Thelytokous Parthenogenesis in the Fungus-Gardening Ant Mycocepurus smithii (Hymenoptera: Formicidae)

The general prevalence of sexual reproduction over asexual reproduction among organisms testifies to the evolutionary benefits of recombination, such as accelerated adaptation to changing environments and elimination of deleterious mutations. Documented instances of asexual reproduction in groups otherwise dominated by sexual reproduction challenge evolutionary biologists to understand the special circumstances that might confer an advantage to asexual reproductive strategies. Here we report one such instance of asexual reproduction in the ants. We present evidence for obligate thelytoky in the asexual fungus-gardening ant, Mycocepurus smithii, in which queens produce female offspring from unfertilized eggs, workers are sterile, and males appear to be completely absent. Obligate thelytoky is implicated by reproductive physiology of queens, lack of males, absence of mating behavior, and natural history observations. An obligate thelytoky hypothesis is further supported by the absence of evidence indicating sexual reproduction or genetic recombination across the species'' extensive distribution range (Mexico-Argentina). Potential conflicting evidence for sexual reproduction in this species derives from three Mycocepurus males reported in the literature, previously regarded as possible males of M. smithii. However, we show here that these specimens represent males of the congeneric species M. obsoletus, and not males of M. smithii. Mycocepurus smithii is unique among ants and among eusocial Hymenoptera, in that males seem to be completely absent and only queens (and not workers) produce diploid offspring via thelytoky. Because colonies consisting only of females can be propagated consecutively in the laboratory, M. smithii could be an adequate study organism a) to test hypotheses of the population-genetic advantages and disadvantages of asexual reproduction in a social organism and b) inform kin conflict theory.For a Portuguese translation of the abstract, please see Abstract S1.     

A New Species of Strumigenys(Hymenoptera: Formicidae) from Korea

Strumigenys choii sp. nov. is described and illustrated from the Is. Soheuksan-do, Korea. Although this species is similar to the congener S. lewisi, from which differs in having a glossy and smooth dorsal plate comprised of a pronotum and propodeum, and spatulate hairs on the head, antennal scapes, alitrunk, pedicel, legs and gaster.     

Reproductive strategies of the exotic Pharaoh's ant,Monomorium pharaonis (L.) (Hymenoptera: Formicidae) in Brazil

Summary

The production of sexual forms in laboratory colonies of Monomorium pharaonis was followed over a 19-month period. Cycles of production occurred at intervals of 4 months, with male investment inversely proportional to the number of gynes produced. There was a tendency for colonies to produce only males or females as total sexual production increased. Sperm counts of known-aged males suggest that they mate twice, in contrast to European populations. Sex-ratio was heavily female-biased, contrary to predictions for polygynous ant species.     

Comparative ultrastructure of ant spermatozoa (Formicidae: Hymenoptera)

Mature spermatozoa from spermathecae of founding queens were obtained from 5 species of ants, representing the major subfamilies Myrmicinae (Acromyrmex versicolor, Crematogaster sp.) and Dolichoderinae (Tapinoma sessile, Conomyrma insana, Conomyrma wheeleri). The ultrastructure of ant spermatozoa has many features in common with that of higher insects and is similar to that of other Hymenoptera. Structural similarities to spermatozoa of other Hymenoptera include an acrosome containing an internal rod that extends into the nucleus, two elongate mitochondrial derivatives, a centriolar adjunct, and an axonemal arrangement of 9 + 9 + 2 that includes well-developed coarse, or accessory, tubules. Spermatozoa obtained from A. versicolor, a species that is known to store and utilize viable sperm from this supply for over 10 years, show greater development of the mitochondrial derivatives than do the other species. The most distinctive feature of ant spermatozoa in comparison to other Hymenoptera is the large size of the centriolar adjunct relative to the other organelles. The centriolar adjunct is located posterior to the nucleus, anterior to the mitochondrial derivatives, and opposite the axoneme.     

Production of females by parthenogenesis in the ant,Cerapachys biroi

Summary Groups of virginCerapachys biroi workers produced females (workers) in the laboratories. This is the first report of thelytoky in Cerapachyinae.     

Sexual functionality of Leptopilina clavipes (Hymenoptera: Figitidae) after reversing Wolbachia-induced parthenogenesis

Females infected with parthenogenesis-inducing Wolbachia bacteria can be cured from their infection by antibiotic treatment, resulting in male production. In most cases, however, these males are either sexually not fully functional, or infected females have lost the ability to reproduce sexually. We studied the decay of sexual function in males and females of the parasitoid Leptopilina clavipes. In western Europe, infected and uninfected populations occur allopatrically, allowing for an investigation of both male and female sexual function. This was made by comparing females and males induced from different parthenogenetic populations with those from naturally occurring uninfected populations. Our results indicate that although males show a decay of sexual function, they are still able to fertilize uninfected females. Infected females, however, do not fertilize their eggs after mating with males from uninfected populations. The absence of genomic incompatibilities suggests that these effects are due to the difference in mode of reproduction.     

