Boa, Linnaeus, 1758
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publication ID |
https://doi.org/ 10.1371/journal.pone.0298159 |
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publication LSID |
lsid:zoobank.org:pub:4FEE3F5C-9213-470D-9877-79AB8FF8D4D0 |
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DOI |
https://doi.org/10.5281/zenodo.12631027 |
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persistent identifier |
https://treatment.plazi.org/id/038B1756-D012-FF93-E43D-FA5B01A7F8D9 |
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treatment provided by |
Felipe |
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scientific name |
Boa |
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Phylogeny and systematics of the genus Boa View in CoL
The genus Boa has been rather taxonomically stable since its original description in 1758 [ 3, 28, 29]. Otherwise, because there was no study focused on the taxonomy for the entire genus, at least through the application of rigorous (statistical or phylogenetic) methodology, several lineages have been traditionally recognized as subspecies [ 5, 25, 29, 74]. Bonny [ 3] presented a review of the names in the genus, even though his study does not present a replicable methodology, examination of available type material, nor is based on large number of specimens to allow statistical confidence. The renewed systematic interest in the genus launched with the study of Hynkovà et al. [ 30]. Since then, several studies have been performed with molecular data, in order to understand the phylogenetic relationships within the genus Boa [ 11, 12, 31, 32].
Despite the rearrangements proposed in previous studies, Reynolds & Henderson [ 32] published a checklist of the Family Boidae , in which they recognized five species for the genus, as such: (i) Boa constrictor (with four subspecies; B. c. constrictor , B. c. longicauda, B. c. occidentalis and B. c. ortonii), (ii) Boa imperator (with two subspecies; B. i. imperator and B. i. sabogae), (iii) B. nebulosa , (iv) B. orophias and (v) B. sigma . In this framework, only one species corresponds to the South American cis-Andean taxa: Boa constrictor , even though two of its subspecies do not belong to the “ B. constrictor Clade” (sensu Hynkovà et al. [ 30]) nor they are cis-Andean (e.g., the trans-Andean B. c. longicauda and B. c. ortonii— here considered as B. i. longicauda and B. i. ortonii).
Actually, the species delimitation into the entire genus, mainly along the cis-Andean populations (= Boa constrictor Clade sensu Hynkovà et al. [ 30]), has never flourished due for a series of reasons taken alone or in combination, as such: (i) large animals with many samples available in disparate and distant scientific collections allied to taxa with wide geographic distribution, implying a great logistic investment and personal commitment for the examination of representative samples; (ii) recently diverged taxa, usually presenting similar external morphology, at least under first inspection, without a more detailed approach establishing geographical boundaries for each taxa; (iii) very scarce or limited samples (morphological or molecular) for several taxa with very restricted distribution like islands (e.g., B. nebulosa , B. orophias , B. i. sabogae, and B. sigma ) or remote trans-Andean regions (e.g., B. i. longicaudata and B. i. ortonii); (iv) most species and subspecies are listed as CITES [ 51], consequently there are difficulties for new collections and loaning the available material; (v) superficial analyses and/or disregarding colour pattern, meristic and morphometric characters as a valid source of taxonomic evidence; (vi) reduced genetic divergence among some taxa and several short branches along the phylogenetic structure along the genus; and (vii) difficulty in amplifying some genes for new samples using primers available in the literature.
Molecular phylogenies obtained herein always recovered Boa c. occidentalis and Boa atlantica sp. nov. with high supports, independently on the markers and the dataset used. B. nebulosa and B. orophias also were recovered in a clade with relatively high support. Our decision in describe Boa atlantica sp. nov. in the specific category is broadly founded in conceptual framework (e.g., [ 75]). For instance, the use of subspecific rank within a historical context of phylogenetic inference is severely restricted, demanding the same kind of evidence (i.e., unambiguous diagnostic features) needed to recognize a species [ 76]. In addition, as recently pointed out by Burbrink and colleagues, ontologically, the rank of subspecies is either identical to that of species or undefined terminal in the context of evolutionary lineages representing spa-tiotemporally defined individuals [ 77]. In following such ideas, we realized that Boa c. occidentalis also displaying robust morphological diagnosability in combination with solid molecular support and divergence (sensu Vences et al., [ 78]. Genetic distances of 3%, 4% and more are robust supports for diagnosis of species in snakes ( Figs 2 View Fig 2 and S 3 View Fig 3 ). For instance, Boa c. occidentalis has always been retrived with high support values in a basal position within the Boa constrictor Clade [ 30, 35, 79], and presents several diagnostic features regarding its congeners [ 3, 80]. Therefore, in order to maintain the reciprocal monophyly between the previously recognized taxa ( Fig 2 View Fig 2 ), we propose here the elevation of Boa occidentalis to full specific rank. On the other hand, a comprehensive phylogeography study is required in order to make a robust taxonomic decision about the validity (or not) of remained subspecies of the Boa constrictor
Clade (i.e., B. c. amarali and B. c. melanogaster) and we refrain here to take any hasty decision in this respect.
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