Sunday, October 1, 2023

[Herpetology • 2023] Hemachatus nyangensis • Museum DNA reveals A New, potentially extinct Species of Rinkhals (Serpentes: Elapidae: Hemachatus) from the Eastern Highlands of Zimbabwe

Hemachatus nyangensis
Reissig, Major, Renk, Barlow, Paijmans, Morris, Hofreiter, Broadley & Wüster,

in Major, Renk, Reissig, Paijmans, Morris, Hofreiter, Barlow, Broadley et Wüster, 2023.

Genetic information plays a pivotal role in species recognition and delimitation, but rare or extinct animals can be difficult to obtain genetic samples from. While natural history wet collections have proven invaluable in the description of novel species, the use of these historical samples in genetic studies has been greatly impeded by DNA degradation, especially because of formalin-fixation prior to preservation. Here, we use recently developed museum genomics approaches to determine the status of an isolated population of the elapid snake genus Hemachatus from Zimbabwe. We used multiple digestion phases followed by single strand sequencing library construction and hybridisation capture to obtain 12S and 16S rDNA sequences from a poorly preserved tissue sample of this population. Phylogenetic and morphological analyses in an integrated taxonomic framework demonstrate that the Zimbabwean rinkhals population represents an old and highly distinct lineage, which we describe as a new species, Hemachatus nyangensis sp. nov. Our phylogenetic dating analysis is compatible with venom spitting having evolved in response to the threat posed by early hominins, although more data are required for a robust test of this hypothesis. This description demonstrates the power of museum genomics in revealing rare or even extinct species: Hemachatus from Zimbabwe are only known from a small area of the Eastern Highlands known for high endemism. No living specimens have been seen since the 1980s, most likely due to dramatic land-use changes in the Eastern Highlands, suggesting that the species could be extinct. In view of its recognition as a highly distinct lineage, urgent action is required to determine whether any populations survive, and to safeguard remaining habitat.

(A and B) Hemachatus nyangensis sp. nov. specimen in life, displaying defensive hooding posture. (C and D) Miombo woodland and grassland habitat of H. nyangensis sp. nov.

Hemachatus nyangensis sp. nov.
Reissig, Major, Renk, Barlow, Paijmans, Morris, Hofreiter, Broadley, and Wüster.

Suggested common name: Nyanga rinkhals.

Diagnosis: Distinguishable from its relative Hemachatus haemachatus, for which we propose the common name “Southern Rinkhals” and which occurs in South Africa, Lesotho, and Eswatini, by its isolated distribution in eastern Zimbabwe. Morphologically, Haemachatus nyangensis sp. nov. generally has overall lower body scale counts than its southern relative: it usually has fewer nape scale rows (16–18 instead of 17–19), midbody scale rows (commonly 17–19 vs usually 19) (Fig 3), fewer subcaudal scales in both females (30–37 vs 35–40 in H. haemachatus) and males (34–38 vs 35–46) and generally fewer ventral scales in both females (126–130 vs 129–148) and males (119–124 vs 117–138) (Table 3). The new species is genetically diagnosable through differences in the 12S and 16S mitochondrial sequence. The description of this species means that the genus Hemachatus is no longer monotypic.

Etymology: The specific epithet nyangensis means “from Nyanga” in Latin and is chosen to reflect the distribution of the species in the Nyanga district of Zimbabwe, the only area in which it has been documented. 

Tom Major, Pia Renk, Jens Reissig, Johanna L. A. Paijmans, Ellie Morris, Michael Hofreiter, Axel Barlow, Donald G. Broadley and Wolfgang Wüster. 2023. Museum DNA reveals A New, potentially extinct Species of Rinkhals (Serpentes: Elapidae: Hemachatus) from the Eastern Highlands of Zimbabwe. PLoS ONE. 18(9): e0291432. DOI: 10.1371/journal.pone.0291432