Phylogenetic utility of the ribosomal internal transcribed spacer 2 in Strumigenys spp. (Hymenoptera: Formicidae)

Sequence variations and phylogenetic relationships of Strumigenys from different localities in Taiwan were inferred from sequences of the internal transcribed spacer 2 (ITS2) of nuclear ribosomal RNA genes. The ITS2 sequences of different species of Strumigenys vary in length from 659 to 953 bp, because there are many large repeated insertion-deletion fragments, and these short tandem repeat units form microsatellites. The average GC content of the ITS2 is 60.8%. Secondary structures from ITS2 sequences are similar and present several conserved structural motifs. Eleven species and three unnamed species were analyzed using both the maximum parsimony and maximum likelihood methods. Although diversity of the ITS2 sequence is high, these data can still be a potential tool for primary analysis of molecular phylogeny and biogeography of Strumigenys at the species level on islands around Taiwan.     

Revision of the dolichoderine ant genus Turneria (Hymenoptera: Formicidae)

Abstract. The Australasian ant genus Turneria is revised. T.bidentata Forel, T.dahlii Forel and T.pacifica Mann are redescribed and a lectotype designated for T.bidentata. T.frenchi Forel is transferred to Stigmacros (comb.n.), and T.butteli Forel is transferred to Iridomyrmex (comb.n.). Three new species, T.arbusta, T.collina and T.postomma, are described from Papua New Guinea. Males of the genus are described for the first time. A key to the workers of recognized species and a distribution map are provided. The group is analysed cladistically and the resulting species relationships are discussed, along with a comment on the use of polymorphic characters.     

Generic-level relationships within the ant subfamily Dolichoderinae (Hymenoptera: Formicidae)

A cladistic analysis was undertaken to determine relationships among extant genera of the ant subfamily Dolichoderinae. Twenty-one of the twenty-two currently recognized genera within the subfamily were examined using 104 morphological characters. A single fully resolved, most-parsimonious tree was found when a combination of ordered and unordered characters was used. When all characters were coded as unordered, seventy most-parsimonious trees were found. The following results were found with both character coding methods. Leptomyrmex was placed basal to the remainder of the subfamily and the monophyletic sets Dolichoderus + Liometopum + Axinidris + Tapinoma + Technomyrmex, Froggattella + Iridomyrmex + Ochetellus + Papyrius + Philidris + Turneria , and Bothriomyrmex + Dorymyrmex + Forelius + Loweriella were suggested. The genera Linepithema and Doleromyrma showed a small amount of instability in moving between neighbouring sister groups when the character coding method changed. The genera Anillidris and Anonychomyrma were difficult to place as they showed major differences in their positions between the two character coding methods.     

Communication in the primitive cryptobiotic ant Prionopelta amabilis (Hymenoptera: Formicidae)

Summary The Neotropical ant Prionopelta amabilis, a cryptobiotic species in the phylogenetically primitive tribe Amblyoponini, lives in subterranean habitats, where it preys preferentially on campodeid diplurans and other small arthropods. Here we report that the species employs chemical recruitment and orientation trails during foraging and nest emigrations. The trail pheromone originates in a hitherto unknown basitarsal gland located in the basitarsus of the hindlegs. Trails are laid by a special foot dragging behavior. During the recruitment process the chemical trail signal is complemented by body shaking on the part of the recruiting ant. Foragers frequently wipe the basitarsal gland opening in the hindlegs with the grooming apparatus of the front legs. This latter structure is equipped with unusual glands evidently specialized for this purpose.     

Molecular phylogeny of the ant tribe Myrmicini (Hymenoptera: Formicidae)

The interrelationships within ant subfamilies remain elusive, despite the recent establishment of the phylogeny of the major ant lineages. The tribe Myrmicini belongs to the subfamily Myrmicinae, and groups morphologically unspecialized genera. Previous research has struggled with defining Myrmicini, leading to considerable taxonomic instability. Earlier molecular phylogenetic studies have suggested the nonmonophyly of Myrmicini, but were based on limited taxon sampling. We investigated the composition of Myrmicini with phylogenetic analyses of an enlarged set of taxa, using DNA sequences of eight gene fragments taken from 37 representatives of six of the seven genera (Eutetramorium, Huberia, Hylomyrma, Manica, Myrmica, and Pogonomyrmex), and eight outgroups. Our results demonstrate the invalidity of Myrmicini as currently defined. We recovered sister‐group relationships between the genera Myrmica and Manica, and between Pogonomyrmex and Hylomyrma. This study illustrates that to understand the phylogeny of over 6000 myrmicine species, comprehensive taxon sampling and DNA sequencing are an absolute requisite. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 482–495.     

A review of Bahamian ant (Hymenoptera: Formicidae) biogeography

Abstract. The results of recent surveys for ants on Staniel Cay, Exumas (and surrounding small cays) and the northeastern region of Andros are presented. These records are compiled with all previously published collection records of ants from the Bahamas into a single database. A list of all known Bahamian species is presented, in accord with current taxonomy. Distributions within the Bahamas are given, along with the status of each species with reference to its origin (endemic, native, or exotic). At present seventy-five named species of ants are known from the Bahamas, which shares 60% of its ant fauna with Florida and 71% with Cuba. More than one third of the species (37%) are exotics, which appear to exist primarily in areas characterized by human disturbance, and apparently have not invaded the native vegetation to a large degree. Both historical and ecological factors are likely to have played important roles in shaping present-day Bahamian ant species diversity and distribution. The number of species on all major Bahamian islands from which ants have been collected is presented as a function of island area. Most islands have not been very thoroughly surveyed. The species-area relationship for the more thoroughly surveyed islands is relatively flat (z= 0.06). Further collecting in this archipelago will probably lead to the discovery of additional species.     

