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Phylogeography of the Colombian water snake Helicops danieli Amaral, 1938 (Reptilia, Squamata, Dipsadidae) with comments on the systematics and evolution of the genus Helicops Wagler, 1828
expand article infoJuan Pablo Hurtado-Gómez‡, Juan M. Daza§, Mario Vargas-Ramírez|, V. Deepak‡#, Uwe Fritz‡
‡ Museum of Zoology, Dresden, Germany
§ Universidad de Antioquia, Medellín, Colombia
| Universidad Nacional de Colombia, Bogotá, Colombia
¶ Universidad Nacional de Colombia, Villavicencio, Colombia
# Newcastle University, Newcastle upon Tyne, United Kingdom

Corresponding author: Uwe Fritz ( uwe.fritz@senckenberg.de )

Academic editor: Robert Jadin
© 2024 Juan Pablo Hurtado-Gómez, Juan M. Daza, Mario Vargas-Ramírez, V. Deepak, Uwe Fritz.
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: Hurtado-Gómez JP, Daza JM, Vargas-Ramírez M, Deepak V, Fritz U (2024) Phylogeography of the Colombian water snake Helicops danieli Amaral, 1938 (Reptilia, Squamata, Dipsadidae) with comments on the systematics and evolution of the genus Helicops Wagler, 1828. ZooKeys 1215: 335-358. https://doi.org/10.3897/zookeys.1215.128795
ZooBank: urn:lsid:zoobank.org:pub:11120B98-7E4D-4E1B-980A-2975059B1C9C
Open Access

Abstract

The genus Helicops Wagler, 1828 comprises 20 species of semiaquatic snakes. It is mostly distributed in the cis-Andean region of South America, with only two trans-Andean species (H. danieli, H. scalaris). Helicops danieli is endemic to Colombia and occurs through most of the trans-Andean region. Herein two mitochondrial and two nuclear genomic markers were sequenced for 16 samples of H. danieli across most of its distribution range to understand its phylogeography. A dated tree was also generated with additional sequences from previous studies to infer the divergence times between H. danieli and its cis-Andean congeners and of lineages within H. danieli. Using previously published data, ancestral states were estimated for putative phenotypic synapomorphies for the major clades of Helicops. For H. danieli, four clades corresponding to the main river basins within its distribution were recovered. Our dated tree suggests that the ancestor of H. danieli diverged from its closest congeners in the late Miocene (8.7 Mya), which can be associated with the closure of the Andalucia Pass, south of the Eastern Cordillera. Divergence within H. danieli commenced 1.1 Mya. Within the genus Helicops, two distinct hemipenial morphologies were observed, which are suggested as putative synapomorphies for the two most basal clades. Recognition of these two clades as distinct subgenera, Helicops sensu stricto and Tachynectes Fitzinger, 1843 is proposed. For the junior homonym Tachynectes von der Mark, 1863, rarely applied to fossil fishes, the replacement name Ichthyotachynectes nom. nov. is introduced. Furthermore, the evolution of another four phenotypic traits in Helicops and their phylogenetic utility are discussed.

Key words

Actinoptergyii, Andalucia Pass, Ichthyotachynectes nom. nov., Myctophidae, Serpentes, subgenera, Tachynectes

Introduction

The genus Helicops Wagler, 1828 currently contains 20 species, distributed through most of the South American subcontinent (Moraes-da-Silva et al. 2022; Schöneberg and Köhler 2022). Snakes in this genus are characterized by having semiaquatic habits, eyes and nostrils dorsally located, dorsal scales keeled, a single internasal scale, and an S-shaped sulcus spermaticus in the hemipenial lobes (Zaher 1999; Schöneberg and Köhler 2022). All Helicops species are distributed in cis-Andean South America, except for H. scalaris Jan, 1865, from the Lake Maracaibo Region, and H. danieli Amaral, 1937, which is confined to the trans-Andean lowlands of Colombia, the inter-Andean valley of the Magdalena River, the Caribbean floodplains, and the Pacific region (Rossman 2002a; Citeli et al. 2021).

Helicops danieli was originally described by Amaral (1937) based on a single specimen from the Río Carare, Santander, Colombia, on the eastern edge of the Magdalena Valley. Later, several authors extended the knowledge about the species’ morphology, describing the overall variation in scalation, measurements, and hemipenial morphology (Yuki 1994; Rossman 2002a; Citeli et al. 2021). Initially, Amaral (1937) suggested that H. danieli was related to H. angulatus and H. scalaris. Later, Nunes (2006) developed a morphology-based phylogenetic hypothesis and included H. danieli in a phylogenetic context for the first time. According to Nunes (2006), H. danieli is sister to a clade containing H. angulatus, H. gomesi, H. pastazae, H. petersi, H. polylepis, and H. scalaris. To date, none of the recent molecular-based phylogenies has included H. danieli (Costa et al. 2016; Moraes-da-Silva et al. 2019, 2021, 2022).

Helicops danieli is widely distributed across the trans-Andean lowlands of Colombia. This region comprises a variety of ecosystems and geographic units, including dry and moist forests (Etter et al. 2021), inter-Andean valleys, Pacific lowlands, the Caribbean plain, and several basins primarily associated with the Magdalena, Cauca, and Atrato rivers (Hernández-Camacho et al. 1992; Lynch et al. 1997; Mesa-S. et al. 2016). This suggests that phylogeographic variation exists in H. danieli.

In recent years, research on the systematics and taxonomy of the genus Helicops has expanded considerably, with six out of the twenty species described in the last two decades (da Frota 2005; Kawashita-Ribeiro et al. 2013; Costa et al. 2016; Moraes-da-Silva et al. 2019, 2021, 2022). Additionally, the number of taxa studied using molecular genetic approaches has increased, with up to 11 Helicops species analyzed to date (Moraes-da-Silva et al. 2021). Recent studies have mapped various phenotypic traits to identify synapomorphies, some of which (e.g., color pattern, subcaudal keels, reproductive mode; Moraes-da-Silva et al. 2022) have been useful for supporting minor clades within Helicops. However, no synapomorphies have been identified for the major clades of Helicops.

For the present study, we generated a dataset of four molecular markers to infer the phylogenetic position as well as the genetic and geographic structure of H. danieli. Additionally, we present a fossil-calibrated time tree for Helicops to estimate the divergence time for H. danieli and its cis-Andean congeners. Finally, we infer the ancestral states for five phenotypic characters of Helicops using our molecular phylogeny, discuss the evolution and phylogenetic value of these traits, and propose a subgeneric classification for Helicops.

