The smooth and the Montandon's newts (Triturus vulgaris and T. montandoni) are genetically similar sister species with highly divergent male secondary sexual traits involved in complex courtship behaviour. Their parapatric ranges overlap at moderate elevations in the Carpathian Mountains where they hybridize readily. Here we present a detailed study of genetic and morphological variation in populations from the area of sympatry. Analysis of variation at seven nuclear markers, mtDNA and male sexual secondary traits was complemented with an ecological survey of breeding sites characteristics. Extensive hybridization was revealed with back-cross individuals similar to either parental species predominating among hybrids. The hybrid zone exhibited a mosaic pattern: the genetic composition of the populations was correlated only weakly with their geographical position. No association with habitat type was found. Departures from Hardy-Weinberg proportions, significant linkage disequilibria and bimodal distribution of genotypes suggest strongly that assortative mating is an important factor shaping the genetic composition of hybrid populations. The pattern of cytonuclear disequilibria did not indicate much asymmetry in interspecific matings. Changes in the frequency of nuclear markers were highly concordant, whereas mtDNA showed much wider bidirectional introgression with 14% excess of T. montandoni haplotype. We argue that the mosaic structure of the newt hybrid zone results mainly from stochastic processes related to extinction and recolonization. Microgeographical differences in mtDNA introgression are explained by historical range shifts. Since morphologically intermediate males were underrepresented when compared to hybrid males identified by genetic markers, sexual selection acting against the morphological intermediates is implied. We discuss the implications of these findings in the context of reinforcement of prezygotic isolation in newts.

The moor frog Rana arvalis is a lowland species with a broad Eurasiatic distribution, from arctic tundra through forest to the steppe zone. Its present-day range suggests that glacial refugia of this frog were located outside southern European peninsulas. We studied the species-wide phylogeographical pattern using sequence variation in a 682 base pairs fragment of mtDNA cytochrome b gene; 223 individuals from 73 localities were analysed. Two main clades, A and B, differing by c. 3.6% sequence divergence were detected. The A clade is further subdivided into two subclades, AI and AII differing by 1.0%. All three lineages are present in the Carpathian Basin (CB), whereas the rest of the species range, including huge expanses of Eurasian lowlands, are inhabited solely by the AI lineage. We infer that AII and B lineages survived several glacial cycles in the CB but did not expand, at least in the present interglacial, to the north. The geographical distribution and genealogical relationships between haplotypes from the AI lineage indicate that this group had two glacial refugia, one located in the eastern part of the CB and the other probably in southern Russia. Populations from both refugia contributed to the colonization of the western part of the range, whereas the eastern part was colonized from the eastern refugium only. The effective population size as evidenced by theta(ML) is an order of magnitude higher in the AI lineage than in the AII and B lineages. Demographic expansion was detected in all three lineages.

Starch gel electrophoresis and morphometric characters were used to assess the geographical variation between 14 populations of the moor frog, Rana arvalis, from northern and southern areas in Central Europe. Six of the 13 screened allozyme loci were polymorphic (95% criterion). No fixed differences in allele composition between the two regions were found. Some of the alleles were region specific. Genetic variability as measured by expected heterozygosity ( He) and number of alleles per locus was significantly lower in the southern samples than in northern ones ( He=0.104 and He=0.156, alleles/locus=1.6 and 1.8 respectively). This is interpreted as a consequence of the different past history of these two groups during the Pleistocene. Population subdivision, as measured by FST, was substantial (0.124 and 0.078 for the southern and northern group, respectively); 59.9% of the between‐locality variation is attributed to this division into two geographical groups. Isolation‐by‐distance was detected by significant negative correlation between the estimate of gene flow (log M^) and log(geographical distance) only for the southern population groups. This indicates that the northern populations have recently recolonized their contemporary distribution area. The mean genetic distance between the northern and southern group of populations was DN=0.062. Despite the relatively low genetic distance between them, the two population groups form two distinct clusters in the maximum likelihood (ML) tree. Discriminant analysis on 11 size adjusted body measurements showed considerable overlap between populations from different geographical areas. An isolated Romanian Reci population which genetically belongs to the southern group of populations was morphologically situated in an intermediate position between northern and other southern populations.

