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Team Argues for Cape Parrot Reclassification Based on Genetic Data

Cape Parrot

NEW YORK (GenomeWeb) – A PLOS One study suggests there's sufficient genetic evidence to reclassify the Cape Parrot as a distinct species rather than as a sub-species within Poicephalus robustus.

South African researchers assessed and compared genetic markers in 138 parrot specimens falling in five Poicephalus species, focusing on almost a dozen microsatellite loci, two mitochondrial gene sequences, and the intron of one nuclear gene. Their phylogenetic look at the data indicated that ancestors of the Cape Parrot — currently known as P. robustus robustus — separated from those of its current co-species P. r. fuscicollis some 2.13 million to 2.67 million years ago.

As such, the study's authors argued that the Cape Parrot belongs to its own species — a designation that they believe will improve the way conservation strategies are developed and put into place to deal with declining Cape Parrot populations in South Africa.

"Our results are sufficient to provide conservation authorities with strong evidence that the South African endemic Cape Parrot should be viewed as a vulnerable species of conservation priority," senior author Sandi Willows-Munro, a life sciences researcher at the University of KwaZulu-Natal, and colleagues explained, noting that "[t]his recognition will in turn assist the biodiversity conservation sector to prioritize, plan, and implement conservation strategies."

The classification of Cape Parrots has been contentious and controversial, the team explained, despite apparent differences between appearance, mating habits, and other features of the birds and their current co-species.

The existence of three P. robustus sub-species is also problematic from a conservation standpoint, the study's authors asserted, since many organizations deal with organisms on the species level rather than evaluating potential threats to individual sub-species.

To tease apart the Cape Parrots' position in the parrot family tree, they started by scrutinizing several different types of genetic markers in 138 Poicephalus parrots, including representatives from four species native to southern Africa and a fifth species found in central Africa.

Along with 32 P. r. robustus parrots from populations in the Eastern Cape, KwaZulu, and Limpopo regions of South Africa, the researchers made a point of sampling representatives from the two other P. robustus sub-species: the Brown-necked parrot (P. r. fuscicollis) and Grey-headed parrot (P. r. suahelicus).

Based on sequence patterns at 11 microsatellite markers, sequences from the cytochrome oxidase I and 16S ribosomal RNA genes in the mitochondrial genome, and intron sequences from the nuclear gene beta-fibrinogen, the researchers found that the Brown-necked parrot and Grey-headed parrot generally clustered together genetically.

The Cape Parrot's position in the tree was somewhat murkier, depending on the type of data considered and the computational approach used, though the dataset as a whole supported the notion that the Cape Parrot is genetically distinct from its current co-species, prompting the team to propose that it be designated P. robustus sensu stricto.

Moreover, the researchers' molecular clock analysis, which included new sequence data and existing sequences for dozens more parrot species drawn from 21 different genera, suggests the Cape Parrot diverged from its co-species more than 2 million years ago, falling into a distinct lineage that first appeared sometime in the Pleistocene epoch.