The smooth newt, European newt, northern smooth newt or common newt (Lissotriton vulgaris) is a species of newt. It is widespread in Europe and parts of Asia, and has also been introduced to Australia. Individuals are brown with a spotted underside that ranges in colour from orange to white. They reach an average length of , with males being larger than females. The newts' skins are dry and velvety when they are living on land, but become smooth when they migrate into the water to breed. Males develop a more vivid colour pattern and a conspicuous skin seam (crest) on their back during the breeding season.
The smooth newt was originally described by Carl Linnaeus as a lizard, and was then given different genus names before being classified as a member of Lissotriton. There are currently three accepted subspecies of smooth newt. Formerly, there were also four subspecies—all with more restricted ranges that are now classified as separate species, because they have been found to be distinct genetically as well as in appearance: the Caucasian smooth newt, the Greek smooth newt, Kosswig's smooth newt and Schmidtler's smooth newt. Together with these four species and the Carpathian newt, the smooth newt forms what is known as a species complex: some of the species hybridise with each other.
For most of the year, smooth newts live on land, are mostly nocturnal, and hide during the day. They can adapt to a wide range of natural or semi-natural habitats, from forests at field edges to parks and gardens. Their diet consists mainly of invertebrates such as insects and earthworms and they are mainly preyed upon by fish, birds and snakes. Between spring and summer, they breed in ponds or similar bodies of water. Males court females with a ritualised underwater display. Females lay their eggs on water plants, and larvae hatch after 10 to 20 days. The larvae develop for around three months before metamorphosing into terrestrial juveniles, at which point they become known as efts. They reach maturity after two to three years, and the adults live for up to 14 years.
The smooth newt is abundant over much of its range and is classified as a species of least concern by the International Union for Conservation of Nature (IUCN). However, it has been negatively affected by habitat destruction and fragmentation, as well as the introduction of new species of fish. Like other European amphibians, the smooth newt has now been listed as a protected species by the Berne Convention.
Taxonomy
Swedish naturalist Carl Linnaeus described the smooth newt in 1758 as Lacerta vulgaris, placing it in the same genus as the green lizards. It was later re-described under several different species and genus names, including Triton, Molge, Salamandra and Lissotriton, with in total 48 species synonyms published. Most recently, it was included in the genus Triturus, along with most European newts. This genus was found to be polyphyletic, containing several unrelated lineages, and the small-bodied newts, including the smooth newt, were therefore split off as separate genus in 2004 by García-París and colleagues. They used the name Lissotriton, introduced by the English zoologist Thomas Bell in 1839 with the smooth newt as type species but then considered a synonym of Triturus. "Lissotriton" is a combination of the Greek (), meaning "smooth", and the name of Triton, an ancient Greek god of the sea, while the species epithet means "common" in Latin.
Three subspecies are accepted by Pabijan, Wielstra and colleagues: L. v. vulgaris, L. v. ampelensis and L. v. meridionalis. These authors, followed by Amphibian Species of the World, recognise four former subspecies from southern Europe and west Asia as separate species, as they are morphologically and genetically distinct: the Greek smooth newt (L. graecus), Kosswig's smooth newt (L. kosswigi), the Caucasian smooth newt (L. lantzi) and Schmidtler's smooth newt (L. schmidtleri). The five smooth newt species and the Carpathian newt (L. montadoni), which is their sister species, have collectively been referred to as the "smooth newt species complex".
To distinguish the smooth newt from its close relatives, the English name "northern smooth newt" has been suggested. Other common names that have been used in the literature include: common newt, great water-newt, common water-newt, warty eft, water eft, common smooth newt, small newt, small eft, small evet, and brown eft.
Evolution
Molecular phylogenetic analyses have shown that the smooth newt is distinct from its four close relatives – the Caucasian, Greek, Kosswig's, and Schmidtler's smooth newt – which were formerly considered to be subspecies (see section Taxonomy above). The relationships within this species complex remain unclear. Within the smooth newt itself, genetic groups do not entirely correspond to the currently accepted subspecies (ampelensis, meridionalis, vulgaris), which were described based on morphology. It is estimated that the five smooth newt species collectively were estimated to have diverged from the Carpathian newt around four to six million years ago.
Genetic analyses have also demonstrated ongoing gene flow between the smooth newt and its relatives. Although the Carpathian newt is clearly different in appearance, hybridisation between the two species is frequent. It has been shown that smooth newt mitochondrial DNA has introgressed into and completely replaced that of the Carpathian newt populations. Partial introgression has also occurred from the smooth newt to the Greek smooth newt. These patterns are likely due to the range expansion and secondary contact of species after the Last Glacial Maximum, which they likely survived in refugia mainly in southern and eastern Europe. The palmate newt (Lissotriton helveticus), although often occurring in the same habitats, almost never hybridises with the smooth newt. Artificial crosses with even more distant species such as the alpine (Ichthyosaura alpestris) and northern crested (Triturus cristatus) newts were successful in laboratory experiments.
