Canadian Journal of Arthropod Identification
 
 

Orthoptera of Alaska: A photographic key, new records, and synonymy of Melanoplus gordonae

CJAI 44 -- April 23, 2021
doi:10.3752/cjai.2021.44

Adam Haberski, Derek A. Woller, and Derek S. Sikes

| Abstract | Introduction | Checklist | Materials & Methods | Taxonomy | DNA Barcoding | Species Key | Acknowledgments | References | PDF | Cite |
 
 

Taxonomy

Melanoplus borealis (Fieber, 1853)
Melanoplus gordonae Vickery, 1969, syn. nov.

We hereby establish M. gordonae Vickery, 1969 as a junior synonym of M. borealis based on accumulated morphological evidence. Melanopus gordonae was described using only five type specimens: male holotype (Fig. 4A,B,E), female allotype (Fig. 4C,D,F), and three nymphs that were collected by a V. Gordon: "U.S.A.: Alaska, nr. Fairbanks, 2 mi. along Gilmore Trail, 13-VIII-1968" (Vickery, 1969). Despite numerous efforts by Vickery and subsequent collectors, including AH and DSS, no more specimens of this species have been found, leading to the presumption that it was a very rare endemic or, possibly, extinct. However, both of these seemed unlikely since macropterous grasshopper species are seldom found to be restricted to a single small area (unlike many brachypterous and apterous species), nor do species with presumed long-range flight abilities tend to go extinct within such short time frames with the possible extraordinary exception of the Rocky Mountain locust (Melanoplus spretus (Walsh, 1866)) (Lockwood, 2004).

Figure 4. Melanoplus gordonae Vickery, 1969 holotype habitus: A) left lateral and B) dorsal; M. gordonae allotype habitus: C) left lateral and D) dorsal; E) holotype and F) allotype labels - note that the specific name on the labels is incorrect; M. borealis (Fieber, 1853) (UAM100269521) habitus: G) left lateral and H) dorsal.

Regardless, these hypotheses were challenged when, during the course of this research, 18 Melanoplus spp. specimens (12 male, 6 female) found in the UAM (14 collected in the vicinity of Fairbanks, three from Palmer, and one from the Kanuti National Wildlife Refuge, Alaska) did not key out smoothly to any of the more common species found in Alaska using the three afore-mentioned taxonomic keys for Alaska and Yukon, Canada. To understand this better, it should first be mentioned that the M. gordonae holotype possesses one primary unique morphological character: the subgenital plate is distinctly trilobate at its apex (Fig. 5C). Two further characters that helped separate it from other species were the combination of wings that extended beyond the apex of the abdomen in both sexes (although this was not explicitly noted in the original description) (Fig. 4A-D) and a lack of banding on the outer face of the hind femora in males, but with some in females (Vickery 1969) (Fig. 4C). Note that the latter character was seemingly misunderstood by Catling (2008) to not be present at all. His confusion was most likely compounded by the fact that the key in Vickery and Kevan (1985 (1986)) mistakenly said that the female lacked the banding.

Figure 5. Melanoplus gordonae Vickery, 1969 holotype external genitalia: A) left lateral, B) dorsal, C) posterior; M. borealis (Fieber, 1853) (UAM100269379) external genitalia: D) left lateral, E) dorsal, F) posterior; M. gordonae holotype internal genitalia: G) left lateral, H) posterior, I) epiphallus (dorsal); M. borealis (ASUHIC) internal genitalia: J) left lateral and K) posterior; L) M. gordonae allotype's subgenital plate (dorsal).

Close examinations of the holotype and allotype specimens from the Lyman Entomological Museum confirmed these unique characters and allowed for careful comparisons to the 18 UAM specimens, which all possess the long wings possessed by the M. gordonae type specimens, but the apices of the subgenital plates of all 12 males would be difficult to describe as distinctly "trilobate." In fact, running all 18 specimens through the three keys repeatedly identified them consistently as M. femurrubrum (De Geer, 1773), which happens to be the species that Vickery (1969) compared M. gordonae against even though it is not found in Alaska (Vickery used specimens from British Columbia, Canada). Despite this, a colleague with over 40 years of rangeland grasshopper-identifying experience also closely examined the UAM specimens, ran them through the same keys and still came to M. femurrubrum, but noted that M. borealis (Fig. 4G&H) would be a better fit in terms of overall habitus (Reuter, personal observations).

