Data Paper |
Corresponding author: Savel R. Daniels ( srd@sun.ac.za ) Academic editor: Robert Jadin
© 2019 Kyle Kullenkampff, Francois Van Zyl, Sebastian Klaus, Savel R. Daniels.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Kulenkampff K, Van Zyl F, Klaus S, Daniels SR (2019) Molecular evidence for cryptic species in the common slug eating snake Duberria lutrix lutrix (Squamata, Lamprophiidae) from South Africa. ZooKeys 838: 133-154. https://doi.org/10.3897/zookeys.838.32022
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We examined the impact of climatic fluctuations on the phylogeographic structure of the common slug eating snake (Duberria lutrix lutrix) throughout its distribution in South Africa. The evolutionary history within the taxon was examined using partial DNA sequence data for two mitochondrial genes (ND4 + cyt b) in combination with a nuclear locus (SPTBN1). Phylogenetic relationships were investigated for both the combined mtDNA and total evidence DNA sequence data. In addition, population and demographic analyses together with divergence time estimations were conducted on the combined mtDNA data. Topologies derived from the combined mtDNA analyses and the total evidence analyses were congruent and retrieved five statistically well-supported clades, suggesting that Duberria l. lutrix represents a species complex. The five clades were generally allopatric, separated by altitudinal barriers and characterised by the absence of shared mtDNA haplotypes suggesting long term isolation. Divergence time estimations indicate that the diversification within the D. l. lutrix species complex occurred during the Plio/Pleistocene as a result of climatic fluctuations and habitat shifts for the species. A taxonomic revision of the D. l. lutrix species complex may be required to delineate possible species boundaries.
snakes, Afrotropical, alpha taxonomy, phylogenetics, altitudinal barriers, southern Africa
Climatic oscillations are thought to be responsible for inducing dramatic impacts on the habitat and eco-physiological characteristics promoting cladogenesis (
The serpent fauna of South Africa contains 116 species, of which 29 are endemic (
The distribution range of Duberria l. lutrix in South Africa is bisected by several large mountain ranges, including the Cape Fold Mountains and the Great Drakensberg escarpment (
Known biogeographic breaks for co-distributed animal species in South Africa, including the A Hottentots Holland Mountains (blue) B The Breede River Valley (red) and C the Bedford gap (Yellow). The Duberria l. lutrix localities sampled throughout South Africa during the present study. Locality numbers correspond to the sample site numbers in Table
Considering the results observed in phylogeographic studies of other co-distributed reptile species, we postulate that D. l. lutrix exhibits similar patterns of genetic differentiation across its distribution in South Africa. The objective of the present study is twofold. First, to examine the phylogeographic relationships within D. l. lutrix in South Africa, and to explore the possible impact of climatic changes on the phylogeographic patterning of the species. Second, to examine the presence of possible cryptic lineages within the taxon. Firstly, we hypothesize that climatic induced evolutionary changes during the Plio/Pleistocene promoted cladogenesis in the species. Secondly, we hypothesize that discrete lineages are present within D. l. lutrix.
Road killed specimens or tissue of Duberria l. lutrix were obtained from the South African National Biodiversity Institute tissue bank (
A list representing the locality, number of samples (N), province, coordinates and number of individuals selected for each gene of Duberria lutrix lutrix samples collected. The sample site number corresponds to Fig.
