Plastic and genomic change of a newly established lizard population following a founder event.

Understanding how phenotypic divergence arises among natural populations remains one of the major goals in evolutionary biology. As part of competitive exclusion experiment conducted in 1971, 10 individuals of Italian wall lizard (Podarcis siculus (Rafinesque-Schmaltz, 1810)) were transplanted from Pod Kopiste Island to the nearby island of Pod Mrcaru (Adriatic Sea). Merely 35 years after the introduction, the newly established population on Pod Mrcaru Island had shifted their diet from predominantly insectivorous towards omnivorous and changed significantly in a range of morphological, behavioural, physiological and ecological characteristics. Here, we combine genomic and quantitative genetic approaches to determine the relative roles of genetic adaptation and phenotypic plasticity in driving this rapid phenotypic shift. Our results show genome-wide genetic differentiation between ancestral and transplanted population, with weak genetic erosion on Pod Mrcaru Island. Adaptive processes following the founder event are indicated by highly differentiated genomic loci associating with ecologically relevant phenotypic traits, and/or having a putatively adaptive role across multiple lizard populations. Diverged traits related to head size and shape or bite force showed moderate heritability in a crossing experiment, but between-population differences in these traits did not persist in a common garden environment. Our results confirm the existence of sufficient additive genetic variance for traits to evolve under selection while also demonstrating that phenotypic plasticity and/or genotype by environment interactions are the main drivers of population differentiation at this early evolutionary stage.

Dampened virulence and limited proliferation of Batrachochytrium salamandrivorans during subclinical infection of the troglobiont olm (Proteus anguinus).

Emerging infections add to existing threats to the survival of amphibians worldwide. The olm (Proteus anguinus) is a vulnerable, troglobiont urodele species with a small European range and restricted to underground karstic systems. Population declines to emerging threats like the chytrid fungus Batrachochytrium salamandrivorans, are likely to go unnoticed due to inaccessibility of the species' habitat. We here studied the interaction between olms and B. salamandrivorans. Experimental inoculation of olms resulted in low-level, asymptomatic but persistent infections, with limbs as predilection sites. The lack of exponential fungal growth in the olms' epidermis correlated with limited fungal proliferation and dampened virulence gene expression after exposure to olm skin compounds. The olm is one of few western Palearctic urodeles that is tolerant to B. salamandrivorans infection and may act as a subterranean disease reservoir, yet costs of subclinical infection may compromise olm fitness on the long term.

Monitoring health and reproductive status of olms (Proteus anguinus) by ultrasound.

The olm (Proteus anguinus) is a troglomorphic, neotenous amphibian with extraordinary life expectancy and unique adaptations that deserve further investigation. A low reproductive rate and habitat decline render it threatened by extinction. Establishing captive populations for maintenance and artificial breeding may one day become crucial to the species. Longitudinal, in-vivo assessment of inner organs is invaluable to our understanding of reproductive physiology, health, and behavior. Using ultrasound, we measured heart rate and assessed health and reproductive status of 13 captive olms at Zagreb Zoo. Heart rate averaged 42.9 ± 4.6 bpm (32-55 bpm), as determined via pulsed-wave Doppler at 4-12 MHz. By using frequencies of up to 70 MHz (ultrasound biomicroscopy), inner organs were visualized in detail. Assessment of the gastrointestinal tract provided insights into feeding status and digestive processes. Several subclinical pathologies were detected, including biliary sludge, subcutaneous edema, ascites, and skin lesions. Detection of skin lesions by ultrasound was more sensitive than visual adspection. Olms with ultrasonographically detected skin lesions tested positive for Saprolegnia and were treated. Three of the four affected individuals survived and subsequently tested negative for Saprolegnia. Sex was reliably determined; only one individual proved male. The reason for this extreme female-biased sex-ratio remains unknown. However, as most of the individuals were flushed from the caves by strong currents in spring, the sample may not be representative of natural populations. In female olms, different stages of ovarian follicular development were observed with diameters ranging between 0.1 and 1.1 mm. Results were confirmed by comparing ultrasound, necropsy, and histological findings of one dead specimen. In summary, ultrasound proved a valuable tool to support conservation and captive breeding programs by allowing non-invasive assessment of physiological parameters, clinical condition, and reproductive status in olms.

Population-specific effects of developmental temperature on body condition and jumping performance of a widespread European frog.

All physiological processes of ectotherms depend on environmental temperature. Thus, adaptation of physiological mechanisms to the thermal environments is important for achieving optimal performance and fitness. The European Common Frog, Rana temporaria, is widely distributed across different thermal habitats. This makes it an exceptional model for studying the adaptations to different thermal conditions. We raised tadpoles from Germany and Croatia at two constant temperature treatments (15°C, 20°C), and under natural temperature fluctuations (in outdoor treatments), and tested how different developmental temperatures affected developmental traits, that is, length of larval development, morphometrics, and body condition, as well as jumping performance of metamorphs. Our results revealed population-specific differences in developmental time, body condition, and jumping performance. Croatian frogs developed faster in all treatments, were heavier, in better body condition, and had longer hind limbs and better jumping abilities than German metamorphs. The populations further differed in thermal sensitivity of jumping performance. While metamorphs from Croatia increased their jumping performance with higher temperatures, German metamorphs reached their performance maximum at lower temperatures. These population-specific differences in common environments indicate local genetic adaptation, with southern populations being better adapted to higher temperatures than those from north of the Alps.