The leafhopper genus Errastunus contains grass-feeding leafhoppers in the deltocephaline tribe Paralimnini. The taxonomy of the genus in the Nearctic region has long been confused, with one to three distinct species recognized by different authors. Some populations have also been suggested to be adventive from Europe. Morphological and molecular data show that there are two distinct species in North America. These taxa are readily distinguishable morphologically although there is evidence of mitochondrial introgression between the species. The distribution of the two species based on historical material in collections suggests that Errastunus sobrinus (DeLong & Sleesman, 1929) is native to North America, while E. ocellaris (Fallén, 1806) includes both native and adventive populations. A lectotype is designated for E. sobrinus and Cicada ocellata Scopoli, 1763 is established as a nomen oblitum with Cicada ocellaris as a nomen protectum.

Cytochrome oxidase I, DNA barcodes, introgression, leafhopper, Paralimnini, taxonomy

The leafhopper genus Errastunus Ribaut, found in Europe and North America, contains boldly marked, grass-feeding leafhoppers (Fig. 1) placed in the deltocephaline tribe Paralimnini based on the racket-shaped connective (Fig. 2). It appears to be closely related to Adarrus Ribaut and has sometimes been treated as synonymous with that genus; it can be distinguished based on the subapical, dorsal gonopore and additional crossveins in the clavus (Dmitriev 1999). Some North American authors have placed the constituent species in Latalus DeLong & Sleesman (e.g., DeLong and Sleesman 1929; Hamilton 1983); however, Errastunus differs from Latalus in having long, pointed subgenital plates with multiple rows of setae, no process on the pygofer, and an elongate median lobe of the style apophysis (Oman 1949). The type species, E. ocellaris (Fallén, 1806), is widespread in the Palearctic region and of uncertain status in the Nearctic region. Two additional taxa have been treated as either distinct species or as synonyms of E. ocellaris by various authors: E. sobrinus (DeLong & Sleesman, 1929) described from North America, and E. ocellaris tatraensis (Heller, 1975) described from Slovakia. Dmitriev (2001) described a separate subgenus Anadarrus to contain E. (A.) daedaleus (Logvinenko), with the other species above placed in the nominate subgenus.

Figure 1. 

Errastunus dorsal habitus A–F Errastunus ocellaris A CNC1317086 (Chatterton, ON) B CNC1317151 (Igls, Austria, 900 m) C CNC1317160 (Oxford, England) D CNC1317521 (Obergurgl, Austria, 1950 m) E CNC1317524 (Obergurgl, Austria, 1950 m) F CNC1615789 (Richardson Mtns, YT, note the extended abdomen is an artifact of preservation) G, H Errastunus sobrinus G CNC#HEM403281 (Parc de la Gaspesie, QC) H CNC1317427 (Elkwater Park, AB).

Figure 2. 

Errastunus ocellaris, male genitalia A–D pygofer, lateral E–H aedeagus, lateral I–L connective and styles, dorsal A, E, I CNC1317192 (King Salmon, AK) B, F, J CNC1317520 (Obergurgl, Austria, 1950 m) C, G, K CNC661822 (Big Muddy, SK) D, H, L CNC1317183 (Leeds, England).

The identities of the species of Errastunus in the Nearctic region have been confused for many years. The earliest Nearctic record listed by Metcalf (1967) is from Osborn and Ball (1897) who recorded E. ocellaris from Colorado (not Iowa as indicated by Metcalf). Lawson (1922) later listed the species from Kansas, Osborn (1922) recorded it from New York, and Downes (1924) added a record from British Columbia. DeLong (1926) repeated these records and considered the species to occur in both Europe and North America. DeLong and Sleesman (1929) later considered Nearctic populations to be distinct from those in the Palearctic, based on differences in body form and the female 7^th sternite. They described these as a variety under the name Latalus ocellaris var. sobrinus, but stated it “is in all probability a separate species.” Only material from Slave Lake, Alberta, and “northern New York State” was explicitly included in this description although the authors imply that this is the only form present in the Nearctic.

Walley (1932) agreed with DeLong and Sleesman that the Nearctic form was specifically distinct from those in Europe, and recorded it (as Deltocephalus sobrinus) from Quebec, Manitoba and British Columbia. Medler (1943) recorded E. sobrinus (and not E. ocellaris) from Minnesota.

