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Details on the specimens included in this study. For each genetic marker, A. fragilis (F) and A. veronensis (V) alleles are indicated. French administrative departments are abbreviated by their two-digits codes, as follow: 04: Alpes-de-Haute-Provence; 05: Haute-Alpes; 06: Alpes-Maritimes; 13: Bouches-du-Rhône; 30: Gard; 34: Hérault; 64: Pyrénées-Atlantiques; 66: Pyrénées-Atlantiques; 83: Var; 84: Vaucluse; 88: Vosges; 93: Seine-Saint-Denis. Geographic coordinates are given alongside their precision (Prec. in meters).
Source publication
With five currently recognized species that form several secondary contact zones, slow worms (Anguidae: Anguis) offer a valuable model to study the fate of evolutionary lineages in the face of hybridization and genetic introgression. The relationships between the Western Slow Worm Anguis fragilis and the Italian Slow Worm Anguis veronensis are part...
Contexts in source publication
Context 1
... genotype scoring, sequence chromatograms were screened visually, and heterozygotes were identified by confirming double peaks at the diagnostic sites. Finally, the ND2 and PLRL datasets were complemented with the information of six specimens collected on Saint-Marguerite Island and barcoded by (2018) (table 1). In each population, the proportions of fragilis/veronensis alleles were computed for each marker separately, and averaged over the three markers, as a hybrid index. ...Similar publications
Range shifts during the Pleistocene shaped the unique phylogeographical structures of many species. Pleistocene range shifts gave currently allopatric species opportunities to occur in sympatry, likely resulting in ancient introgressions between related taxa. In our study, we investigate the range shifts and introgression patterns of three Japanese...
Introgression is pervasive across the tree of life, varying across taxa, geography, and genomes. However, we are only beginning to understand the factors that modulate this variation and how they may be affected by global change. Here, we used 200 genomes and a 15-year site-specific environmental dataset to investigate the effect of mating system d...
Theoretical work suggests that reinforcement can cause the strengthening of prezygotic isolation in sympatry by mitigating the costs of maladaptive hybridization. However, only a handful of studies have simultaneously tested multiple predictions of this theory in natural populations. We investigated reinforcement in a mottled hybrid zone between th...
The extent of interspecific gene flow and its consequences for the initiation, maintenance, and breakdown of species barriers in natural systems remain poorly understood. Interspecific gene flow by hybridization may weaken adaptive divergence, but can be overcome by selection against hybrids, which may ultimately promote reinforcement. An informati...
Citations
... Moreover, hybridisation in this genus was revealed between the species pairs: A. fragilis-A. veronensis in Nothern Italy and SouthernFrance (Gvoždík et al., 2013;Dufresnes et al., 2023), A. fragilis-A. colchica in Hungary (Szabó & Vörös, 2014), Czechia and Slovakia Šifrová, 2017;Benkovský et al., 2021;Harca, 2021). ...
... According to the obtained distribution data of both species' ND2 and RAG1 haplotypes, the Upper Silesia hybrid zone seems to be as narrow as 30-50 km. A similar size for the Anguis hybrid zone was found in France (Dufresnes et al., 2023), and even narrower (estimated to 11 km) in the Czech-Slovak contact zone (Harca, 2021). Putative hybrid specimens found in population 27 confirm Mazovia as the northernmost region of gene flow between the two slow worm species. ...
Background
Legless lizards, the slow worms of the genus Anguis, are forming secondary contact zones within their Europe-wide distribution.
Methods
We examined 35 populations of A. fragilis and A. colchica to identify the level of morphological and genetic divergence in Poland. We applied a conventional study approach using metric, meristic, and categorial (coloration) features for a phenotype analysis, and two standard molecular markers, a mitochondrial (NADH-ubiquinone oxidoreductase chain 2; ND2 ) and a nuclear (V(D)J recombination-activating protein 1; RAG1 ) one.
Results
We found clear differences between A. fragilis and A. colchica in molecular markers and phenotype—in meristic features, e.g., ear opening, number of scales rows around the body, and higher than so far known diversity in ND2 and RAG1 haplotypes. The presence of five hybrids was detected in three populations in the Polish part of the European contact zone. In all hybrids, homozygous alleles of RAG1 were detected, which suggests a back-crossing within the genus.
Conclusions
The ability to produce fertile offspring by A. fragilis x A. colchica hybrids shows inefficient mechanisms of reproductive isolation of the two legless lizards. The hybrids were indistinguishable from parental species in head proportions (principal components and discriminant analyses) but more resembling A. colchica in meristic traits.
... typic genus with developed subspecific taxonomy. Later, Grillitsch and Cabela (1990) presented that the Peloponnese populations form endemic species A. cephallonica Werner, 1894 and recent studies (Gvoždík et al., 2010(Gvoždík et al., , 2013(Gvoždík et al., , 2023 revealed that the genus is represented by five species of different levels of their genetic diversity (Thanou, Giokas and Kornilios, 2014;Jablonski et al., 2016Jablonski et al., , 2017Dufresnes et al., 2023). Two of these species have wider distribution (A. ...
