Pheidole anastasii Emery

Sarnat, Eli M., Fischer, Georg, Guenard, Benoit & Economo, Evan P., 2015, Introduced Pheidole of the world: taxonomy, biology and distribution, ZooKeys 543, pp. 1-109 : 19

Taxon classification Animalia Hymenoptera Formicidae

Pheidole anastasii Emery Figs 74, 88a

Pheidole anastasii . Pheidole anastasii Emery 1896: 76 (s.w.) COSTA RICA, Jiménez, [MCSN]. Queen described Forel 1901: 78. Junior synonym of bilimeki Mayr: Wilson 2003: 378. Revived status: Longino and Cox 2009: 40. Nec M.R. Smith 1933, Naves 1985, Boer and Vierbergen 2008.

Diagnosis among introduced Pheidole .

Color usually dull yellow to dull brownish yellow. MajorHW 0.83-1.05, HL 0.90-1.11, SL 0.49-0.62, CI 88-98, SI 50-61 (n=43, Longino pers. comm.). Head uniform in color (Fig. 35); subquadrate (Fig. 7); often entirely punctate (Fig. 11), but portions of posterolateral lobes can be glossy. Posterolateral lobes never with distinct rugae. Promesonotum in profile forming a single dome (Fig. 4). Postpetiole not swollen relative to petiole (Fig. 3). Postpetiole relatively broad; distinctly more than 2 × petiolar width in dorsal view (Fig. 31). First gastral tergite with anterior third to entire surface matte. MinorHW 0.38-0.50, HL 0.44-0.59, SL 0.44-0.58, CI 82-90, SI 106-120 (n=49, Longino pers. comm.). Head dull, entirely covered by reticulated network of punctures (Fig. 37). Posterior head margin relatively narrow and rounded (Fig. 58). Antennal scapes lack standing hairs (Fig. 55); scapes surpass posterior head margin by a distance equal to or greater than eye (Fig. 40). Promesonotum in profile forming a single dome (Fig. 42), lacking a distinct mound or prominence on the posterior slope. Hairs on mesosoma stout, stiff, of equal length and arranged in pairs (Fig. 53). Postpetiole narrow in dorsal view, only slightly broader than petiole. Gaster with at least anterior 1/3 of first tergite matte (Fig. 33).

Identification, taxonomy and systematics.

Pheidole anastasii , Pheidole bilimeki and Pheidole punctatissima all belong to the Pheidole punctatissima clade ( Economo et al. 2015). These ants are all relatively small species characterized by densely punctate ground sculpture that gives them a dull, matte appearance. Among species treated here, the Pheidole punctatissima clade species are most easily confused with those of the closely related Pheidole flavens complex. Major and minor workers are most reliably diagnosed from those of the Pheidole flavens complex by the relatively broad postpetiole (Fig. 31, major; Fig. 62, minor) and the matte anterior portion of the gaster (Fig. 33) in addition to other characters listed in the key. The minor workers can also be confused with those of Asian native Pheidole parva , but can be distinguished by the more uniform and stout mesosomal hairs (Fig. 53), and by the antennal scapes which lack erect hairs (Fig. 55) and tend to surpass the posterior head margin by a distance equal to or greater than eye (Fig. 40). In the Neotropics, there are many native species that closely resemble Pheidole anastasii ( Wilson 2003), and identification of the minor worker subcaste is especially challenging.

Among introduced members of the clade, the major workers of Pheidole punctatissima are immediately distinguished from those of both Pheidole anastasii and Pheidole bilimeki by the bicolored head (Fig. 33). The minor workers of Pheidole punctatissima tend to have narrower posterior head margins and longer antennal scapes than those of Pheidole anastasii and Pheidole bilimeki . Separating Pheidole anastasii from Pheidole bilimeki is particularly difficult. They are most reliably distinguished by ecological characteristics, with the former preferring to nest arboreally and the latter preferring to nest under stones or in dead wood. The morphological characters separating these two species are highly variable, but the major workers of Pheidole anastasii tend more often towards yellow (versus tending towards brown in Pheidole bilimeki ) and can have relatively wider heads (HW 0.74-1.16 mm vs. 0.71-1.07 mm). The minor workers of Pheidole anastasii tend to have more narrow heads posteriorly then Pheidole bilimeki (Fig. 58 vs. Fig. 57) and relatively longer scapes (SI 103-125 vs. 95-108). See Longino and Cox (2009) for additional details.

