Asio, Brisson, 1760, Brisson, 1760
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publication ID |
https://doi.org/10.11646/zootaxa.5584.3.5 |
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publication LSID |
lsid:zoobank.org:pub:DD94E434-22A9-4EFF-8344-9DE7D08BCF8B |
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DOI |
https://doi.org/10.5281/zenodo.17523816 |
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persistent identifier |
https://treatment.plazi.org/id/3500CF23-AF6B-FFC4-FF0E-F8A164EAED52 |
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treatment provided by |
Plazi |
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scientific name |
Asio |
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Results and Discussion View in CoL
Cladistic analyses based on 35 osteological characters (Appendix, Table 1 View TABLE 1 ) produced a single most parsimonious tree with 50 steps ( Fig. 2 View FIGURE 2 ). The Consistency Index (CI) was 0.72 and the Retention Index (RI) was 0.75. Character descriptions and the consistency index of each character (ci) are provided in the appendix.
Our results reveal the following phylogenetic relationships within Asio : (( A. otus ( A. stygius ( A. clamator / A. grammicus ))) ( A. solomonensis ( A. capensis / A. flammeus ))). This topology corroborates the molecular results of Wink et al. (2009), Zhang et al. (2016) and Salter et al. (2020), except for the position of A. otus ( Figs. 1 View FIGURE 1 and 2 View FIGURE 2 ).
According to Callender-Crowe & Sansom (2022), changes on the skeleton occur relatively earlier in deep branches of birds so, osteological characters can be more consistent with molecular data. Furthermore, osteological data can improve our comprehension of avian evolution and form/function ( Giribet 2015). For example, Asio flammeus is unique among owls for its diurnal activity and inhabits a wide range of environments, from open areas and plantations to forests and tundra ( Marks et al. 1999; Ward et al. 2002; König & Weick 2008). These characteristics likely led to the evolution of a long and narrow tarsometatarsus and femur (characters 27, 28, and 30), adaptations that facilitate the predation of a diverse array of diurnal and nocturnal animals ( Ward et al. 2002). In the same way, similarities in the orbit, tympanic, and forelimb bones between A. otus and the clade A. flammeus / A. capensis have been noted by Olson (1995). These species often prey on small rodents and, occasionally, small mammals and birds with crepuscular or nocturnal habits ( Marks et al. 1999; König & Weick 2008). This suggests a selection for both a similar acute sense of hearing/vision and forelimb morphology, resulting in convergent modifications of these bones for capturing small and crepuscular/nocturnal prey ( Konishi 1973; Csermely 2000). Therefore, based on the topology presented here ( Fig. 2 View FIGURE 2 ) and on the principle of parsimony, we interpret these similarities as resulting from convergent adaptations between A. otus and the A. flammeus / A. capensis clade (two evolutionary steps), rather than an origin at the base of the cladogram with subsequent losses in A. solomonensis and the A. stygius / A. clamator / A. grammicus clade, which would require three evolutionary steps.
Although the clade Asio capensis / Asio flammeus (Node C, Fig. 2 View FIGURE 2 ) is defined solely by character 25 (the narrow and reduced lateral process of the Ala preacetabularis ilii ), this relationship is supported by all phylogenetic analyses based on molecular data ( Wink et al. 2009; Zhang et al. 2016; Salter et al. 2020, Fig. 1 View FIGURE 1 ). Our study identifies two osteological autapomorphies for A. capensis : the presence of a foramen in the prominentia cerebellaris (character 13) and the large, shallow intercoracoidal space of the sternum (character 35). Additionally, we observed significant structural variations within the skeletons of A. flammeus specimens. This species is cosmopolitan in distribution with eleven subspecies exhibiting disjunct distribution and inhabiting different environments, from open areas and plantations to forests and tundra ( Marks et al. 1999; König & Weick 2008). We recommend further taxonomic investigations within the A. flammeus complex.
Asio solomonensis is endemic to the Solomon Archipelago, Bougainville, Choiseul, and Santa Isabel. It is one of the least known and possibly one of the rarest owls, with limited information on its ecology and behavior ( Loyn & Debus 2000). While Wink et al. (2009) and Zhang et al. (2016) did not include A. solomonensis, Salter et al. (2020) considered it most closely related to A. flammeus . Peters (1937) also proposed a close relationship between Nesasio ( A. solomonensis ) and A. flammeus , suggesting that Nesasio may have originated from an A. flammeus lineage. Our findings support this arrangement, along with A. capensis , based on four synapomorphies ( Node B, Fig. 2 View FIGURE 2 ). Peters (1937) proposed Neoasio, a new genus for Pseudoptynx solomonensis Hartert, 1901 , because the type species of Pseudoptynx was a Bubonine and P. solomonensis displayed features unlike an Bubonine but similar to those in species of Asio (see Olson 1995). Our results support those of extensive molecular data ( Salter et al. 2020), and do not support maintaining this taxon as a distinct genus within Asionini . Thus, we support the placement of N. solomonensis in the genus Asio by Salter et al. (2020). The osteological diagnosis for this species is challenging due to the missing structures in the observed specimens (AMNH 23409, 23410). Nevertheless, our results reveal the following autapomorphies (also noted by Olson 1995): the processus postorbitalis descending directly from the postorbital prominence (character 18) and the narrow, shallow recess between the processus postorbitalis and the Ala tympanica (character 21).
