FrogEyes
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Another study compares populations of Cynops pyrrhogaster on the Izu Peninsula, identifying those on the southern end as Tohoku/Kanto species, and those in the center as Sasayama/Intermediate. This suggests that the latter invaded the peninsula later, dividing populations of the former. This would also seem to support status as two species, as the populations have not merged.
Atsushi Tominaga, Masafumi Matsui and Yasuhiro Kokuryo, 2015. Occurrence and Evolutionary History of Two Cynops pyrrhogaster Lineages on the Izu Peninsula. Current Herpetology Volume 34 Issue 1: 19–27.
We investigated phylogenetic positions of Cynops pyrrhogaster from nine localities in the central and southern parts of the Izu Peninsula using the mitochondrial cyt b gene. We revealed that the central and the southern populations are phylogenetically remote. The central Izu lineage belongs to the CENTRAL clade occurring from Chubu through Kinki to Chugoku districts, whereas the southern Izu populations form a lineage sister to the NORTHERN clade, which is distributed in Tohoku and Kanto districts. Genetic differentiation between the southern Izu lineage and the NORTHERN clade is relatively large with the uncorrected p-distance of 3.4%, which suggests their divergence at 3.31 MYA. This estimation indicates their genetic differentiation prior to 1.0 MYA, when the Izu Peninsula was formed through collision of a paleo-oceanic island with Honshu. These results indicate that the ancestor of the southern Izu lineage diverged from the NORTHERN clade somewhere in northern Honshu and then invaded the Izu Peninsula newly formed by collision and settled there. The central Izu lineage thereafter also invaded the peninsula, confining the range of the preceding southern Izu lineage to its current range.
Atsushi Tominaga, Masafumi Matsui and Yasuhiro Kokuryo, 2015. Occurrence and Evolutionary History of Two Cynops pyrrhogaster Lineages on the Izu Peninsula. Current Herpetology Volume 34 Issue 1: 19–27.
We investigated phylogenetic positions of Cynops pyrrhogaster from nine localities in the central and southern parts of the Izu Peninsula using the mitochondrial cyt b gene. We revealed that the central and the southern populations are phylogenetically remote. The central Izu lineage belongs to the CENTRAL clade occurring from Chubu through Kinki to Chugoku districts, whereas the southern Izu populations form a lineage sister to the NORTHERN clade, which is distributed in Tohoku and Kanto districts. Genetic differentiation between the southern Izu lineage and the NORTHERN clade is relatively large with the uncorrected p-distance of 3.4%, which suggests their divergence at 3.31 MYA. This estimation indicates their genetic differentiation prior to 1.0 MYA, when the Izu Peninsula was formed through collision of a paleo-oceanic island with Honshu. These results indicate that the ancestor of the southern Izu lineage diverged from the NORTHERN clade somewhere in northern Honshu and then invaded the Izu Peninsula newly formed by collision and settled there. The central Izu lineage thereafter also invaded the peninsula, confining the range of the preceding southern Izu lineage to its current range.