Biodiversity Data Journal : Single Taxon Treatment
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Corresponding author: David R. Maddison (david.maddison@science.oregonstate.edu)
Academic editor: Borislav Guéorguiev
Received: 23 Oct 2018 | Accepted: 27 Nov 2018 | Published: 04 Dec 2018
© 2018 David Maddison, Kipling Will, Sarah Crews, James LaBonte
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 D, Will K, Crews S, LaBonte J (2018) Bembidion ambiguum (Coleoptera: Carabidae) is established in California. Biodiversity Data Journal 6: e30763. https://doi.org/10.3897/BDJ.6.e30763
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The ground beetle Bembidion (Neja) ambiguum Dejean is native to Europe and north Africa, in the Mediterranean region.
We report it from North America for the first time, from five localities around San Francisco Bay, California. The earliest record is from 2012.
Carabidae, Bembidiini, introduced species, Mediterranean
Of the approximately 2,400 carabid species known from America north of Mexico, 64 are non-native, with the majority of these being native to Europe (
The discovery of a specimen of a Bembidion in Oakland, California, by one of the authors (SC) led to the realization that a ninth European Bembidion species had made its way to North America. This species, Bembidion ambiguum Dejean, is the first representative of the subgenus Neja Motschulsky to be found in North America, and the first introduced Bembidion species natively restricted to Europe and North Africa's Mediterranean region.
Basic methods for studying adult structures, and terms used, are given in
Photographs of body parts were taken with a Leica Z6 Apo lens and DMC4500 camera, and of male genitalia with a Leica DM5500B compound microscope and DMC425C camera. A stack of images from different focal positions was then merged using the PMax procedure in Zerene Systems’s Zerene Stacker; the final images thus potentially have some artifacts caused by the merging algorithm.
Specimens examined are housed in the following collections: Essig Museum Entomological Collection, University of California, Berkeley (EMEC), James R. LaBonte collection, Dallas, Oregon (JRLC) and Oregon State Arthropod Collection, Oregon State University, Corvallis (OSAC).
Distinctive within the North American fauna in having the following combination of characteristics: small (3.5–4.2 mm in length), metallic coloration, with surface dull because of well-impressed, isodiametric sculpticells (Fig.
A Mediterranean species, from Spain and Portugal east to Israel and Iraq, on various Mediterranean islands, and in northern Africa from Morocco to Algeria, Tunisia, and Libya, and the Azores (
The records from California, from the earliest to latest records, are as follows:
In Oakland, California, the beetles were found in a backyard in an urban environment with non-native grasses and a mixture of native and non-native shrubs. Collections were made during the day, and the specimens were found in leaf litter around a small coffeeberry (Frangula californica), under a birdbath on moist soil, and at the base of dandelions (Taraxacum officinale).
The key of
7. 8. elytral stria removed from lateral bead at least half as much as from 7. stria ................. 8
– 8. stria closer to side-margin ................. 7a
7a. Anterior supraorbital seta at the front end of a deep furrow; this furrow is separated from the center of the head by a carina ................. ambiguum group
– Anterior supraorbital setae not in furrow, without carina mesal to this ................. 10
The key of
20. 8. elytral stria removed from lateral bead (at middle) at least half as much as from 7. stria. (All striae evident to apex) ................. 21
– 8. stria much closer to side-margin ................. 20a
20a. Anterior supraorbital seta at the front end of a deep furrow. Pronotum slightly constricted at base. Metallic coloration; with strong isodiametric microsculpture over the entire dorsal surface. Elytra with discal setae in shallow foveae. 3.5–4.2 mm in length ................. B. ambiguum
– Anterior supraorbital seta not in deep furrow. Remaining characters not as above ................. 31
It has been suggested that introduced species establish only 10% of the time or less (
The earliest known record in for B. ambiguum in North America is from 2012. Given the span of its distribution at this time, it is likely well-established. In addition to being adapted to California's climate, B. ambiguum appears to be tolerant of disturbance, can take advantage of urban and agricultural mesic microhabitats, and can withstand high-levels of toxicity in their environment (
We thank Yves Bousquet, David Kavanaugh, and Luca Toledano for their reviews of the manuscript.