New paper on P. machaon

[adamcotton]

Online version just published:

Louis-F. Cassar, Benoit Nabholz, Eliette L. Reboud, Emmanuelle Chevalier, Bérénice J. Lafon, Adam M. Cotton, Fabien L. Condamine 2025. Whole-genome data shed light on speciation and within-species differentiation of the Papilio machaon complex around the Mediterranean Basin. Systematic entomology, DOI: 10.1111/syen.12675, 1-21.

Open access from https://resjournals.onlinelibrary.wiley ... syen.12675

Abstract
Within swallowtail butterflies, the type species Papilio machaon Linnaeus has fostered many studies leading to a complex taxonomy. With >40 subspecies formally recognized in the Palaearctic and recently simplified to 14 subspecies, there is still a need to address the taxonomic delineation within this complex. A previous phylogenomic analysis including Holarctic subspecies has revealed that Palaearctic P. machaon formed several monophyletic groups, leading to treat P. saharae Oberthür as a subspecies and the Nearctic P. machaon as a separate species (P. bairdii Edwards). Here, we aim at testing the taxonomic boundaries and relationships in the Western Palaearctic using whole-genome data of taxa from the Mediterranean region, which include first draft genomes of P. hospiton Géné (41× coverage depth) and P. saharae (51× coverage depth). We refined the species boundary of P. machaon and confirmed the species status of P. saharae. We assessed subspecies limits of Mediterranean P. machaon and P. saharae through Bayesian multi-species coalescent inferences and population genomic analyses, indicating that a taxonomic simplification is needed, with the exclusion of P. machaon from North Africa (P. saharae mauretanica Verity, comb. nov.) and the synonymy of subspecies (P. saharae neosaharae Tarrier, syn. nov.). We revealed heterogeneous levels of heterozygosity between island and continental lineages that warrant further taxonomic actions. We also found evidence of low gene flow between Corsican P. machaon and P. hospiton, endemic to Corsica (and Sardinia). We discuss how the speciation and phylogeographic patterns are in line with past climatic and geological changes of the Mediterranean Basin.

[adamcotton]

Importantly, this paper shows that the NW African taxon mauretanica Verity, 1905 belongs to Papilio saharae Oberthür, 1879, and Papilio machaon Linnaeus, 1758 does not occur in NW Africa.

Also the taxon neosaharae Tarrier, 2015 is genetically identical to Papilio saharae saharae and as a result is synonymised.

Adam.

[Chuck]

“ Finally, P. canadensis, P. glaucus, and P. appalachiensis have identical barcodes (BOLD:AAA6909)”

I’m on my phone without my data, but I question this. The BOLD number does not look correct for canadensis. Surely, the 5’ COI for canadensis and glaucus are not identical. I’ll have to investigate the discrepancy unless someone else is so inclined.

[adamcotton]

“ Finally, P. canadensis, P. glaucus, and P. appalachiensis have identical barcodes (BOLD:AAA6909)”

Note that this is citing Kunte et al. (2011).

I agree this is questionable, and it points towards the progress made in studying the glaucus group since 2011, as well as the limitations of COI and of mt-DNA as a whole. It is quite likely that one or more of these are misidentified, in the light of recent publications. My guess would be the middle one. Personally, I encourage my collaborators not to use older (often difficult to confirm ID) sequences from online sources unless the sample ID can be completely confirmed.

Adam.

[Chuck]

Not to get too far off topic, Kunte does not say that, in fact the opposite, repeatedly. Such as “ Instead, our extensive dataset reveals that glaucus and canadensis mtDNA haplotypes are exclusively species-specific, and that of appalachiensis is like glaucus”

Glaucus is AAA6909

Canadensis is ACE3135

I’m at a loss how the authors came up with that statement; it’s not from Kunte and other sources they cited also are clear that this isn’t correct.

Anyway, I hope their work on the machaon group is better. Enough though. Carry on!

[adamcotton]

Chuck,

Thanks for pointing out this issue. I will pass it on to the geneticists so they are aware of it.

Adam.