Borikenophis Hedges & Vidal

Hedges, Blair, Couloux, Arnaud & Vidal, Nicolas, 2009, Molecular phylogeny, classification, and biogeography of West Indian racer snakes of the Tribe Alsophiini (Squamata, Dipsadidae, Xenodontinae), Zootaxa 2067, pp. 1-28 : 13-14

Genus Borikenophis Hedges & Vidal , New Genus

Type species. Alsophis portoricensis Reinhardt & Lütken 1862:221 .

Diagnosis. Species in this genus have 17–19 midbody scale rows, 163–198 ventrals, 106–145 subcaudals, 1–3 apical scale pits, eight upper labials, 10 lower labial, 16-21 maxillary teeth, and 22-35 dentary teeth ( Table 2). Borikenophis differs in at least one of these characters from all other alsophiine genera except Alsophis and Hypsirhynchus . Except for B. sanctaecrucis (191–198 ventrals), it differs from most Alsophis in having a lower number of ventrals (163–187 versus 184–220 in Alsophis ). Most Hypsirhynchus have 19 midbody scales rows ( H. ater and H. melanichnus have 17 rows) whereas most Borikenophis have 17 rows (those populations from the Virgin Islands usually have 19 rows).

Content. Three species (eight species + subspecies) are included in the genus ( Table 1).

Distribution. Species of Borikenophis are distributed throughout the Puerto Rican Bank, and on the nearby islands of Mona, Desecheo, and Saint Croix ( Fig. 2 ).

Etymology. The generic name refers to its distribution centered on the Puerto Rican Bank; Boriken is the Taino word for Puerto Rico.

Remarks. Species of Borikenophis are moderate-sized (1025 mm, maximum SVL) racers ( Fig. 3 B) and they occur sympatrically with the smaller racers of the Genus Magliophis . Six subspecies are recognized for Borikenophis portoricensis . The species from St. Croix, B. sanctaecrucis , is possibly extinct (Henderson & Powell 1996) and was not included in this study, but it has been considered a close relative of B. portoricensis based on color pattern and scalation ( Schwartz 1966). Although we found B. p. portoricensis and B. p. anegadae to have identical sequences at all genes sampled, the two subspecies are not particularly close morphologically, with different midbody scale row counts (17 versus 19, respectively). Therefore, to resolve geographic variation in the species B. portoricensis , sequences of additional, more variable, genes will be needed. Zaher et al. (2009) included B. portoricensis together with various other West Indian species in the resurrected genus Ocyophis Cope , but our data ( Figs. 1 and 4 ) contradict that decision as the genera Borikenophis , Cubophis and Haitiophis (the latter not sampled by Zaher et al.) do not form a monophyletic group (see Remarks in Hypsirhynchus ).

Figures

FIGURE 2. Map showing the West Indies (including the southern tip of Florida above, Central America to the west, and the northern edge of South America below) and the distributions of the genera of the Tribe Alsophiini, Subfamily Xenodontinae, Family Dipsadidae.

FIGURE 3. Representatives of genera of the snake Tribe Alsophiini (Dipsadidae: Xenonodontinae). Subtribe Alsophiina: Alsophis manselli (Woodlands Spring, Montserrat), Borikenophis portoricensis (1.5 km W. Playa de Tamarindo, Puerto Rico), Cubophis cantherigerus (2.0 km W Viñales, Pinar del Rio, Cuba), Hypsirhynchus ferox (Barahona, Barahona, Dominican Republic), Ialtris dorsalis (3 km N Bois Sec, Grand’Anse, Haiti), and Magliophis stahli (1.9 km NE Vista Alegre, Puerto Rico). Subtribe Arrhytonina: Arrhyton taeniatum (0.2 km WE Windmill Beach, Guantanamo Bay Naval Station, Cuba). Subtribe Uromacerina: Uromacer oxyrhynchus (4.4 km W Canada Honda, La Altagracia, Dominican Republic). Photos by S. B. Hedges.

FIGURE 1. A phylogeny of Alsophiini. Bayesian tree obtained from the combined data set of six genes (RAG 2, 12 S & 16 S rRNA, cytochrome b, ND 2 and ND 4; 3387 sites). Alsophis portoricensis portoricensis and A. p. anegadae have identical sequences at all genes sampled, and therefore the latter taxon is not shown. Values are ML bootstrap values above 70 % followed by Bayesian posterior probabilities above 90 %. The generic taxonomy in this tree reflects usage prior to this study and shows paraphyly and polyphyly of Alsophis (blue), Arrhyton (purple), and Antillophis (orange). See Table 1 and Figure 4 for the new classification proposed here.

FIGURE 4. A timetree of Alsophiini. Divergence times and credibility / confidence intervals are shown in Table 3. Plei = Pleistocene. The generic taxonomy in this tree reflects the new classification proposed here and detailed in Table 1.