Crematogaster detecta, Ward & Blaimer, 2022

Ward, Philip S. & Blaimer, Bonnie B., 2022, Taxonomy in the phylogenomic era: species boundaries and phylogenetic relationships among North American ants of the Crematogaster scutellaris group (Formicidae: Hymenoptera), Zoological Journal of the Linnean Society 194, pp. 893-937 : 914-915

CREMATOGASTER DETECTA SP. NOV.

( FIG. 21 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 4508D17A-F49A-4092-942B-89F3431E117A.

Type material: Holotype worker, US, Nevada, Clark Co.: 4 km NW Calico Basin, 1330 m, 36.16514 −115.44926 ± 5m, 21 Apr 2016, P. S. Ward PSW17509,

under stone, oak-pine woodland (CASENT0863461) ( USNM). Paratypes: nine workers, same data as holotype (CASENT084433, CASENT0863074, CASENT0863459, CASENT0863460,CASENT0863462,CASENT0863463, CASENT0863464, CASENT0863465) (CASC, LACM, MCZC, UCDC) .

Non-type material: Four workers, US, California, San Bernardino Co.: Teutonia Peak , 1720 m, 35°18 ′ N 115°34 ′ W, 30 Mar 2004, P. S. Ward PSW15191, under stone, juniper woodland ( UCDC); four alate queens, one male, US, Utah, Washington Co.: Springdale, 1180 m, 37.18449 −113.00067 ± 5 m, 3 Aug 2019, P. S. Ward PSW18243, at light, roadside ( UCDC) .

Worker measurements (N = 11): HW 0.95–1.17, HL 0.93–1.14, SL 0.76–0.95, WL 1.00–1.37, MtFL 0.80– 1.05, MSC 0, A4SC 0–3, PP-SL/HW 0.08–0.12, CI 1.02– 1.06, OI 0.26–0.30, SI 0.79–0.83, MtFL/HW 0.84–0.93, SPL/HW 0.20–0.24, SPTD/HW 0.43–0.55.

Worker diagnosis: Head slightly broader than long, the sides convex and the posterior margin flat to weakly concave; scapes surpassing the posterior margin of head by less than distal scape width (SI 0.79–0.83, SL/HL 0.80–0.87, SL/WL 0.67–0.79); eye moderately large (OI 0.26–0.30, ED/HL 0.27–0.31, ED/MtFL 0.28–0.36); promesonotum lacking wellmarked pronotal humeri and mesonotal declivity; propodeal spines relatively long (SPL/HW 0.20–0.24, SPL/WL 0.18–0.21) and divergent (SPTD/HW 0.43– 0.55); petiole subtrapezoidal, broadened anteriorly (PTW/HW 0.32–0.39); postpetiole relatively broad (PPW/HW 0.28–0.32), the hemilobes not strongly angulate in profile; legs relatively long (MtFL/HW 0.84–0.93, MtFL/HL 0.86–0.95, MtTL/HW 0.77– 0.81). Mandibles striate; head reticulate to reticulatestriolate, becoming effaced and sublucid medially; mesosoma predominantly reticulate-foveolate and opaque, with overlying irregular rugulae on pronotum and dorsal face of propodeum; declivitous face of propodeum mostly smooth and shiny; petiole and postpetiole reticulate to reticulate-foveolate, subopaque. Standing pilosity sparse on head and absent from mesosoma dorsum; scape with relatively conspicuous decumbent pubescence; postpetiolar seta short (PP-SL/HW 0.08–0.12); standing pilosity absent from most of fourth abdominal (first gastric) tergite, confined to 0–3 short hairs on the posterior margin. Light reddish-brown, head and gaster darker.

