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Miniaturized queens, microgynes, are regarded as an alternative reproductive strategy sparsely present through the ant world. The described roles of miniaturized queens include alternative short-distance dispersal morphs, an adaptation to polygyny and inquiline parasites. Some of these inquiline parasite microgynes have been described as a separate species from their host. In the poneromorph group, miniaturized queens are only reported in two Mexican populations of two Ectatomminae: Ectatomma tuberculatum, in which small queens represent an inquiline species (Ectatomma parasiticum) and Ectatomma ruidum. E. ruidum presents apparently facultative polygyny with microgynes. We used mitochondrial DNA markers and newly developed microsatellite loci to investigate the status as well as the role of microgynes in E. ruidum. We confirmed that microgynes and macrogynes are from the same species. This species is almost exclusively monogynous and monoandrous, supernumerary dealate queens of both types being actually daughters of the mother queen. An apparently polygynous nest was more often headed by a macrogyne than a microgyne. We didn't find any inbreeding or isolation by distance in the studied population, indicating that new gynes are inseminated by unrelated males and can establish a new nest far from their natal nest. However, re-adoption of daughter queens seems to be the rule and rate of microgyny appears to be linked to nest density and environmental factors.

Among social parasites, workerless inquilines entirely depend on their host for survival and reproduction. They are usually close phylogenetic relatives of their host, which raises important questions about their evolutionary history and mechanisms of speciation at play. Here we present new findings onEctatomma parasiticum, the only inquiline ant described in the Ectatomminae subfamily. Field data confirmed its rarity and local distribution in a facultative polygynous population ofE. tuberculatumin Mexico. Genetic analyses demonstrated that the parasite is a sibling species of its host, from which it may have diverged recently. Polygyny is suggested to have favored the evolution of social parasite by sympatric speciation. Nevertheless, host workers from this population were able to discriminate parasites from their conspecifics. They treated the parasitic queens either as individuals of interest or as intruders, depending on their colonial origin, probably because of the peculiar chemical profile of the parasites and/or their reproductive status. We suggest thatE. parasiticumcould have conserved from its host sibling species the queen-specific substances that produce attracting and settling effect on workers, which, in return, would increase the probability to be detected. This hypothesis could explain the imperfect social integration of the parasite into host colonies.

Ectatomma parasiticum Feitosa & Fresneau, sp. nov. Figures 1, 2 Holotype gyne. MEXICO: Apazapan, Veracruz, 19 �� 19 ��� 38 ���N 96 �� 43 ��� 21 ���W, ix. 1999, D. Fresneau col. [INEC]. Paratypes. same data as holotype (1 gyne) [CPDC]; (1 gyne) [UNCB]; (1 gyne) [INEC]; vii. 2000, D. Fresneau & R. Hora cols. (1 gyne) [LACM]; (2 gynes) [MZSP]; (1 gyne) [USNM]. Diagnosis. Size relatively small (WL approximately 3.80 mm); clypeus and frontal area without sculpture; antennal scapes longer than the maximum head width (SI> 108); petiole relatively thick in lateral view. Gyne description. Holotype (paratypes): HL 2.10 (2.06���2.16); HW 1.85 (1.73���1.88); SL 2.04 (1.92��� 2.06); EL 0.51 (0.50���0.58); PW 1.69 (1.62���1.77); WL 3.88 (3.65���4.04); PTL 0.79 (0.78���0.88); PTW 0.92 (0.92���1.07); CI 88.07 (84.11���88.89); SI 110.42 (108.57���113.04); OI 27.50 (27.50���31.25); PTI 85 (82.14��� 85.71). Color yellowish brown to dark reddish brown, including appendages. Mandibles finely and densely striate, with sparse piligerous punctures; clypeus, genae, and frontal area predominantly smooth, but opaque; dorsal surface of head densely and coarsely reticulated, except for the areas of antennal articulations, which are finely punctate; ventral surface of