Psephotellus, Mathews, 1913

Smith, Brian Tilston, Thom, Gregory & Joseph, Leo, 2024, Revised Evolutionary And Taxonomic Synthesis For Parrots (Order: Psittaciformes) Guided By Phylogenomic Analysis, Bulletin of the American Museum of Natural History 2024 (468), pp. 1-87 : 62-63

Psephotellus and Clarkona

Psephotellus comprises a small radiation (here treated as three species) of midsized parrots endemic to Australia. Its three species ( Psephotellus dissimilis , P. chrysopterygius , and the now extinct P. pulcherrimus ) are almost unique in the entire Order Psittaciformes in nesting in terrestrial termite mounds in cavities dug out by the birds themselves. This well-supported clade has a crown age of 6.6 Mya (3.1–9.5; fig. 11). A fourth species, varia , was sister to the other three but on a long branch, having diverged from the other three species at (4–12.2 Mya; fig. 11). This species has usually been placed in Psephotellus . Unlike the three tropical or subtropical Psephotellus species, this species is an arid and semiarid zone species that nests unremarkably in tree hollows. Further, it is phenotypically unlike the other three in having, for example, uniquely patterned head plumage and distinctive vocalizations. On these collective grounds, we advocate recognition of Clarkona Mathews, 1917 , as a genus for the species usually referred to as Psephotellus varius (cf. approach to recognizing Gymnopsittacus weddellii above), but which will become Clarkona varia . Clarkona was clearly and consistently treated as feminine by Mathews (1917a) and by CSIRO (1969). For example, Mathews (1917a) referred to the subspecies he recognized in this species as follows: “ Psephotus varius varius or Clarkona varia varia ,” or “ Psephotus varius exsul or Clarkona varia exsul ,” and so on.

Discordances in patterns of plumage color and phylogeny among the three species retained in Psephotellus are notable. The two species of Australia’s tropics, P. dissimilis of the Northern Territory and P. chrysopterygius of Cape York Peninsula, are extremely similar in having aqua-green underparts and prominent yellow patches on the wing coverts. They occur either side of a well-established biogeographic barrier in northeastern Australia, the Carpentarian Barrier, which can explain the distribution of many similarly distributed pairs. Unexpectedly, therefore, our results and an earlier study based on mitochondrial DNA sequence data ( Christidis and Norman, 1996) found that they are not sister taxa. Instead, the two eastern Australian species, P. chrysopterygius and the now extinct P. pulcherrimus , which had a red wing-covert patch and underparts of a similarly unique, if slightly different shade, of aqua-green, have emerged as sisters. Necessarily, both studies used DNA from historical specimens for the extinct P. pulcherrimus . Our study did likewise for the highly endangered P. chrysopterygius , that of P. dissimilis , with a sample derived from fresh tissue. We are currently sequencing DNA from a fresh P. chrysopterygius sample that has since become available to test this unexpected relationship.

If the pattern of relationships recovered in our study and by Christidis and Norman (1996) is confirmed, then it would imply that P. dissimilis diverged first from the common ancestor of P. chrysopterygius and P. pulcherrimus through vicariance across the Carpentarian Barrier. Next, divergence within eastern Australia led to separation of P. pulcherrimus and P. chrysopterygius (see Bryant and Krosch, 2016, for relevant biogeography). Psephotellus pulcherrimus was extinct by 1930, but genomic analyses show no evidence of a bottleneck prior to its extinction ( Irestedt et al., 2019). Given the discordance just noted between color of wing coverts and relationships, it is notable that the reduced wing-covert patch is sexually dimorphic in C. varia , yellow in males and red in females and younger males.

Lastly, we note that the plumage patterning of adult male P. dissimilis and P. chrysopterygius is, at least within the constraints of natural selection, broadly similar to that of several species of African Poicephalus most especially Poicephalus meyeri (fig. 13) in showing dark upperparts, prominent yellow about the greater wing coverts, and a similarly unusual shade of green on the underparts. Study of the drivers of this convergence in the high-intensity light, mostly tropical savannas that these species inhabit would surely be rewarding.