Gordon H Copp | Search bioRxiv

bioRxiv2015

Genetic evidence challenges the native status of a threatened freshwater fish (Carassius carassius) in England

A fundamental consideration for the conservation of a species is the extent of its native range, however defining a native range is often challenging as changing environments drive shifts in species distributions over time. The crucian carp, Carassius carassius (L.) is a threatened freshwater fish native to much of Europe, however the extent of this range is ambiguous. One particularly contentious region is England, in which C. carassius is currently considered native on the basis of anecdotal evidence. Here, we use 13 microsatellite loci, population structure analyses and approximate bayesian computation (ABC), to empirically test the native status of C. carassius in England. Contrary to the current consensus, ABC yields strong support for introduced origins of C. carassius in England, with posterior distribution estimates placing their introduction in the 15th century, well after the loss of the doggerland landbridge. This result brings to light an interesting and timely debate surrounding our motivations for the conservation of species. We discuss this topic, and make arguments for the continued conservation of C. carassius in England, despite its non-native origins.

Evolutionary Biology↗

bioRxiv2015

Comparing RADseq and microsatellites to infer complex phylogeographic patterns, a real data informed perspective in the Crucian carp, Carassius carassius, L.

The conservation of threatened species must be underpinned by phylogeographic knowledge in order to be effective. This need is epitomised by the freshwater fish Carassius carassius, which has recently undergone drastic declines across much of its European range. Restriction Site Associated DNA sequencing (RADseq) is being increasingly used for such phylogeographic questions, however RADseq is expensive, and limitations on sample number must be weighed against the benefit of large numbers of markers. Such tradeoffs have predominantly been addressed using simulated data. Here we compare the results generated from microsatellites and RADseq to the phylogeography of C. carassius, to add real-data-informed perspectives to this important debate. These datasets, along with data from the mitochondrial cytochrome b gene, agree on broad phylogeographic patterns; showing the existence of two previously unidentified C. carassius lineages in Europe. These lineages have been isolated for approximately 2.2-2.3 M years, and should arguably be considered as separate conservation units. RADseq recovered finer population structure and stronger patterns of IBD than microsatellites, despite including only 17.6% of samples (38% of populations and 52% of samples per population). RADseq was also used along with Approximate Bayesian Computation to show that the postglacial colonisation routes of C. carassius differ from the general patterns of freshwater fish in Europe, likely as a result of their distinctive ecology.

Evolutionary Biology↗