Riolqpical~r/ournal ofthe Linnenn Socie!v (1 999), 67: 343 352.Article ID: bijl. 1998.0306, available online at http://~w.idealibra r)...com o n I D E b b 0 c Sexual isolation between two newt species, -Triturus vulgaris and T montandoni (Amphibia, Urodela, Salamandridae)In the present study we investigated sexual isolation between TrituruJ vulgaris and 7: montandoni in mating experiments run under semi-natural conditions. The two newt species offer a suitable model for studying evolution of reproductive isolation and mating preferences because they arc genetically the most similar species within the genus and readily hybridize in nature. Separate experiments were conducted in which groups of virgin females were placed together (in artificial pools) with groups of homospecific, heterospecific or both types of males. T h r estimates of reproductive isolation and mating propensity were based on the numbers of females producing hybrids and/or non-hybrid progeny. The levels of reproductive isolation, isolation asymmetry (IA) and propensity asymmetry (PA) were significant only for experiments in which females were given a choice between conspecific and heterospecific males. This implies that mating experiments with no interspecific choice may reduce discrimination and affect patterns of IA and PA. Asymmetry in reproductive isolation was also significant when the analysis was confined to just inseminated females. Differences in habitat preferences and condition of females possibly contributed to the relativcly high values of PA. 0 1999 The 1,innean Society of I.ondon

In its general pattern the sexual behaviour of Triturus montandoni most resembles that of Triturus helveticus. The courtship consists of three phases: orientation, static display and retreat display, followed by a spermatophore transfer phase. During display the male performs three tail movements: the fan, the whip, and the wave. The relative frequencies of tail movements and the duration of fanning bouts are the main difference between T montandoni, T. helveticus, and T. vulgaris. The phylogenetic relationships between these three species are discussed.

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Morphometric variation of 11 characters was studied in 14 samples of Rana arvalis from allopatric population groups in Central Europe, representing two subspecies formerly recognised: R. a. arvalis and R. a. wolterstorffi. All samples from Poland (nine) were collected from the area, which is believed to be populated by the nominal form. In addition, the isolated population of R. arvalis from the Eastern Carpathians of Romania was classified to that form. All the Hungarian samples fall into the range of R. a. wolterstorffi. No significant differences in body size between sexes and among the populations from the three geographic regions (Poland, Hungary and Romanian Eastern Carpathians) were found. Multivariate analysis of the differences in body shape among groups showed that the populations from Hungary differed from the nominal form mainly in the relative hindlimb length. However, substantial overlap in overall shape differences resulted in a relatively low percentage of correct classifications to the respective geographic groups in the Discriminant Analysis. Large intrapopulation variation in the values of the two ratios (SVL/TL and TL/IMT) formerly used for differentiate the two European subspecies of R. arvalis makes them unreliable characters for distinguishing the two forms. The pattern of morphometric variation does not match the overall genetic divergence of the R. arvalis populations, which suggests that the body shape differences in this species result from the phenotypic plasticity correlated with local climatic factors.

In polyandrous females the ultimate stage of cryptic female choice may involve egg-sperm interactions during different phases of fertilization. This form of sperm discrimination is possible only when sperm from different males have simultaneous access to eggs at the site of fertilization. In polyandrous newts of the genus Triturus, eggs are fertilized internally by sperm stored for an extensive period of time in the tubular spermatheca. The extent of sperm mixing, which is a necessary condition for cryptic female choice involving sperm-egg interactions, was studied in doubly mated female Alpine newts, Triturus alpestris. Using an allozyme marker the paternity of offspring sired by the two males was established in both series of larvae reared from eggs produced consecutively over short period of time (ca. 2 h) and batches of eggs collected during longer periods of time (up to 26 days). Significant sperm mixing was unequivocally demonstrated by the mixed paternity of the progeny produced in series. The paternity pattern in batches of eggs collected during longer periods of time showed neither significant predominance of either male in the progeny nor any effects of sperm stratification in the tubules of the spermatheca.Résumé : Chez les femelles polyandres, l'étape finale, cryptique, du choix de la femelle peut se faire au niveau des interactions oeufs-spermatozoïdes au cours des différentes phases de la fécondation. Cette forme de discrimination des spermatozoïdes n'est possible que lorsque des spermatozoïdes de mâles différents ont accès aux oeufs simultanément au site de fécondation. Chez les tritons polyandres du genre Triturus, les oeufs sont fécondés à l'intérieur du corps par des spermatozoïdes emmagasinés pour une longue période dans la spermathèque tubulaire. L'importance du mélange des spermatozoïdes, une condition nécessaire au choix de la femelle par interactions oeufs-spermatozoïdes, a été étudiée chez des femelles de Triturus alpestris accouplées à deux mâles. En utilisant un allozyme comme marqueur, la paternité de chacun des mâles a été établie aussi bien dans une série de larves obtenues d'oeufs produits successivement pendant une courte période (ca. 2 h) que dans des masses d'oeufs recueillies pendant des périodes plus longues (jusqu'à 26 jours). Il se fait un important mélange des spermatozoïdes, comme le démontre sans équivoque la paternité mixte de la progéniture produite en série. Dans les masses d'oeufs recueillies sur de plus longues périodes, ni l'un ni l'autre des mâles ne s'est révélé génétiquement prédominant et nous n'avons pas non plus constaté d'effets de stratification des spermatozoïdes dans les tubules de la spermathèque.[Traduit par la Rédaction] 1298Rafi½ski and Osikowski