Two lineages, not one

I’m back, after a long hiatus.  We’ve been busy in the lab looking at the specimens from the Big Loop Trip, and sequencing them.  Over the next few weeks I will report on some of the results.  We’ve discovered some additional new species since I last wrote, and have learned a lot about the species in the southwest.

I’ll begin with a follow-up to my post pondering whether or not two species we discovered (one from the Red River in northern New Mexico, the other from mini talus slopes along Coal Creek in southern Utah) formed a previously undiscovered lineage of Ocydromus Complex species that live in cryptic habitats.

After I wrote that post, I made genitalic preparations of the single known specimen of the Red River species, and one of the talus species.  On seeing the male genitalia of the Red River species I was reminded of the genitalia of Bembidion rupicola, a widespread species  in North America that is related to Old World species in the subgenus Peryphus.  Here’s what B. rupicola looks like:

Bembidion rupicola

Bembidion rupicola

It doesn’t look all that close to the Red River species; here is the Red River species for comparison:

An undescribed species of the Ocydromus complex of Bembidion

An undescribed species of the Ocydromus complex of Bembidion

But the male genitalia are rather similar:

Male genitalia of Red River species

Male genitalia of Red River species

Male genitalia of Bembidion rupicola

Male genitalia of Bembidion rupicola

The male genitalia of the talus species, however, looks rather different, and gave me doubts about whether the Red River and talus species were related:

Male genitalia of talus species

Male genitalia of talus species

Our initial (and preliminary) DNA results confirm that the Red River and talus species are not closely related.  In fact, the Red River species is intermingled in a radiation that is primarily Old Word (as suggested by the genitalic similarities to B. rupicola), whereas the talus species is in the Nearctic Clade (a large clade restricted to the New World).  Here’s where the two species go (approximately) on the phylogeny of the Ocydromus Series of Bembidion from my 2012 paper. Exact placement will await sequencing more genes and a better analysis.

Ocydromus Series mod

While I am ever-so-slightly disappointed that these two new species aren’t the harbingers of a previously unknown radiation in North America, I am still very pleased by the discovery of new members of both the Nearctic Clade and a predominately Old-World radiation.  And, perhaps they are the harbingers of two previously unknown radiations!

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