head with sparse longitudinal striae; antennal scapes finely and longitudinally striate. Mesosoma with variously oriented costulae, from sparse and transverse on dorsum of pronotum and propodeum to dense and subconcentric on the dorsum of scutum and scutellum; forecoxae with dense, fine, regular transverse striation; legs mostly smooth and shining. Lateral and posterior faces of petiolar node with sparse, short, longitudinal costulae; sculpture of gaster consisting of arched, transverse costulae, becoming gradually finer from first to terminal segment. Pilosity cream-colored. Body covered by relatively sparse, long, suberect hairs; antennal scapes and legs with short, suberect hairs; antennal funiculi and tarsi covered by fine apressed pubescence. Head subrectangular, with weakly convex lateral borders and vertexal margin straight; masticatory margins of mandibles multidenticulate and with a large apical tooth; clypeus strongly convex anteriorly; frontal lobes reduced; scapes in repose fairly surpassing the posterolateral margins of vertex; funicular segments gradually thickened distally; compound eyes placed near the posterolateral portions of head; ocelli present and reduced in size. Pronotum with a distinct median eminence directed forward and a conspicuous pair of dorsolateral (humeral) projections; scutum large and rounded; notauli almost indistinct among sculpturation; parapsidial lines feebly visible and subparallel; scutoscutellar sulcus deeply impressed; scutellum relatively narrow and strongly convex, in lateral view; dorsal face of propodeum meeting the declivous face in a pair of reduced, blunt teeth; propodeal spiracle elliptical. Wing venation fully developed. Forewing with a weakly colored stigma; longitudinal veins Sc+R, SR, M, Cu, and A present; SR extending distally beyond stigma, forming 1 R and 2 R cells; cross vein 1 r vestigial, not forming the 2 R cell; M and Cu also extend distally as tubular veins for most of their length; A not extending beyond the junction with Cu; C, R, Cu, 1 M, 1 Cu, and SR cells closed. Hind wing with Sc+R extending beyond point where they connect to M, which continues as a tubular vein as much as Sc+R and then extends as spectral vein to wing distal border; basally M+Cu extending as a tubular vein beyond junction with Anal vein, which continues shortly beyond this point; seven submedian hamuli present. Petiole ventrally carinate; in lateral view, petiolar node thick and subtriangular; anterior slope nearly concave and posterior slope slightly convex. Sternite of first gastral segment with a distinct anterior projection. Worker. Unknown (but see comments bellow). Male. Unknown. Etymology. The specific epithet is a reference to the parasitic nature of this species. Comments. Gynes of the socially parasitic Ectatomma parasiticum can be distinguished from the gynes of its host species, E. tuberculatum, by the following features: sparser sculpture on the body; smaller size (Fig. 2), with WL approximately 3.80 mm (around 5.40 mm in E. tuberculatum); clypeus and frontal area devoid of any sculpture (usually longitudinally striate in E. tuberculatum); antennal scapes longer than the maximum head width, with SI> 108 (E. tuberculatum); propodeal spines reduced to minute teeth; and petiole thicker in lateral view (flattened anteroposteriorly in E. tuberculatum). The reduced size and widener petiole of E. parasiticum are also characteristic of the inquiline syndrome in other ant species (Wilson 1984; Radchenko & Elmes 2003). Males produced by parasitized colonies were of a uniform morphology and indistinguishable from males of E. tuberculatum. Thus it remains unknown if males of E. parasiticum are lacking, present but not yet observed, or observed but indistinguishable from E. tuberculatum. According to Hora et al. (2005), one of the 10 colonies of E. parasiticum reared in laboratory produced four small "workers." However, these workers presented a developed spermatheca and six to 10 ovarioles, in contrast to typical workers of E. tuberculatum which lack the spermatheca and possess only one to four ovarioles (F��ner��n & Billen 1996; Hora et al. 2001). The presence of