Research Article |
Corresponding author: David R. Maddison ( david.maddison@science.oregonstate.edu ) Academic editor: Borislav Guéorguiev
© 2023 David R. Maddison, John S. Sproul, Kipling Will.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Maddison DR, Sproul JS, Will K (2023) Re-collected after 55 years: a new species of Bembidion (Coleoptera, Carabidae) from California. ZooKeys 1156: 87-106. https://doi.org/10.3897/zookeys.1156.101072
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A new species of the carabid beetle genus Bembidion Latreille is described from the Central Valley, Los Angeles Basin, and surrounding areas of California. Bembidion brownorum sp. nov. is a distinctive species, a relatively large member of the subgenus Notaphus Dejean, and within Notaphus a member of the B. obtusangulum LeConte species group. It has faint spots on the elytra and a large, convex, rounded prothorax. Of the 22 specimens from 11 localities, all but one were collected more than 55 years ago. Although the collection of the holotype in 2021 at UV light suggest the species is still extant, the lack of other recent specimens suggests the species may have a more restricted distribution than in the past, and its populations may be in decline.
Bembidiini, DNA, ground beetle, molecular systematics, morphology, phylogeny, Trechinae
Our knowledge of the North American carabid (ground beetle) fauna has benefitted from many decades of significant study and publication (e.g.,
With about 275 species described from the USA and Canada, Bembidion Latreille is the largest genus of carabid beetles in the region (and the world), and one of the groups most likely to contain undiscovered taxa (e.g.,
Although within an hour’s drive of the major metropolitan center of Sacramento, many parts of Colusa County, California remain unsampled and little represented in major California entomology collections. Most of the land in the county is privately owned and used for agricultural production, which limits opportunities for access and sampling. Somewhat serendipitously, access and permission to collect was obtained for a ranch, known locally as “Mountain House,” in Colusa County. Over the course of two years, periodic sampling was conducted to determine the diversity of carabid beetles on the property.
Among the many insects sampled, a single specimen of Bembidion stood out as very distinctive (Fig.
The discovery of this single specimen motivated a search in major carabid collections in California for additional specimens. Only 21 additional specimens were located, all of which were collected more than 55 years ago. The distribution of specimens suggests this was a widespread species, but the lack of recently collected specimens suggests it may now be more restricted in distribution. Given the prospect of a declining and potentially threatened species, we felt it urgent to describe this species to spur the search for additional populations, and prompt research to better understand the species.
Members of Bembidion were examined from the collections listed below. Each collection’s listing begins with the code used in the text.
BMEC Bohart Museum of Entomology, University of California, Davis, USA;
CSAC California State Arthropod Collection, Sacramento, USA;
General methods of specimen preparation for morphological work, and terms used, follow
Photographs of entire beetles, as well as the head and pronotum pictures, were taken with a Leica M165C dissecting scope and a Sony NEX-7 camera, and of male genitalia with a Leica DM5500B compound microscope and DMC425C camera. Microsculpture photographs were taken with a DMC425C camera attached to a DM5500B compound scope equipped with an X-Cite 110LED light source, which provides co-axial illumination, and a 20× epi-illumination objective lens. For all photographs of specimens or body parts, a stack of images from different focal positions was merged using the PMax procedure in Zerene Systems’s Zerene Stacker; the final images thus potentially have some artefacts caused by the merging algorithm. Measurements were made using Leica Application Suite v. 4.9 from images acquired using either a Leica Z6 Apo lens and DMC4500 camera or a Leica DM5500B compound microscope and DMC425C camera.
We obtained new DNA sequence data for the holotype of Bembidion brownorum sp. nov. and 13 specimens of related species of Bembidion. These new data were combined with previously published data from six additional specimens (
Sampling of members of Bembidion (Notaphus) for DNA-based study. Four-digit numbers under “#” are D.R. Maddison DNA voucher numbers, and an abbreviation for state or province of capture under “Loc”; further information on the newly sequenced specimens is given in Table
Locality information for specimens of Bembidion (Notaphus) analyzed for DNA. Four-digit numbers under “#” are D.R. Maddison DNA voucher numbers.
