Mismatch between temperature preferences and morphology in F1 hybrid newts (Triturus carnifex×T. dobrogicus)

1. The influence of interspecific hybridization on temperature preferences and morphology was examined in newts, Triturus carnifex and Triturus dobrogicus, before and after metamorphosis.

2. Thermoregulatory behavior was measured in an aquatic thermal gradient (5–32.5 °C) during 24 h.

3. Hybrid temperature preferences were similar to preferences of maternal species in both premetamorphic larvae and recently metamorphosed individuals.

4. Hybrid morphology (i.e., forelimb length and axilla–groin distance) was intermediate relative to parental species.

5. The mismatch between morphology and thermal preference in hybrid phenotypes indicates potential hybrid disadvantage in both intermediate and parental habitats.

Crest evolution in newts: implications for reconstruction methods, sexual selection, phenotypic plasticity and the origin of novelties

The dorsal crest of newts (Salamandridae) is a novel, phenotypically plastic, sexually selected trait that may evolve in association with complex courtship behaviours. We estimated a near-comprehensive, time-calibrated phylogeny for salamandrids and analysed the evolution of their crests and display behaviour. Different models give conflicting reconstructions for crest evolution, showing that likelihood can estimate incorrect ancestral states with strong statistical support. The best-fitting model suggests that crests evolved once and were lost repeatedly, supporting the hypothesis that sexually selected traits may be frequently lost. We demonstrate the correlated evolution of crests and courtship behaviour and show that species with larger numbers of crest-related traits have larger repertoires of behaviours. We also show that phenotypically plastic morphological traits can be maintained over long macroevolutionary timescales (～25-48 Myr). Finally, we use salamandrids to address how novel structures may arise, and support a model involving the expansion and subdivision of pre-existing structures.     

Dispersal of viviparity across contact zones in Iberian populations of fire salamanders (Salamandra) inferred from discordance of genetic and morphological traits

Abstract.— We used partial sequences of the cytochrome b mitochondrial DNA (mtDNA) gene, obtained from 76 individuals representing 45 populations of Iberian Salamandra salamandra plus 15 sequences of additional species of Salamandra and related genera, to investigate contact zones. These zones, identified by earlier allozymic and morphological analyses, are between populations of viviparous (S. s. bernardezi and S. s. fastuosa ) and ovoviviparous (S. s. gallaica and S. s. terrestris ) salamanders. The distribution of mtDNA and nuclear markers is mostly concordant at one contact zone (between S. s. gallaica and S. s. bernardezi ), but at another (between S. s. fastuosa and S. s. terrestris ) the markers are offset by about 250 km. The observed geographic variation fits a model of mtDNA capture. Among the potential mechanisms responsible for such discordance we favor a combination of range shifts due to climatic fluctuations and biased genetic admixture across moving contact zones. We apply our findings to the issue of possible homoplasy in the evolution of viviparity and conclude that viviparity likely arose only once within S. salamandra .     

Trunk elongation and ontogenetic changes in the axial skeleton of Triturus newts

Body elongation in vertebrates can be achieved by lengthening of the vertebrae or by an increase in their number. In salamanders, longer bodies are mostly associated with greater numbers of vertebrae in the trunk or tail region. However, studies on the relative contribution of the length of single vertebra to body elongation are lacking. In this study, we focus on evolutionary and ontogenetic changes in differentiation of the trunk vertebrae and the relative contribution of individual vertebrae to trunk lengthening in Triturus newts, a monophyletic group of salamanders that shows remarkable disparity in body shape. We compared juveniles and adults of the most elongated T. dobrogicus , which has 17 trunk vertebrae, with juveniles and adults of two closely related species (T. ivanbureschi and T. anatolicus belonging to the T. karelinii species complex) representing a stout and robust morphotype with thirteen trunk vertebrae. We show that trunk vertebrae are uniform in size at the juvenile stage of both analyzed morphotypes. In adults, the trunk vertebrae of the elongated T. dobrogicus are largely uniform, while in those of T. anatolicus , the first two vertebrae differ from the remaining trunk vertebrae. There was no difference in the relative contribution of individual vertebrae to body lengthening between species or stages. We conclude that body elongation in Triturus newts is achieved by increasing the number of vertebrae but not their length.     

Isolation and characterization of seven microsatellite loci in Chioglossa lusitanica (Urodela: Salamandridae)

Seven polymorphic microsatellite markers were isolated and characterized for golden‐striped salamander, Chioglossa lusitanica (Bocage 1864), a salamandrid endemic to the northwestern part of the Iberian Peninsula, from genomic libraries enriched for (GATA)₈ (GACA)₈ (ATG)₉ and (CA)₁₆. These loci were screened in 37–51 individuals from two populations. The number of alleles per locus ranged from five to 19. Heterozygosity ranged from 0.241 to 1.0. The high level of polymorphism revealed by these loci will be extremely useful for the study of population structure and evolutionary history of this species.     

Interfamily variation in amphibian early life-history traits: raw material for natural selection?

