The Bembidion acutifrons story

There are a number of subgroups within Bembidion subgenus Trepanedoris whose structure of gene flow and species boundaries are not understood.  The morphological data indicates several forms within these subgroups, but whether this variation is indicative of separate species is not yet clear.  One such subgroup, and a main focus of the Discovering Insect Species course, is the Bembidion acutifrons subgroup.  In this subgroup, Bembidion canadianum is fairly distinctive (more on that later), but the rest of the subgroup is a bit more confusing.

Of particular interest in our class’s research is the variation in what is now called Bembidion acutifrons.  There are two rather distinctive forms of Bembidion acutifrons:  an eastern form with darker and generally larger adults, and very shiny males, which look like this:


This shiny form is what we were finding at Klamath Marsh.  It is also the form found at the type locality of Bembidion acutifrons, Alamosa, Colorado.  Here’s a picture of Alamosa National Wildlife Refuge, where we found shiny B. acutifrons in 2013:


However, west of the Cascades in Oregon and Washington is a form that is generally smaller, often paler, and with males that are heavily microsculptured and thus dull.  The following two pictures shows a comparison of the left elytron between a shiny male (above) and a dull male (below).

Left elytron of a shiny male, from Klamath Marsh, OR

Left elytron of a shiny male, from Klamath Marsh, OR

Left elytron of a dull male, from Corvallis, OR

Left elytron of a dull male, from Corvallis, OR

We haven’t compared the genitalia of these two forms yet, and we have very limited DNA data.  So far we only have sequences from one specimen from Saskatchewan (a shiny male) and one from Corvallis, Oregon (a dull male).  These two specimens are less than 1% different in the genes COI, CAD, and topoisomerase I, but they do differ by three bases in the sequenced portion of 28S.

We have additional specimens from Colorado, Utah, and Klamath Marsh, OR, of the shiny form ready to be sequenced, and two more specimens of the dull form from Corvallis.  We are rather eager to see what these additional data might say!  We also need to start comparing the internal sac sclerites of the genitalia.

Posted in Fieldwork, Revising Bembidiina, Taxonomic Process, Z499 (Discovering Insect Species) | Tagged , | 3 Comments

The oak tree grows pretty close to where the acorns dropped

Here’s my mom, at age 82, collecting some of what will be the type series of a new species of Bembidion from Jasper National Park in Canada.  This was in 2011, during a great trip she and I made around Saskatchewan and Alberta.  We collected during the day, and stayed at bed and breakfasts or nice hotels in the evening.




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Infer all the branches!!!!!

I’ve already sent this image out into the Twitterverse, but I thought I should record the thought here as well.  Sometimes us phylogeneticists are rather obsessed about having a complete phylogeny. In one moment when I was dreaming of having all Bembidion species incorporated into a phylogenetic hypothesis, I thought of Allie Brosh’s iconic Clean All the Things image, and recombination between those thoughts yielded the following image.


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Return of the Taxa

Those who might follow my blog may have noticed a rather long lull in my posts.  For this I apologize, but life happens, and my attentions were elsewhere.  I hope to make up for that in the coming months.  In the meantime, here are some sequels to two stories previously posted, in case you are hanging on the edge of your seats to find how our heroes and heroines are doing.

Delectable Bembidion wickhami

In two previous posts (here and here), I outlined how subgenus Lindrochthus consisted of two species, both hiding under “Bembidion wickhami“.  One of those species was known only from Mount Tamalpais just north of San Francisco (this species is indicated in pink in the map below), the other from Mount Tamalpais and the Sierra Nevadas (shown in orange, below).  I have one specimen from the Cascades of Oregon, from the pale blue dot below, that I thought might belong to the widespread species, but I was not sure.  I didn’t know which of the species was the true Bembidion wickhami, and whether the other one might have a name, and so I named them “Bembidion wickhami #1″ and Bembidion wickhami #2″.


Since my posts, I have added DNA data from one important specimen, a female from Berry Summit in northwestern California. I had figured this would be a member of the widespread species, but to my surprise, this specimen belongs to the “Mount Tamalpais” species (that is, Bembidion wickhami #2 from my earlier post) indicating that that species is more widespread than I had originally thought.

