Abstract
The rarely collected ant Lenomyrmex inusitatus Fernández 2001 is recorded for the first time in Ecuador. The queen is described. The new record is the southernmost limit of distribution for the genus. A key to the workers of the six Lenomyrmex species and a key for the known queens are provided.
1. Introduction
The myrmicine ant genus Lenomyrmex Fernández and Palacio 1999 includes six species rarely collected from Costa Rica to Ecuador [1–3]. The genus is characterised by elongate mandibles bearing a series of minute peg-like denticles that arise behind the masticatory margin, by frontal lobes that are poorly expanded laterally, by large and deep antennal fossae, and by pedunculate petiole, with a poorly defined node [1]. The fact that Lenomyrmex possesses both primitive (e.g., promesonotal suture well developed) and derived (e.g., specialized morphology of the mandibles) characters makes ascertaining its correct phylogenetic position challenging [1, 2, 4]. The genus was tentatively placed in its own tribe, Lenomyrmecini [5], but its position within the Myrmicinae remains to be determined [5]. Preliminary results of a phylogenetic analysis (Ant-AToL project, http://www.antweb.org/atol.jsp) indicate that Lenomyrmex falls within a clade of predominantly New World ants that includes the tribes Attini, Cephalotini, Dacetini, and the genus Pheidole (T. Schultz and P. Ward, comm. pers.).
The worker of Lenomyrmex inusitatus Fernández 2001 is distinguished from other Lenomyrmex workers by smooth and shiny mesosoma with well-developed propodeal spines and by the foveolate-striate sculpture covering all the dorsal surface of its head [2]. L. inusitatus has an unusual distribution since it is the single Lenomyrmex species recorded east of the Andes [2]. Nevertheless, it was previously only known from the type locality (“Territorio Kofanes”, Nariño, Colombia). Here, the species is recorded for the first time in the Eastern Cordillera of the South-Ecuadorian Andes.
Among Lenomyrmex species, the queen caste has been described only for L. mandibularis Fernández and Palacio 1999 and L. wardi Fernández and Palacio 1999. In this paper, we provide the first record and a description of the queen of L. inusitatus.
2. Materials and Methods
The sampling of Lenomyrmex in the Ecuadorian Andes is part of a rainfall exclusion experiment [6] and was based on the Winkler extraction method. The leaf litter inside a 0.25 or 0.5-m² quadrat was collected and sifted and its fauna was extracted during 48 h. All specimens were collected close to the Podocarpus National Park, within the “Copalinga” property, at 1420 m (Zamora-Chinchipe province, Ecuador). Vegetation corresponds to an evergreen lower montane forest [7]. Mean annual precipitation is about 2100 mm. Mean temperature in the leaf litter from December 2009 to May 2010 was 18.5°C (min–max: 15.7–22.2°C).
A worker (no. 4042619, from sample no. 40426) and a queen (no. 4042602, from the same sample) have been imaged (Figures 1 and 2, resp.) and are available at http://projects.biodiversity.be/ants.
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Measurements and Indices
All measurements are in millimeters. The abbreviations are as follows:
HL:Head length, measured in full face view, from the anterior margin of the medial lobe of the clypeus to the posterior border of the head (excluding the mandibles).HW:Head width, the maximum width of the head measured in full face view, excluding the compound eyes.ML:Mandible length, the maximum length of the mandible measured in dorsal view, from the anteriormost portion of the head to the apex of closed mandibles.EL:Eye length, the maximum diameter of the eye in frontal view.SL:Scape length, excluding the basal condyle and the neck.WL:Weber’s length, measured diagonally in lateral view from the anterior edge of the pronotum to the posterior edge of the propodeal lobe.PL:Petiole length, the axial distance from the dorsal corner of the posterior peduncle to the nearest edge of the propodeal lobe.PW:Petiole width, the maximum transverse distance across the node measured in dorsal view.PPL:Postpetiole length, the axial distance from the base of the node in front to the tip of the posterior peduncle measured in lateral view.PPW:Postpetiole width, the maximum transverse distance across the postpetiole in dorsal view.GL:Gaster length, in lateral view, from the anterior edge of the first tergum to the posterior edge of the last visible tergum.GW:Gaster width, in dorsal view, the maximum transverse distance across the gaster.TL:Total length measured in lateral view (ML + HL + WL + PL + PPL + GL).OI:Ocular index, EL/HW × 100.CI:Cephalic index, HW/HL × 100.SI:Scape index, SL/HL × 100.
Queens and workers have been deposited at the Royal Belgian Institute of Natural Sciences, Brussels, Belgium, (RBINS), the Laboratorio de Entomología—Universidad Técnica Particular de Loja, Loja, Ecuador (UTPL), and the Museo de Insectos, Instituto de Ciencias Naturales—Museo de Historia Natural, Universidad Nacional de Colombia, Santafé de Bogotá D.C., Colombia (ICN).
3. Results (Tables 1 and 2)
3.1. Material Examined
A total of 34 workers and two dealated queens of Lenomyrmex inusitatus were collected. The worker (Figure 1) corresponds to the description of the holotype [2], except that it is slightly smaller.
