 |
| Triturus rudolfi Arntzen, 2024 |
Abstract
Iberian populations of large-bodied newts, with Triturus marmoratus in the north and T. pygmaeus in the south of the peninsula, were studied for external morphology, mitochondrial dna and for a panel of single nucleotide polymorphisms. This confirmed the species’ low level of interspecific hybridization and their parapatric, mosaic-like mutual range border across the peninsula. The genetic data also revealed substantial variation within T. pygmaeus, with narrow (0.43–35.2 km) clinal transitions in the very centre of Portugal. Similar clines were observed for body size and colouration pattern. Pygmy newts in the west of Portugal are larger, with a more striped (less reticulated) green dorso-lateral colouration pattern than those in the east and south of the country. The western group of populations is described as a new species, Triturus rudolfi sp. nov., on account of a long, ca. 2.5 Ma, independent evolutionary history and limited hybridization with its sister-species T. pygmaeus, suggesting selection against hybrid offspring. The range of the newly described species may be restricted to the wider Lisbon Peninsula, stretching northwards along the Atlantic coast to the river Vouga estuary. Inland, the range border may be set by the lower Tejo River, or by the currently wide area of agricultural land at either side of that river, that may accommodate a residual hybrid zone. The close contact between both pygmy newt species is effectively limited to a ca. 20 × 40 km area directly north of the town Entroncamento, where T. rudolfi sp. nov. is sandwiched in between T. marmoratus and the river Tejo.
Keywords: clinal variation; colouration pattern; hybrid zone; Lisbon pygmy newt; mitochondrial dna; morphometrics; Portugal; single nucleotide polymorphisms; Triturus marmoratus; Triturus pygmaeus; Triturus rudolfi sp. nov.
 |
| The Iberian Peninsula with the approximate distributions of four taxa of large-bodied newts as described in table 1. Colour codes are: blue – Triturus marmoratus, dark red – T. pygmaeus pygmaeus, light red – T. p. lusitanicus and brown – Triturus rudolfi nov. sp., i.e., the newly described species from the wider Lisbon Peninsula. Letters indicate the capital cities Lisbon, Portugal (L) and Madrid, Spain (M) as well as Peniche (P) at the Atlantic coast. Major rivers partially coinciding with (sub)species borders are the Guadalquivir, the Vouga and the Tejo. The new species’ type locality Lagoa Seca near Valado dos Frades is indicated by a long arrow. The insert shows an adult male T. marmoratus. |
 |
| Holotype of Triturus rudolfi sp. nov. at right (top) and left lateral view (middle), and in ventral view (bottom). Size bar is 1 cm. Stored at the Museo Nacional de Ciencias Naturales, Madrid, Spain under catalogue number 51784. |
 |
| Triturus rudolfi sp. nov. from Serra de Sintra (top) and from the Colares and Janas region (middle and bottom). |
Triturus rudolfi sp. nov.
Diagnostic features – the newly recognized species is most closely related to, yet morphologically distinguishable from T. pygmaeus, on account of a lower number of green coloured dorso-lateral transversal bands (‘links’). Body size larger than in T. pygmaeus. Significant genetic differences for population groups at either side of the cline near Entroncamento were found at 34 out of 54 investigated nuclear markers, as well as for mitochondrial dna. Body size smaller than in T. marmoratus, with a higher number of links and with a light rather than dark coloured underside.
Derivatio nominis – the species name is chosen in honour of Mr. Rudolf Malkmus, in recognition of his contribution to the knowledge of the Portuguese herpetofauna. Mr. Malkmus placed the Portuguese herpetofauna on the map, not just as a figure of speech, but also literally (Malkmus, 2004).
Suggested vernacular name – Malkmus’ pygmy newt or Lisbon pygmy newt. I further advocate to restrict the name ‘marbled newt’ to T. marmoratus and to use ‘pygmy newts’ for T. pygmaeus and T. rudolfi sp. nov. (see also table 1).
Distribution – the Lisbon Peninsula in Portugal, reaching northward along the Atlantic Ocean up to the river Vouga estuary. Approximate range borders: bounded by T. marmoratus in the north at ca. 39.5 N, separated from T. pygmaeus in the east by the Tejo River and in the northeast by a narrow hybrid zone that is wedged in between T. marmoratus territory and the river Tejo.
Jan W. Arntzen. 2024. Morphological and Genetic Diversification of Pygmy and Marbled Newts, with the Description of A New Species from the wider Lisbon Peninsula (Triturus, Salamandridae). Contributions to Zoology. DOI: 10.1163/18759866-bja10057
