Temnothorax algiricus

Temnothorax algiricus (Forel, 1894) Figure 5 = Leptothorax angustulus var. brunea Santschi, 1918 syn. n. = Leptothorax gazella Santschi, 1932 = Leptothorax gazella var. monticola Santschi, 1932 = Temnothorax mediterraneus Ward, Brady, Fisher, & Schultz, 2014 syn. n. = Temnothorax atlantis veneris Galkowski & Cagniant, 2017 syn. n. Investigated type material: 2 syntype workers of algiricus (Msila Forest, Oran, Algeria) from the MHNG (Geneva, Switzerland), being the mid and bottom specimens of a pin in which the top worker had its head missing with the labels “TYPUS // L. angustulus / Nyl / / [worker symbol] / v. algiricus Forel / Foret de Msila / (Algerie) // Coll. A. Forel // algiricus Forel ”. 1 syntype worker of T. algiricus investigated through AntWeb (CASENT0909011 — MHNG, Geneva, Switzerland). 1 syntype worker of brunea investigated through AntWeb (CASENT0912895 — NHMB, Basel, Switzerland). 1 syntype worker of gazella investigated through AntWeb (CASENT0912940 — NHMB, Basel, Switzerland). 1 syntype worker of monticola investigated through AntWeb (CASENT0912941 — NHMB, Basel, Switzerland). 1 syntype worker of veneris investigated through AntWeb (CASENT0917823 — SIZK, Kiev, Ukraine). 1 syntype worker of mediterraneus (= Leptothorax angustulus kraussei Emery, 1916) (Cagliari, Sardinia, Italy) investigated through AntWeb (CASENT0904755 — MSNG, Genoa, Italy). Investigated non-type material: 79 workers from 39 colonies from Algeria, Italy, Croatia, France, and Spain. Worker redescription. Body either concolor dark brown to blackish, or bicolored, with parts or the entirety of the mesosoma and nodes being reddish or ferruginous and contrasting with the head and gaster. Antennae, legs, and mandibles often lighter than the body. Head subrectangular with rounded margin, clypeus and mandibles rounded. Antennae of 12 segments, antennal clubs of 3 segments. Compound eyes are ovoidal. The mesosoma may or not present a slight metanotal impression visible in lateral view on the dorsal profile. Propodeal spines relatively long and erect, sometimes arched in dorsal view, and slightly curved in lateral view. The petiole has a triangular shape, with a small tooth-like subpetiolar process. The postpetiole has an ordinary ovoidal lateral profile and may appear subhexagonal in dorsal view. Surface sculpture is generally fine, with larger parts of the head becoming dull in smaller specimens; a fine irregular sculpture in the rest of the body, with some striae on the dorsum of the mesosoma, often on the head, and always a central carina in the clypeus. Very sparse, usually erect setae all over the body; dense, fine, and mostly adpressed pilosity on the antennae. Diagnosis. Compared to T. trabutii, the propodeal dorsum has a gentler transition with the rest of the mesosoma and is less steep [PropH2/PropH1: 0.897 (0.732, 1.069)]. Several morphometric characters have an intermediate position between T. atlantis and T. trabutii. Spines form a narrower angle with the mesosoma than in T. atlantis but not as much as in T. trabutii [no range overlaps in SpANG: 130 (119, 139)]. On average, the propodeal spines are shorter than in T. trabutii but longer than in T. atlantis [SPST/CS: 0.329 (261, 409)]. In dorsal view these are divergent at first but may curve inwards in their distal part, the ratio between their maximum width and the width between their tips being averagely larger than in T. atlantis but smaller than in T. trabutii [SPWI/SPBA: 1.382 (1.108, 1.750)]. The ratio between the spines divergence and their length is also intermediate [SPWI/SPST: 0.829 (0.628, 1.222)]. Pigmentation can be concolor dark, or bicolored with dark head and gaster contrasting with the reddish mesosoma and nodes (as in the types of mediterraneus and veneris). Distribution. Southern Spain, Balearic Islands, Morocco, Algeria, Tunisia, Sicily (including circum-Sicilian islands), Sardinia, Corsica, Italian peninsula (including the Tuscan archipelago), and Croatia. Records from the Maltese Islands should be attributed to this species. Taxonomic history. Temnothorax algiricus was described by Forel (1894) from Algeria (Oran province) as a North African variety of the European T. angustulus with a different color. Some following authors kept considering it a variety of angustulus (Santschi 1911; 1918; Emery 1924; Bolton 1995). However, it was mostly treated as a species since Cagniant (1968) elevated it to species rank, although he did not provide a justification for his decision (e.g., Cagniant & Espadaler 1997; Bračko 2006; Cagniant 2006; Guillem 2009; Borowiec 2014; Galkowski & Lebas 2016; Lebas et al. 2016; Galkowski & Cagniant 2017). Later, Cagniant & Espadaler (1997) synonymized under T. algiricus four other taxa. Nonetheless, Galkowski & Cagniant (2017) could not provide a morphological distinction from T. mediterraneus Ward et al., 2014. The name T. algiricus was almost exclusively used in North Africa, with two exceptions: Bračko (2006) listed