I'd like to start by showing that even though the name "concinnus" can be taken to mean "stylistically congruous" it doesn't mean there isn't some interesting variety of them. I think that the early explorers that described this species must have named it that because they mostly saw Northwestern garters, which are highly variable, and chose the name "concinnus" because most every one they saw in an area, was pretty darn close to being the same color and "style".

I've been noticing through my own observations and through pictures (with locality info) that this subspecies tends to change it's look as you travel throughout it's range.

For example, in SW WA counties of Clark, Whahkiakum, Pacific, and perhaps a few others adjacent to the Columbia River, it's very common for them to have lateral stripes, and black heads, looking much like T.s. fitchii. It appears that these populations are dimorphic, meaning there are both laterally striped, and regular, in the same population, and both types give birth to both types in the same litter. This isn't limited to WA. It happens in Oregon counties which are adjacent to the Columbia, from Multnomah County, all the way the coast, and also where Oregon's Willamette River meets the Columbia in Multnomah County.

Interestingly enough, the Columbia River gorge serves as path through the barrier of the Cascades range. T.s. fitchii, and many other species that normally only occur east of the Cascades in So. WA, often occur on the west side of the Cascades, in the mouth of the Columbia river gorge. Could it be that the two subspecies intergrade here, or that they intergraded at some time in the distant past? Maybe these concinnus' that carry the laterally striped genes do so because they crossed with T.s. fitchii in the past? Could it be that T.s. concinnus became a separate subspecies only after they were separated from T.s. fitchii after the Cascade range was formed?



Clatsop County Oregon (Near the mouth of the Columbia on the Oregon coast) T.s. concinnus' laterally striped adults:


T.s. fitchii, Deschutes County, Oregon (east of the cascades) for comparison: