Research Article |
Corresponding author: Cristiane Apolinario ( cris.snt4@gmail.com ) Academic editor: Sionei Ricardo Bonatto
© 2019 Cristiane Apolinario, Luis Fabio Silveira.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Apolinario C, Silveira LF (2019) Hybridism between Cyanocorax chrysops and Cyanocorax cyanopogon (Aves: Corvidae) in Brazil. Zoologia 36: 1-7. https://doi.org/10.3897/zoologia.36.e32138
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Cyanocorax chrysops (Vieillot, 1818) and Cyanocorax cyanopogon (Wied, 1821) are widespread jays. They are considered sister species according to recent molecular phylogenies. When analyzing museum specimens of both species, we found two individuals with intermediate plumage characteristics. They were collected near the range limits of both species, and we classified them as hybrids. Based on the sites where these specimens were found, we discuss the possible factors leading the interbreeding and compare our findings with information available in the literature. This is the first documented case of natural hybridization in jays in Brazil and the second case involving sister species within the New World jays.
Contact zones, hybrids, interbreeding, jays
Hybridization is a phenomenon of basic relevance in biology (
Hybridization can occur in a contact zone, there is, in areas where the ranges of two populations overlap; and those can become a hybrid zone, where hybridization occurs regularly (
New World jays do not hybridize as often or as extensively as Old-World ones. Some records mention occasional hybridization involving congeneric species, for instance Cyanocorax morio (Wagler, 1829) and Cyanocorax formosus (Swainson, 1827) (
The Neotropical jays belonging to the genus Cyanocorax Boie, 1826 comprise a very distinct group of New World corvids. Cyanocorax chrysops (Vieillot, 1818), the Plush-crested Jay, is a polytypic species widely distributed in South America, ranging from northern Brazil to northern Argentina, with four subspecies currently accepted: C. c. chrysops (Vieillot, 1818), C. C. diesingii Pelzeln, 1856, C. C. insperatus Pinto and Camargo, 1961 and C. C. tucumanus Cabanis, 1883. This species is found in various types of lowland forests and temperate rainforest, also inhabiting patches of forest in open areas, riparian forests and even disturbed areas. Cyanocorax cyanopogon (Wied, 1821), the White-naped Jay, in turn, inhabits mostly areas of ‘caatinga’ and ‘cerrado’, but it is also seen in secondary woodland, riparian forests, and in the borders of tropical deciduous forests. It is Brazilian endemic, distributed from the state of Maranhão to the state of Minas Gerais, also occurring in southeastern Pará, eastern Mato Grosso and Goiás (
Cyanocorax chrysops and C. cyanopogon are considered sister species (
We analyzed 80 specimens of C. chrysops and 137 of C. cyanopogon housed at Museu de Zoologia da Universidade de São Paulo (MZUSP) and Museu Paraense Emílio Goeldi (MPEG) (see Supplementary Material S1) in order to describe the plumage pattern of each hybrid and then compare it with the plumage of their parents. We analyzed plumage coloration following
We found two specimens, one from Três Lagoas, state of Mato Grosso do Sul (MZUSP 64191), and a second from Comendador Gomes, state of Minas Gerais (MZUSP 103009), showing intermediate plumage characters between C. cyanopogon and the nominate form C. c. chrysops. The most remarkable plumage characters exhibited by these particular specimens were: (1) back and wings dark grayish brown, (2) tail indigo blue or dark grayish brown + indigo blue and (3) nape light bluish gray/dull violaceous blue or white/lavender blue (Table
Comparison of plumage characters of the hybrids between Cyanocorax chrysops chrysops and Cyanocorax cyanopogon.
