006).
Flight calls between hybrids of B. z. zonarius and B. z. semitorquatus are intermediate compared to parental taxa (Baker, 2008), and within the hybrid zone calls belong to roost-specific dialects (Baker, 2000). Two hybrid zones have been studied morphologically: B. z. zonarius x semitorquatus and B. z. zonarius x barnardi (Baker, 2010).
A phylogeographic study on the Burrowing Parrot (Cyanoliseus patagonus) revealed a secondary contact zone between two populations (andinus and patagonus) which resulted in an intermediate phenotype (conlara) in the Andes (Masello et al., 2011).
The situation of interbreeding between Red-crowned Parakeet (Cyanoramphus novaezelandiae) and the rare Forbes’ Parakeet (C. forbesi) illustrates the balance between the pros and cons of hybridization. On the one hand, the Forbes’ Parakeet is losing its genetic integrity (Chan et al., 2006), while on the other hand hybrids have an increased immune response (Tompkins, Mitchell & Bryant, 2006).
And a taxonomic review of the genus Eunymphicus mentions captive hybridization between certain genera (Boon et al., 2008).
The Crimson Rosella (P. elegans) has a circular distribution in Australia with a hybrid zone between the starting and ending populations of this ring. However, detailed analyses showed that it cannot be seen as a classical ring species (Joseph et al., 2008). Vocal studies of this species complex also provided little evidence for the ring species hypothesis (Ribot et al., 2009), although some vocal traits are concordant with genetic clines in contact zones (Ribot et al., 2012). Despite these patterns, subspecies (elegans and flaveolus) did not respond differently to heterospecific calls in playback experiments (Ribot et al., 2013). A phylogenetic analysis of the entire group of Australian Rosella Parrots uncovered discordance between mitochondrial and nuclear data which may be the result of asymmetrical mitochondrial hybridization from P. adscitus into P. eximius (Shipham et al., 2015).
A phylogenetic analysis of the beak and feather virus indicated that the virus nicely followed the ring-species hypothesis. In addition, hybrids and intermediate phenotypes showed lower prevalence and load compared to parental taxa (Eastwood et al., 2014).
Several other studies mention hybridization between parrot species. The genus Poicephalus contains two parapatric species – Cape Parrot (P. robustus) and Brown-necked Parrot (P. fusciollis) – that do not seem to hybridize (Perrin, 2005).
An intergeneric hybrid between Spix’s Macaw (Cyanopsitta spixii) and Illiger’s Macaw (Propyrrhura maracana) was described and confirmed by genetic analysis (Miyaki et al., 2001).
Baker, M. C. (2000). Cultural diversification in the flight call of the Ringneck Parrot in Western Australia. Condor 102, 905-910.
Baker, M. C. (2008). Analysis of a cultural trait across an avian hybrid zone: Geographic variation in plumage morphology and vocal traits in the Australian Ringneck Parrot (Platycercus zonarius). Auk 125, 651-662.
Baker, M. C. (2010). Hybrid zones and cultural traits of the Australian ringneck Platycercus zonarius. Journal of Avian Biology 41, 50-63.
Boon, W. M., Robinet, O., Rawlence, N., Bretagnolle, V., Norman, J. A., Christidis, L. & Chambers, G. K. (2008). Morphological, behavioural and genetic differentiation within the Horned Parakeet (Eunymphicus cornutus) and its affinities to Cyanoramphus and Prosopeia. Emu 108, 251-260.
Chan, C. H., Ballantyne, K. N., Aikman, H., Fastier, D., Daugherty, C. H. & Chambers, G. K. (2006). Genetic analysis of interspecific hybridisation in the world’s only Forbes’ parakeet (Cyanoramphus forbesi) natural population. Conservation Genetics 7, 493-506.
Eastwood, J. R., Berg, M. L., Ribot, R. F. H., Raidal, S. R., Buchanan, K. L., Walder, K. R. & Bennett, A. T. D. (2014). Phylogenetic analysis of beak and feather disease virus across a host ring-species complex. Proceedings of the National Academy of Sciences of the United States of America 111, 14153-14158.
Joseph, L., Dolman, G., Donnellan, S., Saint, K. M., Berg, M. L. & Bennett, A. T. D. (2008). Where and when does a ring start and end? Testing the ring-species hypothesis in a species complex of Australian parrots. Proceedings of the Royal Society B-Biological Sciences 275, 2431-2440.
Joseph, L. & Wilke, T. (2006). Molecular resolution of population history, systematics and historical biogeography of the Australian ringneck parrots Barnardius: are we there yet? Emu 106, 49-62.
Masello, J. F., Quillfeldt, P., Munimanda, G. K., Klauke, N., Segelbacher, G., Schaefer, H. M., Failla, M., Cortes, M. & Moodley, Y. (2011). The high Andes, gene flow and a stable hybrid zone shape the genetic structure of a wide-ranging South American parrot. Frontiers in Zoology 8.
Miyaki, C. Y., Faria, P. J., Griffiths, R., Araujo, J. C. C. & Barros, Y. M. (2001). The last wild Spix’s Macaw and an Illiger’s Macaw produced a hybrid. Conservation Genetics 2, 53-55.
Perrin, M. R. (2005). A review of the taxonomic status and biology of the Cape Parrot Poicephalus robustus, with reference to the Brown-necked Parrot P fusciollis fusciollis and the Grey-headed Parrot P-f suahelicus. Ostrich 76, 195-205.
Ribot, R. F. H., Berg, M. L., Buchanan, K. L. & Bennett, A. T. D. (2013). Is there variation in the response to contact call playbacks across the hybrid zone of the parrot Platycercus elegans? Journal of Avian Biology 44, 399-407.
Ribot, R. F. H., Berg, M. L., Buchanan, K. L., Komdeur, J., Joseph, L. & Bennett, A. T. D. (2009). Does the ring species concept predict vocal variation in the crimson rosella, Platycercus elegans, complex? Animal Behaviour 77, 581-593.
Ribot, R. F. H., Buchanan, K. L., Endler, J. A., Joseph, L., Bennett, A. T. D. & Berg, M. L. (2012). Learned Vocal Variation Is Associated with Abrupt Cryptic Genetic Change in a Parrot Species Complex. Plos One 7.
Shipham, A., Schmidt, D. J., Joseph, L. & Hughes, J. M. (2015). Phylogenetic analysis of the Australian rosella parrots (Platycercus) reveals discordance among molecules and plumage. Molecular Phylogenetics and Evolution 91, 150-159.
Silveira, L. F., De Lima, F. C. T. & Hofling, E. (2005). A new species of Aratinga Parakeet (Psittaciformes : Psittacidae) from Brazil, with taxonomic remarks on the Aratinga solstitialis complex. Auk 122, 293-305.
Tompkins, D. M., Mitchell, R. A. & Bryant, D. M. (2006). Hybridization increases measures of innate and cell-mediated immunity in an endangered bird species. Journal of Animal Ecology 75, 559-564.