We identified the right angle (approximately 90°) of the processus supraorbitalis relative to the os frontale (character 3, state 0) as the sole autapomorphy for A. otus . Although the systematic position of A. otus within the clade with A. stygius , A. clamator , and A. grammicus is not controversial, the intra-clade relationships of O. otus herein does not corroborate the molecular studies. Wink et al. (2009) and Zhang et al. (2016) indicated that A. otus is most closely related to A. clamator , but A. stygius and A. grammicus were absent from these studies ( Fig. 1 View FIGURE 1 ). Salter et al. (2020) included A. grammicus but placed it most closely related to A. otus . This arrangement is not corroborated by osteological data (Node D, Fig. 2 View FIGURE 2 ). In fact, an additional 18 steps would be required to support A. otus as the sister group to A. clamator (Node E and F, Fig. 2 View FIGURE 2 ) and our study reveals that it is a sister group to the clade A. stygius / A. clamator / A. grammicus (Node E, Fig. 2 View FIGURE 2 ).
The systematic position of A. stygius has been unknown, as it is absent from all phylogenetic studies including species of Asionini ( Randi et al. 1991; Wink et al. 2000, 2009; Zhang et al. 2016; Salter et al. 2020, Fig. 1 View FIGURE 1 ). Our study reveals that this species forms a sister group to the clade A. clamator / A. grammicus ( Fig. 2 View FIGURE 2 ). The current distribution of all three species ( Marks et al. 1999) suggests a common origin in the Neotropical region, supported by robust evidence based on eight synapomorphies (Node E, Fig. 2 View FIGURE 2 ). Asio stygius is one of the largest species of Asio ( 38 to 46 cm, approximately 700 grams) with dark plumage in both sexes and six disjunct subspecies restricted to the Neotropical region. It is a non-migratory owl that preys on birds, bats, and frogs ( Sick 1997; Marks et al. 1999; Weick 2006). The only osteological difference observed in A. stygius is that the linea intermuscularis cranialis (cranial region of the os femur) originates from the facies articularis antitrochanterica, whereas in other species of Asio it starts from the midpoint of the crista trochanteris.
Significant modifications in the skeletal components of A. grammicus and A. clamator compared to other species of Asio result in 17 synapomorphies (Node F, Fig. 2 View FIGURE 2 ). Olson (1995) also noted distinct osteological characteristics in A. grammicus / A. clamator , particularly in the Ala tympanica and postorbital process. Olson (1995) suggested that this clade represents relictual forms of a once widespread Asioninae lineage, with cranial bones in A. grammicus / A. clamator resembling those of non-Asioninae owls. However, our phylogenetic analysis, based on comparisons with species of Ptilopsis , shows that of the 17 synapomorphies, ten are new modifications in the skull (caudal portion of the skull: characters 11, 13; processus postorbitalis: 17, 18; ala tympanica : 20, 21; processus medialis ossa mandibulae: 23), as well as in the post-cranial bones (characters 26, 33, and 34). This indicates that A. grammicus and A. clamator form a derived group within Asionini , a relationship further supported by their shared distribution in the Neotropical region ( Marks et al. 1999). In molecular studies by Wink et al. (2009) and Zhang et al. (2016), A. clamator was resolved as sister group to A. otus , but A. grammicus was missing ( Fig. 1 View FIGURE 1 ). Salter et al. (2020) included all three species, with A. grammicus most closely related to A. otus . Thus, both morphological and molecular data support the inclusion of A. grammicus in Asio . This species, primarily insectivorous, occasionally preys on small amphibians and mammals ( König & Weick 2008). According to the topology presented in our study, the endemic A. grammicus of Jamaica ( Marks et al. 1999; König & Weick 2008) likely evolved from an isolated ancient lineage shared with A. clamator . Our study identified one autapomorphy for A. grammicus : the reduced and narrow lateral process of the ala preacetabularis ilii (character 25).
Asio clamator is a relatively large species ( 30–38 cm, 320–546 grams) with long ear tufts. It is nocturnal, feeding on bats, birds, and small mammals ( Marks et al. 1999; Aguiar & Naiff 2009). It has four disjunct subspecies distributed across Central and South America ( Marks et al. 1999; König & Weick 2008). Olson (1995) synonymized Rhinoptynx ( R. clamator ) with Pseudoscops . Molecular studies ( Wink et al. 2009; Zhang et al. 2016; Salter et al. 2020) suggest that A. clamator should be classified within the genus Asio ( Fig. 1 View FIGURE 1 ), and our findings corroborate this taxonomic placement. Our study also reveals the following autapomorphies for A. clamator : the narrow, caudally curved pars ventralis of the os ectethmoidale (character 1) and several characteristics not included in the phylogenetic analysis, including a prominent tuberculum laterosphenoidale on the cranium, a more prominent processus intermetacarpalis on the carpometacarpus, and a larger (triangular) cranial extremity of the spina externa on the sternum. Additionally, this species has four disjunct subspecies distributed to Central and South America ( Marks et al. 1999; König & Weick 2008; Pacheco et al. 2021) and we observed considerable variation in bone structures among specimens of A. clamator , suggesting further taxonomic investigations within the A. clamator complex.
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