Background Hyperdiverse mtDNA with more than 5% of variable synonymous nucleotide sites can lead to erroneous interpretations of population genetic differentiation patterns and parameters (φST, DEST). We illustrate this by using hyperdiverse mtDNA markers to infer population genetic differentiation and connectivity in Melarhaphe neritoides, a NE Atlantic (NEA) gastropod with a high dispersal potential. We also provide a recent literature example of how mtDNA hyperdiversity may have misguided the interpretation of genetic connectivity in the crab Opecarcinus hypostegus. Results mtDNA variation surveyed throughout the NEA showed that nearly all M. neritoides specimens had haplotypes private to populations, suggesting at first glance a lack of gene flow and thus a strong population genetic differentiation. Yet, the bush-like haplotype network, though visually misleading, showed no signs of phylogeographic or other haplotype structuring. Coalescent-based gene flow estimates were high throughout the NEA, irrespective of whether or not mtDNA hyperdiversity was reduced by removing hypervariable sites. Conclusions Melarhaphe neritoides seems to be panmictic over the entire NEA, which is consistent with its long-lived pelagic larval stage. With hyperdiverse mtDNA, the apparent lack of shared haplotypes among populations does not necessarily reflect a lack of gene flow and/or population genetic differentiation by fixation of alternative haplotypes (DEST ≈ 1 does not a fortiori imply φST ≈ 1), but may be due to (1) a too low sampling effort to detect shared haplotypes and/or (2) a very high mutation rate that may conceal the signal of gene flow. Hyperdiverse mtDNA can be used to assess connectivity by coalescent-based methods. Yet, the combined use of φST and DEST can provide a reasonable inference of connectivity patterns from hyperdiverse mtDNA, too.
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RBINS Staff Publications 2019
Alongside horses, donkeys and their first-generation hybrids represent members of the Equidae family known for their social, economic and symbolic importance in protohistoric and historical France. However, their relative importance and their respective roles in different regions and time periods are difficult to assess based on textual, iconographic and archaeological evidence. This is both due to incomplete, partial and scattered historical sources and difficulties to accurately assign fragmentary archaeological remains at the proper taxonomic level. DNA- based methods, however, allow for a robust identification of the taxonomic status of ancient equine osseous material from minimal sequence data. Here, we leveraged shallow ancient DNA sequencing and the dedicated Zonkey computational pipeline to obtain the first baseline distribution for horses, mules and donkeys in France from the Iron Age to the Modern period. Our collection includes a total of 873 ancient specimens spanning 128 ubiquitous and the most dominant species identified, our dataset reveals the importance of mule breeding during Roman times, especially between the 1st and 3rd centuries CE (Common Era), where they represented between 20.0% and 34.2% of equine assemblages. In contrast, donkeys were almost absent from northern France as-semblages during the whole Roman period, but replaced mules in rural and urban commercial and economic centers from the early Middle Ages. Our work also identified donkeys of exceptional size during Late Antiquity, which calls for a deep reassessment of the true morphological space of past equine species. This study confirmed the general preference toward horses throughout all time periods investigated but revealed dynamic manage-ment strategies leveraging the whole breadth of equine resources in various social, geographic and temporal contexts.
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RBINS Staff Publications 2021
