# RES

Project Title: Genomic Aspects of Rapid Evolution in the Italian Wall Lizard (Podarcis siculus)

Partners: Faculty of Science, University of Zagreb

Project Duration: 2016 – 2021

Status: Completed

Species: Italian Wall Lizard (Podarcis siculus)

IUCN Red List Status: Least Concern (LC)

National Red List Status in Croatia: Least Concern (LC)

Project Overview:

The “Genomic Aspects of Rapid Evolution in the Italian Wall Lizard” project was designed to investigate the genetic basis of evolutionary changes within the population of the Italian wall lizard (Podarcis siculus). Rapid evolution is a compelling biological process in which adaptations within a population become observable within only a few generations.

An example of such rapid change occurred in 1971 when five pairs of Italian wall lizards were transferred from the islet of Pod Kopište to the nearby island of Pod Mrčaru in the Lastovo archipelago in the Adriatic Sea. On Pod Mrčaru, where this species had not previously been present, the newly introduced population of lizards faced different environmental conditions that led to visible changes in morphology and behavior over a few decades.

Research beginning in 2004 revealed that the lizards on Pod Mrčaru exhibited several phenotypic changes compared to the original Pod Kopište population. For example, due to an increased plant-based diet, Pod Mrčaru lizards developed larger and stronger teeth, a modified jaw structure, and, for the first time, cecal valves—an anatomical feature in the digestive system previously unrecorded in this species. The aim of this project was to determine the genetic basis of these changes and answer whether they represented an evolutionary adaptation to new conditions or merely phenotypic plasticity.

Zagreb Zoo provided specialized facilities to house and maintain the lizards in environments adapted to reptiles, playing an active role in conducting crossbreeding experiments. Our team ensured that lizards from both populations—Pod Kopište and Pod Mrčaru—were accommodated in controlled conditions, undergoing acclimatization before the start of breeding. The “common garden” experiment, conducted at the Zoo, enabled an assessment of heritability in the phenotypic traits of this species. Thanks to our expertise in maintaining reptiles in controlled environments, our specialists facilitated the successful implementation of experiments that required specific care, particularly for territorial males and the grouping of females.

The research yielded significant insights into the speed at which evolutionary processes can occur. Results indicated that phenotypic traits related to head shape, such as jaw size and structure, are moderately to highly heritable. Genomic analysis confirmed that the populations of Pod Mrčaru and Pod Kopište are genetically distinct, identifying 18 loci likely under selection and associated with divergent phenotypic characteristics and ecological differences. These adaptations indicate a strong selective pressure that compelled the Pod Mrčaru lizards to adapt to new dietary and ecological conditions.

Findings from research conducted at Zagreb Zoo also showed that phenotypic divergence is influenced not only by the immediate environment but also by a strong genetic component. These conclusions suggest that rapid changes in the environment can reflect on a genomic level within a relatively short time, a discovery particularly relevant in today’s context of accelerating ecosystem changes.

Summary:

The “Genomic Aspects of Rapid Evolution in the Italian Wall Lizard” project explored the genetic basis of rapid evolution in the Italian wall lizard (Podarcis siculus) after its relocation to a new island. Results revealed significant morphological and genetic adaptations related to dietary and environmental shifts, demonstrating how evolutionary changes can occur within a short timeframe.