Formica fennica

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Formica fennica
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Formicini
Genus: Formica
Subgenus: Coptoformica
Species: F. fennica
Binomial name
Formica fennica
Seifert, 2000

A polycalic colony comprising 40 nests was found near Puhos/Finland on 13 July 1996. It spread over a fresh-dry grassland that was situated between the southern margin of a medium-aged Betula wood and the S-exposed slope of a road ditch. Plant species growing near the nests were Dianthus sp., Prunella sp., Galium sp., Melampyrum nemorosum, Dactylis glomerata, Potentilla erecta, Scabiosa sp., Alchemilla sp. The nest construction was of typical Coptoformica type and the largest nest mound measured 70 × 45 cm (diameter by height). Queens were deep in the soil and only three dealate queens could be collected at ground level. The Caucasian sample of fennica was found on a short-grassy, 20°N-exposed mountain pasture at 1600 m and collected from an isolated monodomous colony. The large size of the workers in this nest strongly suggests monogyny. (Seifert 2000)

At a Glance • Temporary parasite  

 

Identification

Seifert (2000) - Close relationship of Formica fennica to Formica manchu is indicated by the similarity of workers. The two taxa differ from all other Palaearctic Coptoformica species by significantly longer heads (CL/CW 1.067-1.073). F. manchu and fennica further share the character combination of conspicuous eye hairs (mean EyeHL 23-28 μm), complete absence of setae from first gaster tergite (mean TERG 2.9-3.4), rare occurence of setae in the ocellar region, and very dilute tergite pubescence (mean sqrtPDG 7.6-7.9).

The Formica manchu cluster represented by seven nest samples with 34 workers from Mongolia, N Tibet, and Manchuria differs from the W Palaearctic fennica cluster represented by six nest samples with 27 workers by significantly larger SL/CL (p < 0.0001) and by significantly smaller TERG (p < 0.001), nHTFL (p < 0.0001), and sqrtPDF (p < 0.0001). The manchu workers constantly show an additional set of conspicuous setae in the anterior portion of the sculptured surface of third tergite and the setae on outer hind tibial flexor margin are shorter, finer, and less numerous than in fennica (compare Figs 2, 17C and 18C). In the fennica workers, setae may be present at the caudal margin of third tergite but never in the anterior portion of the sculptured surface of third tergite. A numeric separation of the fennica and manchu workers is possible with by a linear discriminant score D(4) calculated as D(4) = 0.155 sqrtPDF + 0.134 TERG + 0.064 nHTFL-0.416 SL/CL.

Formica fennica differs from Formica bruni by the much longer and much more dilute frontal and tergite pubescence, by the longer head, and the larger nHTFL; sometimes the acute occipital corners may be diagnostic.

The differences between the workers of fennica and bruni are repeated in the queens. An additional difference is the significantly larger body size of the fennica queens.

Single workers of extremely pilosity-reduced Formica exsecta morphs may be confused with fennica. However, nest sample means of three workers provide a safe separation with the characters nCOXA (exsecta 2.6-15.5, fennica 0.4-1.4), TERG (exsecta 1.0-2.33, fennica 3.0-4.0), OceSet (exsecta 0.33-1.0, fennica 0-0.33), and ClySet (exsecta 2.0-4.5, fennica 1.0-2.0) as confirmed for 88 nest samples of exsecta and six nest samples of fennica. The usually more acute occipital corners of fennica are no reliable discriminator from exsecta because of big intraspecific variability of head shape in Coptoformica.

Males: Eyes with numerous long hairs; EyeHL 30-45 μm. Clypeus without setae of third to fifth level; ClySet 1-2. Mesosoma with few semierect setae. Craniad profile of forecoxae with three to five standing setae. Pubescence in the ocellar triangle and on second gaster tergite dilute and long; sqrtPDF 4.1-4.6, sqrtPDG 5.0-7.3. Head elongated; CL/CW 0.853 ± 0.017. Separation from pilosity-reduced males of Formica exsecta difficult.

Seifert (2019) provides details for separating this species from the morphologically similar Formica exsecta.

