Abstract from Taft, J.
M., Maritz, B., & Tolley, K. A. (2021).
Climate shifts during the Quaternary Period have driven changes in regional
range dynamics for many species, influencing population structure of species and
in some cases promoting speciation. Within southern Africa, the psammophine
snakes Psammophis trinasalis and P. namibensis were historically
considered subspecies of P. leightoni but were elevated to species rank
based on
ecological differences. Preliminary phylogenetic analyses suggested
intraspecific, not interspecific genetic variation between these taxa, but this
finding was based on very limited data and could not be confirmed. To assess the
level of genetic differentiation within the P. leightoni species complex,
we explored the evolutionary history of these snakes by combining phylogenetic
analyses, species
distribution modelling and an examination of morphology. We generated a
comprehensive, multi-gene phylogeny for Psammophis that included wider
geographic sampling of the three species in the complex. Using this phylogeny,
Bayesian and distance-based species delimitation analyses showed intraspecific,
not interspecific divergences between taxa in the complex, suggesting that they
collectively represent a single taxon. Furthermore, non-metric multidimensional
scaling analysis of scalation characters showed no differences between the
species.
Moreover, palaeo-modelling at three time periods since the last interglacial
period suggest tat there have been varying levels of connectivity between these taxa, which has likely facilitated gene flow between them. Given the evidence,
we propose that the P. leightoni complex represents a single species and
therefore formally synonymise the three species.
Discussion paragraph in Taft e.a. 2021:
"The currently described species within the Psammophis leightoni
complex form a single, well-supported clade. Genetic structure within this clade
divergences are shallow compared to other species in the genus, and our analyses
indicate the clade represents a single, widespread taxon rather than three
separate species. Likewise, species distribution models suggest that there has
been connectivity among the distributions of the three taxa, but the degree of
connectivity has varied over time. Despite some variation in body coloration and
patterning across the range, there are no morphological differences to support
their status as separate species. Therefore, we revise the taxonomy by formally
relegating both P. namibensis Broadley, 1975 and P. trinasalis
Werner, (1902) into synonymy with P. leightoni Boulenger, 1902.
Psammophis leightoni Boulenger, 1902 published in February 1902 takes
precedence over P. trinasalis Werner, 1902 published in March 1902.
Subspecies | Psammophis leightoni trinasalis WERNER 1902 and Psammophis leightoni namibensis BROADLEY 1975 have been elevated to full species status, but Taft e.a. 2021 revised this again. |
Common Names | Cape Sand Snake |
Synonym | Psammophis leightoni BOULENGER 1902 Psammophis leightoni — BROADLEY 2002 Psammophis leightoni — MATTISON 2007: 111 |
Distribution | Republic of South Africa (W Cape Province) Reptile Atlas of Southern Africa: click here to find a distribution map |
Comment | Nomenclature: PETERS’ name is a junior homonym of
Psammophis furcatus (BIANCONI 1859) = Psammophis punctulatus DUMÉRIL &
BIBRON 1854. Distribution: see map in BROADLEY 2002. Description: (24 specimens examined). Nostril pierced between 3 nasals, upper posterior with a posterior prolongation; preocular 1, in broad contact with frontal; postoculars 2; temporals basically 2+2+3, but with frequent fusions; supralabials 8, fourth & fifth entering orbit; infralabials 10 (rarely 9), the first 4 in contact with anterior sublinguals; dorsal scales in 17-17-13 rows; ventrals 155-169; cloacal shield divided; subcaudals 92-112. Brandstätter (1995, Fig. 45) has published a SEM micrograph of a dorsal scale from NMZB 3570 from the Cape Flats. Dark brown above, top of head with a yellow stripe along the internasal/prefrontal sutures, most of supralabials, pre- and post-oculars yellow, two yellow bars across back of head. Vertebral scale row with a fine yellow line (often broken up), a yellow lateral stripe passes through scale rows 3 & 4 or fourth only, scales in outer row white at base (Broadley 1983, Fig. 84). The “chain pattern” on the side of the neck is illustrated by Boulenger (1902, pl. xii). Chin with a pattern of black streaks, ventrals with a mottled grey median band, widened at the free edge of each ventral and fading posteriorly [from BROADLEY 2002]. |
References |
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Hunter and Habitat in the Central Kalahari Desert, by George B. Silberbauer:
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