Species | # | Locality |
---|---|---|
B. obtusidens | 2042 | Canada: Alberta: Burbank, junction of Red Deer and Blindman Rivers, 52.3542°N, 113.7556°W |
B. scudderi | 1471 | Canada: Alberta: Bow River at highway 36, 50.246°N, 112.077°W |
B. consimile | 2506 | USA: Colorado: Huerfano Co., Butte Road at I-25, 1825m, 37.7454°N, 104.832°W |
B. flohri | 3049 | Canada: Alberta: Birch Lake, 640 m, 53.362°N, 111.5231°W |
B. flohri | 3046 | USA: Oregon: Harney Co., Harney Lake, NE corner, 1237 m, 43.2750°N, 119.0902°W |
B. flohri | 1753 | USA: Nevada: Lyon Co., Carson River near Weeks, 390 m, 39.2866°N, 119.2778°W |
B. flohri | 3061 | USA: Utah: Salt Lake Co., Great Salt Lake Marina, 1280 m, 40.7482°N, 112.1856°W |
B. flohri | 5234 | USA: New Mexico: Torrance Co., Laguna del Perro, 1861 m, 34.6003°N, 105.9252°W |
B. mormon | 3044 | USA: Oregon: Harney Co., 00 Ranch Road NW Harney Lake, 1240 m, 43.2804°N, 119.1976°W |
B. mormon | 2142 | USA: Utah: Salt Lake Co., Great Salt Lake Marina, 390 m, 40.7482°N, 112.1856°W |
B. mormon | 3045 | USA: Utah: Salt Lake Co., Great Salt Lake Marina, 1280 m, 40.7482°N, 112.1856°W |
B. mormon | 4977 | USA: Nevada: Mineral Co., Walker Lake, Twenty Mile Beach, 1200 m, 38.7503°N, 118.7577°W |
B. mormon | 2039 | USA: California: Inyo Co., Owens Lake, 1100 m, 36.4684°N, 117.8585°W |
B. obtusangulum | 2051 | Canada: Alberta: Kenilworth Lake, 10.vi.1993. DRM 93.054 |
B. obtusangulum | 3151 | CANADA: Alberta: High Level, 330 m, 58.5073°N, 117.1385°W |
B. obtusangulum | 3594 | USA: Colorado: Alamosa Co., Alamosa NWR, 2292 m, 37.4435°N, 105.7722°W |
B. obtusangulum | 3043 | USA: California: Mono Co., Mono Lake, 1940 m, 37.97780°N, 119.13000°W |
B. callens | 4936 | USA: Arizona: Coconino Co., Havasu Indian Reservation, Havasu Springs, 36.2176°N, 112.6871°W |
B. callens | 4939 | USA: Arizona: Tucson |
B. brownorum | 5864 | USA: California: Colusa Co. Antelope Valley, Freshwater Creek, 39.13841°N, 122.34621°W |
Genes studied, and abbreviations used in this paper, are: 28S: 28S ribosomal DNA (D1–D3 domains); COI: cytochrome c oxidase subunit I; CAD: part 4 of carbamoyl phosphate synthetase domain of the rudimentary gene; Topo: topoisomerase I.
For specimens collected into 95–100% ethanol (all but the paralectotype of B. callens DNA4939), DNA was extracted using a Qiagen DNeasy Blood and Tissue Kit. Fragments for the four genes were amplified using the Polymerase Chain Reaction on an Eppendorf Mastercycler Pro Thermal Cycler, using TaKaRa Ex Taq and the basic protocols recommended by the manufacturers. Primers and details of the cycling reactions used are given in
DNA extraction and sequencing of the paralectotype of Bembidion callens DNA4939 followed
Newly acquired sequences are all of “genseq-4” (
COI, CAD, and Topo were easily aligned by eye, as there were no insertions or deletions (indels) evident in the sampled sequences. Alignment of 28S was conducted in MAFFT v. 7.130b (
A maximum-likelihood (ML) analysis was conducted for each gene individually using IQ-TREE v. 2.1.3 (
Sequences of the studied genes have been deposited in GenBank with accession numbers OQ284076 to OQ284089, OQ286105 to OQ286118, and OQ288575 to OQ288602. Files containing the untrimmed gene sequences for each specimen as well as the inferred trees for each gene have been deposited in Dryad (data available from the Dryad Digital Repository at https://doi.org/10.6078/D17416.
The single specimen of Bembidion brownorum sequenced is quite distinctive in DNA sequences of 28S, COI, and Topo, and clearly outside the bounds of sequence variation in the other species sampled. This is evident both by the gene trees (Fig.
Maximum-likelihood trees of the Bembidion obtusangulum group for four individual genes as well as the concatenated matrix. Scale bars: 0.01 nucleotide substitutions per nucleotide site, as reconstructed by IQ-TREE. Outgroups not shown; in all single-gene and concatenated analyses, the five species shown here formed a clade, with a bootstrap value of 100% in the concatenated analysis.
Three of the genes (28S, COI, and Topo) individually suggest that the nearest relatives of B. brownorum are B. callens and B. obtusangulum; in the ML tree of the concatenated matrix of all four genes, the latter two species form a clade with B. brownorum as its sister group (Fig.
Bembidion brownorum has a distinctively convex and rounded prothorax (Fig.
