DOI: 10.5061/dryad.573n5tb46
title: Drivers of amphibian population dynamics and asynchrony at local and regional scales

description: Identifying the drivers of population fluctuations in spatially distinct
 populations remains a significant challenge for ecologists. Whereas
 regional climatic factors may generate population synchrony (i.e., the
 Moran effect), local factors including the level of density-dependence may
 reduce the level of synchrony. Although divergences in the scaling of
 population synchrony and spatial environmental variation have been
 observed, the regulatory factors that underlie such mismatches are poorly
 understood. Few previous studies have investigated how density-dependent
 processes and population-specific responses to weather variation influence
 spatial synchrony at both local and regional scales. We addressed this
 issue in a pond-breeding amphibian, the great crested newt (Triturus
 cristatus). We used capture-recapture data collected through long-term
 surveys in five T. cristatus populations in Western Europe. In all
 populations – and subpopulations within metapopulations – population size,
 annual survival and recruitment fluctuated over time. Likewise, there was
 considerable variation in these demographic rates between populations and
 within metapopulations. These fluctuations and variations appear to be
 context-dependent and more related to site-specific characteristics than
 local or regional climatic drivers. We found a low level of demographic
 synchrony at both local and regional levels. Weather has weak and
 spatially variable effects on survival, recruitment and population growth
 rate. In contrast, density-dependence was a common phenomenon (at least
 for population growth) in almost all populations and subpopulations. Our
 findings support the idea that the Moran effect is low in species where
 the population dynamics more closely depends on local factors (e.g.
 population density and habitat characteristics) than on large-scale
 environmental fluctuation (e.g. regional climatic variation). Such
 responses may have far-reaching consequences for the long-term viability
 of spatially structured populations and their ability to response to
 large-scale climatic anomalies.
description: The study was conducted on
 five populations in France and the United Kingdom using the
 capture–recapture method. Two populations (POP1 and POP2) are located in
 southeastern England and are 2.5 km apart and separated from each other by
 dispersal barriers, such as roads and unsuitable habitat. Another
 population (POP3) is located in western France. The last two populations
 (POP4 and POP5) are located in southeastern France. The populations POP2,
 POP3 and POP4 occupy single breeding sites. POP1 and POP5 are spatially
 structured populations, both composed of four distinct subpopulations. In
 POP1, the four subpopulations occupy four distinct ponds, separated from
 each other by distances ranging from 200 to 800 m. There is a low level of
 adult movement among subpopulations with dispersal mainly occurring during
 the subadult phase. In POP5, the four subpopulations occupy four distinct
 pond groups. Each group was composed of three very close (15-30 m) ponds
 between which annual dispersal rates are high (&lt;0.20). The pond
 groups were separated from each other by a distance ranging from 60 to 430
 m; the number of breeding dispersal events among pond groups was low (i.e.
 12 out of 2282 individuals captured during the period 1996-2015),
 resulting in a mean dispersal rate of &lt; 0.01. These 12 individuals
 were discarded from our analyses. Newts were
 surveyed over periods ranging from 8 to 20 years between 1995 and 2016.
 The newts were captured using bottle traps (POP1 and POP2, see Griffiths
 et al. 2010), funnel traps (POP3), dipnets (POP4) and seine net (POP5).
 The number of capture sessions performed each year varied from 1 (POP5) to
 33 (POP1) during the newt activity period in ponds. Note that in
 capture-recapture analyses, we merged the observations of intra-annual
 sessions, considering one single session per year. Newts were individually
 identified using pit-tags in POP3 and POP5, and by photographs of belly
 pattern markings in POP1, POP2 and POP4. Providing the image quality is
 high and the identification is done by trained personnel, belly patterns
 are a highly reliable method for identifying individual newts. Each
 individual was classified as adult or juvenile, and adults were sexed on
 the basis of the presence of a swollen cloaca and a large crest on the
 back in males. As the number of juveniles was low in our datasets
 (juveniles only occasionally found in the ponds), the following analyses
 were restricted to adults.
description: No missing values. Contact the first author (Hugo Cayuela,
 hugo.cayuela@gmail) for additional information.