Phylogeography and species delineation of the genusPhoxinusRafinesque, 1820 (Actinopterygii: Leuciscidae) in the Iberian Peninsula

Abstract

The genus Phoxinus is comprised of at least 15 currently recognized species inhabiting Eurasia. Morphological traits have been traditionally used to delineate species in Phoxinus; however, the high level of phenotypic plasticity observed in the genus has confounded this process. Molecular genetic analyses have revealed a higher than expected genetic structure within Phoxinus. Here, we analyzed both nuclear and mitochondrial molecular genetic markers to infer the phylogeography and divergence times of Phoxinus in the Iberian Peninsula. Our results show that the Iberian lineages of Phoxinus were polyphyletic. They also support the co‐existence of three species in the Iberian Peninsula, two corresponding to two previously recognized species (Phoxinus bigerri and Phoxinus septimaniae) and a third undescribed species (Phoxinus sp.). Phoxinus bigerri is structured into western Cantabrian, eastern Cantabrian, and Artibai basins. We hypothesize that this structure is a consequence of glaciation–deglaciation cycles during the Pleistocene. While the presence of P. septimaniae in the Iberian Peninsula is possibly the result of human translocation, that of Phoxinus sp. in lower Ebro rivers may be attributed to past fluvial captures. Our study represents the first report to show a relationship among Phoxinus populations from central Pyrenean rivers of Spain and France. Furthermore, we found genetic hybridization between Phoxinus sp. and P. septimaniae in the shared localities, a likely consequence of anthropogenic activities. Overall, our findings provide insight into the genetic structure of Iberian Phoxinus populations, including the presence of an undescribed species and the putative introduction of some species that may have implications for conservation.

Species composition of introduced and natural minnow populations of the Phoxinus cryptic complex in the westernmost part of the Po River Basin (north Italy)

“…The results revealed, for the first time, the presence and co-existence of three European species of the Phoxinus genus in the westernmost part of the Po River basin of Italy: P. lumaireul, P. csikii and P. septimaniae. Whilst the three species have minimal morphological differences (Kottelat and Freyhof 2007), they formed independent and well-supported groups that were also in agreement with recent phylogenetic studies (Palandačić et al 2017;Corral-Lou et al 2019). P. lumaireul Schinz (1840) (subclade 1a sensu Palandačić et al 2017) has been revalidated as an endemic to the north Adriatic basin (Kottelat and Freyhof 2007;Palandačić et al 2017Palandačić et al , 2020.…”

“…The RAG 1 results revealed only a few of the least frequent haplotypes that were separated from the main haplotype by several mutational steps (four to five), could possibly belong to other species than the native P. lumaireul. The utility of RAG 1 marker was limited in depicting the phylogenetic relations between minnows that produced an uninformative network where well-defined mitochondrial lineages were not clear, as was evident in other studies (Corral-Lou et al 2019;Palandačić et al 2020). Although this could be due to the tendency of this species to hybridize (Corral-Lou et al 2019), issues including incomplete lineage sorting and artefacts resulting from the gametic phasing or sequencing processes cannot be excluded from the evaluation of these results (Palandačić et al 2020).…”

“…Its natural distribution is the lower and middle part of the Danube River watershed of the Balkan Peninsula (Palandačić et al 2020). P. septimaniae was originally described by Kottelat (2007) as native to the French Mediterranean basins (south-eastern France); it has been also detected in river basins in north-eastern Spain (Corral-Lou et al 2019;Garcia-Raventós et al 2020). Although its natural or introduced origin could not be unambiguously discerned in this area of Spain, its geographic distribution resembles the Catalano-Provenzal endemics Squalius laietanus and Barbus meridionalis (Doadrio 2002) that do not naturally populate rivers of the north Adriatic basin.…”

“…For the nuclear RAG1 dataset, the haplotype phases were solved using the PHASE algorithm available in DnaSP v 6 (Rozas et al 2017). The phylogenetic analyses were exclusively performed on the COI mtDNA, as the RAG1 nDNA fragment had a low signal that could not cluster supported phylogenetic clades (Palandačić et al 2017;Corral-Lou et al 2019). The COI dataset was enlarged with 191 evolutionary related sequences (Online resources Table ESM 3), with trees rooted on P. phoxinus (MF407769) sensu Palandačić et al (2017).…”

“…Museth et al 2007;Miró and Ventura 2015). Natural hybridization zones can further increase the complexity in defining the actual distribution ranges of these species (Palandačić et al 2017;Corral-Lou et al 2019), despite the relevance of this information for planning suitable strategies for conserving the native lineages and managing the distributions of alien ones. As a result of these processes, there is now minimal information available on the composition of the Phoxinus communities in many areas in southern Europe, including in the River Po basin.…”