I’ve also looked more at the specimen from Oregon, and I think that is probably the widespread species.   So here’s where we were at:


In order to determine what the names of these species might be, I borrowed the primary type specimens of the three names within this subgenus.  Those three names are:

  • Bembidium wickhami Hayward, 1897
  • Bembidion delectum Casey, 1918
  • Bembidion carlhi Erwin and Kavanaugh, 1981

The type localities and details about the primary type specimens are as follows:

  • Bembidium wickhami Hayward. Type locality: Dunsmuir, Siskiyou County, California.  Lectotype male in the Museum of Comparative Zoology, Harvard University (MCZ)
  • Bembidion delectum Casey. Type locality: Gilroy Hot Springs, Santa Clara County, California.  Lectotype male in the National Museum of Natural History, Smithsonian Institution (USNM)
  • Bembidion carlhi Erwin and Kavanaugh. Type locality: Steamboat Falls, Douglas County, Oregon. Holotype female in the California Academy of Sciences (CAS)

I’ve looked at these primary types, and done the work to determine the species to which each belongs. Whatever species the lectotype of Bembidium wickhami Hayward belongs will be called Bembidion wickhami.  If any of the other types belong to that same species, then those names will be junior synonyms of Bembidion wickhami.  The name of the other species will depend upon what type specimens fall within it; the name of the species will be the oldest name whose type belongs in the species.  If no types belong in that second species, then the species will be unnamed, and I would need to describe the species and give it a new name.  (For more explanation about this process, see my earlier post about name-bearers.)

Here’s a map showing the localities of the type specimens, with the type specimen’s dots shown in white, indicating that I didn’t know before I looked at them in detail to which species they belonged:


Because the holotype of the name Bembidion carlhi is a female, it will be difficult to place that to species.  If DNA work is done on the holotype, or more specimens are collected from near the type locality, then it may be possible to place it with certainty.  For the moment, let’s leave that name aside.

However, the lectotypes of the names Bembidium wickhami Hayward and Bembidion delectum Casey are males, and their genitalia would allow certain placement of the specimens to species.   I borrowed the specimens from the MCZ and USNM, did genitalic dissections, and to my surprise the lectotype of Bembidium wickhami belongs to the rarer species (“Bembidion wickhami #2″) and the lectotype of Bembidion delectum belongs to the widespread species. Thus, the name of the widespread species (orange dots on the map) is Bembidion delectum, and the name of the species from Mount Tamalpais, Berry Summit, and Dunsmuir (the locality where the type specimen of Bembidion wickhami was collected), shown with pink dots, is Bembidion wickhami.  The revised distribution map is shown below, with Bembidion wickhami in pink and B. delectum in orange.


The specimen I have sequenced from the Cascades of Oregon, and the holotype of Bembidion carlhi, are likely both members of Bembidion delectum.  I hope to do more collecting in that area to confirm this.  I have shown their localities in orange in the above map. (I’ve changed to color from pale blue to orange to indicate they are likely just members of B. delectum.)

And now there are six…

In three previous posts I have talked about the complexity of what is called “Bembidion curtulatum”.  At first I thought it consisted of three species, then four, then five.   The last post in the series gives a summary of the story.  Since then we have sequenced DNA of more specimens, and better understand the distribution of the species.

The two most significant recent specimens were sent to me via Foster Purrington.  These specimens were collected by Dick Maxey from Whitewater Creek in western New Mexico, near the town of Glenwood.  I had never seen Bembidion curtulatum-like specimens from anywhere near there, and was quite surprised to see them.   Genitalic dissection suggested they were extremely close (maybe identical to) to an eastern member of the B. curtulatum species group, Bembidion basicorne, which suggested to me that the specimens may have been mislabelled as to their localities.  But as Dick specifically remembers collecting the (now dried and pointed) specimens, I decided to see if I could sequence DNA from them.  I managed to get 28S rDNA sequences from both specimens, and the sequences made it very clear that these are not B. basicorne, but a separate, surely undescribed species.  This is thus the six species that would be hiding within “Bembidion curtulatum“.  It is marked with a yellow dot in the map below.

B. curtulatum group Distribution

Now I am pondering when I might go to Whitewater Creek, and find the “yellow dot” species in nature!  I’ve been in touch with the Forest Service folks down there (in particular Pat Morrison, recently retired), and they are excited about an expedition to find it.

I’ve also looked at the type specimens of more of the names, and I now suspect that species 3, 5, and 6 are undescribed.  Species 4 might also be undescribed, but it might have a name from specimens described in the Russian far east (although I don’t yet know if the species lives there).


Posted in Fieldwork, Revising Bembidiina, Taxonomic Process | Tagged , , , , , , | 4 Comments