Phenotypic differentiation of the slow worm lizards (Squamata: Anguis) across their contact zone in Central Europe

Background The application of molecular-phylogenetic approaches to taxonomy has had a dramatic effect on our understanding of the diversity of reptiles. These approaches have allowed researchers to reveal previously hidden lineages as well as taxonomic overestimation in morphologically plastic taxa. Slow worms, legless lizards of the genus Anguis (Squamata: Anguidae), were previously considered to comprise either one or two species, and morphology-based intraspecific taxonomy of Anguis fragilis remained controversial throughout the 20th century. After the discovery of deep genetic divergences within the genus, its taxonomy was reconsidered, and as a result, five extant species have been recognized. In order to better understand the patterns of their interspecific differentiation, here we studied phenotypic differences between the two most widespread of them—A. fragilis and A. colchica, and their putative hybrids across the contact zone of both species in Central Europe. Methods We used multivariate and univariate statistics and analyzed ten metric, eleven meristic, and six categorical phenotypic variables in material comprising a total of 326 individuals. We also genotyped individuals from the contact zone for one mitochondrial and two nuclear DNA fragments in order to delineate the distribution of individuals of hybrid and non-hybrid origin. The clines in morphological traits were studied using HZAR. Results We show that the two species are morphologically differentiated. Anguis fragilis has a less robust head, fewer scales covering the body, lower frequency of the external ear opening presence, lower frequency of separated prefrontal scales, higher frequency of prefrontal scales in contact with each other, and body coloration more similar to the juvenile coloration than A. colchica. Slow worms from the contact/hybrid zone are characterized by an intermediate morphology, with more similarities to A. fragilis than to A. colchica. Discussion None of the analyzed characters alone proved to be fully diagnostic, although more than 90% of all individuals could be successfully assigned to one or another species based on numbers of scales around the body. Our results indicate concordant, coincident, and steep clines in character states change. We present several hypotheses on the origin and evolutionary maintenance of the morphological divergence between both species and suggest that different evolutionary histories of the taxa rather than recently acting selection explain the observed morphological variation.

THE PROPOSAL OF MONITORING OF SLOW-WORM ANGUIS FRAGILIS L. AND EASTERN SLOW-WORM ANGUIS COLCHICA (NORDMANN, 1840) IN POLAND

The paper presents the proposal for monitoring methods of two species from Anguidae family occurring in Poland such as slow-worm A. fragilis and Eastern slow-worm A. c. incerta. Until recently, both species were considered to be the same taxon. Thanks to genetic research the Eastern slow-worm was isolated from the species A. fragilis. In recent years, phenotypic differences between A. fragilis and A. c. incerta have been described, but it has not been noticed whether there are any behavioral or habitat preference differences. Only the approximate boundary of the occurrence of both species in Poland is known. It may be important to distinguish common areas, as there are known cases of hybridization of A. c. incerta with A. fragilis in the Czech Republic and Hungary. Due to the recent isolation of the Eastern slow-worm, it is still not legally protected in Poland, unlike the partially protected slow-worm.

Embryonic development and perinatal skeleton in a limbless, viviparous lizard, Anguis fragilis (Squamata: Anguimorpha)

Despite the long history of embryological studies of squamates, many groups of this huge clade have received only limited attention. One such understudied group is the anguimorphs, a clade comprising morphologically and ecologically very diverse lizards. We describe several stages of embryonic development of Anguis fragilis, a limbless, viviparous anguimorph. Interestingly, in several clutches we observe high morphological variation in characters traditionally important in classifying embryos into developmental stages. The causes of this variation remain unknown but environmental factors do not seem to be very important. Additionally, we describe the state of ossification in several perinatal specimens of A. fragilis. The cranial skeleton is relatively poorly ossified around the time of birth, with all of the bones constituting the braincase unfused. On the other hand, the vertebral column is well ossified, with the neurocentral sutures closed and the neural arches fused in all postatlantal vertebrae. Such an advanced state of ossification may be related to the greater importance of the vertebral column in locomotion in limbless species than in ones with fully-developed limbs. Numerous factors seem to affect the state of ossification at the time of hatching or birth in squamates, including phylogenetic position, mode of reproduction and, potentially, limblessness. However, data from a greater number of species are needed to reach firmer conclusions about the relative importance of these variables in certain clades.

Two species of slow worm (Anguis fragilis, A. colchica) present in the Baltic region

Five European slow worms (Anguis) have mostly parapatric distributions. Two species, A. fragilis and A. colchica, are widely distributed across the western and eastern parts of the genus range. Their contact zone runs from the north-eastern Balkans, through Pannonia to northern Central Europe. In northern Poland, the contact zone has been located approximately between the North and East European Plains. Here, we present the first mitochondrial and nuclear DNA data from Finland and the coastal Baltics. We demonstrate that A. fragilis enters the East European Plains, where it is presumably distributed along the Baltic coast. Our data indicate that A. colchica is present more inland and to the north of Riga. The genetic structure suggests three independent postglacial colonization events in the Baltics (two by A. colchica). The presence of the two species, A. fragilis and A. colchica, should be considered by the conservation legislations of Lithuania, Latvia and Russia.