To accommodate B. brownorum, couplet 169 in
169 | 3.5–4.0 mm. Upper surface unmetallic. Prothorax with evident latero-basal carina (fig. 171b) | 102. B. nudipenne |
– | 4.4–5.0 mm. Upper surface unmetallic or only slightly metallic. Latero-basal carina evident, long (this paper, Fig. |
B. brownorum |
– | 4.3–5.9 mm. Metallic above. Latero-basal carina thin, usually rudimentary, or absent (fig. 187). Prothorax convex | 171 |
Holotype. Male, in
Paratypes. (13 males, 8 females). “Borax Lake, Lower Lake, Lake Co., Cal. May 14 1922” (2,
The specific epithet brownorum is treated as a noun in the genitive case and refers to Jerry and Anne Brown, former Governor and First Lady of California, respectively. The name is formed in their honor as it was their hospitality and openness to allowing access for research of insects on their ranch, the type locality, which led to the discovery of this species. Additionally, this honors their long commitment to environmentalism and continued efforts in the international climate-change movement.
A relatively large Bembidion (Notaphus), superficially similar to B. mormon (with which it has been confused in collections), with which it shares a pale subapical band on the elytra. However, B. brownorum has a much more convex pronotum, giving it an inflated appearance; the pronotum has more rounded sides and is more constricted posteriorly. From B. callens and B. obtusangulum, in addition to the prothorax shape, it is distinguished by presence of pale elytral spots, which those two species lack.
(based upon the holotype and 21 paratypes). Body length 4.4–5.0 mm. Body dark brown or dark reddish brown, with head and pronotum slightly darker than elytra; elytra each with one diffuse pale spot at about the posterior fourth. Legs uniform in color, reddish brown; antennae brown, with first antennomere paler, at least ventrally. Mentum with anterior lateral regions large, with apical portion broadly rounded, not angulate; medial tooth simple (not bifid) with truncate tip; frontal furrows weakly defined, shallow; eyes prominent (Fig.
All 18 specimens examined for wing condition are macropterous. The capture of two specimens from Woodlake in a rotary trap (
None noted.
Central Valley, Los Angeles Basin, and surrounding areas of California (Fig.
The only specimen with detailed collecting data including an exact locality is the holotype. Because it was collected at a UV light, the specimen was not found in its natural microhabitat, and we do not know how far it had flown from a suitable habitat. However, the type locality might provide some hints about possible habitat of the species. The type locality lies on the east side of Antelope Valley in the northern part of the Cortina Ridge, which marks the western edge of the Colusa Basin region of the Sacramento Valley. The ridge is formed of tilted sandstone beds, mudstone, and siltstone formed from the eroded sediments of the Sierran–Klamath terrane. As members of subgenus Notaphus are almost universally found at the edges of bodies of water (with exceptions for some species found at high elevation), we expect B. brownorum to live on lake, pond, marsh, river, or creek shores. The UV light was set up next to Freshwater Creek (Fig.
The other known localities do not clearly suggest a specific habitat, nor do the known localities of related species. Bembidion brownorum localities include a lake with sodium borate deposits (Borax Lake, Lake County), a city with a lake with extensive, flat shores (Bravo Lake in Woodlake), and a site near the Pacific Ocean that once had a salt lake (Redondo). At least the latter two are habitats similar to the saline, pond and lake shore habitats frequented by B. obtusangulum and B. mormon, near relatives of B. brownorum. The specimen labeled as from 6000 feet elevation at Forest Home, San Bernardino Mts (presumably around 34.083°N, 116.893°W) suggest instead a less saline, creek shore habit, but we doubt the veracity of that label (see above). The only specimen of the related B. callens with known habitat data is a specimen collected by Larry Stevens in gravel around the calcium-carbonate-rich waters of Havasu Springs, Arizona, at 36.2176°N, 112.6871°W (Larry Stevens pers. comm. 2022).
Much attention has recently been drawn to the apparent decline of insect populations (
It is likely that B. brownorum is yet another unlucky carabid beetle species. After our initial collection and recognition of B. brownorum we searched relevant collections for additional specimens. The small number of specimens located were only found in the
Bembidion brownorum’s large range (Fig.
Though details on the microhabitat are unknown, it seems probable that habitat specialization and the degradation of that habitat led to this species’ decline. At a very general level, most of the locations at which B. brownorum was historically collected presently have no apparent, natural habitat, and are entirely highly developed (Atwater, Woodlake, Redondo [Beach], Pasadena, and Azusa) or are largely developed with little potential habitat (Riverside and Poway). Perhaps the Borax Lake region, which is only 33 km southwest of the type locality, holds the best odds for a persistent population. In addition, lakes near previous localities may also harbor populations (e.g., Bravo Lake, within 4 km of the Woodlake collection site, or East Park Reservoir, about 25 km NNE of the type locality, or Indian Valley Reservoir, about 17 km W of the type locality).
The recent collection of B. brownorum raises our hopes that the species persists in more locations, and we encourage efforts to sample for it, but we are concerned that the species still has the potential to disappear forever. Rediscovery or re-collection does not mean a species is doing well. As pointed out by
We thank Jerry and Anne Brown for allowing access to their property and encouraging collecting and research activities. We thank collection personnel of the entomological collections for allowing us to examine their holdings and borrow materials, in particular Christopher Grinter (
This project was supported by the Harold E. and Leona M. Rice Endowment Fund at Oregon State University.