Workers
ECUADOR: Zamora-Chinchipe province: Zamor-a: Bombuscaro: Copalinga property; Lat: −4.083; Long: −78.967; 26.IV-01.V.2010; collected by Delsinne T. and Arias Penna T.; 34 workers in 23 Winkler samples (number of specimens/Winkler sample: 1–4); sample codes: 40343, 40367, 40369, 40374, 40375, 40382, 40387, 40391, 40395, 40417, 40418, 40424, 40426, 40428, 40437, 40439, 40440, 40446, 40449, 40453, 40455, 40457, 40459, 40461; RBINS, UTPL, ICN.
Worker Measurements (no. 4042619)
TL 4.23, HL 0.74, HW 0.64, ML 0.41, SL 0.60, EL 0.16, WL 1.15, PL 0.62, PW 0.20, PPL 0.30, PPW 0.24, GL 1.11, GW 0.76, CI 86, OI 24, SI 81.
Queens
ECUADOR: Same data as workers; two queens in two Winkler samples; sample codes: 40426 and 40343; RBINS, UTPL.
Queen Measurements (no. 4042602)
TL 4.34, HL 0.75, HW 0.65, ML 0.41, SL 0.59, EL 0.20, WL 1.16, PL 0.64, PW 0.21, PPL 0.27, PPW 0.24, GL 1.11, GW 0.78, CI 86, OI 31, SI 79.
Queen Diagnosis (Figure 2)
The queen is similar to the worker [2] but differing in the following characters: anterior margin of clypeus mostly convex, with a slight median notch or concavity; compound eyes bigger, with 11-12 facets in maximum diameter; three ocelli present; mesosoma robust; dorsum of pronotum smooth and shiny, with sparse punctures; mesoscutum foveolate, with longitudinal striae; scutellum and axillae foveolate, with smooth and shiny interspaces; dorsum of propodeum completely smooth and polished; propodeal spines long and stout but shorter than distance between their bases; mesopleuron with anepisternum clearly separated from katepisternum by a suture; lateral face of pronotum, anepisternum, katepisternum, metapleuron, and lateral face of propodeum mostly smooth and shiny, with some sparse punctures; punctures of lateral and dorsal faces of petiole and postpetiole more defined and deeper than in workers; short and appressed pilosity more abundant on mesosoma than in workers.
4. Discussion
Lenomyrmex inusitatus is, with L. wardi and L. foveolatus, the third Lenomyrmex species collected in Ecuador [1, 8]. To our knowledge, the new record represents only the tenth locality known for the entire genus and constitutes its southernmost limit of distribution. The range of the species and of the genus increases nearly 510 km and 415 km to the South, respectively. Although data remain insufficient to understand the biogeography of Lenomyrmex, it is interesting to note that the new record confirms the presence of L. inusitatus on the Eastern side of the Cordillera Oriental of the Andes.
Lenomyrmex species were collected from elevations close to sea level to 1800 m but seem to be mainly restricted to mid-elevations, that is, 1100–1500 m ([1–3], this study). The degree of queen-worker dimorphism is weak, suggesting small colony sizes and absence of claustral independent colony foundation [9]. Lenomyrmex ants seem always locally rare and it is in fact the first time that up to 34 workers have been collected within a relatively small area (400 m²). A thorough inspection of the dead wood laying on the ground and of soil samples failed to uncover any nest of L. inusitatus. This and the fact that both workers and dealate queens were extracted from the leaf litter (Winkler method) may indicate that this species nests and forages in the leaf litter. The unusual morphology of the mandibles suggests that Lenomyrmex is a specialist predator on an unknown prey. This habit is possibly linked to its apparent rarity and restricted elevational distribution. More data are needed to accurately determine the biology and biogeography of these interesting ants.
N.B. After submitting the paper, two additional workers were found within a soil sample, at slightly higher elevation (1500 m), within the “Copalinga” property. The two workers were maintained alive during six days. They moved relatively slowly and feigned death when disturbed. They did not feed on any offered food items (alive and dead termites, millipedes, mites, various insect parts, sugar/water, tuna, biscuits). The information for these specimens are ECUADOR: Zamora-Chinchipe province: Zamora: Bombuscaro: Copalinga property; Lat: −4.082; Long: −78.968; 13.IV.2011; collected by Delsinne T. and Arias Penna T.; two workers in one soil sample (= a thorough visual search for ants for twenty person-minutes from a -cm core of soil); specimen codes: 4649901 and 4649902; RBINS.
Acknowledgments
The authors thank C. Vits and B. de Roover from “Copalinga” for allowing them to sample ants within their property, J. Bendix, the “Deutsche Forschungsgemeinschaft” (DFG)-Research Unit 816, and the team of the “Estación Científica San Francisco” for allowing and extensively facilitating their work, I. Bachy, Y. Laurent, and M. Leponce for ant digitization, J. Peña and T. M. Arias Penna for assistance with fieldwork, and two anonymous referees for helpful suggestions on the paper. This research was funded by the Belgian Science Policy (BELSPO) and was carried out in the framework of EDIT (European Distributed Institute of Taxonomy). In accordance with section 8.6 of the ICZN’s International Code of Zoological Nomenclature, printed copies of the edition of Psyche containing this article are deposited at the following six publicly accessible libraries: Green Library (Stanford University), Bayerische Staatsbibliothek, Library—ECORC (Agriculture & Agri-Food Canada), Library—Bibliotheek (Royal Belgium Institute of Natural Sciences), Koebenhavns Universitetsbibliotek, University of Hawaii Library.