Touit, G. R. Gray, 1855

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 : 25-29

Touit , Bolborhynchus , Nannopsittaca , and Psilopsiagon

The four genera in this group ( Touit , Bolborhynchus , Nannopsittaca , and Psilopsiagon , whether in Amoropsittacini or Touitini as discussed above) comprise small-bodied and largely green-plumaged species occasionally broken up with traits such as black barring, small areas of other colors about the head and face, differently colored underwing coverts, or, as in one species, a crown demarcated from the upperparts and underparts. Tails vary from long and attenuate to short and blunt. Touitini is generally more morphologically uniform than Amoropsittacini. Species in Touit have small, stocky bodies with round tails, whereas Amoropsittacini shows greater variation in gross morphology, tail morphology and body size. Sexual dimorphism is also much more pronounced.

Turning to species-level relationships, we first report the relationships inferred from the concatenated tree. Touit stictopterus of central Colombia to northern Peru diverged from the remaining Touit at 10.1 Mya (5.9–13.1; fig. 5). The next divergence represents a mostly eastwest break across the Andes. The clade comprising sister species T. dilectissimus and T. costaricensis diverged across the Andes at 5.5 Mya (3.1–7.6) from the other clade entirely east of the Andes ( T. surdus , T. purpuratus , T. batavicus , T. melanotus , and T. huetii ; fig. 5). The divergence across the Isthmus of Panama between T. dilectissimus and T. costaricensis occurred 1.1 Mya. This timeframe aligns with other humid forest birds that colonized North America (Smith et al., 2012). The first divergence in the clade east of the Andes was between T. huetii and the other taxa (fig. 5). Touit huetii is widespread across Amazonia in relatively small allopatric populations. Touit melanonotus of southern Brazil and T. batavicus of northern Colombia, Venezuela, Suriname, the Guianas, and northern Brazil are highly disjunct with respect to each other, separated by the Amazon Basin and the South American dry diagonal, including the Caatinga and Cerrado Biomes. That disjunction dates to the late Pliocene–early Pleistocene. A second large disjunction is between sister species T. purpuratus of northern Amazonian and T. surdus of southeastern Brazil. In contrast, the species tree found notable differences in relationships. However, some taxa ( T. costaricensis , T. melanonotus , and T. surdus ) with lower-quality samples could not be accurately placed in the species tree. The most notable difference was the placement of T. huetii , which was sister to T. purpuratus in the species tree.

The species in the other three genera occur primarily in montane regions, except Nannopsittaca dachilleae of lowland western Amazonia. The traditionally recognized genera Bolborhynchus and Nannopsittaca , however, are not monophyletic. That is, two of three nominal species within Bolborhynchus ( B. ferrugineifrons and B. orbygnesius ) and the two species of Psilopsiagon ( P. aymara and P. aurifrons ) comprise a clade that represents a radiation across the high Andes, with its species-level divergences ranging from 3.6–7.6 Mya (fig. 5). The concatenated and species trees represented here are mostly concordant. Bolborhynchus ferrugineifrons was accurately placed in the same clade in both phylogenomic trees but had a significant amount of missing data at parsimony informative sites. The order of P. aymara and P. aurifrons also differed in the species tree, but they were still paraphyletic with respect to each other, a result that we note with much caution. Although B. lineola and the two species in Nannopsittaca form a clade, they are biogeographically less cohesive. Nannopsittaca panychlora occurs disjunctly in small, restricted parts of Venezuela in the tepui region from 750 to 1850 m ( Forshaw and Knight, 2010). Bolborhynchus lineola is widely distributed in montane regions from Mexico to Peru. Nannopsittaca panychlora was sister of N. dachilleae and B. lineola , and so Nannopsittaca was paraphyletic.

We consider five alternative taxonomic scenarios for addressing the paraphyly within Bolborhynchus , Nannopsittaca , and potentially Psilopsiagon (see fig. 5). They are:

1. Most expediently, all species could be placed in the oldest of the three generic names, Bolborhynchus Bonaparte, 1857 . Previous authors have indeed treated Psilopsiagon aymara and P. aurifrons within Bolborhynchus ( De Schauensee and Eisenmann, 1966, Forshaw and Knight, 2010). This would produce a genus with high interspecies morphological disparity reflected temporally in the clade dating to the mid-Miocene. Conversely, there is no precedent elsewhere within Psittaciformes for a genus having a crown age as deep as 16.9 Mya, which reflects a timespan encompassing substantial evolutionary divergence. Recalling Ford’s (2006) suggestion that a genus should make sense to someone not familiar with it, we reject this option.