Individual constancy of local search strategies in the giant tropical ant,Paraponera clavata (Hymenoptera: Formicidae)

Paraponera clavata workers engage in a period of local search after encountering a small amount of artificial nectar. Giving-up times from local search are not distributed normally; there is a strong skew to longer times. There is no statistically significant relationship between the amount of time required to collect the food and the subsequent search time. Giving-up time in response to the first reward presented to an ant is positively correlated with that ant's response to a second such reward. However, giving-up times diminish when an ant is presented with a series of rewards. Local search is a function of individual strategies, which remain relatively constant in the short term.     

Population genetics of the black ant Formica lemani (Hymenoptera: Formicidae)

Colony kin structure and spatial population structure were studied in multiple populations of the ant Formica lemani , using allozymes and DNA microsatellites. Average genetic relatedness between nestmate workers varied little between populations ( r  = 0.51–0.76), indicating that the average colony kin structure was relatively simple. Worker genotypes could not be explained with a single breeding pair in all nests, however, and the distribution of relatedness estimates across nests was bimodal, suggesting that single- and multi-queen colonies co-occur. We studied spatial population structure in a successional boreal forest system, which is a mixture of different aged habitats. Newly clear-cut open habitat patches are quickly colonized by F. lemani , where it is able to persist for a limited number of generations. Newly-founded populations showed signs of a founder effect and spatial substructuring, whereas older populations were more homogenous. This suggests that new populations are founded by a limited number of colonizers arriving from more than one source. Genetic differentiation among local populations was minor, indicating strong migration between them. There were, however, indications of both isolation by distance and populations becoming more isolated as habitat patches grew older.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 247–258.     

Exocrine chemistry of the myrmicine ant Zacryptocerus pusillus (Hymenoptera: Formicidae)

Minor workers of the ant Zacryptocerus pusillus have unusual exocrine secretions in both their mandibular and Dufour glands. The mandibular glands contain a 3:1 mixture of 4-heptanone and 4-heptanol, a mixture found only in the related species Z. varians. The Dufour gland contains a mixture of 13 aldehydes from C9 to C18, not previously encountered in ant secretions. The venom glands gave variable results with only nonanal present consistently.     

Second species in the Australian ant genus Peronomyrmex Viehmeyer (Hymenoptera: Formicidae)

A second species of the rare Australian ant genus Peronomyrmex is described from Victoria. This new species, P. bartoni , represents only the third time the genus has been collected, the previous records being the holotype of P. overbecki Viehmeyer from north-eastern New South Wales and a collection, subsequently lost, from northern Queensland.     

Agonistic relationships among sympatric mediterranean ant species (Hymenoptera: Formicidae)

The potential aggressiveness of nine ant species belonging to the same community was estimated by means of two laboratory approaches: individual confrontations and group confrontations. Interspecific aggressiveness was not directly related to size of species in individual tests, although in group tests mortality of smaller ants increased with increasing size difference between the opponents. Tempo was related to the defense strategy of species (low-tempo species used immobility as a mechanism to avoid attacks, while high-tempo species tended to escape when coming into contact with more aggressive ones), but not with their potential aggressiveness: the most aggressive ants in individual and group tests were both low-tempo and high-tempo species when only these two categories were considered. No specific level of aggression was related to the subfamily to which the species belong (both myrmicines and formicines dominated in individual and group tests) or to the degree of taxonomic similarity between species.     

Microsatellites for the Neotropical ant,Camponotus leydigi (Hymenoptera: Formicidae)

Ants (Hymenoptera: Formicidae) are dominant social insects that play important ecological roles in terrestrial ecosystems. Camponotus leydigi (Forel) is widely distributed in the Neotropical region and is frequently found in the Brazilian cerrado savanna interacting with plants and other insects. Field observations indicate that C. leydigi has a polydomous nesting habit, but little is known about the genetic relationship among workers. In this study, we identify the first nine microsatellite loci for C. leydigi that will allow further investigation on its genetic diversity. We used a microsatellite-enriched library method. According to this method, repetitive sequences are captured with (CT)₈ and (GT)₈ biotin-linked probes, with subsequent recovery by streptavidin magnetic-coated beads. We observed that eight loci were polymorphic. The mean (± standard error) observed and expected heterozygosities were 0.55 ± 0.23 and 0.73 ± 0.28, respectively. The rarified allelic richness ranged from 1 to 5.32. The polymorphism contents were similar to diversity estimates found in markers previously developed for other Camponotus ants. These markers will be useful for future studies on population genetics and ecology of Camponotus ants in cerrado, including nesting ecology, colony structure, dispersal and conservation.