developed reproductive structures in these specimens suggests that they are possibly intermediate (intercaste?) reproductive forms of E. parasiticum and not true workers. Up to now, the occurrence of this species is restricted to Apazapan, state of Veracruz, Mexico. However, its host, E. tuberculatum, is widely distributed in the Neotropics, from Mexico to northern Argentina. We expect that the excavation and detailed examination of E. tuberculatum colonies in different localities could reveal new populations of E. parasiticum. A detailed behavioral and genetic study on the interaction between E. tuberculatum and E. parasiticum (so far undescribed and treated as ���microgynes���) was conducted by Hora et al. (2005). Gynes and workers of E. tuberculatum and gynes of E. parasiticum were sequenced for the cyt b region and the results showed two haplotypes. The haplotypes differed in seven variable sites, with a nucleotide sequence difference of 0.93 %. They clearly discriminate E. parasiticum from the group composed of workers and gynes of E. tuberculatum. According to the findings of Hora et al. (op. cit.), E. parasiticum is a genetically distinct social parasite producing of almost exclusively sexual offspring. The co-occurrence of E. parasiticum and E. tuberculatum in the field (nine mixed colonies found) suggests that the parasite usurps established colonies of the host, but does not kill the resident gynes. Agonistic interactions were also observed, exclusively from workers and gynes of E. tuberculatum against the parasites. Microgynes are also found in Ectatomma ruidum; however, this is a truly gyne-polymorphic species, and the offspring of both microgynes and normal gynes consist of workers, males, and both microgynes and normal gynes. It was therefore suggested that the two gyne morphs in E. ruidum represent alternative phenotypes adapted to different ways of dispersal and colony founding. Ectatomma ruidum microgynes are thought to disperse and to found new colonies solitarily, while the macrogynes are a stationary morph (Lachaud et al. 1999). The study of Hora et al. (2005) and the present paper raise the possibility of the occurrence of similar undescribed social parasites within other basal ant lineages., Published as part of Feitosa, Rodrigo M., Hora, Riviane R., Delabie, Jacques H. C., Valenzuela, Jorge & Fresneau, Dominique, 2008, A new social parasite in the ant genus Ectatomma F. S m i t h (Hymenoptera, Formicidae, Ectatomminae), pp. 47-52 in Zootaxa 1713 on pages 49-52, DOI: 10.5281/zenodo.180970, {"references":["Wilson, E. O. (1984) Tropical social parasites in the ant genus Pheidole, with an analysis of the anatomical parasitic syndrome. Insectes Sociaux, 31, 316 - 334.","Radchenko A. G. & Elmes G. W. (2003) A taxonomic revision of the socially parasitic Myrmica ants (Hymenoptera: Formicidae) of the Palaearctic Region, Annales Zoologici, 53, 217 - 243.","Hora, R. R., Doums, C., Poteaux, C., Feneron, R., Valenzuela, J., Heinze, J. & Fresneau, D. (2005) Small queens in the ant Ectatomma tuberculatum: a new case of social parasitism. Behavioral Ecology and Sociobiology, 59, 285 - 292.","Feneron, R. & Billen, J. (1996) Ovarian cycle in Ectatomma tuberculatum workers (Formicidae, Ponerinae). Journal of Invertebrate Reproduction and Development, 29, 79 - 85.","Hora, R. R., Feneron, R., Valenzuela, J., Favila, M. E. & Fresneau, D. (2001) Queen-size dimorphism in the ant Ectatomma tuberculatum (Hymenoptera: Formicidae: Ponerinae). Sociobiology, 38, 407 - 420.","Lachaud, J. - P., Cadena, A., Schatz, B., Perez-Lachaud, G. & Ibarra-Nunez, G. (1999) Queen dimorphism and reproductive capacity in the ponerine ant, Ectatomma ruidum Roger. Oecologia, 120, 515 - 523."]}