Discrimination of Three Kinds of Visual Stimuli by Slow-Worm Lizards (Anguis fragilis)

Visual abilities to discriminate between spatial and color stimuli was studied, which is ecologically significant for reptiles. Namely: the behavior of slow-warm lizards in a Tshaped maze was investigated in visual discrimination between red and green color tones and sizes of geometric figures of a round shape. The main behavioral characteristics of decisionmaking were analyzed when choosing between possible options: a percentage of erroneous choices, time of choice and a number of lizards’ turns towards alternative ways in the maze, leading to comparable stimuli, before choosing one of them. In case of color discrimination, all the three named behavior characteristics were minimal, while in case of the figures sizes discrimination these values were higher. Thus, discrimination of red and green colors was more successful and less difficult than discrimination of round-shaped geometric figures sizes in the lizards.

Estimation of amphibian and reptile diversity in the Kurghalsky Wildlife Sanctuary

Kurghalsky Wildlife Sanctuary occupies an extreme western position in the Leningrad Region (with the main city of St. Petersburg). The fauna of the Kurghalsky Wildlife Sanctuary is quite diverse and includes 6 species of amphibians and 5 species of reptiles. The core of herpetofauna is formed by several species (Lissotriton vulgaris, Bufo bufo, Rana arvalis, Rana temporaria, Anguis fragilis, Zootoca vivipara, Vipera berus) widely distributed in the boreal zone of Eurasia. It is enriched by a few subboreal species (Pelobates fuscus, Pelophylax ridibundus, Lacerta agilis, Natrix natrix), regionally rare in the taiga zone. The highest diversity of amphibians and reptiles (8 species) was registered in the boreal and intrazonal groups of plant communities such as the forb-grassy meadows, greenmoss and light pine heath forests. The greatest similarity of herpetofaunas is characteristic for communities of spruce and small-leaved forests (93%), small-leaved forests and meadows (93%), broad-leaved forests and bogs (89%), pine and spruce forests (88%) and small-leaved forests and bogs (83%). Differences in the species composition of the local herpetofaunas are associated with a tendency to depletion of the number of species in boreal communities: from coniferous and mixed forests to bogs, reed communities and beaches. The general depletion of herpetofauna of the north is associated primarily with the loss of subboreal elements. The diversity and relatively high density of amphibian and reptile populations indicate the good preservation of forest and coastal ecosystems.

Distribution of the slow worm (Anguis fragilis complex) with possible species delimitation in Serbia

U ovom radu, prikazujemo ažurirane podatke o distribuciji kompleksa vrsta slepića (Anguis fragilis complex) u Srbiji. Podaci se sastoje iz nalaza objavljenih u literaturi ili na Internetu, zajedno sa prethodno neobjavljenim distribucionim podacima sakupljenim na terenu. Od dve vrste kompleksa prisutne u Srbiji, Anguis fragilis je rasprostranjen u zapadnim i južnim krajevima naše zemlje dok je Anguis colchica prisutan u severoistočnim i istočnim krajevima. U najsevernijim delovima naše zemlje konstatovano je odsustvo obe vrste, zbog nedostatka odgovarajućeg staništa. Nalazi su brojniji u planinsko-kotlinskom regionu i ređi i raštrkaniji u peripanonskom i panonskom regionu, što se delimično može objasniti nesistematskim uzorkovanjem. Lokacija i širina kontaktne zone dve vrste slepića u Srbiji je još uvek nedovoljno poznata. Pretpostavlja se da se pruža duž doline Velike Morave ka jugu a zatim prati granicu između Rodopskog i Karpatsko-Balkanskog planinskog masiva ka jugo-istoku, ali postoje indicije da se hibridna zona nalazi i zapadnije. Postoji izvesno neslaganje, u literaturi, između kontaktne zone predložene na osnovu morfoloških analiza i one predložene na osnovu molekularnih analiza. Ovo ukazuje na potrebu za opsežnijim uzorkovanjem i daljim analizama. Konačno, pošto razdvajanje dve kriptičke vrste slepića do sada nije prepoznato u našoj nomenklaturi, u ovom radu predlažemo zvanične srpske nazive za navedene vrste. Vrsta Anguis fragilis će zadržati standardno srpsko ime "Slepić", dok za vrstu Anguis colchica predlažemo ime "Istočni slepić".