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.