Sample number | Locality | N | Museum / |
Province | Coordinates | Genbank Accesion numbers | ||
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ND4 | cyt b | SPTBN1 | ||||||
1 | Jacobs Bay | 1 |
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Western Cape | 32°58'8.27"S, 17°53'27.35"E | MK518189 | MK518103 | MK518271 |
2 | Klipheuwel | 2 | unaccessioned | Western Cape | 33°41'46.42"S, 18°43'26.97"E | MK518249–50 | MK518108–09 | MK518274 |
3 | Kraaifontein | 1 | unaccessioned | Western Cape | 33°50'57.39"S, 18°42'46.34"E | MK518200 | MK518117 | No Sequence |
4 | Kirstenbosch | 3 |
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Western Cape | 33°59'10.89"S, 18°26'12.16"E | MK518190–92 | MK518104–06 | MK518272 |
5 | Vlakkenberg | 1 |
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Western Cape | 34°1'38.81"S, 18°23'37.87"E | MK518180 | MK518093 | MK518287 |
6 | Bergvliet | 1 | unaccessioned | Western Cape | 34°3'27.89"S, 18°27'6.26"E | MK518177 | MK518089 | MK518261 |
7 | Tokai | 1 |
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Western Cape | 34°3'37.40"S, 18°25'44.61"E | MK518232 | MK518157 | MK518285 |
8 | Silvermine | 1 |
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Western Cape | 34°5'29.69"S, 18°25'12.32"E | MK518219 | MK518136 | No Sequence |
9 | Lakeside | 1 |
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Western Cape | 34°5'22.09"S, 18°27'14.02"E | MK518202 | MK518119 | MK518277 |
10 | Stellenbosch | 4 |
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Western Cape | 33°54'23.90"S, 18°51'17.47"E | MK518227–31 | MK518145–48 | MK518282 |
11 | Somerset West | 8 |
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Western Cape | 34°4'36.34"S, 18°50'40.88"E | MK518220–26, 51 | MK518137–44 | MK518281 |
12 | Pringle Bay | 4 |
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Western Cape | 34°20'43.89"S, 18°49'58.08"E | MK518213–16 | MK518130–33 | No Sequence |
13 | Kleinmond | 1 | unaccessioned | Western Cape | 34°20'6.03"S, 19°0'44.03"E | MK518248 | MK518107 | MK518273 |
14 | Villiersdorp | 5 |
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Western Cape | 33°59'8.86"S, 19°17'10.18"E | MK518234–38 | MK518159–63 | MK518286 |
15 | Caledon | 1 |
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Western Cape | 34°13'51.55"S, 19°25'31.35"E | MK518178 | MK518091 | MK518263 |
16 | Genadendal | 1 |
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Western Cape | 34°2'29.91"S, 19°33'45.08"E | MK518181 | MK518094 | MK518265 |
17 | Greyton | 3 |
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Western Cape | 34°3'8.18"S, 19°36'47.06"E | MK518182–84 | MK518096–98 | MK518266 |
18 | Napier | 6 |
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Western Cape | 34°27'59.60"S, 19°53'59.71"E | MK518203–08 | MK518120–25 | MK518278 |
19 | Agulhas | 3 | unaccessioned | Western Cape | 34°48'11.21"S, 19°57'35.67"E | MK518243–45 | MK518078–80 | MK518259 |
20 | Struis Bay | 1 | unaccessioned | Western Cape | 34°45'42"S, 20°2'26.90"E | MK518252 | MK518149 | MK518283 |
21 | Bredasdorp | 1 | unaccessioned | Western Cape | 34°30'20.84"S, 20°4'2.12"E | MK518246 | MK518090 | MK518262 |
22 | Ashton | 8 |
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Western Cape | 33°50'4.56"S, 20°3'17.09"E | MK518169–76 | MK518081–88 | MK518260 |
23 | Swellendam | 7 |
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Western Cape | 34°1'45.81"S, 20°26'42.59"E | MK518253–58 | MK518150–56 | MK518284 |
24 | Herbertsdale | 1 |
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Western Cape | 34°1'1.25"S, 21°46'0.25"E | MK518185 | MK518099 | MK518267 |
25 | Oudtshoorn | 1 |
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Western Cape | 33°39'37.07"S, 22°10'24.69"E | MK518210 | MK518127 | MK518280 |
26 | Natures Valley | 1 |
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Western Cape | 33°58'50.40"S, 23°33'22.79"E | MK518209 | MK518126 | MK518279 |
27 | Humansdorp | 1 |
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Eastern Cape | 34°1'59.61"S, 24°45'59.39"E | MK518188 | MK518102 | MK518270 |
28 | Port Elizabeth‡ | 1 |
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Eastern Cape | 33°47'52.79"S, 25°40'18.74"E | FJ404356 | FJ494305 | No Sequence |
29 | Hope Fountain | 1 |
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Eastern Cape | 33°31'27.29"S, 26°24'3.91"E | MK518187 | MK518101 | MK518269 |
30 | Grahamstown | 1 | unaccessioned | Eastern Cape | 33°17'59.89"S, 26°31'37.88"E | MK518247 | MK518095 | No Sequence |
31 | Port Alfred | 1 |