Other authors continued to record E. ocellaris from North America, such as DeLong and Knull (1945) who repeated DeLong’s (1926) records of this species but also recorded E. sobrinus from Alberta. Oman (1949) listed E. ocellaris from the northeastern, central, and northwestern regions of the Nearctic, and E. sobrinus from Alberta. Strickland (1953) recorded both species from Alberta, based on determinations by Bryan Beirne (then at the Canadian National Collection). There are specimens in the Canadian National Collection identified as E. sobrinus by Beirne in 1950–1951, although Beirne (1956) later treated E. sobrinus as a junior synonym of E. ocellaris.

Hamilton (1983) later reviewed the status of these taxa (under the genus Latalus), treating E. ocellaris and E. sobrinus as distinct species, both present in the Nearctic. He regarded E. sobrinus as a native Nearctic species occurring in the boreal zone, while E. ocellaris was treated as a Palearctic species introduced into eastern Canada and the adjacent United States. Later, Hamilton (1997) recorded E. tatraensis (as a full species) from northwestern North America in Alaska, Yukon, and Northwest Territories. However, characters separating these taxa have not been clearly described and some authors (e.g., Dmitriev et al. 2022) currently consider E. sobrinus and E. tatraensis as synonyms of E. ocellaris. Here I review the status of the taxa present in the Nearctic, provide characters for their separation and detail their distribution.

Specimens examined (see Suppl. material 1) and types are from the following collections, with abbreviations:

BIOUG Biodiversity Institute of Ontario (Guelph, Ontario, Canada);

CNC Canadian National Collection of Insects, Arachnids, and Nematodes (Ottawa, Ontario, Canada);

INHS Illinois Natural History Survey (Champaign, Illinois, United States);

OSUC C. A. Triplehorn Insect Collection, The Ohio State University (Columbus, Ohio, United States);

UNHC University of New Hampshire Insect Collection (Durham, New Hampshire, United States);

USNM Smithsonian National Museum of Natural History (Washington, D.C., United States).

Images were taken using a Leica M205C stereomicroscope with 1.6× objective, stacked using Zerene Stacker (Zerene Systems, Richland, WA, USA), edited using Adobe Photoshop CS6, and assembled into plates using Adobe Illustrator CS6 (Adobe Inc., San Jose, CA, USA). Maps were created using QGIS v.3.20.0 (QGIS.org). Synonymies presented here are not complete and emphasize significant nomenclatural changes since Metcalf (1967).

Published COI sequences for specimens held in the CNC (Foottit et al. 2014; Gwiazdowski et al. 2015) and BIOUG (Hebert et al. 2016) were combined with additional COI sequences generated for this project (Table 1). For new sequences, DNA was extracted from single legs of specimens using 10 uL of QuickExtract buffer (Lucigen, Middleton, WI, USA), incubated at 56 °C overnight followed by 95 °C for 5 mins. A 418 bp fragment of COI (corresponding to the 3’ end of the standard DNA barcode region) was amplified using the primers BF3 (5’-CCHGAYATRGCHTTYCCHCG; Elbrecht et al. 2019) and C_LepFolR (5’-TAAACTTCWGGRTGWCCAAAAAATCA; Hernández-Triana et al. 2014) with 9 bp index tags attached. PCRs were carried out with 15 uL reaction volumes with 0.3 units KAPA2G Robust polymerase (KAPA Biosystems, Cape Town, South Africa), 0.33 µM of each primer, 2 mM MgCl₂, and 0.2 mM dNTPs in 1X KAPA buffer B, with 1 µL of template. Cycling conditions were 95 °C × 180 s; 5 cycles of 95 °C × 15 s, 45 °C × 15 s, 72 °C × 30 s; 35 cycles of 95 °C × 15 s, 51 °C × 15 s, 72 °C × 30 s; 72 °C × 60 s. PCRs were carried out on 96-well plates (with material for unrelated projects), and each specimen had a unique combination of tags.

