| Περίληψη: | In this thesis we study the population and behavioural ecology of two syntopic newt species in southern Greece. The study site is a temporary pond in northern Peloponnese, near the town of Kalavryta. Two newt species, the alpine newt, Ichthyosaura alpestris (Laurenti 1768), and the smooth newt, Lissotriton vulgaris (Linnaeus 1758), are syntopic at the pond, which they use for breeding. The study area is the southern limit of both species' distribution.
The correct identification of individuals is a requirement of Capture-Mark-Recapture (CMR) methods, and it is commonly achieved by applying artificial marks or by mutilation of study-animals. An alternative, non-invasive method to identify individuals is to utilize the patterns of their natural body markings. We explore the use of pattern mapping for the identification of adult individuals in the alpine (Ichthyosaura alpestris) and smooth (Lissotriton vulgaris) newts (Amphibia, Salamandridae), using the freely available, open-source software Wild-ID. Our photographic datasets comprised nearly 4000 captured animals’ images, taken during a three-year period. The spot patterns of individual newts of both species did not change through time, and were sufficiently varied to allow their individual identification, even in the larger datasets. The pattern-recognition algorithm of Wild-ID was highly successful in identifying individual newts in both species. Our findings indicate that pattern mapping can be successfully employed for the identification of individuals in large populations of a broad range of animals that exhibit natural markings.
Amphibian breeding migrations are strongly influenced by environmental conditions, due to the distinctive physiological, ecological and behavioural characteristics of amphibians. Furthermore, the breeding-migration patterns of individual animals might be influenced by their sex, size, physiological state, and/or overall reproductive quality. From 2012 to 2014 we collected mark-recapture data for two syntopic populations of alpine and smooth newts in southern Greece (i.e. the southern limit of their species’ distribution), as well as morphometric data for individual newts and data on environmental factors. Using these data we studied the reproductive dynamics of these populations and assessed whether individual traits and environmental covariates influence their breeding-migration patterns. Alpine and smooth newts followed a similar temporal pattern of migration. Breeding-migration patterns were not influenced by individual traits (body condition and fecundity). Inward migration was not influenced by ground temperature, rainfall or photoperiod; the onset of reproduction seems to be determined by the filling of the breeding pond with water. In contrast, outward migration was not influenced by water availability, but it was triggered by increasing water temperatures. Our findings corroborate the few available studies of newt-populations occurring near the southern edge of their distribution. However, compared to numerous studies of northern newt-populations, our results suggest distinct breeding-migration patterns, as well as contrasting effects of environmental factors on these migration patterns.
Amphibian populations have been declining globally for the last several decades, and climate change is often regarded as one of the most important factors driving these declines. We performed a laboratory experiment to investigate how temperature affects ovipositing females, eggs and hatchlings in two syntopic populations of alpine and smooth newts. Female newts were assigned to two different oviposition temperatures (11 oC and 14 oC) for the duration of their oviposition period. Deposited eggs were equally divided and assigned to three different incubation temperatures (11 oC, 14 oC and 17 oC). Using this fully factorial design we examined the influence of temperature on females’ reproductive output, and the interactive effects of oviposition and incubation temperatures on embryonic and larval traits (embryonic mortality, days to hatch and hatchling length). We found strong interspecific differences in the effects of oviposition and incubation temperatures on almost all examined adult, embryonic and hatchling traits. Our results illustrate the significance of preferred oviposition-temperature range for amphibian reproduction and highlight the heterogeneity of responses to climatic changes among amphibian species.
Consumption of conspecific and heterospecific eggs and larvae is common in many animal taxa, including many amphibians. Adult newts often co-occur temporally and spatially with conspecific and heterospecific newt eggs and larvae and adult individuals may benefit from their consumption, but little is known on the degree of discrimination in the newts’ predatory behaviour towards them. We performed two laboratory experiments to examine whether adult male and female alpine and smooth newts discriminate between conspecific and heterospecific eggs and larvae in their predatory behaviour. We found no differences in predatory behaviour towards conspecific and heterospecific eggs, or between males and females in either species. Similarly, we found no evidence for the occurrence of discriminative predatory behaviour towards conspecific and heterospecific larvae. In our experiments the criterion for whether a newt would consume a prey item (egg or larva) was not the prey’s identity (species), but the newts’ ability to detect, capture and/or ingest it. Our results suggest that newts of both species follow an opportunistic foraging strategy, consuming whatever prey (i.e. egg or larva) they manage to capture.
The two syntopic newt populations seem to be more strongly influenced during their breeding period by environmental conditions rather than by competitive interactions; their responses to environmental cues are similar in some respects (e.g. the patterns of their breeding migrations) but dissimilar in others (e.g. oviposition behaviour, embryonic and hatchling traits).
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