The embryonic development and time to hatching of eggs can be highly adaptive in some species, and thus under selective pressure. In this study, we examined the underlying interfamily variation in hatching timing and embryonic development in a population of an oviparous amphibian, the rough-skinned newt (Taricha granulosa). We found significant, high variability in degree of embryonic development and hatching timing among eggs from different females. Patterns of variation were present regardless of temperature. We also could not explain the differences among families by morphological traits of the females or their eggs. This study suggests that the variation necessary for natural selection to act upon is present in the early life history of this amphibian.     

Synchrotron analysis of a ‘mummified’ salamander (Vertebrata: Caudata) from the Eocene of Quercy,France

An incomplete ‘mummy’ from the Phosphorites du Quercy (presumed Eocene) was identified as a salamander during the 19^th century. The specimen has now been computed tomography (CT) scanned, and this revealed the incomplete skeleton (with perfectly preserved bones) and soft tissues (lung). The fossil represents a new, well‐characterized taxon. Despite the absence of the skull, several features allow a phylogenetic analysis. The fossil belongs to pseudosaurian caudates; it is tentatively assigned to the Salamandridae, although affinities with Plethodontidae cannot be definitely ruled out.     

Morphological integration and serial homology: A case study of the cranium and anterior vertebrae in salamanders

Serial homology or the repetition of equivalent developmental units and their derivatives is a phenomenon encountered in a variety of organisms, with the vertebrate axial skeleton as one of the most notable examples. Serially homologous structures can be viewed as an appropriate model system for studying morphological integration and modularity, due to the strong impact of development on their covariation. Here, we explored the pattern of morphological integration of the cranium and the first three serially homologous structures (atlas, first, and second trunk vertebrae) in salamandrid salamanders, using micro-CT scanning and three-dimensional geometric morphometrics. We explored the integration between structures at static and evolutionary levels. Effects of allometry on patterns of modularity were also taken into account. At the static level (within species), we analyzed inter-individual variation in shape to detect functional modules and intra-individual variation to detect developmental modules. Significant integration (based on inter-individual variation) among all structures was detected and allometry is shown to be an important integrating factor. The pattern of intra-individual, asymmetric variation indicates statistically significant developmental integration between the cranium and the atlas and between the first two trunk vertebrae. At the evolutionary level (among species), the cranium, atlas, and trunk vertebrae separate as different modules. Our results show that morphological integration at the evolutionary level coincides with morphological and functional differentiation of the axial skeleton, allowing the more or less independent evolutionary changes of the cranial skeleton and the vertebral column, regardless of the relatively strong integration at the static level. The observed patterns of morphological integration differ across levels, indicating different impacts of developmental and phylogenetic constraints and functional demands.     

瘰螈属(有尾目,蝾螈科)一新种

作者在贵州省织金县采集到一批蝾螈科瘰螈属动物标本,与该属已知物种比较后,确定其为1新种,即织金瘰螈Paramesotriton zhijinensis sp.nov。新种与尾斑瘰螈Paramesotriton caudopunctatus相似,但新种成体头部后端两侧各有3条退化的鳃迹,明显呈童体型;体背嵴两侧各有1条土黄色纵纹;指、趾两侧无缘膜,无内、外掌突;肛后尾腹鳍褶橘红色或橘黄色,约在后3/4处此颜色消失。本文统计并记述了新种的外形、头骨特征、生物学资料。     

Molecular phylogenetics and historical biogeography among salamandrids of the "true" salamander clade: rapid branching of numerous highly divergent lineages in Mertensiella luschani associated with the rise of Anatolia

Phylogenetic relationships among salamandrids of the "true" salamander clade are investigated using 2019 aligned base positions (713 parsimony informative) of 20 mitochondrial DNA sequences from the genes encoding ND1 (subunit one of NADH dehydrogenase), tRNA(Ile), tRNA(Gln), tRNA(Met), ND2, tRNA(Trp), tRNA(Ala), tRNA(Asn), tRNA(Cys), tRNA(Tyr), and COI (subunit I of cytochrome c oxidase), plus the origin for light-strand replication (O(L)) between the tRNA(Asn) and the tRNA(Cys) genes. Parsimony analysis produces a robust phylogenetic estimate for the relationships of the major groups of "true" salamanders. Strong support is provided for the sister taxon relationship of Chioglossa and Mertensiella caucasica and for the placement of Salamandra and Mertensiella luschani as sister taxa. These relationships suggest two vicariant events between Europe and Anatolia caused by the formation of seaways in the Mediterranean Basin. Molecular divergence indicates an Early Miocene separation of Chioglossa and M. caucasica and a Late Miocene separation of Salamandra and M. luschani. The traditional phylogenetic hypothesis of a monophyletic Mertensiella is statistically rejected, indicating that southwestern and northeastern Anatolian populations have separate historical biogeographic origins. Therefore, we recommend placement of M. luschani in the genus Salamandra. Within M. luschani, six highly divergent lineages showing 7.6 to 10.1% pairwise sequence divergence are identified. Tests using four-taxon subsamples suggest that these lineages diverged nearly simultaneously in the Late Miocene, approximately 6 to 8 million years ago, when extensive uplifting of Anatolia occurred in response to the Arabian collision.