2. Given that Bolborhynchus lineola (Cassin, 1853) = Psittacula lineola Cassin, 1853 , is the type species of Bolborhynchus (and, parenthetically, of Grammopsittaca Ridgway, 1912 ), the two species of Nannopsittaca Ridgway, 1912 , although paraphyletic with respect to each other, could be placed in Bolborhynchus with B. lineola . This is consistent with O’Neill et al.’s (1991) case that they are congeneric notwithstanding that we here advocate placing them in the same genus as B. lineola . Two other species currently in Bolborhynchus ( ferrugineifrons , orbygnesius ) could then be placed in Psilopsiagon with P. aymara and P. aurifrons . However, this option also produces genera with species that are morphologically disparate albeit less so than the previous option.

3. As option 2 but reinstating monotypic Amoropsittaca Richmond, 1915 , only for aymara .

4. Retention of N. panychlora in monotypic Nannopsittaca , although counter to O’Neill et al.’s (1991) view that Nannopsittaca is ditypic, opens this fourth option. Notwithstanding the superficial similarity in gross morphology of the two species usually placed in Nannopsittaca (e.g., fig. 5), we find this a reasonable option for two main reasons: (1) N. panychlora diverged from N. dachilleae / B. lineola at 7.5 Mya (4.2–9.8), a depth of divergence that was similar to deeper intra- and intergeneric splits within Psittaciformes, and (2) it was the only Neotropical parrot endemic to the Pantepui region of northern South America (e.g., Mayr and Phelps, 1967). By this option, B. ferrugineifrons and B. orbygnesius and aymara and aurifrons could be placed in Psilopsiagon as already suggested, and N. dachilleae would be moved to Bolborhynchus because it was sister to the type species of that genus, B. lineola . Bolborhynchus lineola and N. dachilleae are strongly associated with bamboo albeit of different genera, i.e., Chusquea spp. and Guadua spp. , respectively ( O’Neill et al., 1991; del Hoyo et al., 1997; Harvey et al., 2014).

5. As option 4 but with aymara in Amoropsittaca .

Choosing among these options inevitably becomes subjective. We favor option 4, arguing that retention of aymara in Psilopsiagon is prudent until its position relative to the other species in that genus is clarified. Similarly, the position of aurifrons was poorly supported (UFBS = 74%). This is consistent with our generic decisions made elsewhere to convey as accurately as possible well-supported phylogenomic diversity (e.g., Licmetis vs. Cacatua ; Zanda vs. Calyptorhynchus ; Psephotellus vs. Clarkona ; Aratinga vs. Nandayus ), regardless of the patterns of phenotypic diversity among the various species. Further, it retains all three recognized genera albeit with some inevitable but minimal disruption to their usage, and it presents no conflict between classification and phylogeny. Although it places in the same genera species that are somewhat different in gross morphology, e.g., relative tail length and shape, this is common to either of the arrangements we discussed (see fig. 6). The difficulty of discerning phenotypic traits in diagnosing the three genera as so circumscribed

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) tographs warrants brief comment. We suggest that this likely arises from very strong selective pressures on these species for cryptic, largely green plumage (see fig. 6). This could feasibly apply to either species inhabiting and primarily foraging in lowland or upland rainforest canopies, such as dachilleae and panychlora , respectively, or to those foraging in other montane habitats such as lower, scrubby hillside vegetation and terrestrial bogs, as in most of the other species.

We stress that the need for recognition of these three genera and their circumscriptions as we have suggested have arisen largely from our concerns with reflecting the phylogenomic data and structure among them. In summary, we advocate the following taxonomy with phenotypic notes (fig. 6):

• Psilopsiagon Ridgway, 1912 : P. ferrugineifrons , P. orbygnesius , P. aurifrons , P.aymara . Predominantly green plumage with patterning that does not involve barring and moderate to long tails. Species membership in Psilopsiagon is tentative pending clearer resolution of phylogenetic relationships. Amoropsittaca Richmond, 1915 is available for aymara if warranted.

• Nannopsittaca Ridgway, 1912 : N. panychlora . Short-tailed, green plumage with little or no blue particularly in the crown but with a distinctive “broken” ring of yellow periophthalmic feathering. Orbital region mostly feathered ( Ridgway, 1916). Bill and cere generally dark gray.

• Bolborhynchus Bonaparte, 1857 : B. lineola , B. dachilleae . Diagnostic phenotypic traits shared by the two species are difficult to discern beyond both being short-tailed green parrotlets. Bolborhynchus lineola has barred dorsal plumage, which we postulate to be derived, recalling that of Australian Pezoporus and Melopsittacus and arising from black feather centers on the ventral surface especially under the tail. B. dachilleae has generally plainer green plumage, which we postulate as ancestral, apart from a distinctive blue crown. In B. dachilleae , the orbital region’s bare skin is whitish and the bill and cere are pinkish buff, not dark gray as in Nannopsittaca ( O’Neill et al., 1991) whereas the similarly colored bill of B. lineola is often distally tipped dark. Bolborhynchus lineola and N. dachilleae are strongly associated with bamboo (see option 4 above), an ecological preference, to our knowledge that has not been observed in N. panychlora .