Libraries were then prepared for pooled PCR products from each plate using a PCR-free protocol modified from standard Illumina library preparation protocols (Meyer and Kircher 2010). Pooled amplicons were cleaned using SPRI beads and 1 µg used for library preparation. Pools were phosphorylated with T4 polynucleotide kinase (1 µL in 50 µL 1× T4 ligase buffer), A-tailed with Taq polymerase (1 µL in 50 uL 1× Taq buffer, with 0.2 mM dATP and 1.5 mM MgCl₂), and Lucigen NxSeq adaptors (Lucigen, Middleton, WI, USA) added with T4 DNA ligase (2.5 µL in 50 µL 1× T4 ligase buffer, with 10% PEG-8000 and 2.5 µL adaptor) (all enzymes and buffers NEB Canada, Whitby, ON). Each plate was tagged with a unique i7 index. Libraries were cleaned up between each step using SPRI beads or PEG-NaCl solution (Fisher et al. 2011).

Libraries were sequenced on the Illumina MiSeq platform (2 × 300 bp reads). Resulting fastq files were demultiplexed and trimmed with CutAdapt (Martin 2011), unique sequence variants identified with dada2 (Callahan et al. 2016), and the most abundant variant retained for each sample.

Sequences were analysed using MEGA11 (Tamura et al. 2021). Sequences were initially aligned using the Muscle algorithm (Edgar 2004) and then refined by eye. The neighbour-joining trees and distance metrics were both produced using p-distances. Sequences from two species of the related genus Latalus were used as outgroups.

Based on morphology, specimens of Errastunus from North America can be divided into two groups, which correspond to E. sobrinus and E. ocellaris. In males, there is a consistent and obvious difference in the shape of the pygofer lobe which is entirely convex along the postero-ventral margin in E. ocellaris and indented in E. sobrinus. There are also less distinct differences in the length of the subgenital plates and shape of the flange at the base of the aedeagal shaft (Figs 2, 3), as detailed in the below key. In addition, the style apophysis is typically shorter and the posterior part of the connective proportionally broader and more evenly rounded in E. sobrinus, although these differences are subtle and difficult to use for identification. The only previously published character suggested to separate males is longer aedeagal processes in E. sobrinus (Hamilton 1983). This presumably refers to the longer dorsal rather than the inconspicuous ventral processes, but both vary considerably in both species with extensive overlap and are not useful for separation.

Figure 3. 

Errastunus sobrinus, male genitalia A–C pygofer, lateral D–F aedeagus, lateral G–I connective and styles, dorsal A, D, G CNC1317444 (Atlin, BC) B, E, H CNC1317472 (Waskaganish, QC) C, F, I CNC1317518 (Waterton Lakes, AB).

The first character suggested to separate the species was the shape of the female 7^th sternite (DeLong and Sleesman 1929), with E. sobrinus having a broad projection with rounded teeth and E. ocellaris having a narrower projection with pointed teeth. These character states are usually clearly distinct and readily separate most females of the two species (Figs 4, 5). However, there is some variation among both species in this character and a few unassociated females from areas where both species may occur could only be identified with low confidence (Fig. 6).

Figure 4. 

Errastunus ocellaris, female genitalia A genital capsule, ventral B first valvula, with enlargement C second valvula, with enlargement D–I sternite 7, ventral A–D CNC1317157 (Oxford, England) E CNC1317039 (Brockville, ON) F CNC1316995 (Mt. Washington, NH) G CNC1317204 (King Salmon, AK) H CNC1615794 (Richardson Mtns, YT) I CNC1317205 (King Salmon, AK).

Figure 5. 

Errastunus sobrinus, female genitalia A genital capsule, ventral B first valvula C second valvula D, E sternite 7, ventral A–D CNC1317465 (Waskaganish, QC) E CNC1317360 (La Plata Co., CO) F CNC1317260 (Whitefox, SK) G CNC1317270 (Rycroft, AB).

Figure 6. 

Errastunus females from Alaska and Yukon, sternite 7 A–C presumed E. sobrinus D presumed E. ocellaris A CNC1317218 (Skagway, AK) B CNC1317220 (Circle Hot Springs, AK) C CNC1317219 (Matanuksa, AK) D CNC1317217 (Carmacks, YT).

Specimen data suggests distinct distributions for the two species, with only partial overlap (Fig. 7). Errastunus sobrinus has a boreo-montane distribution, occurring across Canada and the adjacent United States, south in the Rocky Mountains to Colorado.

Figure 7. 