Character | C. c. chrysops | Hybrid 1 (MZUSP 64191) | Hybrid 2 (MZUSP 103009) | C. cyanopogon |
Nape | Light sky blue (S 168D)/Campanula (S 71) | Light bluish Gray (M 10B 8/1)/Dull violaceous blue (S 170B) | White (M 2.5Y 8/1)/Lavender blue (S 170D) | White (M 2.5Y 8/1) |
Superciliar spot | Smalt blue (S 170)/Light Sky blue (S 168D) | Smalt blue (S 170)/Light Sky blue (S 168D) | Light Sky blue (S 168D) | Light Sky blue (S 168D) |
Malar spot | Campanula (S 71) | Campanula (S 71) | Smalt blue (S 70) | Cyanine blue (S 74) |
Infraocular spot | Smalt blue (S 170) | Smalt blue (S 170) | Smalt blue (S 170) | Smalt blue (S 170) |
Abdomen and underparts | Pale Yellow (M 2.5Y 8/3) | Pale Yellow (M 2.5Y 8/3) | White (M 2.5Y 8/1) | White (M 2.5Y 8/1) |
Central rectrices and outer vanes of lateral rectrices | Indigo Blue (S 73) | Indigo Blue (S 73) | Dark grayish brown (S 20) + Indigo blue (S 173) | Sepia (S 119) |
Rectrices tips | Pale Yellow (M 2.5Y 8/3) | Pale Yellow (M 2.5Y 8/3) | White (M 2.5Y 8/1) | White (M 2.5Y 8/1) |
Back, rump and wing coverts | Indigo blue (S 73) | Dark grayish Brown (S 20) | Dark grayish Brown (S 20) | Sepia (S 119) |
There are specimens of both species from Três Lagoas, C. c. chrysops (MZUSP 64192) and C. cyanopogon (MZUSP 73779) (Figs
Identifying the causes of hybridization requires understanding how ecology, demography and phenotype influence mate choice in a particular species (
We are not able to ascertain if there is a stable hybrid zone, and there is no information about an area where individuals of C. chrysops and C. cyanopogon interbreed regularly. Possible reasons for the paucity of records of intermediate individuals could come from the great similarity of the parental species, which are often erroneously identified: individuals of C. chrysops are misidentified as C. cyanopogon and vice-versa. When the parental taxa are similar, the phenotype of the offspring produced by hybridization might be also more similar to one of the parents, making it difficult to identify visually as intermediate so they could just have remained unnoticed. On the other hand, the lack of intermediate individuals could just reflect the rarity of the interbreeding, as hybridization between other species of Cyanocorax is rare. For instance, C. chrysops is sympatric with other congeneric species, C. cyanomelas (Vieillot, 1818) and C. caeruleus (Vieillot, 1818) in part of its range (
Hybridization is more common in areas where two related species meet and one of them is rarer. Thus, restricted mate choice drives the interbreeding (
Deforestation and habitat modification affect the range of the species, and those inhabiting non-forest environments are expanding their distribution throughout Brazil, for instance Patagioenas picazuro (Temminck, 1813) (
The two sites where the hybrids were collected are transitional areas from drier vegetation formations (Cerrado, southwestern Minas Gerais and eastern Mato Grosso do Sul) to areas of humid forests (western São Paulo), and this may explain the differences in abundance of both species, easing the possibility of hybridization. Moreover, with the advance of deforestation, we detected putative new contact areas. Both species were recorded on some urban surroundings in the cities of Araxá (WA 1333137 and WA 745949), Belo Horizonte (WA 2006717 and WA 47372) in Minas Gerais, and Meridiano (WA 1702233 and WA 775584) in São Paulo state, showing that C. chrysops and C. cyanopogon can also meet in very modified environments and new events of hybridization are likely to occur.
In summary, the best predictors to explain the occurrence of hybrids between C. chrysops and C. cyanopogon are those from morphological and behavior similarity coupled with a putative rarity of conspecific pairs. Our findings highlight the need to conduct further studies in areas of range overlap to investigate the rate and frequency of hybridization and its consequences for the genetic integrity of the species involved.
We thank Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) (grant 2013/22026-1). LFS is supported by Conselho Nacional de Desenvolvimento Cientifico e Tecnológico research productivity fellowship (process #302291/2015-6). We are thankful to Alexandre Aleixo (MPEG) for the specimens’ loan and Gustavo Bravo for assisting with the procedures associated with the loan. Thiago Costa and two anonymous reviewers helped us to improve an earlier version of this manuscript.
Specimens examined