Ireland is home to only one native lizards’ species, the viviparous lizard and one of the few areas of the world where there are no native snakes. However, since the end of the 19th century, there have been reports indicating the presence of legless lizards, Anguis fragilis Linnaeus, 1758 population whose origin is unknown. As this genus has been intensively studied genetically and taxonomically in the past decade, we have decided to investigate newly obtained mtDNA sequences (ND2 gene) to trace affiliation of the Anguis population in Ireland. We genetically examined 12 individuals from the Burren area (western Ireland) and compared them to available data. The Irish population was identified as belonging to A. fragilis, specifically to the most common haplotype of the Illyrian-Central European haplogroup. This genetic affiliation is shared by populations across a wide European region, including the western Balkans, Spain, France, western Hungary, Austria, Germany, Latvia, Poland, the Czech Republic, Russia, Sweden, Norway, and Great Britain. Our findings showed that the Irish population does not exhibit unique mitochondrial variability. This haplotype is present across the range of the species, including Great Britain, which is not in contrast with the earlier hypothesis that nearby populations from this area, along with human-mediated introductions, could be the source of Anguis populations in Ireland. This is thus potentially the first documented case of Anguis introduction out of the native range. However, further research, including broader sampling in Great Britain and genomics, is required to determine and trace its exact origin.
... Phylogenetic controversy exists for A. veronensis, which, according to mtDNA, represents a sister lineage to A. cephallonica, but this is likely the result of ancient mitochondrial capture (Gvoždík et al. 2023). Some degree of hybridization has been documented between A. fragilis and A. colchica (Szabó and Vörös 2014, Gvoždík et al. 2015, Benkovský et al. 2021, A. fragilis and A. graeca (Mikulíček et al. 2018), and A. fragilis and A. veronensis (Gvoždík et al. 2013, Dufresnes et al. 2023. Therefore, the question arose as to whether and to what extent the speciation events were associated with karyotype changes and how much their karyotypes may be differentiated while still allowing gene flow. ...
... The youngest sister-species pair A. fragilis-A. veronensis with a MRCA dated to about 2.7 Mya then forms a rather narrow hybrid zone (Dufresnes et al. 2023) despite similar karyotypes. ...
Karyotype divergence may strongly affect the degree of hybridization between species. Western Palearctic slow worms (Anguis) are legless lizards forming different types of secondary contact zones. To identify the level of chromosomal variation in slow worms, we examined karyotype in multiple populations of all species except one and Pseudopus apodus as an outgroup. We applied conventional and molecular cytogenetic methods and whole-chromosome painting using macrochromosome probes from Varanus komodoensis to interpret results within the evolutionary framework of the common clade Anguiformes. All Anguis species and P. apodus have conserved karyotype structures composed of 44 chromosomes. Despite the conserved chromosome morphology, the phylogenetically oldest Anguis cephallonica living in partial sympatry with Anguis graeca, and parapatric Anguis colchica vs. Anguis fragilis exhibit distinct patterns of constitutive heterochromatin distribution and telomeric repeat accumulation. In contrast, the sister species A. colchica and A. graeca living in allopatry display highly similar karyotype features. Our findings thus indicate karyotype stasis in Anguis and Pseudopus for > 20 Myr, with fixed species-specific differences present in sympatric and parapatric species. These differences in repetitive DNA patterns may play a role as intrinsic factors co-maintaining species divergence. They may also be used as cytotaxonomic markers to identify slow worm species in practice.
The Italian geographic region is characterized by complex and diversified biogeographic patterns and is represented by a high number of endemic species. Endemic species characterized by a limited distribution range should be a primary concern in conservation. This article aimed to investigate the phylogenetic and biogeographic relationships of 2 Italian endemic species of the wingless blister beetle genus Meloe Linnaeus, 1758: Meloe (Eurymeloe) apenninicus and Meloe (E.) baudii. Our inferences, based on morphological characters, 2 mitochondrial (16S and COI) and 2 nuclear (CAD and 28S) markers and the use of 3 species delimitation analyses approaches, pointed out the presence of a new Italian endemic species (M. (E.) digiuliorumsp. n.), here described, and 3 different patterns of phylogenetic and biogeographic affinities. M. digiuliorum is close to the Spanish endemic M. orobatescomb. n., revealing a possible fragmentation of the ancestor range in the Pleistocene (ca. 0.84 Mya) followed by isolation in Italy and Spain. M. apenninicus is the sister species of the European-Anatolian M. rugous and M. cfr. rugosus, and this pattern originated around the Plio-Pleistocene boundary (ca. 2.83 Mya) likely influenced by the climatic fluctuations and the presence of the Alpine barrier. Finally, 2 subspecies were referred to M. baudii: the nominal one, endemic to Italy, and the Turanian-E European M. b. glazunovistat. n., disclosing a third more recent (ca. 0.64 Mya) pattern of biogeographic disjunction.
