Crematogaster rossi, BUREN, 1968

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 : 926

CREMATOGASTER ROSSI BUREN, 1968 , STAT. REV.

Crematogaster rossi Buren, 1968: 111 . Holotype worker, San Jose del Cabo , Baja California Sur, Mexico (USNM) ( USNMENT00531965 ) (examined).

Junior synonym of C. vermiculata: Morgan & Mackay, 2017: 396 ; here overturned.

Worker measurements (N = 6): HW 0.90–1.1, HL 0.83– 1.04, SL 0.76–0.86, WL 0.95–1.25, MtFL 0.80–0.99, MSC 0–8, A4SC 25–34, PP-SL/HW 0.15–0.19, CI 1.06– 1.13, OI 0.25–0.27, SI 0.78–0.85, MtFL/HW 0.87–0.92, SPL/HW 0.24–0.26, SPTD/HW 0.53–0.60.

Discussion: Phylogenomic (UCE) data reveal a close relationship of C. rossi to C.californica and C. opuntiae ; it has no close affinity to C. vermiculata ( Fig. 1 ). Crematogaster rossi is recognizable by the combination of a predominantly shiny head, conspicuously rugulose promesonotum on a reticulate-foveolate background and abundant standing pilosity on the gaster. The mesosomal sculpture is superficially similar to that of C. vermiculata , but the two species differ in numerous ways. Crematogaster rossi is larger (HW 0.90–1.10, WL 0.95–1.25), with disproportionately longer scapes (SI 0.78–0.85) and legs (MtFL/HW 0.87–0.92) and with propodeal spines that are straight, longer and more divergent posteriorly (SPL/WL 0.22–0.24, SPTD/HW 0.53–0.60) (compare with equivalent measurements for C. vermiculata below). There are up to two isolated standing hairs on each pronotal humerus and usually a few short standing hairs on the mesonotal declivity (MSC 0–7), but the pilosity on the gaster is particularly well-developed (A4SC 25–34, compared with A4SC 9–20 in C. vermiculata ). From the closely related species, C. californica and C. opuntiae , C. rossi can be distinguished primarily by its promesonotal sculpture and abundant standing pilosity on the gaster.

Distribution and biology: Crematogaster rossi is known from the Mexican states of Baja California Sur and Baja California, and (more doubtfully) Nayarit. Specimens with habitat information come from ‘oak woodland’ and ‘dry wash next to oak woodland’ but others have been collected from sites in more xeric locations. The species is apparently a ground-nester.

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).