Materials and methods

Sampling and laboratory procedures

We used 16 samples of H. danieli from most of its range (Fig. 1A) and one of H. pastazae from tissues deposited in the Banco de Tejidos de la Biodiversidad, Instituto de Genética, Universidad Nacional de Colombia, Bogotá, Colombia (BTBC) and the Museo de Herpetología, Universidad de Antioquia, Medellín, Colombia (MHUA) (Suppl. material 1: table S1). DNA was extracted using the innuPREP DNA Micro Kit (Analytik Jena GmbH, Jena, Germany) following the manufacturer’s protocol. We obtained sequences from two mitochondrial (16S: 532 bp, cyt b: 770 bp) and two nuclear markers (C-mos: 566 bp, Rag1: 826 bp). PCR was conducted in a reaction volume of 25 µl, containing 20–40 ng of DNA, 1 unit Taq polymerase (Bioron GmbH, Ludwigshafen, Germany), the buffer recommended by the supplier (complete, 10×, containing MgCl2), 0.2 µM of each dNTP (Carl Roth GmbH + Co. KG, Karlsruhe, Germany), and 0.4 µM of each primer. Primers and PCR cycling conditions are described in the Suppl. material 1: table S2. Purification and sequencing followed Fritz et al. (2012). Sequences were edited with GENEIOUS 9.1.8 (Kearse et al. 2012) and aligned using MAFFT 7.39 (Katoh and Toh 2010) as implemented in GENEIOUS. To obtain a more robust hypothesis for the relationships within Helicops, we generated a concatenated alignment of 4624 bp length for the phylogenetic trees (see below). This alignment included three additional markers (mtDNA = 12S; nDNA = BDNF, NT3) available from previous studies (Moraes-da-Silva et al. 2019, 2021). Additional sequences for Helicops species and outgroups were downloaded from GenBank (Suppl. material 1: table S1). The sequences for 13 colubroid outgroup taxa originate from Zaher et al. (2019); the most distant species, the viperid Bothrops atrox, served for tree rooting. The individual alignments were concatenated using SEQUENCE MATRIX 1.8 (Vaidya et al. 2011). For the phylogenetic analyses, we included only one sample per species, except for H. danieli, for which we included all individuals, and for H. angulatus, which was recently retrieved as non-monophyletic (Murphy et al. 2020). For H. angulatus, we included one sample from Trinidad and another one from Brazil (Suppl. material 1: table S1). For the calculation of uncorrected p distances (see below), we included all available mitochondrial 16S and cyt b sequences.

Figure 1. 

A Genetic sampling and clades for Helicops danieli B Bayesian tree for H. danieli lineages (cropped from the complete tree, see Suppl. material 2: fig. S1) based on the concatenated alignment of three mitochondrial and four nuclear molecular markers (4624 bp); values above branches indicate Bayesian posterior probabilities (> 0.85), below branches are UltraFastBootstrap values (> 90) from the ML tree (Suppl. material 2: fig. S2) C haplotype network for H. danieli based on the concatenated mtDNA alignment of 16S and cyt b sequences D Neighbor-Net for H. danieli samples based on the same concatenated mtDNA alignment E haplotype network for H. danieli samples based on the nuclear Rag 1 fragment.

Phylogenetic analyses and time-calibrated tree

The best partition scheme and substitution models for analyzing the concatenated sequences were determined using MODELFINDER (Kalyaanamoorthy et al. 2017) as implemented in IQ-TREE 2.2 (Minh et al. 2020). Model selection was performed with the parameter ‘testmerge’ for model selection option (-m), which implements the ‘greedy’ algorithm of PARTITIONFINDER 2.0 (Lanfear et al. 2016) (Suppl. material 1: table S3).

Phylogenetic trees were constructed using Maximum Likelihood (ML) and Bayesian Inference (BI). The ML tree was calculated with IQ-TREE 2.2, using partitions and substitution models obtained with MODELFINDER (Suppl. material 1: table S3). Node support for the ML tree was assessed with 5000 Ultrafast Bootstrap replicates (UFB), considering branches with support values of 95% and above as highly supported (Minh et al. 2013). For the BI and the relaxed molecular clock calculations (see below), we used BEAST 2.7.5 (Bouckaert et al. 2019) and two independent chains of 50 million generations, sampling every 5000th generation. For the BI analysis, we used the partitions obtained with MODELFINDER. However, substitution models were determined using BMODELTEST (Bouckaert and Drummond 2017) exploring all available models (Suppl. material 1: table S3). The Yule model was used for tree inference. For the time-calibrated tree, we applied the fast-normal relaxed clock model and three fossil calibration points from Zaher et al. (2019), as follows (fossil, minimum age, reference): (i) stem Colubroidea (Colubridae indet., 35.2 Mya; Smith 2013); (ii) stem Dipsadidae (Paleoheterodon tiheni, 12.5 Mya; Holman 1964, 1977); and (iii) crown Natricidae (Natricidae incertae sedis, 13.8 Mya; Rage and Szyndlar 1986). Chain convergence and burn-in (20%) were examined using TRACER 1.7.1 (Rambaut et al. 2018). A maximum credibility tree was summarized with TREEANNOTATOR 2.7.5 implemented in BEAST 2.7.5 (Bouckaert et al. 2019). For tree annotation, plotting, and layout, we used the R program v. 4.3.1 (R Core Team 2023) in RSTUDIO (RStudio Team 2023) along with the packages ‘ape’ (Paradis and Schliep 2019), ‘phangorn’ (Schliep 2011), ‘phytools’ (Revell 2012), and the INKSCAPE software (https://www.inkscape.org).

Haplotype networks, Neighbor-Nets, and genetic distances

Two parsimony networks were drawn for the H. danieli samples using the R package PEGAS 1.2 (Paradis 2010), one for the nuclear fragment Rag1 and the other for the concatenated mitochondrial alignment (16S and cyt b), acknowledging that mtDNA represents a single locus. Due to the low variation in the C-mos alignment, no network was calculated for this marker.

Phylogenetic networks for the concatenated mitochondrial alignment (16S and cyt b) were computed using the Neighbor-Net algorithm (Bryant and Moulton 2004), implemented in the R package ‘phangorn’ (Schliep 2011). Given that the algorithm does not run with alignments with approximately 50% missing data (JPHG pers. obs.), specimens with only the 16S marker in the mitochondrial alignment (the shortest one) were excluded from this analysis. Due to the limited variation in the concatenated nuclear alignment, no Neighbor-Net was drawn for it.

