Errastunus ocellaris ( Fallen )

Kits, Joel H., 2023, The genus Errastunus in the Nearctic region (Hemiptera, Cicadellidae, Deltocephalinae), ZooKeys 1178, pp. 143-164 : 143

Errastunus ocellaris ( Fallen)

Figs 1A-F , 2 , 4

Cicada ocellata Scopoli, 1763: 116 (nomen oblitum).

Cicada ocellaris Fallén, 1806: 20. Type locality: Scania, Sweden (nomen protectum).

Jassus = Jassus (Deltocephalus) notatifrons Kirschbaum, 1868: 141 (syn. Wagner 1939).

Deltocephalus sachalinensis = Deltocephalus sachalinensis Matsumura, 1915: 168 (syn. Vilbaste 1969).

Latalus ocellaris ( Fallén) - DeLong and Sleesman 1929 (comb. nov.).

Errastunus ocellaris ( Fallén) - Ribaut 1946 (comb. nov.).

Adarrus (Errastunus) ocellaris ( Fallén) - Emeljanov 1966 (comb. nov.).

Adarrus ocellaris tatraensis Heller 1975 (new subspecies).

Latalus (Adarrus) tatraensis (Heller) - Hamilton 1997 (revised status).

Material examined.

368 specimens (see Suppl. material 1).

Distribution.

Widespread in the Palearctic region, from western Europe and northern Africa to Korea and the Russian Far East ( Nast 1972). In the Nearctic region, occurs in the northwest (Alaska, Yukon, Northwestern Territories and northern British Columbia) and across southern Canada and the northern United States, with records concentrated in the east.

Host plants.

Feeds on a variety of cool season grasses. Nickel (2003) reports grasses including Dactylis glomerata , Elymus repens , Calamagrostis spp., and Holcus spp. as hosts in central Europe. Recorded hosts for Nearctic specimens are Elymus trachycaulus (Bourget, ON), Bromus sp. (Oxbow, MI and Gravel Lake, YT), Calamagrostis canadensis (Richardson Mountains, YT), and Calamagrostis sp. (King Salmon, AK and Aho Lake, AK).

Remarks.

The oldest name for this species, Cicada ocellata Scopoli, 1763, is a nomen oblitum as it has not been used as a valid name after 1899 (Article 23.9.1.1 of the International Code of Zoological Nomenclature (ICZN 1999)). To my knowledge, the most recent use of this name other than those excluded under Article 23.9.6 is Claus (1884, p. 892). Cicada ocellaris Fallén, 1806 is a nomen protectum based on the works listed in the Appendix 1 which fulfill the criteria of Article 23.9.1.2. The valid name of this species is thus Cicada ocellaris Fallén in accordance with Article 23.9.2.

Hamilton (1997) treated the northwestern populations of this species as a distinct species, Latalus (Adarrus) tatraensis (Heller). He linked these to high elevation populations from the Tatra Mountains in Slovakia which Heller (1975) had described as a subspecies. Heller distinguished his new subspecies based on dramatic colour differences, as well as slight differences in the male and female genitalia.

The status of the high elevation populations in Europe has not been definitively resolved. Remane and Fröhlich (1994) discussed this form (as Errastunus ocellaris tatraensis ) based on populations in the Alps but were unsure whether these populations were taxonomically distinct as even a subspecies, or simply ecophenotypic variation. Nickel (2003) indicates specimens from the Bavarian Alps show characters of both forms.

Specimens examined for this project from northwestern North America had variable but generally darker colouration than specimens from eastern North America and low elevations in Europe, although none with the extreme dark forms sometimes seen in high elevation European populations (e.g., Fig. 1E ). Slight genitalic differences were also observed, with northwestern specimens typically having shorter subgenital plates (1.38-1.50 times pygofer length, compared to 1.47-1.61, N = 5 for each group), more frequent presence of flanges at the base of the aedeagus, and slightly shorter styles.

These differences do not appear to be taxonomically significant. Latitudinal and altitudinal variation in pigmentation (de Oliveira et al. 2004) and genitalic structure ( Le Quesne and Woodroffe 1976) are known to occur in other leafhoppers, and these differences do not seem to rise above what might be expected from such variation.

The COI sequences obtained for this study also indicate relatively slight differentiation between these northwestern populations and those elsewhere. Although specimens from northwestern North America and high elevations (1950 m) in the Austrian Alps differ slightly from lower elevation E. ocellaris , they are also relatively closely related to a specimen from England which appears to be typical E. o. ocellaris .

