Diversifying into the branches: Species boundaries in African green and bush snakes, Philothamnus (Serpentes: Colubridae)

Pinto

Baptista

et al. 2019

Biodiversity of Angola

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This review summarises the current status of our knowledge of Angolan reptile diversity, and places it into a historical context of understanding and growth. It is compared and contrasted with known diversity in adjacent regions to allow insight into taxonomic status and biogeographic patterns. Over 67% of Angolan reptiles were described by the end of the nineteenth century. Studies stagnated during the twentieth century but have increased in the last decade. At least 278 reptiles are currently known, but numerous new discoveries have been made during recent surveys, and many novelties await description. Although lizard and snake diversity is currently almost equal, most new discoveries occur in lizards, particularly geckos and lacertids. Poorly known Angolan reptiles and others from adjacent regions that W. R. Branch (deceased) National Geographic Okavango Wilderness Project, Wild Bird Trust, Hogsback,

“…Some species, e.g. Philothamnus nitidus loveridgei, however, have been shown to lack genetic support for recognition (Engelbrecht et al 2018) and are now not recognised.…”

Section: Recent Discoveriesmentioning

confidence: 99%

The Reptiles of Angola: History, Diversity, Endemism and Hotspots

Pinto

Baptista

et al. 2019

Biodiversity of Angola

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“…The Afrotropical region accommodates several wide‐ranging species in the family Colubridae; including those in the genera Crotaphopeltis, Dasypeltis, Dipsadoboa, Dispholidus, Hapsidophrys, Meizodon, Natriciteres, Philothamnus, Rhamnophis , Telescopus, Thrasops, and Toxicodryas (Uetz, Freed, & Hošek, 2019; Wallach, Williams, & Boundy, 2014). Although some representative species within these genera were included in phylogenetic studies addressing higher taxonomic classifications (Cadle, 1994; Chen et al, 2013; Lawson, Slowinski, Crother, & Burbrink, 2005; Pyron et al, 2011, 2014; Pyron, Burbrink, & Wiens, 2013; Tonini, Beard, Ferreira, Jetz, & Pyron, 2016; Vidal et al, 2007; Zheng & Wiens, 2016), few genera have received detailed and comprehensive molecular phylogenetic investigations (Eimermacher, 2012; Engelbrecht et al, 2019; Trape, Mediannikov, & Trape, 2012). This hampers our understanding of the diversity and distribution of African colubrids, particularly for wide‐ranging species where cryptic diversity is likely to be present.…”

Section: Introductionmentioning

confidence: 99%

“…This hampers our understanding of the diversity and distribution of African colubrids, particularly for wide‐ranging species where cryptic diversity is likely to be present. For Dasypeltis and Philothamnus , several new cryptic taxa have been identified within what had been previously thought to be single wide‐ranging species (Bates & Broadley, 2018; Engelbrecht et al, 2019; Trape et al, 2012). These findings imply that wide‐ranging African colubrids often comprise cryptic lineages, and therefore, more comprehensive molecular phylogenetic investigations are required to better understand their taxonomy and evolutionary history.…”

Section: Introductionmentioning

confidence: 99%

African Herald snakes,Crotaphopeltis, show population structure for a widespread generalist but deep genetic divergence for forest specialists

Engelbrecht

J. Zool. Syst. Evol. Res.

Greenbaum

et al. 2020

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The African colubrid snake genus Crotaphopeltis currently comprises six species and occurs throughout sub‐Saharan Africa. The most widespread of these, Crotaphopeltis hotamboeia, inhabits most biomes, aside from rainforest and hyper‐arid regions, and its catholic niche has presumably facilitated substantial gene flow. Despite this, the geographical range is large enough that ecological or physical barriers might exist, facilitating allopatric diversification. In contrast, most of the other species are habitat specialists with limited distributions (e.g., Crotaphopeltis tornieri) and would be expected to show strong genetic structure. We therefore examined species boundaries within Crotaphopeltis in a phylogenetic context using five markers (16S, cyt b, ND4, c‐mos, and RAG‐1) for four of the six species. Species delimitation methods included two coalescent‐based and one barcoding approach. Widespread geographical sampling of C. hotamboeia allowed examination of genetic structuring across its range. The species status of Crotaphopeltis barotseensis, C. degeni, and C. hotamboeia was confirmed, whereas the Afromontane species C. tornieri comprised two candidate species. Crotaphopeltis hotamboeia did not show cryptic speciation, although its phylogeographic structure corresponded with the spatiotemporal pattern of the African savanna. Our results show how the heterogeneous African environment could influence genetic partitioning of habitat specialist and generalist species at broad geographical scales.

