Summary 1.Trends of animal populations are of great interest in ecology but cannot be directly observed owing to imperfect detection. Binomial mixture models use replicated counts to estimate abundance, corrected for detection, in demographically closed populations. Here, we extend these models to open populations and illustrate them using sand lizard Lacerta agilis counts from the national Dutch reptile monitoring scheme. 2. Our model requires replicated counts from multiple sites in each of several periods, within which population closure is assumed. Counts are described by a hierarchical generalized linear model, where the state model deals with spatio-temporal patterns in true abundance and the observation model with imperfect counts, given that true state. We used WinBUGS to fit the model to lizard counts from 208 transects with 1-10 (mean 3) replicate surveys during each spring 1994-2005. 3. Our state model for abundance contained two independent log-linear Poisson regressions on year for coastal and inland sites, and random site effects to account for unexplained heterogeneity. The observation model for detection of an individual lizard contained effects of region, survey date, temperature, observer experience and random survey effects. 4. Lizard populations increased in both regions but more steeply on the coast. Detectability increased over the first few years of the study, was greater on the coast and for the most experienced observers, and highest around 1 June. Interestingly, the population increase inland was not detectable when the observed counts were analysed without account of detectability. The proportional increase between 1994 and 2005 in total lizard abundance across all sites was estimated at 86% (95% CRI 35-151). 5. Synthesis and applications. Open-population binomial mixture models are attractive for studying true population dynamics while explicitly accounting for the observation process, i.e. imperfect detection. We emphasize the important conceptual benefit provided by temporal replicate observations in terms of the interpretability of animal counts.

Habitat loss, together with less obvious land-use changes such as intensified farming practice, can have significant adverse impacts on biodiversity. An important factor in determining the ability of species to cope with such changes is their potential to sustain a populations network by dispersal across the landscape. Habitat quality and structure are particularly important for surface-dwelling species with low dispersal abilities, such as amphibians. To assess this ecological function, ponds in a coastal and typically rural area of northern France were surveyed for amphibians in 1974, 1992 and 2011. These repeated surveys yielded different outcomes for different species groups. Three rare species persisted in more or less specialized habitat types. Two moderately common species declined, but kept strongholds in coastal dunes and associated marshes. Five common species with broad ecological niches remained equally widespread. The Northern crested newt declined markedly and the Midwife toad declined dramatically, as did their breeding habitats in vegetated ponds and cattle drinking troughs. One species, the Moor frog, may have gone locally extinct. A model of relative resistance to amphibian dispersal was created for different landscape types, on a scale from 0 (low resistance) to 1 (high resistance). This generated values of 0.23 for pasture, 0.72 for arable and 0.98 for urban and transport. As pasture declined in the study area, while arable and urban/transport infrastructure increased, amphibian dispersal became more difficult. However, dispersal paths proved difficult to evaluate in a patchy landscape like the one surveyed, due to a paucity of spatial 123Biodivers Conserv (2017) 26:1411-1430 DOI 10.1007/s10531-017-1307 signal. Pond loss is a more tractable reason for the observed amphibian species decline than is the quality of intervening terrestrial habitat matrix. In 2011, 22 newly created ponds had species richness in line with pre-existing ponds and this will have counteracted a dwindling metapopulation structure, indicating that habitat creation/restoration can play a valuable role in conservation. The colonization of new ponds may also prove more informative for gauging the potential for amphibian dispersal in the landscape than the preceding decline.

A field study has been made in the relatively narrow sympatric zone of Triturus cristatus and T. marmoratus, in the department Mayenne (France). Ecological data have been analysed. In the sympatric area specific preferences appear to exist: ecological isolation has developed in some areas. Typical T. marmoratus areas are hilly and wooded, provided with many terrestrial hiding-places, while forest pools and springs especially serve as spawning sites. T. cristatus areas are flat and open. Comparison with distribution data of 24 years ago shows expansion of T. cristatus at the expense of T. marmoratus, which presumably is true for the whole sympatric zone. The preferences of the species in combination with changes in environment by human intervention explain the detected changes in distribution. Ecological isolation as a phenomenon in the speciation of both species is discussed.

When related species meet upon postglacial range expansion, hybrid zones are frequently formed. Theory predicts that such zones may move over the landscape until equilibrium conditions are reached. One hybrid zone observed to be moving in historical times (1950–1979) is that of the pond‐breeding salamanders Triturus cristatus and Triturus marmoratus in western France. We identified the ecological correlates of the species hybrid zone as elevation, forestation, and hedgerows favoring the more terrestrial T. marmoratus and pond density favoring the more aquatic T. cristatus. The past movement of the zone of ca. 30 km over three decades has probably been driven by the drastic postwar reduction of the “bocage” hedgerow landscape, favoring T. cristatus over T. marmoratus. No further hybrid zone movement was observed from 1979 to the present. To explain the changing dynamics of the hybrid zone, we propose that it stalled, either because an equilibrium was found at an altitude of ca. 140 m a.s.l. or due to pond loss and decreased population densities. While we cannot rule out the former explanation, we found support for the latter. Under agricultural intensification, ponds in the study area are lost at an unprecedented rate of 5.5% per year, so that remaining Triturus populations are increasingly isolated, hampering dispersal and further hybrid zone movement.

The banded newt, Triturus vittatus is suggested to consist of two species (T. ophryticus and T. vittatus). The northern taxon, T. ophryticus, is subdivided into two geographic fragments: the "western group" of populations from western Anatolian Turkey, and the "eastern group" distributed in the remaining part of the Pontic Turkey and western Caucasus. The western samples are characterized by a peculiar combination of various features. In this group the modal number of trunk vertebrae is equal to 12, like in T. v. vittatus and T. v. cilicensis, whereas the eastern group of T. ophryticus has 13 vertebrae. The amount of DNA per diploid nucleus, determined by flow cytometry, is higher in the western group (66.8-68.8 pg vs. 62.5-63.7 pg in the eastern group). Significant differences between both groups of T. ophryticus were revealed in allozymes (D Nei ' 72 = 0.383 in average) as well. We allocate the western group of T. ophryticus to a separate subspecies, Triturus ophryticus nesterovi, subsp. nov. A paleogeographic scenario for T. vittatus and other newts is proposed. The taxonomic structure of the paraphyletic genus Triturus is discussed. We proposed to split the genus in four monophyletic genera Triturus sensu stricto, Lophinus, Mesotriton and Ommatotriton.