Finding. A polyploid, all-female weevil lineage in Japan has one birth, a hybrid passport, and a fast walk north. Unmated females have daughters. Sexual populations are already thinning and genetically quieter toward the north before the two forms even meet. The simplest story is mate limitation: when males get scarce, a female who does not need one keeps going. Mitochondrial DNA and genome-wide SNPs draw that history.
Why this paper matters
Geographic parthenogenesis is a plant cliché and an animal rarity with few reconstructed origins. This group adds an independent case and picks mate limitation over a grab-bag of northern-advantage theories. mtDNA is a narrator, not a patient.
What they actually measured
Range survey, mtDNA and SNPs, ploidy, virgin rearing, Ne proxies declining northward south of contact.
How to read the score
Low sixties. Score 62.
What to do with it
If you work on asexual range expansion or insect mtDNA phylogeography, pull the hybrid-origin and Ne-cline plots. Skip if you wanted bioenergetics. The directional implication is that a single hybrid polyploid weevil can occupy the north because sex is already failing at the sexuals’ own margin.