TL;DR: The lionfish species Pterois miles and P. volitans were identified using dorsal and anal fin ray counts as well as geographic origin, but neither meristics nor geography are always definitive and their taxonomic status as separate species has been questioned as discussed by the authors.
Abstract: The lionfish species Pterois miles and P. volitans are popular aquarium fishes that have
gained recent notoriety as invasive species along the east coast of the United States and the Bahamas.
The two species can usually be identified using dorsal and anal fin ray counts as well as geographic
origin, but neither meristics nor geography are always definitive, and their taxonomic status as separate
species has been questioned. Analyses of two mitochondria-encoded cytochrome b sequence data sets
resolved specimens of P. miles and P. volitans in distinct monophyletic clades. There was also a .4%
difference in the maximum intraspecific and minimum interspecific sequence divergences between
specimens of the two species. These results are comparable to those of other analyzed Pterois and
Dendrochirus sister species, and support their recognition as separate species. The cytochrome b analyses
also show that Dendrochirus and Pterois are not reciprocally monophyletic as currently circumscribed,
and that a comprehensive study is needed to resolve the taxonomy of Pteroinae genera
TL;DR: The results support the proposed allopatric or parapatric distribution in the Indian and Pacific Ocean and cannot reveal if P. miles and P. volitans are separate species or two populations of a single species, because the observed separation in different clades can be either explained by speciation or lineage sorting.