Finally, using MEGA 11 (Tamura et al. 2021) and the pairwise deletion option, uncorrected p distances were computed for the 16S and cyt b alignments for Helicops species and clades retrieved for H. danieli in the phylogenetic trees.

Phenotypic data and ancestral state estimation

To identify putative phenotypic synapomorphies for the genus Helicops, we used the compiled data for all species from Murphy et al. (2020) and Moraes-da-Silva et al. (2022) on color pattern, keels on dorsal scales, subcaudal keels, and reproductive modes. Additionally, we incorporated all available information on hemipenial morphology from the literature, which included data for all Helicops species but H. yacu. The five phenotypic characters are: 1) dorsal color pattern, 2) strength of dorsal scale keels, 3) subcaudal keels, 4) reproductive mode, and 5) hemipenial lobe length.

To evaluate whether these phenotypic traits represent synapomorphies for the clades within Helicops, we performed an ancestral state estimation (ASE). First, we inferred the best fitting evolutionary model for each of the five characters, selecting among the three models equal rates (ER), symmetric rates (SYM), and all rates different (ARD) using the function ‘fitdiscrete’ in the R package ‘geiger’ (Harmon et al. 2007). The model with the lowest Akaike Information Criterion (AIC) value was chosen (Suppl. material 1: table S4).

For the ancestral state estimation, we used the function ‘ace’ in the R package ‘ape’. The Bayesian phylogenetic tree cropped to the genus Helicops served as input, along with the chosen model for each character. Since H. angulatus exhibits both oviparous and viviparous reproductive modes, we coded each of the two tips for the species with a different state.

Results and discussion

Our phylogenetic trees returned Helicops as maximally supported monophylum under both the ML and BI approaches (Fig. 2; Suppl. material 2: figs S1, S2). Within Helicops, two main clades were consistently recovered. The first clade, termed ‘leopardinus clade’, included H. infrataeniatus, H. leopardinus, H. modestus, and H. phantasma (Fig. 2). The second clade, the ‘angulatus clade’, comprised the remaining species: H. angulatus, H. boitata, H. carinicaudus, H. danieli, H. gomesi, H. hagmanni, H. nentur, H. pastazae, and H. polylepis. Notably, H. pastazae, which was studied for the first time using DNA sequence data, was found to be the sister taxon of H. hagmanni with high support (Fig. 2; Suppl. material 2: figs S1, S2).

Figure 2. 

Bayesian time tree for the genus Helicops obtained with the concatenated alignment of three mtDNA and four nDNA markers, cropped from the complete tree (Suppl. material 2: fig. S1). Helicops danieli clades are collapsed (see Fig. 1B; Suppl. material 2: figs S1, S2). Values above branches are age estimates in million years; bluish green bars at nodes indicate 95% confidence intervals; circles at nodes represent Bayesian posterior probabilities (see legend). Boxes on branch tips and vertical names on the right indicate the subgeneric classification proposed in the present study. Abbreviations: BR, Brazil; MM, middle Magdalena; TT, Trinidad and Tobago. Photographs right: top, H. leopardinus (Corrientes, Argentina; A. Sabaliauskas, iNaturalist observation 94157056); center, H. angulatus (Guaviare, Colombia; J. P. Hurtado-Gómez); bottom, H. pastazae (Boyaca, Colombia; D. Gómez-Sánchez); photo left bottom, H. danieli (Los Katíos, Colombia; Juan M. Daza, MHUAR15536).

Helicops danieli was recovered as monophyletic with high support by both tree-building approaches (Figs 1B, 2; Suppl. material 2: figs S1, S2) and as sister to the clade containing H. hagmanni and H. pastazae in a poorly supported clade (Fig. 2; Suppl. material 2: figs S1, S2). Within H. danieli, four main clades were revealed: one from the lower Atrato River, one from the lower Magdalena River, and two from the middle Magdalena River. In the middle Magdalena Basin (as defined by Mesa-S. et al. 2016), one clade (‘black’) occurs east and another one (‘yellow’) west of the river (Figs 1A, B, 2; Suppl. material 2: figs S1, S2). These clades were corroborated by the mitochondrial haplotype networks and Neighbor-Nets (Fig. 1C, D), though not by the nuclear Rag1 haplotype network (Fig. 1E). Our mitochondrial Neighbor-Net analysis indicated that the middle Magdalena groups (east and west) are well differentiated. In contrast, those from the lower Atrato (‘red’) and lower Magdalena (‘green’) show a high degree of interconnection, despite forming separate clusters (Fig. 1D). The relationships between clades varied significantly between analyses, but with relative higher node support in the BI tree (Figs 1B, 2; Suppl. material 2: figs S1, S3).

Diversity and phylogeny of Helicops

The uncorrected p distances for the mitochondrial 16S fragment among Helicops species averaged 5.6%, ranging from 1.0% (between H. leopardinus and H. infrataeniatus) to 8.0% (between H. gomesi and H. phantasma; Table 1). For the cyt b marker, distances between Helicops species ranged from 9.7% (between H. angulatus and H. pastazae) to 14.3% (between H. danieli and H. infrataeniatus), averaging 11.7% (Table 1). Within H. danieli, uncorrected p distances for 16S and cyt b showed contrasting differentiation between the clades (Table 2). For the 16S marker, distances ranged from 0.1% (between the lower Magdalena and middle Magdalena east) to 2.0% (between the lower Atrato and middle Magdalena east). For the cyt b marker, distances ranged from 1.0% (between lower Atrato and lower Magdalena) to 2.0% (between lower Magdalena and middle Magdalena west).

Table 1.
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Means of interspecific uncorrected p distances (percentages) for 16S (below diagonal) and cyt b (above diagonal) sequences for Helicops. Sequence of taxa corresponds to Fig. 2. Cyt b sequences were only available for four taxa. BR, Brazil; TT, Trinidad and Tobago.