Keys including this Species

Distribution

Seifert (2019): Formica fennica is currently known from southern Finland, Azerbaijan and Georgia. Data on zoogeography combined with the species' narrow habitat spectrum and climate niche indicate that it is unlikely to occur in Norway (the report of its occurrence in Norway by Suvak (2013) was based on a misidentification of the Rubens morph of F. exsecta by Seifert in 2012). As F. fennica apparently does not spread north to the boreal zone and does not elevate to the subalpine zone (Seifert 2018), the high Skandinavian Fjäll should represent a strong distributional barrier for post-glacial immigration from the east. The much narrower climate niche of F. fennica is explicitly indicated by the mean air temperature TAS of the sites from 1 May to 31 August. TAS is 11.98 ± 3.28 [4.75, 18.44] °C for 111 sites of F. exsecta and 13.78 ± 0.90 [12.72, 15.09] °C for the six known sites of F. fennica. Immigration to Norway, if at all, appears only possible via Skåne (Sweden) and along the Oslo Fjord.

It should be noted that while F. fennica is known from Azerbaijan and Georgia, some 2500km southeast of the Finnish population and in a very different climatic zone, no mention of the significance of this distribution pattern or its potential impact on habitat preferences within Scandinavia was made by Seifert (2019).

Distribution based on Regional Taxon Lists

Palaearctic Region: Azerbaijan, Finland (type locality), Georgia.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

As a member of the subgenus Coptoformica this species is likely to be a temporary parasite of another species of Formica, but its host is unknown.

Life History Traits

  • Compound colony type: temporary parasite
  • Colony founding: social parasite
  • Nest site: thatch mound

Castes

Worker

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • fennica. Formica fennica Seifert, 2000a: 534, figs. 1F, 2-5, 12 (w.q.m.) FINLAND.

Type Material

1 queen holotype and 6 worker paratypes are labelled “FIN: 62.07N, 29.48E, road No. 71, Kitee-17W, Puhos-6.5WNW, leg. Seifert 1996.07.13-119”; 1 queen paratype, 5 worker paratypes from the same polycalic colony and same date but different nest number “FIN...1996.07.13-86”; 3 male paratypes, 6 worker paratypes from the same polycalic colony and same date but different nest number “FIN...1996.07.13-105”; 5 worker paratypes labelled “FIN: 63.27N, 27.10E, Iisalmi-13 km S, Kotikylä, 1998.07 leg. J. Sorvari”; 7 paratype workers labelled “CAU: 42.23N, 45.42E, Schenako, 1600 m, 1985.08.01, 20°N-exp. Kurzgrasige Weide”. All these mounted type specimens (plus 55 worker paratypes in ethanol) are stored in SMN Goerlitz. In the collection of Zoological Museum of the University of Turku Turku are stored 1 paratype queen “FIN: 62.07N, 29.48E, road No. 71, Kitee-17W, Puhos-6.5WNW, leg. Seifert 1996.07.13” and 1 worker paratype “FINLAND: Ilomantsi, Maukkula (695: 69)”.

Taxonomic Notes

Hakala et al. (2018) note that the description of F. fennica was based on morphological characters and the species status has not been confirmed by molecular methods. In their study, they used thirteen DNA microsatellite markers and a partial mitochondrial COI gene sequence to assess the species status of F. fennica, by comparing the genetic variation among samples identified as F. fennica and six other boreal Formica (Coptoformica) species. Most of the species studied form separate, discontinuous clusters in phylogenetic and spatial analyses with only little intraspecific genetic variation. However, both nuclear and mitochondrial markers fail to separate the species pair Formica exsecta and F. fennica despite established, although not clear cut, morphological differences. The genetic variation within the F. exsecta/fennica group is extensive, but reflects spatial differences rather than the proposed morphological differences. It is impossible to divide these samples into two separate species based on the molecular data. The geographically restricted sampling did not allow full species delimitation, but the result concerning the status of F. fennica is clear. Finnish F. fennica populations studied so far should not be considered a separate species, but merely a morph of F. exsecta.

Seifert (2019) considered the work of Hakala et al. (2018) and noted that they found no genetic differences between two subjectively established morphological clusters. Within Hakala et al.'s material, they classified 38 samples as Formica exsecta and 33 samples as F. “fennica”. Seifert speculates that the lack of separation by microsatellite data in these samples is easily explained by the fact that >90% of their F. “fennica” samples actually belonged to the Rubens morph of F. exsecta. However, Seifert (2019) did not explain why the remaining ca. 10% of the samples, representing true F. fennica, were not distinct from F. exsecta. This lack of separation suggests that Hakala et al.'s conclusions hold, even given the suggested misidentification of the majority of samples.