While resolving the status of E. ocellaris tatraensis within the European context is not the objective of this study, within the Nearctic region the best treatment appears to be to treat this northwestern population simply as E. ocellaris . These populations are considered to be a native element of the fauna, representing the easternmost extent of the species Holarctic distribution.

Hamilton’s (1983) view that populations of Errastunus ocellaris in the eastern Nearctic represent an introduction from Europe appears to be correct. The earliest specimens of these populations examined are from Hudson Falls, NY (1950, CNC) and Sainte-Flore, QC (1951, CNC). Moore (1944) had earlier recorded this species from Hudson Heights near Montreal, QC beginning in 1942. Although I was not able to examine Moore’s specimens, specimens taken in 1956 from the same locality are all E. ocellaris and no E. sobrinus have ever been collected from the Ottawa River lowlands, suggesting these are the earliest records of the introduced population. Mapping specimens by collection date (Fig. 8 ) shows a clear signature of expansion from early records in southern Quebec, eastern Ontario, and northern New York. Montreal is the closest major port to these early records and may represent the point of introduction. COI sequences also provide some support for this population being introduced, with very low divergence between a sequenced specimen from lower elevations in Austria and all eastern Nearctic specimens. Specimens from the Vancouver area (earliest from 1960) likely also represent introductions, although whether these represent a secondary introduction from the East or a separate introduction from the Palearctic is not clear.

The species now occurs commonly in eastern Canada and is easily collected, suggesting that historical records accurately depict its distribution. There are much earlier specimens in the CNC of abundant native species that now often co-occur with E. ocellaris in eastern Canada such as Endria inimicus (Say) (earliest from Trenton, ON, 1901) and Diplocolenus evansi (Ashmead) (earliest from Montreal, QC, 1905), indicating collecting effort that should have yielded specimens of E. ocellaris had it been present. In comparison, specimens in the CNC of the native E. sobrinus were collected as early as the 1920s, despite its absence from much of southern Ontario and Quebec where early collections were concentrated.

The status of the northwestern population as native or introduced cannot be tested on the same basis. The earliest record of this population is from 1948 (Reindeer Depot, NWT), only slightly predating those from eastern Canada. However, there was very little entomological research in northwestern North America prior to the Northern Insect Survey beginning in 1947 ( Freeman 1959), and indeed the first record of E. sobrinus in the region is from 1951 (Big Delta, AK). However, this population is mostly likely to be native on the basis of several lines of evidence. First, COI sequences from this population are divergent from the introduced Eastern population, suggesting a different origin. COI haplotypes appearing to originate from this population have also been found in specimens of E. sobrinus from as far south as Colorado (see discussion below), and it seems unlikely such introgressed haplotypes could travel so far within a few decades if the population were recently introduced. Finally, the leafhopper fauna in this area is otherwise entirely native, including a number of otherwise Palearctic species restricted in North America to Beringia ( Hamilton 1997).

The current extent of distribution for the introduced eastern population is unclear based on the material examined. Collections in the CNC are sparse after approximately 1990 due to reduced collection effort and as the distribution appears to be expanding the current range is probably larger than depicted in the map. A specimen collected in southern Saskatchewan in 2015 (CNC) represents the westernmost confirmed record, excepting the populations around Vancouver. Images of Errastunus which may represent E. ocellaris are available from online databases and suggest a wider distribution (e.g., from North Carolina https://bugguide.net/node/view/1000457/bgimage and Edmonton, AB https://bugguide.net/node/view/596209/bgimage). However, these records cannot be definitively identified and are not included in the mapped distributions.

Figures

Figure 1. Errastunus dorsal habitus A-F Errastunus ocellaris A CNC 1317086 (Chatterton, ON) B CNC 1317151 (Igls, Austria, 900 m) C CNC 1317160 (Oxford, England) D CNC 1317521 (Obergurgl, Austria, 1950 m) E CNC 1317524 (Obergurgl, Austria, 1950 m) F CNC 1615789 (Richardson Mtns, YT, note the extended abdomen is an artifact of preservation) G, H Errastunus sobrinus G CNC # HEM 403281 (Parc de la Gaspesie, QC) H CNC 1317427 (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 CNC 1317192 (King Salmon, AK) B, F, J CNC 1317520 (Obergurgl, Austria, 1950 m) C, G, K CNC 661822 (Big Muddy, SK) D, H, L CNC 1317183 (Leeds, England).

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 CNC 1317157 (Oxford, England) E CNC 1317039 (Brockville, ON) F CNC 1316995 (Mt. Washington, NH) G CNC 1317204 (King Salmon, AK) H CNC 1615794 (Richardson Mtns, YT) I CNC 1317205 (King Salmon, AK).

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.