Adding to the already confusing taxonomy separating Pheidole anastasii and Pheidole bilimeki is the widespread application of the name Pheidole floridana Emery to populations across the southern United States. The first record of Pheidole floridana from Florida was the type series described by Emery from Coconut Grove (Miami area) in 1895. Smith (1930) recorded Pheidole floridana in his original list of Florida ants, and added Pheidole anastasii three years later (1933), stating only "This species [ Pheidole anastasii ], which was originally described from Costa Rica, is recorded here for Florida on the basis of information secured from Dr. Wheeler … I have seen the same species in greenhouses in the District of Columbia, New Jersey, and Illinois." The previous year (1932) Wheeler, who had received type material of Pheidole floridana from Emery ( Wheeler 1908c), included Pheidole floridana and Pheidole anastasii in his own list of Florida ants.

Naves (1985) in his study of Florida Pheidole , also recognized both species and distinguished Pheidole anastasii from Pheidole floridana by the matte base of the gaster in the former and the glossy gaster in the latter. Indeed, the type specimens of Pheidole floridana from Coconut Grove are consistent with this characterization (CASENT0904424, CASENT0904425). Naves wrote that the Miami area was the only place where he was able to locate Pheidole floridana . Pheidole anastasii , in contrast, was reported by Naves as widely distributed across the state.

Deyrup et al. (1988), lamenting the taxonomic confusion surrounding Pheidole floridana , Pheidole flavens and Pheidole anastasii in Florida, stated, "Traditionally ( Creighton 1950; Smith 1979) the name Pheidole floridana has been applied to a widespread upland species that has a distinctive matte area on the base of the first gastral tergite and very evenly rugose head … This is the species we report from the Keys [Florida]." Subsequent reviews of Florida ants have thus excluded Pheidole anastasii from their lists ( Deyrup 2003; Deyrup et al. 2000; Moreau et al. 2014). Wilson (2003) followed Deyrup in treating all outdoor populations from the United States as Pheidole floridana , but conceded that his concept of Pheidole floridana could represent a northern geographic variant of Pheidole bilimeki or an endemic species modified by intergradation with a Pheidole bilimeki immigrant population.

With respect to all outdoor North American records, we follow Wheeler (1932), Smith (1933), and Naves (1985) in treating the localized glossy-gaster Pheidole floridana as distinct from the widespread matte-gaster species referred to as Pheidole anastasii by the aforementioned authors. However, the relatively short scapes and posteriorly broad heads of the minor workers, together with the habitat and nesting preferences of the matte-gaster species suggests the name Pheidole bilimeki Mayr more accurately applies to this widespread taxon than does Pheidole anastasii Emery. The issue is discussed in further detail under the Pheidole bilimeki section.

Biology.

Pheidole anastasii , named by Emery on behalf of Sig. Anastasio Alfaro, is a Neotropical species that is occasionally found indoors beyond its native range. Although at least some arboreal colonies appear to be polydomous, Pheidole anastasii is a low-impact adventive that has thus far shown little capacity for becoming a significant invader. The biology of Pheidole anastasii , especially across its native range in Costa Rica and in comparison to Pheidole bilimeki was reviewed by Longino and Cox (2009). The species was noted as being among the most abundant ants in the low arboreal forest understory of La Selva Biological Station (Costa Rica). Although tolerant of disturbance, Pheidole anastasii requires some vegetation cover and does not occur in open areas. All collections reviewed by Longino and Cox were from wet forest habitats. Most were from below 500 m elevation, but several ranged to a maximum of 1200 m. The propensity for the species to be inadvertently transported to greenhouses across the world is predicted by its arboreal foraging and nesting habits. Longino and Cox (2009) observed the species nests in almost any kind of cavity or sheltered space, including live stems, and that workers often build galleries and tunnels with carton or earthen construction. The species was reported to occur in lowland second growth, evergreen forest, coffee plantation, limestone, ravine, mixed hardwood-pine forest, wet forest, on karst, and cloud forest. It was also reported to nest in dead sticks and branches on or above the forest floor, under bark flaps on tree trunks, beneath epiphytes and under stones.

Distribution.

Pheidole anastasii is a Neotropical native that ranges from Mexico to southern Central America or northern South America. We consider many of the outdoor records of Pheidole anastasii from the southern United States to refer instead to Pheidole bilimeki (see discussion above). There are, however confirmed records of the species from heated indoor locations - especially greenhouses. In North America there are records from hothouses in Washington D.C. and New York ( Longino and Cox 2009), and also from Massachusetts. In Europe, the Netherlands occurrences reported as Pheidole anastasii by Boer and Vierbergen (2008) refer to Pheidole bilimeki (Boer, pers. comm.). The records from Denmark and Norway might also refer to Pheidole bilimeki , but until specimens can be examined we follow the authors’ use of Pheidole anastasii ( Birkemoe and Aak 2008; Lomholdt 1986).

Risk statement.

Pheidole anastasii is a synanthropic species with a high tolerance for habitat disturbance. It is occasionally found in human habitations and in greenhouses. There is little indication that is causes significant impact to agricultural systems or native ecosystems. The species is a quarantine risk, and is thought to be transported with fresh plant material.