They are using a microsatellite marker to confirm the genetics but the PCR they present as evidence seems a bit odd. It isn't well explained in the methods, so I infer that samples 1-2, 3-5, 6-8, and 9-10 are respectively replicate PCRs from the same individual or possibly even replicate lanes loaded from the same reactions (I make this assumption because of the extreme similarity within each group). The two parental samples (1-2 and 9-10) appear to be homozygous for markers at ~210bp and ~250bp, respectively (btw, these are reported as 160bp and 200bp in the results text...), while the offspring samples appear to be heterozygous for markers at 250bp and clearly something either a little smaller (3-5) or a little larger (6-8) than the ~210bp marker from 1-2. This indicates that 3-8
may be the offspring of 9-10, but are
not the offspring of 1-2.
Given that eggs were pooled from three individuals from each species and sperm was pooled from three different individuals from each species, for a total of only 12 individuals, there is no reason to not run PCR on all parental broodstock. This single figure could have been the slam dunk to prove hybridization, but instead I'm left scratching my head.
Also, the authors report a suspiciously strong similarity between the hybrid's shell characteristics and the characteristics of the conspecific fertilization pool that matches the maternal species. Frankly, this is what I would expect is self fertilization occurred in the hybrid treatment.
I'd be pretty excited to see convincing evidence of hybridization; unfortunately this article comes up a bit short in my opinion.