Helicops species 1 2 3 4 5 6 7 8 9 10 11 12 13
1 H. danieli - 11.4 12.9 - - 13.4 - - - - 14.3 -
2 H. polylepis 5.5 - - - - - - - - - - -
3 H. angulatus TT 5.7 4.5 7.6 - - 9.7 - - - - 11.1 -
4 H. angulatus BR 5.6 5.6 2.6 - - 11.2 - - - - 11.8 -
5 H. gomesi 5.8 5.4 1.5 2.3 - - - - - - - -
6 H. hagmanni 6.4 5.4 4.7 5.1 4.8 - - - - - - -
7 H. pastazae 4.5 4.7 4.0 4.4 4.0 3.3 - - - - 14.1 -
8 H. boitata 6.7 6.8 7.3 7.6 7.8 7.1 7.5 - - - - -
9 H. carinicaudus 6.6 5.6 6.3 6.0 6.8 6.8 5.9 5.4 - - - -
10 H. nentur 6.9 4.9 6.8 6.4 7.3 5.9 6.3 4.2 2.3 - - -
11 H. phantasma 7.3 5.2 7.3 7.1 8.0 5.9 6.4 5.4 2.8 2.8 - -
12 H. infrataeniatus 6.0 5.5 6.2 6.8 6.9 6.7 5.6 6.1 4.8 4.8 4.0 -
13 H. leopardinus 6.3 6.1 6.7 7.1 7.2 6.9 6.3 6.1 5.5 5.5 4.2 1.0
14 H. modestus 5.9 5.3 6.1 6.9 6.9 6.8 6.0 6.1 5.4 5.3 4.5 1.2 1.6
Table 2.
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Means of uncorrected p distances (percentages) for 16S (below diagonal) and cyt b (above diagonal) sequences for Helicops danieli clades. MM, middle Magdalena.

H. danieli lineage 1 2 3 4
1 Lower Atrato - 1.7 1.1 1.0
2 MM west 1.8 - 1.9 2.0
3 MM east 2.0 0.6 - 1.1
4 Lower Magdalena 1.7 0.1 0.4 -

Our dated phylogenetic tree suggests that diversification within Helicops commenced in the upper Miocene, approximately 8.7 Mya (Fig. 2; Suppl. material 2: fig. S1). The ‘angulatus clade’ started to diversify shortly after, around 7.7 Mya (upper Miocene). In contrast, the ‘leopardinus clade’ began to radiate more recently, in the early Pliocene, approximately 4.3 Mya. Speciation events continued throughout the Pliocene and Pleistocene. Helicops danieli diverged from its cis-Andean congeners at least 6.1 Mya during the upper Miocene. Differentiation within H. danieli commenced in the early Pleistocene, approximately 1.1 Mya.

For all five phenotypic traits, the Equal Rates (ER) model was determined to be the best fit (Suppl. material 1: table S4). The ancestral state estimation (ASE) for the hemipenial lobe length indicates that each state represents a synapomorphy for the major clades within Helicops (Figs 3A, 4; Table 3). Short-lobed hemipenes (Fig. 4A) are prevalent among all species in the ‘leopardinus clade’ (which includes H. infrataeniatus, H. leopardinus, H. modestus, and H. phantasma). Conversely, long-lobed hemipenes (Fig. 4B) are characteristic of the species in the ‘angulatus clade’, including H. angulatus, H. boitata, H. carinicaudus, H. danieli, H. gomesi, H. hagmanni, H. nentur, H. pastazae, and H. polylepis.

Figure 3. 

Ancestral state estimation using the summarized phylogeny for the genus Helicops for five phenotypic characters (A hemipenial lobe length B reproduction C subcaudal keels D strength of the dorsal scale keels E dorsal color pattern, and F summary of synapomorphies and secondary modifications for the nodes discussed in the text. Abbreviations (in bold) in F represent unambiguous synapomorphies. BR, Brazil; TT, Trinidad and Tobago.

Figure 4. 

Hemipenes of A H. leopardinus (based on UFMTR1504 from Moraes-da-Silva et al. 2021) and B H. danieli (based on MHUAR15565) in sulcate (left) and asulcate (right) views. Scale bars: 10 mm. The hemipenis of H. leopardinus represents the morphology with short lobes characteristic for the subgenus Tachynectes; the hemipenis of H. danieli represents the morphology with long lobes characteristic for the subgenus Helicops. Note that the hemipenis is homogeneously covered with spinules in (A), whereas large spines are confined to the hemipenial body (i.e., excluding the lobes) on the sulcate surface and the lateral regions in (B). Drawings: V. Deepak.

Table 3.
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Classification of Helicops species as proposed in the present study and respective morphological character states.

Species Subgenus Dorsal pattern Dorsal keel strength Subcaudal keels Reproductive mode Hemipenial lobes References
H. acangussu 1 Helicops Spots Moderate Absent Oviparous Long Moraes-da-Silva et al. (2022)
H. angulatus Helicops Saddles Strong Present Bimodal Long Cope (1895), Zaher (1999), Nunes (2006)
H. apiaka 1 Helicops Saddles Strong Present Unknown Long Kawashita-Ribeiro et al. (2013)
H. boitata Helicops Blotches Moderate Absent Unknown Long Moraes-da-Silva et al. (2019)
H. carinicaudus Helicops Stripes Weak Absent Viviparous Long Zaher (1999), Nunes (2006)
H. danieli Helicops Spots Moderate Absent Viviparous Long Zaher (1999), Nunes (2006)
H. gomesi Helicops Saddles Strong Present Oviparous Long Nunes (2006)
H. hagmanni Helicops Spots Strong Absent Oviparous Long Nunes (2006), Moraes-da-Silva et al. (2022)
H. nentur Helicops Uniform Weak Absent Unknown Long Costa et al. (2016)
H. pastazae Helicops Spots Strong Absent Oviparous Long Zaher (1999), Nunes (2006)
H. petersi 1 Helicops Spots Strong Absent Unknown Long Rossman (1976)
H. polylepis Helicops Spots Strong Absent Viviparous Long Zaher (1999), Nunes (2006), Moraes-da-Silva et al. (2022)
H. scalaris 1 Helicops Blotches Strong Present Viviparous Long Nunes (2006)
H. trivittatus 1 Helicops Stripes Moderate Absent Viviparous Long Nunes (2006)
H. yacu 1 Helicops Spots Unknown Unknown Unknown Unknown Rossman and Dixon (1975), Rossman (1976)
H. infrataeniatus Tachynectes Stripes Moderate Absent Viviparous Short Yuki and Lema (2005), Nunes (2006)
H. leopardinus Tachynectes Spots Moderate Absent Viviparous Short Zaher (1999), Nunes (2006), Moraes-da-Silva et al. (2021)
H. modestus Tachynectes Stripes Weak Absent Viviparous Short Zaher (1999), Nunes (2006)
H. phantasma Tachynectes Bands Moderate Absent Viviparous Short Moraes-da-Silva et al. (2021)
H. tapajonicus 1 Tachynectes Uniform Weak Absent Unknown Short da Frota et al. (2005)

1 Species not sampled for molecular phylogenetics.

We additionally observed that hemipenes with short lobes have the organ body homogeneously covered with spinules, occasionally together with few enlarged spines (e.g., H. phantasma; Moraes-da-Silva et al. 2021) and body pockets immediately below the lobular crotch (Fig. 4A). On the other hand, hemipenes with long lobes have spinules and/or spines throughout the body (i.e., excluding the lobes), with the spines mainly located on the sulcate surface and the lateral regions of the hemipenial body; the lobes are ornamented with papillate calyces or flounces (Fig. 4B).

