Is there a hybrid zone between subspecies of the Scarlet Macaw?

A genetic study took a closer look at this colorful parrot.

Linneaus described The Scarlet Macaw (Ara macao) in 1758. The father of modern nomenclature considered it a monotypic species (i.e. no subspecies). However, a study of museum specimens led to the recognition of two subspecies: cyanoptera and macao. The former subspecies, which ranges from southern Mexico to central Nicaragua, is more robust and has a wide band of yellow feathers on its wing. The other subspecies can be found from southern Nicaragua to Brazil and has more pronounced green coloration on the wing. In 1994, David Wiedenfeld described an intergradation of these color variants in southern Nicaragua and norther Costa Rica. Could this be a hybrid zone?


The Scarlet Macaw © Morrisdelta | Wikimedia Commons


Hybrid Zone

A recent study in the journal Ibis used mitochondrial DNA to check whether there is a hybrid zone. Analyses of 100 samples revealed a clear distinction between the two subspecies, which probably diverged between 320,000 and 850,000 years ago. There was, however, no evidence for a hybrid zone. The subspecies were clearly separated in southern Nicaragua and did not share any mitochondrial variants.


Population Structure

Interestingly, the northern subspecies (cyanoptera) showed more population structure than the southern subspecies (macao). In the map below, you can see more mitochondrial haplotypes (represented by different colors) in cyanoptera compared to macao. The authors suggest that the cyanoptera populations were isolated into separate refugia during climatic oscillations. The macao populations, on the other hand, remained more stable during these shifts in climatic conditions.


Population structure in the Scarlet Macaw. The northern subspecies (cyanoptera) shows more fragmented population structure compared to the northern subspecies (macao). From: Schmidt et al. (2019) Ibis



Schmidt, K. L., Aardema, M. L., & Amato, G. (2019) Genetic analysis reveals strong phylogeographic divergences within the Scarlet Macaw Ara macaoIbis. Early View.


This paper was added to the Psittaciformes page.


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