Comments: The workers of this species are similar to those of C. depilis yet phylogenomic data place C. detecta as sister to C. vetusta and more distant from C. depilis ( Fig. 1 ). As in C. depilis , the mesosoma dorsum of C. detecta is densely reticulate-foveoleate and opaque and lacks standing pilosity (MSC 0); standing pilosity is correspondingly sparse on the head and gaster and confined on the fourth abdominal tergite to a few or no (0–3) short standing hairs on the posterior margin. Crematogaster detecta differs from C. depilis by the less strongly developed rugulose sculpture on the dorsal face of the propodeum which contrasts less with the sculpture on the mesonotum than in C. depilis , and by a tendency to have more conspicuously uplifted pubescence on the scape. These features are somewhat difficult to evaluate, however, and they show considerable variation among putative workers of C. depilis . Larger workers (HW> 1.05 mm) can be separated by morphometric differences: C. detecta exhibits longer legs and a more slender mesosoma than both C. depilis and the closely similar C. larreae ( Figs 43, 44 ) such that, for these larger workers of C. detecta, MtFL /HW 0.87–0.91, MtTL/HW 0.77–0.79, ED/MtFL 0.29–0.32 and WL/ HW 1.08–1.17. Corresponding combined values for C. depilis and C. larreae (of all sizes) are: MtFL/HW 0.80–0.87, MtTL/HW 0.71–0.77, ED/MtFL 0.32–0.37 and WL/HW 0.97–1.09. However, small workers of C. detecta cannot be recognized on this basis ( Figs 43, 44 ). Crematogaster detecta can be distinguished from C. colei by its shorter scapes (SL/HL 0.80–0.87 vs. 0.88–0.96 in C. colei ) and legs (MtFL/HL 0.86–0.95 vs. 0.99–1.08 in C. colei ); denser sculpture on the mesosoma, petiole and postpetiole; and more rounded (less angulate) hemilobes of the postpetiole, as seen in lateral view.

Distribution and biology: The type series from Clark County, Nevada (PSW17509) consists of a series of workers collected under a stone in a sandy wash with Pinus monophylla Torr. & Frém., Quercus turbinella Greene, Arctostaphylos pungens Kunth, Garrya flavescens S.Watson, Fraxinus anomala Torr. ex S.Watson, Purshia DC. sp. and various cacti. Otherwise this species is known only from (1) workers collected under a stone in juniper woodland in San Bernardino County, California (PSW15191) and (2) four alate queens and one male collected at light in southern Utah (PSW18243). These specimens were identified as conspecific with the type series through phylogenomic (UCE) data. Other material undoubtedly exists in collections, masquerading as C. depilis . Based on limited locality data it seems that C. detecta prefers more wooded habitats than C. depilis .

Etymology: The name is derived from Latin detectus, past participle of detegere, to discover or disclose, referring to the initial detection of this cryptic species from DNA sequence data.

Figures

Figure 1. Phylogeny of the North American Crematogaster scutellaris group. Maximum likelihood phylogenetic tree estimated from the 90% taxon completeness matrix after application of spruceup trimming with a 0.98 cut-off (90%-0.98-spruceup), using a combined best tree and ultrafast bootstrap (N = 1000) search in IQ-TREE v.1.6.12 and implementing 746 partitions. The analysis was rooted using the most distantly related outgroup taxon C. cf.rogenhoferi; the long branch leading to this taxon has been shortened for space-saving purposes. All nodes have bootstrap support = 100% unless labelled otherwise. Species images courtesy of AntWeb (www.antweb.org).

Figures 19–24. Crematogaster workers, showing lateral view of body (A), full-face view of head (B) and dorsal view of body (C). 19, C. mutans worker (CASENT0922736); 20, C. colei (CASENT0922726); 21, C. detecta holotype (CASENT0863461); 22, C. larreae paratype (CASENT0005943); 23, C. depilis (CASENT0005668); 24, C. californica lectotype (CASENT0923319). Images courtesy of AntWeb (www.antweb.org); photographers Wade Lee (19, 20), Zachary Griebenow (21), April Nobile (22, 23), Michele Esposito (24).

Figures 40–47. Bivariate plots of selected worker measurements in the Crematogaster scutellaris group. 40, PP-SL (postpetiole seta length) by HW (head width) in C. browni (N = 16) and C. cerasi (N = 17); 41, ED (eye diameter) by MtFL (metafemur length) in C. californica (N = 22) and C. coarctata (N = 21); 42, MtFL (metafemur length) by HW (head width) in C. californica (N = 22), C. colei (N = 12) and C. opuntiae (N = 10); 43, MtFL (metafemur length) by HW (head width) in C. depilis (N = 15), C. detecta (N = 11) and C. larreae (N = 5); 44, MtTL (metatibia length) by HW (head width) in C. depilis (N = 15), C. detecta (N = 11) and C. larreae (N = 5); 45, SPL (propodeal spine length) by HW (head width) in workers of C. hespera (N = 18), C. laeviuscula (N = 25) and C. parapilosa (N = 15); 46, SL (scape length) by HW (head width) in C. emeryana (N = 12) and C. marioni (N = 18); 47, SPTD (propodeal spine tip distance) by HW (head width) in C. lineolata (N = 26) and C. punctulata (N = 15).