ASE for the reproductive mode suggests that viviparity is the most probable ancestral state for Helicops (Fig. 3B; Table 3). Viviparity is common among all sampled Helicops species (no data available for H. boitata and H. nentur), except for four species from two different clades: (i) H. angulatus and H. gomesi as well as (ii) H. hagmanni and H. pastazae. These four species are oviparous, with H. angulatus having both reproductive modes. Furthermore, ASE showed that subcaudal keels are present only in the clade containing H. angulatus and H. gomesi, representing an unambiguous synapomorphy of these two species (Fig. 3C; Table 3).

Each of the three character states regarding the strength of the dorsal scale keels corresponds to a synapomorphy for three clades within Helicops (Fig. 3D): i) for the clade containing H. nentur and H. carinicaudus, weak dorsal scale keels represent a synapomorphy; ii) for the ‘leopardinus clade’ (i.e., H. infrataeniatus, H. leopardinus, H. modestus, H. phantasma), moderately keeled dorsal scales are a synapomorphy, with a modification in H. modestus, which has weak keels; and iii) for the clade containing H. angulatus, H. danieli, H. gomesi, H. hagmanni, H. pastazae, and H. polylepis, strongly keeled dorsal scales are a synapomorphy, with a modification in H. danieli having moderately strong keels (Fig. 3D; Table 3).

ASE for the dorsal color pattern suggests that a spotted pattern is a synapomorphy for the clade comprised of H. angulatus, H. danieli, H. gomesi, H. hagmanni, H. pastazae, and H. polylepis. Within this group, a change occurs in the clade composed of H. angulatus and H. gomesi, for which a saddle pattern is an unambiguous synapomorphy (Fig. 3E; Table 3).

Phylogeography of Helicops danieli

Our results retrieved Helicops danieli as monophyletic with a distinct geographic structure (Figs 1, 2; Suppl. material 2: figs S1, S2). We distinguish the four retrieved clades based on the Colombian freshwater ecoregions (Mesa-S. et al. 2016): lower Atrato, lower Magdalena, and two in the middle Magdalena, one on the eastern side and the other on the western side of the river course (Figs 1A, 2; Suppl. material 2: figs S1, S2). A similar differentiation pattern was observed in the pitviper Bothrops asper, where independent lineages were identified in the middle Magdalena, lower Magdalena, and in the Pacific lowlands (Saldarriaga Córdoba et al. 2017), with the latter partially corresponding to the lower Atrato clade of H. danieli (Figs 1A, B, 2; Suppl. material 2: figs S1, S2). Notably, the cladogenetic pattern found for B. asper by Saldarriaga Córdoba et al. (2017) resembles that of H. danieli in the Magdalena Basin, where the lower and middle Magdalena clades form a more inclusive clade. However, Saldarriaga Córdoba et al. (2017) did not find an east-west differentiation in B. asper. Given the recent diversification history of H. danieli (< 0.9 Mya), determining the causes of lineage differentiation is challenging due to the lack of detailed information on geological or climatic events in the distribution area during the relevant diversification period. Nonetheless, factors like isolation by distance or alterations in the river course have most likely influenced the genetic structuring of H. danieli. Further downstream, there is no clear east-west pattern in the Magdalena region. Records of the ‘yellow’ and ‘green’ clades are on both sides of the river, reflecting that the lower Magdalena is slow flowing and corresponds to a swamp system in the Momposina Depression.

However, for the middle Magdalena River, the phylogeography suggests an east-west differentiation of H. danieli, with the respective clades (‘black’ and ‘yellow’) being non-sister (Figs 1B, 2; Suppl. material 2: figs S1–S3). This pattern suggests that the Magdalena River acts as a significant barrier to gene flow. This is at first glance counterintuitive in the face of the semiaquatic habits of H. danieli. However, the species is typically found in ponds and small streams in shaded areas within associated vegetation (JPH-G, MV-R pers. obs.), like other Helicops species (Duellman 1978; Teixeira et al. 2017) and seems to avoid fast-flowing river sections like the middle Magdalena.

An east-west differentiation as in H. danieli has not been reported for other lowland reptiles in the middle Magdalena region (Mabuya spp., Pinto-Sánchez et al. 2015; Podocnemis lewyana, Vargas-Ramírez et al. 2012; Rhinoclemmys melanosterna, Vargas-Ramírez et al. 2013; Caiman crocodilus, Díaz-Moreno et al. 2021; Bothrops asper, Saldarriaga Córdoba et al. 2017) or other vertebrates (Ateles hybridus, Link et al. 2015) and, to our best knowledge, such a differentiation pattern is reported here for the first time for any vertebrate.

Moraes-da-Silva et al. (2022) previously suggested that the wide and fast flowing Madeira River acts as a barrier between H. acangussu and its closest relative H. hagmanni (based on morphology), as these species occur on opposite river sides. Even though this idea was not tested with a phylogenetic hypothesis (i.e., no molecular data available for H. acangussu), it supports that fast-flowing rivers are a barrier to gene flow in Helicops. Our study, therefore, provides the first detailed phylogeographic analysis of any Helicops species, offering direct evidence for the role of fast-flowing rivers as barriers to gene flow.

Genetic distances of the H. danieli clades ranged from 0.1 to 2.0% (16S) and from 1.0 to 2.0% (cyt b) (Table 2). For the 16S gene, the lineage from the lower Atrato (1.7–2.0%) showed the highest divergence from the others, while for cyt b, it was the lineage from the middle Magdalena west (1.7–2.0%). These distances are considerably lower than the mean distances observed between Helicops species (5.6% for 16S; 10.0% for cyt b) as well as interspecific distances found in other species within the dipsadid radiation (e.g., Hydrodynastes, Carvalho et al. 2020; Caaeteboia, Montingelli et al. 2020). This suggests that the four identified lineages of H. danieli represent early stages of genetic divergence that do not warrant taxonomic distinction.

