Crematogaster punctulata, EMERY, 1895

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 : 925-926

CREMATOGASTER PUNCTULATA EMERY, 1895

( FIGS 5A , 16 )

Crematogaster punctulata Emery, 1895: 287 . Syntype workers, Colorado (Pergande) (MHNG, MSNG, NHMW) (MHNG and MSNG workers examined). One worker from MHNG here designated lectotype (CASENT0923318).

Crematogaster opaca var. punctulata Emery ; Wheeler, 1919: 111.

Crematogaster lineolata punctulata Emery ; Creighton, 1950: 214.

Senior synonym of Crematogaster opaca texana Santschi : Buren in Smith, 1958: 127; here affirmed (syn. rev.); see discussion below.

Junior synonym of Crematogaster lineolata (Say) : Johnson, 1988: 319.

Status as species: Enzmann, 1946: 33; Smith, 1958:

127; Buren, 1968: 92; Bolton, 1995: 160; Mackay &

Mackay, 2002: 100; Morgan & Mackay, 2017: 330.

Worker measurements (N = 15): HW 0.71–0.99, HL 0.67–0.92, SL 0.58–0.75, WL 0.75–1.05, MtFL 0.62– 0.83, MSC 16–28, A4SC 28–55, PP-SL/HW 0.13–0.19, CI 1.00–1.11, OI 0.22–0.25, SI 0.74–0.82, MtFL/HW 0.82–0.87, SPL/HW 0.17–0.21, SPTD/HW 0.39–0.46.

Discussion: This species is characterized by its relatively small size (HW 0.71–0.99), reticulate-foveolate sculpture on the mesosoma dorsum, posteriorly directed propodeal spines (SPTD/HW 0.39–0.46, SPTD/PPW 1.11–1.40) and abundant, short, standing pilosity (MSC 16–28, A4SC 28–55). Crematogaster lineolata is similar, but usually has some striae or rugulae on the mesosoma dorsum, generally oriented longitudinally and often intermingled with reticulatefoveolate sculpture. In addition the propodeal spines of C. lineolata are directed more posterolaterally (SPTD/ HW 0.46–0.63, SPTD/PPW 1.38–1.76) ( Fig. 47 ). There are reports of intergradation between the two taxa in the midwestern and south-eastern United States ( Creighton, 1950; Johnson, 1988; Morgan & Mackay, 2017), however, so the status of C. punctulata remains uncertain.

We provisionally treat C. punctulata as a species, recognized by the combination of features cited above, and largely confined to the midwestern states. In populations of C. lineolata from south-eastern United States there is considerable (and seemingly continuous) variation in the degree of development of rugulae or striae on the mesosoma dorsum, such that at one end of the spectrum the sculpture is essentially like that of C. punctulata . However, in south-eastern punctulata - like workers that we have examined, the propodeal spines conform to the C. lineolata pattern (SPTD/ HW> 0.46, SPTD/PPW> 1.36). Does C. punctulata occur in the south-eastern States, where it introgresses with C. lineolata , or is this just part of the natural variation of C. lineolata in areas where it is allopatric to the midwestern C. punctulata ? Is there gene flow between the two forms where they meet in the midwest? These questions cannot be answered without further study. It is worth noting that both species have been reported from overlapping regions in Kansas ( DuBois, 1985) and Texas ( O’Keefe et al., 2000).

There are two infraspecific forms that had been considered synonyms of C. punctulata , namely C. lineolata subopaca Emery (type locality Virginia) and C. opaca texana Santschi (type locality Bonham, Texas) (synonymy by Buren in Smith, 1958: 127). Johnson (1988: 320) cited the former as a synonym of C. lineolata , when he synonymized C. punctulata under C. lineolata , but he made no statement about C. opaca texana. Morgan & Mackay (2017) treated C. punctulata as a good species, but placed its two former synonyms under C. lineolata , without explanation. An imaged syntype worker on AntWeb of C. opaca texana (CASENT0912717) has the posteriorly directed propodeal spines (SPTD/HW ~0.41) and sculptural features of C. punctulata , not C. lineolata . Therefore, it is here removed from synonymy under C. lineolata ,and again placed under synonymy of C. punctulata (syn. rev.).