Ectatomma parasiticum Feitosa & Fresneau, sp. nov. Figures 1, 2 Holotype gyne. MEXICO: Apazapan, Veracruz, 19��19'38"N96��43'21"W, ix.1999, D. Fresneau col. [INEC]. Paratypes. same data as holotype (1 gyne) [CPDC]; (1 gyne) [UNCB]; (1 gyne) [INEC]; vii.2000, D. Fresneau & R. Hora cols. (1 gyne) [LACM]; (2 gynes) [MZSP]; (1 gyne) [USNM]. Diagnosis. Size relatively small (WL approximately 3.80 mm); clypeus and frontal area without sculpture; antennal scapes longer than the maximum head width (SI> 108); petiole relatively thick in lateral view. Gyne description. Holotype (paratypes): HL 2.10 (2.06-2.16); HW 1.85 (1.73-1.88); SL 2.04 (1.92- 2.06); EL 0.51 (0.50-0.58); PW 1.69 (1.62-1.77); WL 3.88 (3.65-4.04); PTL 0.79 (0.78-0.88); PTW 0.92 (0.92-1.07); CI 88.07 (84.11-88.89); SI 110.42 (108.57-113.04); OI 27.50 (27.50-31.25); PTI 85 (82.14- 85.71). Color yellowish brown to dark reddish brown, including appendages. Mandibles finely and densely striate, with sparse piligerous punctures; clypeus, genae, and frontal area predominantly smooth, but opaque; dorsal surface of head densely and coarsely reticulated, except for the areas of antennal articulations, which are finely punctate; ventral surface of head with sparse longitudinal striae; antennal scapes finely and longitudinally striate. Mesosoma with variously oriented costulae, from sparse and transverse on dorsum of pronotum and propodeum to dense and subconcentric on the dorsum of scutum and scutellum; forecoxae with dense, fine, regular transverse striation; legs mostly smooth and shining. Lateral and posterior faces of petiolar node with sparse, short, longitudinal costulae; sculpture of gaster consisting of arched, transverse costulae, becoming gradually finer from first to terminal segment. Pilosity cream-colored. Body covered by relatively sparse, long, suberect hairs; antennal scapes and legs with short, suberect hairs; antennal funiculi and tarsi covered by fine apressed pubescence. Head subrectangular, with weakly convex lateral borders and vertexal margin straight; masticatory margins of mandibles multidenticulate and with a large apical tooth; clypeus strongly convex anteriorly; frontal lobes reduced; scapes in repose fairly surpassing the posterolateral margins of vertex; funicular segments gradually thickened distally; compound eyes placed near the posterolateral portions of head; ocelli present and reduced in size. Pronotum with a distinct median eminence directed forward and a conspicuous pair of dorsolateral (humeral) projections; scutum large and rounded; notauli almost indistinct among sculpturation; parapsidial lines feebly visible and subparallel; scutoscutellar sulcus deeply impressed; scutellum relatively narrow and strongly convex, in lateral view; dorsal face of propodeum meeting the declivous face in a pair of reduced, blunt teeth; propodeal spiracle elliptical. Wing venation fully developed. Forewing with a weakly colored stigma; longitudinal veins Sc+R, SR, M, Cu, and A present; SR extending distally beyond stigma, forming 1R and 2R cells; cross vein 1r vestigial, not forming the 2R cell; M and Cu also extend distally as tubular veins for most of their length; A not extending beyond the junction with Cu; C, R, Cu, 1M, 1Cu, and SR cells closed. Hind wing with Sc+R extending beyond point where they connect to M, which continues as a tubular vein as much as Sc+R and then extends as spectral vein to wing distal border; basally M+Cu extending as a tubular vein beyond junction with Anal vein, which continues shortly beyond this point; seven submedian hamuli present. Petiole ventrally carinate; in lateral view, petiolar node thick and subtriangular; anterior slope nearly concave and posterior slope slightly convex. Sternite of first gastral segment with a distinct anterior projection. Worker. Unknown (but see comments bellow). Male. Unknown. Etymology. The specific epithet is a reference to the parasitic nature of this species. Comments. Gynes of the socially parasitic Ectatomma parasiticum can be distinguished from the gynes of its host species, E. tuberculatum, by the following features: sparser sculpture on the body; smaller size (Fig. 2), with WL approximately 3.80 mm (around 5.40 mm in E. tuberculatum); clypeus and frontal area devoid of any sculpture (usually longitudinally striate in E. tuberculatum); antennal scapes longer than the maximum head width, with SI> 108 (, Published as part of Feitosa, R. M., Hora, R. R. & Delabie, J. H. C., 2008, A new social parasite in the ant genus Ectatomma F. Smith (Hymenoptera, Formicidae, Ectatomminae)., pp. 47-52 in Zootaxa 1713 on pages 49-52