We dated the split between the ancestor of H. danieli and its cis-Andean counterparts to the late Miocene, around 6.1 Mya (Fig. 2; Suppl. material 2: fig. S1). Fossil and geological evidence suggest that the trans-Andean and Amazon aquatic fauna were connected in Colombia until at least 5 Mya (Lundberg et al. 1998; Ballen and Moreno-Bernal 2019; Montes et al. 2021; Rodriguez-Muñoz et al. 2022) through a corridor south of the Eastern Cordillera called the Andalucia Pass. Given that most Helicops species and the whole Hydropsini radiation (also including the genera Hydrops and Pseudoeryx) are distributed in the cis-Andean region, it is likely that the ancestor of H. danieli migrated during the late Miocene from this region to the trans-Andean region, through this corridor, before the connection between the Magdalena and the Amazon Basins was interrupted by the upfold of the bridge between the Eastern and Central Cordilleras due to volcanic activity and fault propagation (Montes et al. 2021).

Systematics of Helicops

A proposal for a subgeneric classification for Helicops

Our study provides the most comprehensive phylogenetic framework for the genus Helicops to date, covering 13 of the 20 currently recognized species (Moraes-da-Silva et al. 2022). Our phylogenetic trees (Fig. 2; Suppl. material 2: figs S1, S2) consistently recovered two more inclusive and highly supported clades within Helicops: the ‘angulatus clade’ and the ‘leopardinus clade’. These clades have also been consistently retrieved in previous molecular phylogenetic studies, even with different taxonomic sampling (Zaher et al. 2009, 2019; Grazziotin et al. 2012; Moraes-da-Silva et al. 2019, 2021). Notably, hemipenial morphology is diagnostic for each of the clades (Figs 3A, 4; Table 3). This morphological distinctiveness, combined with the strong phylogenetic support, allows the recognition of these two clades as subgenera of Helicops (Figs 2, 3; Table 3).

Based on this morphological and phylogenetic evidence, we propose assigning taxa in the ‘angulatus clade’ to the subgenus Helicops Wagler, 1828 sensu stricto (type species by monotypy: Coluber carinicaudus Wied-Neuwied, 1824 = Helicops carinicaudus). Additionally, we propose placing the taxa in the ‘leopardinus clade’ in another subgenus for which the name Tachynectes Fitzinger, 1843 is available (type species by indication: Homalopsis leopardina Schlegel, 1837 = Helicops leopardinus); see below under ‘Systematic account’.

Putative morphological synapomorphies for clades within Helicops and allocation of unsampled species

Beyond the hemipenial morphology that supports our proposed subgeneric classification, our ASE analysis for four additional phenotypic traits provides further phylogenetic information for various lineages within Helicops (Fig. 3; Table 3). These findings also allow us to tentatively assign unsampled species.

Our ASE analysis indicates that viviparity is the ancestral state for Helicops, with exceptions in two non-sister clades (Fig. 3B, F): one containing H. hagmanni and H. pastazae, and the other including H. angulatus and H. gomesi (with H. angulatus exhibiting both oviparity and viviparity; Table 3). According to our ASE analysis and phylogenetic hypothesis, oviparity has independently evolved twice within the subgenus Helicops (Fig. 3B; Table 3). Conversely, results of Moraes-da-Silva et al. (2022) suggest a single origin for oviparity, but this was because they inferred that all oviparous species (H. angulatus, H. gomesi, H. hagmanni, H. pastazae) are monophyletic.

The reproductive mode of six Helicops species remains unknown (Table 3), including two species in our phylogeny (H. boitata and H. nentur; Fig. 3B). Braz et al. (2016) proposed a geographic pattern for the bimodal reproductive mode in H. angulatus, but given that H. angulatus seems to be a species complex (cf. the deeply divergent non-sister samples of H. angulatus in our phylogeny; Fig. 2; Suppl. material 2: figs S1, S2), this bimodality might correspond rather to distinct taxa. Therefore, addressing these knowledge gaps requires a more comprehensive analysis for a definitive understanding of the evolution of reproductive modes in Helicops.

Moraes-da-Silva et al. (2022) proposed strong dorsal scale keels as a synapomorphy for the clade containing H. angulatus, H. gomesi, H. hagmanni, and H. polylepis. Our ASE results corroborate this hypothesis. Notably, H. danieli exhibits a modification with moderately strong dorsal keels. This putative synapomorphy is exclusive to this clade, with all other Helicops taxa having weak or moderate dorsal keels (Fig. 3D; Table 3).

Our ASE results also indicate that moderately keeled dorsal scales represent a synapomorphy for the subgenus Tachynectes (referred to as the ‘leopardinus clade’ above), with a subsequent modification in H. modestus (with weak dorsal keels). Additionally, weak dorsal scale keels are identified as a synapomorphy for the clade containing H. nentur and H. carinicaudus (Fig. 3D, F). This is the first time that weak or moderate states of this character are identified as synapomorphies for clades within Helicops, highlighting the phylogenetic informativeness of dorsal scale carination.

Our results further suggest that the spotted dorsal pattern is also a synapomorphy for the clade containing H. angulatus, H. danieli, H. gomesi, H. hagmanni, H. pastazae, and H. polylepis, albeit with a secondary modification observed in the subclade H. angulatus + H. gomesi, which exhibits a dorsal pattern characterized by saddle-shaped blotches (Fig. 3E, F). The only other species in our study with a spotted pattern, H. leopardinus (subgenus Tachynectes), likely represents a case of convergence, as no other closely related species shares this pattern.

For the subclade H. angulatus + H. gomesi, Moraes-da-Silva et al. (2022) previously suggested the dorsal color pattern consisting of saddle-shaped spots and subcaudal keels as putative synapomorphies, a hypothesis supported by our ASE results (Fig. 3E, F; Table 3). These traits are also shared by H. apiaka (Kawashita-Ribeiro et al. 2013), a species not included in our trees (Figs 2, 3; Suppl. material 2: figs S1, S2), which likely belongs to this clade (Table 3).

Subcaudal keels are also reported in H. scalaris, another unsampled species. While H. scalaris exhibits a polymorphic dorsal color pattern with individuals showing blotches (see photos in Rossman 2002b; Natera-Mumaw et al. 2015), some also display a saddle-like pattern (see iNaturalist observations: 129359317, 63932552, 19896494; Rossman 2002b). This suggests that H. scalaris might belong to the clade with saddle-shaped spots and subcaudal keels. However, H. scalaris is viviparous. If it truly belongs to this clade, it would support the idea of flexible reproductive modes within Helicops because H. gomesi is oviparous and H. angulatus exhibits both reproductive strategies. Regardless, both H. apiaka and H. scalaris possess hemipenes with long lobes, suggesting that they belong to the subgenus Helicops (Table 3).