Description
General characteristics
Adult male smooth newts reach a head-to-tail length of around and are thus slightly larger than the females, which reach . Adult body weight varies between , decreasing during the breeding season. The head is longer than it is wide and has two to three longitudinal grooves on the top. The elongated snout is blunt in the male and rounded in the female. The skin is velvety and water-repellent on land but smooth during the aquatic phase. It contains mucus and toxin glands and the upper layer is shed off regularly.
Outside of the breeding season, both sexes are yellow-brown, brown or olive-brown. Males have dark, round spots, while females have smaller spots of the same colour, which sometimes form two or more irregular lines along the back. Males have an orange stripe the underside of the tail and an orange to white throat and belly in males with small dark, rounded spots (these are lighter with smaller spots in females). Size and colour vary with the environment, and newts tend to be smaller in northern latitudes. Albinistic and leucistic individuals have been described.
The smooth newt is diploid (i.e. it has two copies of each chromosome), with 24 chromosomes in total.
Breeding characteristics
During the aquatic breeding season, males develop an uninterrupted skin crest running along their back and tail. This crest is high at mid-body, but higher along the tail. The tail also has a lower fin and a pointed end. The cloaca (the single digestive, urinary and reproductive orifice) of breeding males is swollen, round and dark-coloured. Depending on the subspecies, the hindfeet have more or less developed toe flaps. Colours are generally more vivid than during the land phase. The dark spots grow larger, and the crest often has vertical dark and bright bands. There are five to seven longitudinal stripes on the head. The lower edge of the tail is red with a silver-blue flash and black spots. Females have develop low straight tail fins, but no crest or toe flaps, and are more drably coloured.
Subspecies differ slightly in terms of the male secondary characteristics: L. v. ampelensis has strongly developed toe flaps and a tail that tapers into a fine thread (but not a distinct filament). The body is also slightly square in cross-section. L. v. meridionalis also has toe flaps and a pointed tail, its crest is smooth-edged, and its body is square-shaped. In the nominate subspecies, L. v. vulgaris, the crest is clearly denticulated, toe flaps are only weakly developed and the body is round.
Larvae
The aquatic larvae are long and yellow-brown with two longitudinal stripes at hatching. They initially have, In addition to their gills, they initially have only two balancers at the sides of their heads, short appendages for attaching to plants which are resorbed within a few days. As with all salamanders, the forelegs develop before the hindlegs. The colour of the larvae changes to a more cryptic, darkly marbled yellow to brown as they grow. Larvae are very slender and resemble those of the palmate newt. They develop a skin seam running from the neck to the pointed tail, which is as long as the head and trunk combined. The larvae grow to , which is also the size of the efts (terrestrial juveniles) just after metamorphosis.
Similar species
The smooth newt resembles the other, less widespread Lissotriton species. It can be confused especially with the closely related "smooth newt complex" species (marked with * in the table below) and the more distant palmate newt, which often occurs in the same area. Females are particularly challenging to distinguish, as the distinguishing features are primarily observed in the males during the breeding season.
Comparison of the smooth newt and related Lissotriton species Species Distribution Breeding male characteristics Other Body shape Dorsal crest Toe flaps (hind feet) Tail end Smooth newt*L. vulgaris widespread from British Isles to Central Asia round to square (depending on subspecies) smooth or denticulated (depending on subspecies) weakly to well developed (depending on subspecies) pointed to elongated, no filament Bosca's newtL. boscai West Iberian Peninsula slightly square none none short filament belly with some dark spots, especially at sides Carpathian newt*L. montandoni Carpathians square very low, smooth-edged weakly developed blunt, with filament belly unspotted Caucasian smooth newt*L. lantzi Caucasus slightly square high (less than at mid-body), denticulated (almost spine-shaped) moderately developed pointed, but no filament Greek smooth newt*L. graecus Southern Balkans square low (less than at mid-body), smooth-edged well developed long filament lower tail fin unspotted Italian newtL. italicus Southern Italy slightly square none none pointed, no filament very small, ; throat with few or no spots; golden-yellow patch behind eyes in both sexes Kosswig's smooth newt*L. kosswigi Northern Anatolia square low (less than at mid-body) but higher at tail base strongly developed long filament Palmate newtL. helveticus Western Europe square low, smooth-edged strongly developed long filament (both sexes) throat unspotted Schmidtler's smooth newt*L. schmidtleri Anatolia and eastern Balkans slightly square high (more than at mid-body), denticulated weakly developed elongated, no filament very small,
Distribution
Native range