Gryllus vulcanus Weissman & Gray, 2019

Weissman, David B. & Gray, David A., 2019, Crickets of the genus Gryllus in the United States (Orthoptera: Gryllidae: Gryllinae), Zootaxa 4705 (1), pp. 1-277 : 229-233

Gryllus vulcanus Weissman & Gray , n. sp.

New Mexico Lava Field Cricket

Figs 222–224 , 230–235 , Table 1

‘ Gryllus #41’ in DBW notebooks.

Distribution. Known only from two lava flows in central New Mexico.

Recognition characters and song. A small to medium, always short hind wing, almost totally black (except for inside of hind femurs which can be reddish colored) Gryllus with medium length cerci longer than ovipositor tip in situ ( Fig. 234 ), and a file tooth count greater than 160. Song ( Fig. 230 , R07-68) usually with 4–5 p/c (range 3–7), PR <14 and pulses almost countable at 25°C. Distinguished from only other US obligate lava field cricket, G. leei , from Utah, in minimal overlap in number of teeth ( Fig. 231 , Table 1 , p. 18), no overlap in pulse rate, and different DNA (Gray et al. 2019).

Morphologically and genetically most similar to sister species G. longicercus but G. vulcanus matures earlier (despite being at higher elevation), is smaller with fewer file teeth ( Fig. 232 ), shorter cerci, habitat (only on lava as opposed to rocky areas), and shorter ovipositor ( Fig. 233 ).

From microsympatric, off-lava G. veletis at the type locality, the two taxa are easily separated ( Table 1 , p. 18) by cerci length and pulse rate.

Holotype. Male ( Fig. 234 ). USA, New Mexico, Cibola Co., El Malpais National Monument adjacent to Hwy 117 at mile post sign 31 [or 31 m S I40], 14-vi-2007, 2161m. 34° 47’ 17.16” -107° 56’ 13.92” DB Weissman, DC Lightfoot, S 07-52, R07-81 & 84, G1146. 16S ribosomal RNA GenBank accession # MK 446541 ; ITS2 GenBank accession # MK 441986 . BL 17.72, HF 10.56, RC 11.53. Right tegmen removed: 171 teeth, file length 3.4, TL 10.3, TW 4.4. Type deposited in CAS, Entomology Type #19275.

Paratypes. ( Total : 36♂ 22♀). New Mexico, Cibola Co., El Malpais National Monument, type locality, 6870 ’, 18-viii-1993 (S93-71) 6♂ 4♀; 1-vii-1994 (S94-41) 2♂; 1-vii-1994 (S94-42) 2♂; 14-vi-1996 (S96-68) 12♂ 2♀; 14- vi-2007 (S07-52) 2♂ 1♀. Lincoln Co., Valley of Fires State Park along Hwy 380, 5 m W Carrizozo at mile post 60, 5090’, 33° 42.115’, -105° 56.249 ’, 2-vii-1994 (S94-48) 9♂ 8♀; 13-vi-2007 (S07-46) 3♂ 7♀.

Derivation of name. Named with reference to ancient Roman myth: Vulcan (Latin: Vulcanus) is the god of lava and smoke, including the fires of volcanoes, because lava flows have created this cricket’s habitat.

Geographic range. ( Fig. 235 ). The two known localities are separated by about 210 km distance and are not connected by any lava flows visible on Google Earth.

Habitat. From 1550-2094m elevation. Both lava flow sites are well vegetated with various annuals, shrubs and small trees. The type locality site has bordering grazed grasslands on sandy substrate with pinyon-juniper woodlands nearby.

Life cycle and seasonal occurrence. One generation/year. Adults known from mid-June to mid-August with most August individuals having damaged cerci. It appears that the higher elevation type locality individuals mature before those from Valley of Fires given the presence of many nymphs seen at S07-46 (13-vi-2007) and none ever seen at the type locality on similar dates.

Variation. Body size: lower elevation (1550m elevation) Valley of Fires adults somewhat larger than type locality (2094m elevation) adults.

DNA. Multilocus 2016-025 (type locality) and G1030 (Valley of Fires State Park, S07-46) sister species (Gray et al. 2019) to G. longicercus from Kofa Mts., Arizona (2016-039, type locality), G1433 (New Mexico, S09-59) and G3386 (Texas, S16-4). ITS2 does not separate G. longicercus and G. vulcanus ( Fig. 224 ). 16S shows minimal variation either within or between these taxa (509 bp of 16S; N = 10 G. vulcanus ; N = 69 G. longicercus ; mean ± SD Tamura-Nei distance: within G. vulcanus = 0.0019 ± 0.0018, within G. longicercus = 0.0016 ± 0.0018, between G. vulcanus and G. longicercus = 0.0018 ± 0.0018) and does not separate them.