Seifert (2019) says he was prompted by the paper of Hakala et al. (2018) to perform another attempt to convince morphology-based alpha-taxonomists to abandon idiosyncratic approaches and to adopt reproducible numeric character description and evaluation when aiming to investigate the real structure of biodiversity. The counterpoint to this is that Seifert's NUMOBAT procedures rely on statistical analyses of morphology alone while ignoring genetic data and evolutionary considerations. This overlooks the principles of integrated taxonomy where all relevant data should be considered and explained (Schlick-Steiner et al., 2010; note that Seifert is a co-author on this paper). One has to wonder if these "morphology-based alpha-taxonomists" are unnecessarily limiting their contributions or, in some cases, the old saying "There are three kinds of lies: lies, damned lies, and statistics" might be relevant.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Medium-sized species (CL 1340 ± 110, 1087-1514; CW 1257 ± 106, 1012-1426). Head with acute and well-pronounced occipital corners (Fig. 1F) and significantly longer than in other European species (CL/CW 1.067 ± 0.016, 1.036-1.103). Scape of average length (SL/CL 0.989 ± 0.021, 0.945-1.035). Setae only present on anterior clypeus (Fig. 3, ClySet 1.67 ± 0.56,1-3). Lateral semierect setae in the ocellar triangle rarely present (OceSet 22%). Eye hairs strongly developed (EyeHL 23.2 ± 3.1, 17-30). Pubescence hairs in the occellar triangle long and very sparse (sqrtPDF 6.68 ± 0.67, 5.19-8.19; Figs 4; 12). Craniad profile of forecoxae without or very few subdecumbent setae (nCOXA 0.91 ± 0.83, 0-3). Dorsal mesosoma, lateral metapleuron and ventrolateral propodeum without standing setae (nMET 0.0 ± 0.0). Outer edge of the hind tibial flexor side with well-developed subdecumbent setae and subdecumbent pubescence (Fig. 2, nHTFL 8.13 ± 2.33, 4.0-14.0). Semierect setae on gaster tergites beginning at the posterior border of third to fifth tergite (TERG 3.37 ± 0.56, 3-5), anterior part of third tergite always without setae. Pubescence density on first gaster tergite very low (sqrtPDG 7.89 ± 0.46, 6.99-8.73).

Queen

Rather large, in size between Formica exsecta and Formica bruni (CL 1543 ± 47, 1490-1582; CW 1520 ± 26, 1492-1544; ML 2611 ± 53, 2551-2651). Head significantly slender than in exsecta (CL/CW 1.015 ± 0.014, 0.999-1.025), scape of average length (SL/CL 0.918 ± 0.008, 0.911-0.927). Setae restricted to anterior clypeus (ClySet 1.67 ± 0.58, 1-2). Clypeus lateral of the tentorial pit level with pubescence hairs surpassing the anterior margin by more than 10 μm. Lateral semierect setae in the ocellar triangle absent. Eye hairs long (EyeHL 35.3 ± 5.5, 30-41). Pubescence in the occellar triangle decumbent, very long, and sparse PDF 6.07 ± 0.73, 5.55-6.91). Occipital corners of head with long, decumbent to almost appressed pubescence (OccHD 27.7 ± 2.1, 26-30). Dorsal head surface relatively matt and weakly sculptured (GLANZ 1.33 ± 0.29, 1.0-1.5). Craniad profile of forecoxae without or very few semierect setae (nCOXA 0.67 ± 0.76, 0-1.5). Mesonotum with decumbent to appressed pubescence and without real setae (MnHL 63.6 ± 53.2, 0-97, these are long pubescence hairs). Outer edge of the hind tibial flexor side with numerous subdecumbent setae and long decumbent pubescence (nHTFL 9.50 ± 1.80, 8.0-11.5). Semierect setae on gaster tergites beginning on the fourth tergite (TERG 4.0±0.0). Pubescence on first gaster tergite long and very sparse (sqrtPDG 8.11 ± 0.81, 7.47-9.02).

References