it among the species of Croatia, and Guillem (2009) recorded it in the Balearic Islands. Leptothorax angustulus algiricus bruneus Santschi, 1911 is an unavailable infrasubspecific name (Santschi 1911), while Santschi (1918) made the first available use of the name as Leptothorax angustulus var. brunea Santschi, 1911. It was described from Algeria (Yakouren) and defined as more strongly sculptured than T. algiricus, darker than T. trabutii, and “transitional” to silvanus (Forel, 1907). Cagniant & Espadaler (1997) synonymized this taxon under T. atlantis, considering it a dark-colored variety and speculating that the darker pigmentation could be caused by an association with more humid environments. Galkowski & Cagniant (2017) raised it to the subspecies level as T. atlantis brunea, again suggesting the same mechanism behind the dark pigmentation and stronger sculpture. In general, selective pressure for darker pigmentation in ants has been demonstrated to be associated with either high UV exposure on one hand or low temperatures on the other (Law et al. 2019; Bishop et al. 2021). Leptothorax gazella Santschi, 1932 was described from Tunisia (Sousse, see Santschi 1932) and said to be similar to “ L. angulatus ” (almost certainly a mistype of T. angustulus, as no “ L. angulatus ” has ever been described). Santschi (1932) differentiated L. gazella from “ L. angulatus ” due to the first having a less pronounced metanotal impression. In the same paper, Santschi (1932) described L. gazella var. monticola, also from Tunisia (Aïn Draham), based on a darker gaster and minor sculpture differences from L. gazella s. str. Both taxa were considered synonyms of T. algiricus by Cagniant & Espadaler (1997) without providing an explanation. Temnothorax mediterraneus Ward, Brady, Fisher, & Schultz, 2014 is a replacement name for Temnothorax kraussei Emery, 1916 (= Leptothorax angustulus kraussei Emery, 1916), a junior secondary homonym of Temnothorax kraussei Emery, 1915. The latter is a socially parasitic species originally described as Epymyrma kraussei, but the genus Epymyrma was found to be a synonym of Temnothorax by Ward et al. (2014). Under either of the two different names, this species has long been considered part of the faunas of Italy (Baroni Urbani 1971; Schifani 2022), France (Casevitz-Weulersse & Galkowski 2009), Malta (Schembri & Collingwood 1995), and Spain (Arcos & Garcia 2023). The original description by Emery (1916) as a variety of T. angustulus (Leptothorax angustulus var. kraussei) considered it to occur in Corsica, Sardinia, and Sicily, and the type is from Sardinia. Emery (1916) distinguished the var. kraussei by having a stronger head sculpture and sometimes a ferruginous mesosoma (in other specimens very dark). While Baroni Urbani (1971) treats T. mediterraneus as a distinct species based on its sympatry with T. angustulus in Sicily, Rigato & Toni (2011), in a faunistic paper on Sardinian ants, suggested potential synonymy between T. mediterraneus and T. angustulus. Eventually, Espadaler & Collingwood (1989), working on Iberian ants, defined the presence of a middle clypeal carina and the reddish mesosoma as distinctive features separating T. mediterraneus from T. angustulus. Ultimately, the taxon was redescribed by Galkowski & Cagniant (2017), who further demonstrated its distinctiveness from T. angustulus. In addition, they separated the populations of mainland Iberia and mainland France that were until that point considered to belong to T. mediterraneus by describing them as T. continentalis, while considering T. mediterraneus a valid species exclusive to Corsica, Sardinia, and Sicily. Coherently with the original description, T. mediterraneus was defined as a taxon of variable pigmentation (with a reddish to dark mesosoma), different from T. continentalis because of the longer and differently shaped spines, and together with T. continentalis separate from T. angustulus by the middle clypeal carina (Galkowski & Cagniant 2017). However, Galkowski & Cagniant (2017) could not identify any character separating T. mediterraneus from T. algiricus. Leptothorax angustulus trabutii veneris Santschi, 1918 is an unavailable (infrasubspecific) name (Bolton 1995). Santschi (1918) described it from Tunisia (Le Kef) as similar in color to T. trabutii but characterized by a stronger sculpture and different spines. Galkowski & Cagniant (2017) described the subspecies T. atlantis veneris based on one of the syntypes of the taxon described by Santschi, providing a valid name for it. However, they could not find characters to separate the subspecies veneris from the nominal subspecies of T. atlantis (Galkowski & Cagniant 2017). At the same time, Galkowski & Cagniant (2017) also considered other syntypes (all from the same locality), including “CASENT0912897”, as “typical T. mediterraneus ” and one as T. santschii (Forel, 1905) due to its longer spines [T. santschii is a species with a long petiolar peduncle considered clos