Distribution of Errastunus in North America A E. ocellaris, adventive (orange circles) and native (purple squares) populations. Shaded areas outline cumulative distribution of the eastern population by decade, from 1960 (darkest) to 1990 (lightest) B E. sobrinus (blue circles). Localities for specimens with introgressed COI indicated by stars.

Records for E. ocellaris are clustered in the east, primarily from the Great Lakes to the Atlantic coast, and in the northwest including Alaska, Yukon, and adjacent parts of the Northwest Territories and British Columbia. There are a few records from the southern Prairie provinces and near Vancouver. There is a clear signal of range expansion in the east (Fig. 7A). The earliest records are clustered in southern Quebec, eastern Ontario, and northern New York, with later records gradually spreading from this area.

Eastern North American E. ocellaris are not separable morphologically from European specimens, while northwestern specimens differ only slightly in the shape of the style and length of the subgenital plates, and are quite similar to higher elevation European specimens.

Newly sequenced and previously published DNA barcodes for five specimens of E. sobrinus, five specimens of northwestern E. ocellaris, six specimens of eastern E. ocellaris, and four specimens of European E. ocellaris, all from specimens in the CNC, were analysed. These initial sequences were divided into two distinct clusters, largely matching the morphological species concept. However, a single specimen identified morphologically as E. sobrinus fell within the cluster containing E. ocellaris specimens, clustering near sequenced specimens from Yukon. Based on this, additional specimens from BIOUG which had previously been sequenced and fell in the same cluster were examined; a number of these were morphologically identified as E. sobrinus. Analysis of sequences from all morphologically identified specimens (Fig. 8) show two clusters separated by a mean p-distance of 9.18% (mean distance within clusters 0.86–1.82%).

Figure 8. 

Neighbour-joining tree of COI sequences from Errastunus specimens. Tip labels indicate the taxon (based on morphological characters), collection locality, and specimen identifier.

Although the two species of Errastunus in the Nearctic have mostly distinct ranges, they do overlap both in the east and northwest, and the area of potential overlap is increasing with expansion of the range of adventive populations of E. ocellaris.

In the east, although there is broad geographic overlap, actual overlap between the two species may be limited as E. sobrinus appears to be absent from most of the lower elevation areas where E. ocellaris occurs. One of the few exceptions is at Mt. Washington, NH. The first record seen from that locality is a female of E. sobrinus collected in 1929. By 1954, E. ocellaris was present, with one collection in 1958 including two male E. sobrinus and two female E. ocellaris. Recent collecting trips have not yielded either species (Don Chandler, pers. comm.). The few examined collections from the Adirondack Mountains after 1950 were also E. ocellaris, while E. sobrinus had been present historically based on specimens from Lake Placid (1904, USNM) and Cascade Lake (1908, USNM) (see also Osborn 1922). This may indicate a displacement of E. sobrinus, although more thorough collecting effort is needed to determine the current status in these areas.

Geographic overlap between northwestern populations of the two species is also extensive, although there are no known cases where both species have been collected at a single locality. It is possible there is some differentiation in habitat preference that keeps the species apart. However, given the apparent mitochondrial introgression observed in E. sobrinus there has clearly been at least historic contact between these populations.

Given the fairly deep divergence between the species and their respective distributions, it seems likely that the two species speciated while on separate continents, with E. ocellaris in Eurasia and E. sobrinus in North America. A population of E. ocellaris may have then entered North America via the Beringian land bridge and hybridized with E. sobrinus either within Beringia or after coming into contact during later glacial retreat. There is no evidence of ongoing introgression in current areas of overlap or mitochondrial introgression from E. sobrinus into E. ocellaris, but more sequencing effort in these areas would be needed to test this thoroughly.

Thanks to the curators who loaned specimens, provided specimen data, and searched for types: Jayme Sones and Allison Brown (BIOUG), Tommy McElrath (INHS), Luciana Musetti (OSUC), Don Chandler (UNHC), Stewart McKamey (USNM), and Victor Shegelski (Spencer Entomological Museum, University of Alberta). Joanne Elsaesser (CNC) provided technical support for the project. Dmitry Dmitriev (INHS) discussed nomenclature. Thanks to Chris Dietrich, one anonymous reviewer and subject editor Mick Webb for comments on the manuscript.

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