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Eastern Cape | 33°35'35.60"S, 26°53'3.55"E | MK518211 | MK518128 | No Sequence |
32 | Port St John | 1 |
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Eastern Cape | 31°37'45.67"S, 29°32'11.45"E | MK518212 | MK518129 | No Sequence |
33 | Kwancele | 1 |
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Eastern Cape | 31°11'41.74"S, 29°47'46.19"E | MK518201 | MK518188 | MK518276 |
34 | Kokstad | 7 |
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KwaZulu-Natal | 30°33'14.70"S, 29°25'38.49"E | MK518193–99 | MK518110–16 | MK518275 |
35 | High Water | 1 |
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KwaZulu-Natal | 28°46'52.79"S, 32°5'54.60"E | MK518186 | MK518100 | MK518268 |
36 | Sabie | 2 |
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Mpumalanga | 25°5'19.90"S, 30°47'31.58"E | MK518217–218 | MK518134–35 | No Sequence |
37 | Wolkberg | 1 | unaccessioned | Limpopo | 24°00'04.3"S, 30°04'37.4"E | MK518242 | MK518164 | MK518288 |
38 | Entabeni | 1 |
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Limpopo | 23°0'27.66"S, 30°15'49.80"E | MK518179 | MK518092 | MK518264 |
39 | 1 |
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Uganda | – | MK518233 | MK518158 | No Sequence |
DNA was extracted from ethanol preserved muscle or liver tissue biopsies. A MacheryNagel DNA extraction kit was used for the DNA extraction, following the manufacturer’s protocol. Extracted DNA was stored at -20 °C until needed for the polymerase chain reaction (PCR). Three gene regions were targeted using the PCR, these included two mitochondrial (mtDNA) loci: nicotinamide adenine dinucleotide dehydrogenase subunit 4 (ND4) using the primer pairs listed in
All PCR amplification was performed using standard protocols. PCR conditions were as followed: 94 °C for 4 min., 94 °C for 30 sec., the annealing temperature of the primers varied between 48 °C to 50 °C for 35 sec., 72 °C for 40 sec., for 35 cycles and a final extension at 72 °C for 10 min. A list of the six primer pairs used are provided in Table
List of the primer pairs and their respective reference used during the present study on Duberria lutrix lutrix.
Locus | Protein coding | Primer name and sequence | Primer reference |
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ND4 | Yes | ND4: 5’-ACC TAT GAC TAC CAA AAG CTC ATG TAG AAG C-3’ |
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H12763V: 5’-TTC TAT CAC TTG GAT TTG CAC CA-3’ |
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cyt b | Yes | L14910: 5’- GAC CTG TGA TMT GAA AAA CCA YCG TTG T-3’ |
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LycodryasG3R: 5’-TGG AAT GGR ATT TTR TCG AT-3’ |
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SPTBN1 | Yes | SPTBN1F APR-2010: 5’-TTGGTC GAT GCC AGT TGT A-3’ |
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SPTBN1R APR-2010: 5’-CAG GGT TTG TAA CCT KTC CA-3’ |
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The mtDNA and nuDNA sequences were aligned in CLUSTAL W (
The combined mtDNA data set was subjected to a Bayesian inference (BI). The BI analysis was performed in MrBayes v3.2.6 (
Both
Haplotype networks were constructed for the combined mtDNA data, as well as for the nuclear SPTBN1 using TCS version 1.3 using a 95% connection limit (
We used BEAST v1.8.3 (
The MP and BI analyses retrieved near identical tree topologies, hence only the BI topology is shown and discussed. For MP, of a total of 1350 characters, 278 characters were found to be parsimony informative, and recovered 167 trees with a tree length of 597 steps with a consistency index (CI) of 0.59 and a retention index (RI) of 0.88. The BI topology (Fig.
A Bayesian inference topology derived from the combined mtDNA analyses (ND4 + cyt b) amongst the South African Duberria l. lutrix. The posterior probability value (pP) values are presented above each node. Only pP values >0.95 are shown. Values below each node are bootstrap values for MP. Only bootstrap values >75% are shown. An asterisk (*) below or above a node indicates the absence of statistical support. The insert shows the typical Duberria lutrix lutrix.
For the ND4 locus the maximum uncorrected sequence divergence between the first and second clades was 1.68%. Between the second and third clade the maximum uncorrected sequence divergence was 3.84%. Between the third and the fourth clades the maximum uncorrected sequence divergence was 5.95%. Finally, the maximum uncorrected sequence divergence between clades four and five was 6.75% (Suppl. material
A total of 35 haplotypes were retrieved for the 87 Duberria l. lutrix specimens using the combined mtDNA (Fig.