The form described as C. lineolata subopaca from Virginia is part of that complex variation described above in south-eastern populations of C. lineolata . A syntype worker (CASENT0904537) imaged on AntWeb has a reticulate-foveolate mesosoma, but the propodeal spines are divergent (SPTD/HW ~0.49), like those of C. lineolata . We leave this as a synonym of C. lineolata , while emphasizing that the C. lineolata / punctulata complex needs a thorough genetic investigation.

Although larger sample sizes are desirable, our UCE phylogeny ( Fig. 1 ) provides support for treating C. lineolata and C. punctulata as different species. Based on three population samples of C. lineolata and two each of C. punctulata and C. emeryana , we find that C. emeryana , a south-western species, is the sister-taxon of C. lineolata , while C. punctulata is more distantly related (sister to these two).

Type notes: Morgan & Mackay (2017) reported examining 30 syntype workers of C. punctulata in a collection cited as ‘MNHG’, an apparent misspelling of MHNG (Muséum d’Histoire Naturelle, Geneva). We have located and examined a total of 24 syntype workers, but only four are in MHNG. The remaining 20 specimens are in MSNG ( Genoa ). There is also an image on AntWeb (CASENT0919708) of a syntype worker in NHMW. The four workers in MHNG are labelled ‘Cotypus’, ‘ Crematogaster | punctulata Em |Colorado’, and ‘Sp. C. punctulata |Em’, while those in MSNG bear the labels: ‘TYPUS| Crematogaster |punctula ta|det. Emery, 1895’ and ‘MUSEO GENOVA|coll. C. Emery |(dono 1925)’. Each type label is red, and has a large question mark handwritten at the right side of the first three lines. The MSNG workers (20 workers on five pins) also bear different handwritten numbers on each pin (N. 5 Ga, N. 562, N. 513a, N. 513 and 513) that possibly refer to different nest series. This would be consistent with Emery’s (1895: 287) statement that Pergande had supplied him with four nests. The workers from MHNG and MSNG are all similar and match Emery’s original description. Nevertheless, because no locality is given on the labels of the MSNG specimens and because there is a question mark on the type labels, we have chosen a lectotype from one of the four syntype workers in MHNG .

Distribution and biology: Based on our current concept of C. punctulata , this is a midwestern species occurring from the Great Plains south to northern Mexico, and west to Arizona. We have not seen definitive records east of Mississippi, but the status of some eastern samples remains ambiguous (see above). This species is ground-nesting and occurs in woodlands, grasslands and other open habitats.

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 3–12. Crematogaster worker features useful for identification. 3, petiole shape, dorsal view, C. lineolata (CASENT0863235) (3A) and C. torosa (CASENT0795540) (3B); 4, sculpture on declivitous face of propodeum, C. dentinodis (CASENT0863070) (4A) and C. depilis (CASENT0863478) (4B); 5, mesosomal pilosity, C. punctulata (CASENT0863277) (5A) and C.emeryana (CASENT0863099) (5B); 6, position and shape of propodeal spines, dorsal view, C.isolata (CASENT0863072) (6A) and C.pinicola (CASENT0882129) (6B); 7, petiole shape, dorsal view, C.mutans (CASENT0862488); 8, subpetiolar tooth, lateral view, C.mutans (CASENT0862488); 9, promesonotal sculpture, C.californica (CASENT0221085)(9A) and C.coarctata (CASENT0221962) (9B); 10, postpetiolar seta, C. browni (CASENT0863144) (10A) and C. cerasi (CASENT0795541) (10B); 11, cephalic pilosity, C. torosa (CASENT0795540) (11A) and C. missouriensis (CASENT0221041) (11B); 12, mesosomal profile, C. crinosa (CASENT0795543) (12A) and C. torosa (CASENT0863226) (12B).

Figures13–18. Crematogaster workers,showing lateral viewof body (A),full-faceview of head(B) and dorsalview ofbody (C). 13, C. dentinodis (CASENT0102830); 14. C. vetusta holotype (CASENT0863254); 15, C. navajoa worker (CASENT0064826); 16, C. punctulata lectotype (CASENT0923318); 17, C. isolata (CASENT0922731); 18, C. sp. cf. opaca (MCZENT00589113). Images courtesy of AntWeb (www.antweb.org); photographers Jen Fogarty (13), Michele Esposito (14, 16), April Nobile (15), Wade Lee (17), Zachary Griebenow (18).

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).