Discussion. We contemplated the possibility that G. vulcanus is simply G. longicercus on lava, given the fact that multilocus DNA analysis shows them as sister species. They do separate with the regression of hind femur length vs. ovipositor length ( Fig. 233 ), but this could be explained by the simple fact that G. longicercus is a larger cricket. A similar result, and possible explanation, is seen ( Fig. 232 ) when regressing number of file teeth vs. tegmen length. Despite these results, we have decided to treat them as separate species because of two factors: (1) G. vulcanus , despite living at higher, cooler elevations, appears to reach adulthood before most populations of G. longicercus . Specifically, the entire type locality population of G. vulcanus was adult by mid-June and by mid-August, many individuals had damaged cerci, apparently indicating old adult age. In contrast, during several early to mid- June, Arizona field trips, we collected more late instar G. longicercus nymphs, than adults, at the following locali- ties: Mt. Graham (S12-19), Mt. Lemmon (S12-23), and Fort Bowie (S13-19), despite these localities being lower and warmer than the New Mexico G. vulcanus sites. (2) Lava flows are not a typical Gryllus habitat, as confirmed by our extensive checking of such areas. G. leei , from west-central Utah, appears to be another lava exception and is isolated to the Black Rock Desert of western Utah.

Although we treat G. vulcanus here as separate from G. longicercus , further work is clearly warranted. Especially given the similarity in song, pre-zygotic reproductive isolation, to the extent that it exists, may be driven solely by ecology and/or phenology. Given that the two known lava flow localities in New Mexico are not connected and are of very different ages, we suspect that the two flightless G. vulcanus populations represent separate derivations from G. longicercus ; this also could be tested in future work. DNA markers more sensitive than ITS2 and 16S would be required (e.g. SNPs).

The type locality is part of the 3,000-year-old McCarty lava flow: http://geoinfo.nmt.edu/tour/federal/monuments/el_malpais/zuni-bandera/pahoehoe.html ( Laughlin et al. 1993). However, volcanism in adjacent areas dates as far back as 115,000 years ( Laughlin et al. 1994). There are many deep lava cracks and fissures from which G. vulcanus sing, making their song soft and the crickets difficult to collect, despite their boldness. With patience, singing males can frequently be coaxed from deep cracks with a slim twig, as they do not dive down. Nevertheless, collecting time is better spent walking the edges of the lava flow at night after laying of an oatmeal trail there during the late afternoon. One male singing from a crack in the ground several meters from lava’s edge at El Malpais (S96-68).

Many fewer singing males at Valley of Fires in 2007 (S07-46) than in 1994. At Valley of Fires State Park, there are fewer and more shallow cracks in the surface lava and more dirt and grassy areas within the lava flow area when compared to the type locality. This lava flow has been dated to ca. 5,200 ±700 years of age ( Dunbar 1999). At Valley of Fires all crickets were in the open with many males singing totally exposed away from cracks but still on lava. They were also easy to approach while singing and active jumpers. Many singing males had females near them. In 2007 (13-vi-2007, S07-46), several medium instar nymphs, and adult females, were seen walking around.

Figures

FIGURE 222. Five second waveforms of typical calling songs of (A) G. longicercus and (B) G. vulcanus. (A) G. longicercus: (R15-159) Torrance Co., NM (S15-52), at 25.3°C; (B) G. vulcanus: (R07-68) from type locality, at 25°C.

FIGURE 223. One second spectrograms of typical calling songs of (A) G. longicercus and (B) G. vulcanus, same males as in Fig. 222.

FIGURE 224. ITS2 gene tree. Collection stop numbers for G. longicercus samples: S09-64 (G1388, G1395); S11-93 (G2175, G2176); S12-23 (G2245, G2247, G2260, G2261); S15-52 (G3086, G3276); S15-56 (G3160, G3179); S15-63 (G3149, G3223, G3303); S15-77 (G3177); S15-110 (G3213); S16-2 (G3418); S16-4 (G3386, G3390, G3392, G3401, G3453); S17-4 (G3522, G3523, G3528). Collection stop numbers for G. vulcanus samples: S07-46 (G1030, G1032, G1033); S07-52 (G1050, G1146); type locality (2016-025).

FIGURE 230. Calling song (R07-68) of G. vulcanus from type locality, recorded at 25°C.

FIGURE 231. Regression tegmina width vs. file teeth number in G. vulcanus vs. G. leei.

FIGURE 232. Regression file teeth number vs. tegmina length in G. vulcanus vs. G. longicercus.

FIGURE 233. Regression hind femur length vs. ovipositor length in G. vulcanus vs. G. longicercus.

FIGURE 234. Holotype male (left) of G. vulcanus. Female (right) also from type locality (S07-52).

FIGURE 235. Known distribution of G. vulcanus.