To further support this, several morphological features of the unidentified UAM specimens, including shape variation of the male subgenital plate, female subgenital plate similarities, overall cerci shape, supra-anal plate similarities, and larger body size (Figs. 4A-D, G&H; 5A-F, L), combined with their geographic location, suggested greater similarity between M. gordonae and M. borealis than M. gordonae and M. femurrubrum. However, the primary distinctions between M. gordonae and M. borealis were three-fold: 1) subgenital plate shape in males (Fig. 5C&F), 2) slight banding on outer hind femora of females (Fig. 4C) (seemingly absent in M. borealis (Fig. 69 in key)), and 3) wing length in both sexes (Fig. 4A-D, G&H). This latter character is what particularly stymied us and Reuter because, according to the three keys and other reliable sources of information (e.g., Pfadt 2002), the wings of M. borealis rarely extend beyond the apices of hind femora. These conflicts are what prompted the decision to borrow the type specimens of M. gordonae and compare the internal genitalia of the holotype to those of some of the UAM specimens and the internal genitalia of multiple male specimens of M. femurrubrum and M. borealis (all with hind wings not extending beyond the apices of hind femora). The holotype's internal genitalia (Figs. 5G-I; 6A&C) closely matched those of the UAM males, which, in turn, all closely matched those of M. borealis (Figs. 5J&K; 6B&D), both short and long-winged morphotypes. Differences in internal genitalia, particularly the shape of the valves of aedeagus, are often quite useful for delimiting Caelifera species, particularly melanoplines (Hubbell 1932), which certainly appears to be the case here.

Figure 6. Close-up comparison of the valves of aedeagus of internal genitalia of Melanoplus gordonae Vickery, 1969 holotype: A) left lateral and C) posterior vs. M. borealis (Fieber, 1853) (ASUHIC): B) left lateral and D) posterior

Additional support for M. gordonae actually being M. borealis came from several other sources, the first being Gurney and Brooks (1959) who noted that M. borealis borealis (M. borealis has a complex taxonomic history and its subspecies are no longer recognized (Cigliano et al. 2020)) has variable wing length, which can be both shorter or longer than the abdomen. This species is found throughout Canada, across Alaska, and in several other northern U.S. states (Gurney and Brooks 1959; Vickery and Kevan 1985 (1986); Pfadt 2002; Catling 2008), meaning its known distribution encompasses that of M. gordonae. Several longer-winged specimens of M. borealis were confirmed by colleagues to exist in two reputable collections: the Pfadt Collection at the University of Wyoming (Wyoming specimens) and the National Museum of Natural History's melanopline collection. To further test our conspecificity hypothesis, we asked the colleague overseeing the latter collection to dissect the internal genitalia of two of these specimens from Fairbanks and Beaver, Alaska, and they were confirmed to be remarkably similar to the M. gordonae holotype.

Therefore, the preponderance of morphological evidence (similar body size, similar shape of male terminalia structures, wing length) support the synonymizing of M. gordonae with the earlier-named M. borealis. Two odd details do remain: 1) the trilobate apex of M. gordonae's subgenital plate in the holotype (Fig. 5C) and 2) the slight banding on the outer face of M. gordonae's hind femur in the allotype (Fig. 4C). But both of these can be explained as unusual population variation details, especially since the past use of the subspecies concept for M. borealis was based on high levels of population variation across regions. Some of the previously unidentified UAM male specimens do exhibit vague similarities and a range of variation (same for the previously identified M. borealis specimens examined) of the aforementioned unique male character, but none are admittedly as eye-catching as the specimen Vickery (1969) used to describe M. gordonae. Vickery (1969) simply seems to have gotten very lucky and would probably have noticed sufficient variation that might have led him to draw different conclusions if he had a larger series of specimens to examine. Finally, it should be noted that several collecting efforts made by AH and DSS in the type locality have only yielded M. borealis specimens: long-winged males and short-winged females (curiously, conversely to the M. gordonae allotype). Based on this and other Alaska-collected long-winged M. borealis specimens suggests that the region may contain relatively high numbers of this particular morphological variation, which warrants further investigation.