Discovery of a Pelophylax saharicus (Anura, Ranidae) population in Southern France: a new potentially invasive species of water frogs in Europe

Abstract

We report the discovery of a population of the exotic North African Water Frog Pelophylax saharicus around the Etang de Berre, on the Mediterranean coast of France, about 25 km north-west of Marseille. The animals had been originally identified as P. perezi or P. kl. grafi by a combination of acoustic and morphological characters and their true identity was not revealed until three samples from one locality were included in a large-scale genomic work dedicated to the genus Pelophylax. Mitochondrial barcoding of the samples from other areas around Etang de Berre did not detect any native P. perezi or P. kl. grafi and confirmed that P. saharicus has spread to several localities, does reproduce and has been present since 2011 at least. We suggest that dedicated field work is needed as soon as possible to (i) map the extant of P. saharicus’s distribution around the Etang de Berre, (ii) establish if populations of the native P. perezi – kl. grafi system still persist around the Etang de Berre or not and (iii) check if P. saharicus has spread to neighboring areas or not. Depending on the answers to these three questions, local conservationists will need to evaluate the feasibility and relevance of any action to control the spread of this new invasive species and attempt to eradicate it.

Piecing the barcoding puzzle of Palearctic water frogs (Pelophylax) sheds light on amphibian biogeography and global invasions

“…(we cannot distinguish them with the genes analyzed, Figure 4) and both differ from the Moroccan lineage A-a pattern also retrieved by phylogenomic analyses (Doniol-Valcroze et al, 2021). Second, as shown by Komaki et al (2015), P. plancyi is highly differentiated from P. nigromaculatus (Figure 6), despite bearing similar mtDNA.…”

“…Mitogroup distributions in Pelophylax ridibundus are detailed in Figure 2. The tree shows the Bayesian analysis of full and partial mitogenomes (~16.8 kb); see Figure S1 for terminal branches and for the Maximum‐Likelihood analysis; node circles illustrate branch support; the grey line (bottom of the tree) indicates the placement of saharicus B based on nuclear phylogenomics (Doniol‐Valcroze et al., 2021; see also Figure 4). Native ranges were adapted from IUCN Red list (2023) modified according to occurrence data from GBIF ( www.gbif.org) and MNHN ( https://inpn.mnhn.fr).…”

“…Some archipelagos also have a long history of hosting introduced Pelophylax , such as P. perezi in the Balearic (Silva‐Rocha et al., 2018), the Canary (Gervais, 1836), Madeira and the Azores Islands (Malkmus, 2004). In the latter, the shallow COX1 divergence between the Azores and Iberian populations (Doniol‐Valcroze et al., 2021) runs against a natural colonization of the Atlantic islands (e.g., through rafting), which was initially considered based on patterns of allozyme differentiation (Balletto et al., 1990). The introduced populations are composed of multiple P. ridibundus lineages and additional species ( P. shqipericus , P. saharicus , P. perezi ) which altogether represent a third of the WP phylogeographic diversity.…”

“…Mitochondrial DNA (mtDNA) has been preferentially sequenced to identify and map phylogeographic lineages, but mtDNA sequences are scattered across more than a hundred publications that vary in taxonomic scales, geographic scopes, sets of genes analyzed, and further differ in the way these lineages are delimited, labelled and taxonomically treated (e.g., Akın et al., 2010; Bellati et al., 2023; Bülbül et al., 2011; Dufresnes, Di Santo, et al., 2017; Hoffmann et al., 2015; Komaki et al., 2015; Liu et al., 2010; Lymberakis et al., 2007; Min et al., 2008; Nicolas et al., 2015; Papežík et al., 2023; Plötner et al., 2008; Svinin et al., 2021; Toli et al., 2023; Ualiyeva et al., 2022; Wang et al., 2017). Moreover, mitochondrial barcoding may not be reliable due to hybridization, that cause mitochondrial transfer between sympatric and parapatric species (e.g., Doniol‐Valcroze et al., 2021; Komaki et al., 2015; Liu et al., 2010), including the parental species of hybridogenetic hybrids (Plötner et al., 2008).…”

“…The nuclear analyses conducted in parallel primarily aimed at distinguishing hybrid forms from their parental species, and most datasets are not combinable per design, for example, microsatellites (e.g., Dufresnes, Di Santo, et al., 2017; Papežík et al., 2021; Sagonas et al., 2020), allozymes (e.g., Hotz et al., 2013), and RAD‐sequencing (e.g., Doniol‐Valcroze et al., 2021; Dubey, Maddalena, et al., 2019; Dufresnes & Dubey, 2020). The only re‐usable nuclear markers are targeted gene sequences (e.g., Cuevas et al., 2022), but these also differ between geographic areas and species complexes, and each gene provides little phylogenetic resolution if not combined in multilocus analyses (e.g., Komaki et al., 2015).…”