This year, two teams worked in parallel to pursue our studies on Podarcis diversification; Nathalie, Gwenaëlle and Tobias went to the western Mediterranean, while Guannan, Ivan and Quentin went to Brittany. The western Mediterranean team was complemented by Natalia and Iris from the MPI in Plön and our long-term collaborators and friends Geoff While and Daniele Salvi, who all joined us for part of our field season.
Mediterranean field work
The Mediterranean field work started mid-April in north-western Italy. First, Geoff and Natalia joined to sample the Southern Alps and Central Italy lineages of Podarcis muralis. It was great fun to return to some places that were sampled more than 10 years ago! Besides re-visiting mainland Italy, the team also explored the Tuscan Archipelago with islands such as Pianosa, Capraia or the highly protected Montecristo. And some of those islands held some surprises, even for the experienced field worker: on Argentarola islet, P. muralis come in amazing dark blue coloration, something that one wouldn’t expect in the repertoire of our old friend P. muralis! Even if the weather wasn’t perfect in April with many days of rain, a total of 13 populations of P. muralis were sampled, as well as some extra populations of Podarcis siculus. Only one of the seven islands of the Tuscan Archipelago was out of reach this year –Gorgona– but we will return!
Early May, the team moved to Sardinia to visit small island populations of Podarcis tiliguerta in the South and in the North. Already last year we had the chance to visit Sardinia, but several islands still remained on our to-do list and so we returned this year. Geoff and Natalia left but were replaced by Iris and Daniele. The weather was great and a total of nine P. tiliguerta populations were sampled, as well as four extra populations of P. siculus (including the heaviest siculus individual of the field season: 14.4 g!). The team experienced some fun boat jumping adventures to land on Toro Island, which was definitely the highlight of this trip: we were greated by black and yellow/green P. tiliguerta that occupy the island in extremely high densities! Unfortunately, we didn’t get the chance to visit the blue lizards on Isola di Molarotto, providing us with an excuse to come back once more!
Finally, at the end of May, the team went to Formentera Island where a different sampling approach was used to study the amazing diversity in coloration and color patterns of the Ibiza wall lizard Podarcis pityusensis. Iris designed a transect from Cap de Barbaria to La Mola to sample 20 populations that form a nice gradient from the baby-blue phenotypes in the West to the apple-green phenotypes in the East. More to come on this project soon! The team also took he opportunity to spend a day with our collaborator Oriol Lapiedra and his team on Ibiza Island, sharing updates and discussing future project ideas. Unfortunately, we left Ibiza Island without seeing a single P. pityusensis lizard, a sad consequence of the introduction of horseshoe whipsnakes some 20 years ago that is now threatening the survival or our beloved Ibiza wall lizards.
In total, 1133 lizards were captured, measured, and released during this year’s field season in the Mediterranean, meaning a lot of promising data to analyze!
Brittany field work
While the ‘nigriventris syndrome’ is now well described in Italy (see here), some P. muralis in Brittany were described having flashy green dorsal coloration and large blue spots on the sides, opening the question of repeated evolution of this syndrome on islands off the coast of Brittany. Nine populations were already sampled last year, and Guannan, Quentin and Ivan returned to Brittany in early May to fill in same gaps in our sampling and to extend the sampling range.
They started by sampling populations in the Languedoc Roussillon region in France, to resolve the origin of the Brittany lineage. Then, they used the publication from Blanchard (1891) to design the sampling map, as he was the first to describe the P. muralis from Brittany that he named ‘calba’. They started in Les Sables d’Olonne, corresponding to the Southern limit and went north to reach the Rance valley, the North-Eastern limit. On the way, they sampled lizards on several islands including Yeu Island, Belle île, or islands in the Chausey archipelago.
They found some striking diversity in terms of color patterns. As expected, the phenotypes were quite impressive on several islands with intense green and large blue spots – but these ‘nigriventrish’ phenotypes were not exclusively found on islands. They also encountered some other surprises, such as the lizards from Belle île that have brown dorsal coloration, but pistachio ventral coloration or some small brown lizards found in Saint Pol de Léon (city at the limit of the known distribution area) close to train tracks, which might correspond to an introduced population.
In total, 21 populations were sampled this year. Field work often reserve some improbable encounters. While searching for lizards on a cold windy day, the team met the best hand lizard catcher from Britany, Martin Bonhomme (MCLterra, design office in herpetology). They were also interviewed by a journalist who wrote an article about the study in the regional journal La Manche Libre.
Text by Gwenaëlle Deconninck.