Fu’s Fs values were positive for Agulhas, Kokstad, Pringle Bay and Swellendam and indicate an excess of intermediate polymorphisms due to recent population bottlenecks or balancing selection, however none of these were statistically significant. Two of the Fu’s Fs values were negative for Somerset West and Napier indicating an excess of low frequency polymorphisms consistent with population expansions or positive directional selection. However, only the Somerset West population was statistically significant (P < 0.02). The remaining sample localities had a Fu’s Fs of zero. For Tajima’s D, five sample localities, Swellendam, Pringle Bay, Napier, Somerset West and Kokstad were negative, while only Napier and Kokstad were statistically significant (P < 0.05). The remaining sample localities has a Tajima’s D of zero. Negative Tajima’s D indicates an excess of low frequency polymorphism, population expansion or purifying selection.
Ten haplotypes were retrieved for the 30 specimens using the TCS analyses (network not shown). For a list of the sample localities per haplotype consult Suppl. material
The combined mtDNA and nuDNA sequence data yielded a total of 2110 bp. The MP and the BI analyses retrieved highly congruent tree topologies, hence only the BI topology is shown. For the MP analyses, 293 characters were found to be parsimony informative, tree length of 627 steps, 730 trees, with CI = 0.58 and RI = 0.77. The total evidence BI topology (Fig.
A Bayesian inference topology for the total evidence data sets (ND4 + cyt b + SPTBN1) amongst the South African Duberria l. lutrix species complex. The posterior probability value (pP) values are presented above each node. Only pP values >0.95 are shown. Values below each node are bootstrap values for MP. Only bootstrap values >75% are shown. An asterisk (*) below or above a node indicates the absence of statistical support.
Clade five diverged from the remaining D. l. lutrix clades 3.42 Mya (4.13 Mya to 2.72 Mya; 95% HPD). These divergences dates fall into the Pliocene and Pleistocene epochs. Clade four diverged from clades one, two and three occurred 2.05 Mya (1.34 Mya to 2.95 Mya; 95% HPD). The divergence between clade three from clades one and two occurred 1.23 Mya (0.74 Mya and 1.81 Mya; 95% HPD). Cladogenesis between clades one and two occurred 0.46 Mya (0.27 Mya and 0.69 Mya; 95% HPD) (Suppl. material
The phylogeographic results demonstrated the presence of five mtDNA clades across the sampled distribution range of Duberria l. lutrix in South Africa, implying that the snake represents a species complex. Furthermore, these five clades were characterised by the absence of shared mtDNA haplotypes and marked sequence divergences values for both the ND4 and cyt b loci, suggesting possible genetic isolation and limited dispersal. However, the nuclear DNA sequences data failed to retrieve patterns congruent with the mtDNA data, hence it is not possible to exclusively imply the presence of five possible taxa within the Duberria l. lutrix species complex, and requires further taxonomic delineation. In addition, the divergence time estimates suggest that cladogenesis in the D. l. lutrix species complex occurred during the Plio/Pleistocene epochs, a period that was characterised by increased aridification throughout South Africa, resulting in the contraction of mesic adapted species. Our results reflect the impact of Plio/Pleistocene climatic driven fragmentation on a snake species resulting in possible cladogenesis. The latter result is in line with what has been reported for the widely distributed puff adder in South Africa (
During the late Miocene, climatic profiles changed dramatically, resulting in decreasing levels of precipitation and marked aridification, a trend that was enhanced in the Plio/Pleistocene (
Although the climatic fluctuation would have forced species to retreat into refugia (
The combined mitochondrial and nuclear data set retrieved five clades that show evidence for geographically distinct Duberria lutrix lutrix lineages. The mtDNA data shows, high levels of uncorrected sequence divergence values.
These sequence divergence values are similar to values observed in other snake lineages within Colubroidea and the Malagasy Pseudoxyrhophiinae that are considered genetically different (
We would like to thank the South African National Biodiversity Institute (
Uncorrected ("p") distance matrix for the ND4 locus for all the Duberria lutrix lutrix samples used during the present study
Data type: molecular data
Uncorrected “p” distances for the cyt b for the Duberria lutrix lutrix sampled during the present study
Data type: molecular data
Distribution of the 35 haplotype frequency for the combined mtDNA loci sequence data for the 87 Duberria lutrix lutrix specimens
Data type: molecular data
Explanation note: The haplotype numbers (N) corresponds to the numbers on the minimum spanning network (Fig.