“…The species and putative species identified within Philothamnus ( Engelbrecht et al, 2019 ) and Crotaphopeltis ( Engelbrecht et al, 2020 ) were used to estimate diversification dates and to reconstruct ancestral habitats. Our analyses therefore include the currently recognised species as well as undescribed species (i.e., lineages that show species level divergence but are not yet described as species).…”

Section: Methodsmentioning

confidence: 99%

“…We refer to both the described and undescribed species as ‘taxa’ throughout. Outstanding taxonomic issues are that Philothamnus semivariegatus is paraphyletic, comprising four cryptic lineages, P. carinatus contains two cryptic lineages while P. dorsalis and P. giraradi appear to be a single taxon that require synonymising ( Engelbrecht et al, 2019 ). Similarly, previous analyses of Crotaphopeltis indicated that Crotaphopeltis tornieri is not monophyletic, and consists of at least two separate taxa that are not sister clades ( Engelbrecht et al, 2020 ).…”

Section: Methodsmentioning

confidence: 99%

Snakes on an African plain: the radiation of Crotaphopeltis and Philothamnus into open habitat (Serpentes: Colubridae)

Engelbrecht

Tolley

2021

PeerJ

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Background The African continent is comprised of several different biomes, although savanna is the most prevalent. The current heterogeneous landscape was formed through long-term vegetation shifts as a result of the global cooling trend since the Oligocene epoch. The overwhelming trend was a shift from primarily forest, to primarily savanna. As such, faunal groups that emerged during the Paleogene/Neogene period and have species distributed in both forest and savanna habitat should show a genetic signature of the possible evolutionary impact of these biome developments. Crotaphopeltis and Philothamnus (Colubridae) are excellent taxa to investigate the evolutionary impact of these biome developments on widespread African colubrid snakes, and whether timing and patterns of radiation are synchronous with biome reorganisation. Methods A phylogenetic framework was used to investigate timing of lineage diversification. Phylogenetic analysis included both genera as well as other Colubridae to construct a temporal framework in order to estimate radiation times for Crotaphopeltis and Philothamnus. Lineage diversification was estimated in Bayesian Evolutionary Analysis Sampling Trees (BEAST), using two mitochondrial markers (cyt–b, ND4), one nuclear marker (c–mos), and incorporating one fossil and two biogeographical calibration points. Vegetation layers were used to classify and confirm species association with broad biome types (‘closed’ = forest, ‘open’ = savanna/other), and the ancestral habitat state for each genus was estimated. Results Philothamnus showed an ancestral state of closed habitat, but the ancestral habitat type for Crotaphopeltis was equivocal. Both genera showed similar timing of lineage diversification diverging from their sister genera during the Oligocene/Miocene transition (ca. 25 Mya), with subsequent species radiation in the Mid-Miocene. Philothamnus appeared to have undergone allopatric speciation during Mid-Miocene forest fragmentation. Habitat generalist and open habitat specialist species emerged as savanna became more prevalent, while at least two forest associated lineages within Crotaphopeltis moved into Afromontane forest habitat secondarily and independently. Discussion With similar diversification times, but contrasting ancestral habitat reconstructions, we show that these genera have responded very differently to the same broad biome shifts. Differences in biogeographical patterns for the two African colubrid genera is likely an effect of distinct life-history traits, such as the arboreous habits of Philothamnus compared to the terrestrial lifestyle of Crotaphopeltis.