Among the remaining species missing in our phylogenetic tree, H. acangussu Moraes-da-Silva et al. 2022, H. petersi Rossman, 1976, and H. trivittatus (Gray, 1849) possess hemipenes of the long-lobed morphotype and are therefore allocated to the subgenus Helicops (see Systematic account and Fig. 2; Table 3). Helicops acangussu and H. petersi both exhibit a spotted dorsal pattern and have been associated with H. hagmanni and H. pastazae, respectively, primarily based on scale counts (Rossman 1976; Moraes-da-Silva et al. 2022). Thus, H. acangussu and H. petersi most likely belong to the clade formed by H. hagmanni and H. pastazae. This is further supported by the fact that H. petersi has strong dorsal scale keels, a putative synapomorphy of species in this clade, and H. acangussu is oviparous, a reproductive mode only occurring within the subgenus Helicops (Fig. 3; Table 3).

Another unsampled species is H. yacu, a taxon with a spotted dorsal pattern (Table 3), for which information regarding the hemipenial morphology is unavailable. Nevertheless, Rossman and Dixon (1975) and Rossman (1976) associate H. yacu with H. polylepis, H. pastazae, and H. petersi, based on scalation and color pattern. Later, Rossman and Abe (1979) suggested that H. yacu might be conspecific with H. pastazae (i.e., a subspecies). Therefore, based on the reported similarities in scutellation with the aforementioned species and its spotted dorsal pattern, we tentatively assign H. yacu to the subgenus Helicops.

The last species not included in our molecular phylogeny is H. tapajonicus da Frota, 2005. This species has hemipenes with short lobes and is therefore allocated to the subgenus Tachynectes (see Fig. 2; Table 3; Systematic account).

Comments on recent taxonomic changes regarding Helicops angulatus

Helicops cyclops Cope, 1868 was recently resurrected from the synonymy of H. angulatus by Murphy et al. (2020) solely based on the morphology of the holotype (i.e., scale counts, color pattern, head shape). However, these traits show considerable overlap with H. angulatus (Murphy et al. 2020: table 2). Additionally, the locality of the holotype is imprecise (Bahia [State], Brazil), and Murphy et al. (2020) did not discuss the potential distribution range of H. cyclops. In the face of these limitations, we propose that H. cyclops should remain in the synonymy of H. angulatus pending additional evidence for its validity.

Diversification of Helicops

According to our results, the genus Helicops began to diversify in the late Miocene, around 9 Mya (Fig. 2; Suppl. material 2: fig. S1), aligning with the recent findings of Zaher et al. (2019), who suggested a similar time frame of 10.9 Mya. This period coincides with the existence of the Pebas System, a vast wetland that once covered most of the present-day Amazon Basin from approximately 20 to 5 Mya. The Pebas System was characterized by dynamic changes in landscape due to geological events and marine incursions throughout the Miocene (Hoorn et al. 2010, 2022). This dynamic wetland environment likely played a key role in the diversification of Helicops, and potentially the entire Hydropsini tribe (Suppl. material 2: fig. S1). This tribe includes semiaquatic snakes that diversified during the Miocene and are currently predominantly distributed in the Amazon Basin (Schöneberg and Köhler 2022).

Systematic account

Phylum: Chordata

Subphylum: Vertebrata

Superclass: Tetrapoda

Class: Reptilia

Order: Squamata

Family: Dipsadidae

Genus: Helicops Wagler, 1828

Helicops Wagler, 1828

Type species

Coluber carinicaudus Wied-Neuwied, 1824 (designated by Fitzinger 1843).

Diagnosis

Members of the subgenus Helicops have long hemipenial lobes decorated with papillate flounces or calyces extending to the tips, but without spinules. The hemipenial body is covered both with spines and spinules; spines are concentrated on the sulcate surface and the lateral regions of the hemipenial body (Fig. 4B).

Content

15 species, Helicops (Helicops) acangussu Moraes-da-Silva et al., 2022, H. (H.) angulatus (Linnaeus, 1758), H. (H.) apiaka Kawashita-Ribeiro, Ávila & Morais, 2013, H. (H.) boitata Moraes-da-Silva et al., 2019, H. (H.) carinicaudus (Wied-Neuwied, 1824), H. (H.) danieli Amaral, 1938, H. (H.) gomesi Amaral, 1922, H. (H.) hagmanni Roux, 1910, H. (H.) nentur Costa et al., 2016, H. (H.) pastazae Shreve, 1934, H. (H.) petersi Rossman, 1976, H. (H.) polylepis Günther, 1861, H. (H.) scalaris Jan, 1865, H. (H.) trivittatus (Gray, 1849), H. (H.) yacu Rossman & Dixon, 1975.

Comments

Wagler (1828) coined the generic name Helicops to allocate Coluber carinicaudus (= Helicops carinicaudus) and suggested that Coluber angulatus Linnaeus, 1758 (= Helicops angulatus) and Coluber erytrogrammus Palisot de Beauvois in Sonnini & Latreille, 1801 (= Farancia erytrogramma) belonged to Helicops because of their similarity. Two years later, Wagler (1830) included in Helicops the following species: H. carinicaudus, C. erytrogrammus, C. plicatilis, C. angulatus, and Natrix aspera Wagler, 1824 (= Helicops angulatus), without designation of a type species. Fitzinger (1843) designated H. carinicaudus as valid type species of Helicops. Since Wagler (1828) erected the name Helicops, the correct authorship has to be credited to Wagler (1828) and not Wagler (1830), as frequently seen (e.g., da Frota 2005; Kawashita-Ribeiro et al. 2013; Murphy et al. 2020; Schöneberg and Köhler 2022).

Tachynectes Fitzinger, 1843

Type species

Homalopsis leopardina Schlegel, 1837.

Diagnosis

Members of the subgenus Tachynectes have short hemipenial lobes decorated with spinules. The hemipenial body is homogeneously covered with spinules (Fig. 4A), occasionally a few enlarged spines may occur, e.g., in H. (T.) phantasma.

Content

Five species, Helicops (Tachynectes) infrataeniatus Jan, 1865, H. (T.) leopardinus (Schlegel, 1837), H. (T.) modestus Günther, 1861, H. (T.) phantasma Moraes-da-Silva et al., 2021, H. (T.) tapajonicus da Frota, 2005.

Comments

Tachynectes von der Mark, 1863, erected for a genus of fossil fishes, is a primary junior homonym of Tachynectes Fitzinger, 1843. As Tachynectes von der Mark, 1863 has only been used four times in the past 50 years according to our searches (Google Scholar, Zoological Record: Sepkoski 2002; Albert et al. 2009; Dietze 2009; Schwarzhans and Carnevale 2021), it fails to meet the criterion in Article 23.9.2 of the International Code of Zoological Nomenclature (ICZN 1999) for prevailing usage and is therefore unavailable. As a replacement name for Tachynectes von der Mark, 1863, we propose Ichthyotachynectes nom. nov. to accommodate the fossil fish species previously assigned to Tachynectes von der Mark, 1863.

Phylum: Chordata

Subphylum: Vertebrata

Superclass: Actinoptergyii

Class: Teleostei

Order: Myctophiformes

Family: Myctophidae

Ichthyotachynectes nom. nov.

https://zoobank.org/3B4D09B3-9E5A-4F4F-82FF-CBCE571D0533

Synonymy

Tachynectes von der Mark, 1863 (invalid junior homonym of Tachynectes Fitzinger, 1843)

Type species

Tachynectes macrodactylus von der Marck, 1863.

Diagnosis

For diagnosis and synapomorphies, see von der Marck (1863) and Dietze (2009).

Content

Three species according to Dietze (2009), Ichthyotachynectes macrodactylus (von der Marck, 1863), comb. nov., I. longipes (von der Marck, 1863), comb. nov., I. brachypterygius (von der Marck, 1863), comb. nov.

Etymology

The new name (male gender) means “fish that swims fast” (from the classic Greek ichthyos = fish, tachys = fast, nectes = swimming). The name intends to keep the initial meaning of Tachynectes (fast swimmer), but adding a prefix indicating the taxonomic group.

Comments

The homonymy of Tachynectes Fitzinger, 1843 and Tachynectes von der Mark, 1863 was already acknowledged by White and Moy-Thomas (1941), but overlooked by subsequent authors.

Conclusions

Our study reveals a pronounced phylogeographic pattern in H. danieli, with four distinct lineages (Figs 1, 2; Suppl. material 2: figs S1, S2). Interestingly, these lineages exhibit clear differentiation on the eastern and western sides of the middle Magdalena River, suggesting this river acts as a barrier to gene flow for this aquatic snake species. Although our sampling did not extend to the southwestern Pacific region of Colombia, it is plausible that populations there are sister to the lower Atrato lineage, mirroring patterns observed in other taxa (e.g., Mabuya spp., Pinto-Sánchez et al. 2015; Bothrops asper, Saldarriaga Córdoba et al. 2017).

Moreover, we propose a subgeneric classification for Helicops based on the molecular phylogeny and hemipenial morphology with two subgenera: Helicops and Tachynectes. Additionally, we offer a new interpretation of four further phenotypic and natural history traits (i.e., reproductive mode, dorsal scale keel strength, subcaudal keels, dorsal color pattern) and their value as putative synapomorphies for lineages within the subgenus Helicops. This reinterpretation allows us to propose the most plausible phylogenetic placement for the seven Helicops species not included in our molecular phylogeny.

Acknowledgements

We thank Juan Camilo Arredondo for discussions on Helicops hemipenial morphology and Sebastián Cuadrado for discussions on ancestral state estimation. Ralf Britz discussed the nomenclatural issues of Tachynectes von der Mark, 1863 with us. John Murphy and Robert Jadin made helpful comments on an earlier version of this study.

Additional information

Conflict of interest

The authors have declared that no competing interests exist.

Ethical statement

No ethical statement was reported.

Funding

JPHG was supported by a scholarship of the German Academic Exchange Service (DAAD). JMD was partially funded by the interinstitutional agreement 014-2023 between the Parques Nacionales Naturales de Colombia and the Universidad de Antioquia. MVR was supported by the Alexander von Humboldt Foundation with another research stay in Dresden, which made his contribution to the present work possible.

Author contributions

Conceptualization: JPHG, JMD, MVR, UF. Data curation: JPHG. Formal analysis: JPHG. Funding acquisition: JPHG, JMD, MVR, UF. Investigation: JPHG. Methodology: JPHG. Project administration: JPHG, UF. Resources: JPHG, JMD, MVR, UF. Supervision: MVR, UF. Visualization: JPHG, VD. Writing – original draft: JPHG, UF. Writing – review and editing: JPHG, JMD, MVR, VD, UF.

Author ORCIDs

Juan Pablo Hurtado Gómez https://orcid.org/0000-0003-4351-2834

Mario Vargas-Ramírez https://orcid.org/0000-0001-8974-3430

V. Deepak https://orcid.org/0000-0002-8826-9367

Uwe Fritz https://orcid.org/0000-0002-6740-7214

Data availability

All of the data that support the findings of this study are available in the main text or Supplementary Information.

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Supplementary materials

Supplementary material 1 

Supplementary tables

Juan Pablo Hurtado-Gómez, Juan M. Daza, Mario Vargas-Ramírez, V. Deepak, Uwe Fritz

Data type: xlsx

Explanation note: table S1. Samples and their respective GenBank/ENA accession numbers and (only for the newly generated sequences) localities for the individuals used in the molecular analyses. table S2. Primers, sources, and PCR conditions for each of the four molecular markers. table S3. Partitions obtained with MODELFINDER as implemented in IQ-TREE for the concatenated analysis of six molecular markers (mtDNA = 12S, 16S, cyt b; nDNA = BDNF, C-mos, NT3, Rag1). table S4. Akaike Information Criterion values obtained for each of the five morphological characters and the three tested models.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
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Supplementary material 2 

Supplementary figures

Juan Pablo Hurtado-Gómez, Juan M. Daza, Mario Vargas-Ramírez, V. Deepak, Uwe Fritz

Data type: pdf

Explanation note: fig. S1. Complete Bayesian dated tree obtained with the concatenated alignment of three mtDNA and four nDNA molecular markers. BR, Brazil; TT, Trinidad and Tobago. fig. S2. Complete Maximum Likelihood tree obtained with the concatenated alignment of three mtDNA and four nDNA markers. Values above branches indicate UltraFast bootstrap support. BR, Brazil; TT, Trinidad and Tobago. fig. S3. Detailed comparison between the Bayesian (left) and Maximum Likelihood (right) topologies obtained for Helicops danieli, cropped from Suppl. material 2: figs S1, S2, respectively. Values above branches on the left tree indicate Bayesian posterior probabilities, and on the right tree, UltraFast bootstrap support.

This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited.
Download file (406.54 kb)
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