The ants of North and Central America: the genus Mycocepurus (Hymenoptera: Formicidae)

Mackay, William P.; Maes, Jean-Michel; Fernández, Patricia; Luna, Gladys

doi:10.1093/jis/4.1.27

Cited by 21 publications

(16 citation statements)

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“…Although separated by as much as 2,000 km, the sexual populations are located along the Rio Amazonas and the Rio Negro, suggesting the existence of a central widespread sexual (or facultatively sexual/asexual) population that has repeatedly generated asexual, clonally reproducing lineages. These asexual lineages have rapidly dispersed throughout much of Latin America, leading to the current widespread geographic distribution of the species (32,33). The high clonal diversity in some populations indicates that independently evolved clonal lineages have colonized these habitats separately and repeatedly through time.…”

Section: Resultsmentioning

confidence: 99%

“…To study the origin and maintenance of parthenogenesis and to elucidate the mechanisms generating genetic diversity in parthenogenetic lineages, we investigated the evolutionary history of the asexual fungus-growing ant M. smithii. To test for obligate asexuality in M. smithii, we developed highly variable short tandem repeat (or microsatellite) markers and analyzed colonies from multiple populations across the species's broad range, extending from Mexico to Argentina and including some Caribbean islands (32,33). To identify the genetic structure within and between populations of M. smithii and to infer the cytogenetic mechanism underlying parthenogenetic reproduction, we genotyped sterile workers and reproductive queens from 234 colonies.…”

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Cryptic sexual populations account for genetic diversity and ecological success in a widely distributed, asexual fungus-growing ant

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Gonzales

Schultz

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Sex and recombination are central processes in life generating genetic diversity. Organisms that rely on asexual propagation risk extinction due to the loss of genetic diversity and the inability to adapt to changing environmental conditions. The fungus-growing ant species Mycocepurus smithii was thought to be obligately asexual because only parthenogenetic populations have been collected from widely separated geographic localities. Nonetheless, M. smithii is ecologically successful, with the most extensive distribution and the highest population densities of any fungus-growing ant. Here we report that M. smithii actually consists of a mosaic of asexual and sexual populations that are nonrandomly distributed geographically. The sexual populations cluster along the Rio Amazonas and the Rio Negro and appear to be the source of independently evolved and widely distributed asexual lineages, or clones. Either apomixis or automixis with central fusion and low recombination rates is inferred to be the cytogenetic mechanism underlying parthenogenesis in M. smithii. Males appear to be entirely absent from asexual populations, but their existence in sexual populations is indicated by the presence of sperm in the reproductive tracts of queens. A phylogenetic analysis of the genus suggests that M. smithii is monophyletic, rendering a hybrid origin of asexuality unlikely. Instead, a mitochondrial phylogeny of sexual and asexual populations suggests multiple independent origins of asexual reproduction, and a divergence-dating analysis indicates that M. smithii evolved 0.5-1.65 million years ago. Understanding the evolutionary origin and maintenance of asexual reproduction in this species contributes to a general understanding of the adaptive significance of sex.Attini | clonality | Formicidae | thelytoky | mutualism T he vast majority of metazoans reproduces sexually, enjoying the benefits of genetic recombination (1-3) such as rapid adaptability to novel ecological conditions (4, 5) and the purging of deleterious mutations from their genomes (6, 7). However, relative to sexually reproducing organisms, an asexual female doubles its fitness by transmitting its entire genetic material to the next generation (8). Despite such obvious short-term fitness advantages, asexual organisms occur only sporadically throughout the tree of life and are predicted to be evolutionarily short-lived and doomed to early extinction (9-11). In contrast to the short-term advantages of asexuality, the adaptive value of sexuality, that is, genetic recombination, is expected to be of long-term benefit (2, 12-14). There remain in evolutionary biology significant unexplored questions about whether sexual reproduction is favored by natural selection over short evolutionary time spans and, if not, why sexual reproduction persists as the prevalent mode of reproduction, given that the selective benefits are deferred. Studying the origin and evolution of parthenogenetic lineages, and understanding how genetic diversity is generated and preserved in such linea...

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

Cryptic sexual populations account for genetic diversity and ecological success in a widely distributed, asexual fungus-growing ant

Rabeling

Gonzales

Schultz

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…M. smithii has one of the widest distributions of any fungus-growing ant, ranging from Mexico and the Caribbean to Argentina (Mackay et al 2004;Fernández-Marín et al 2005). Moreover, no males have been found in extensive nest excavations of M. smithii from throughout the Americas (Rabeling 2004;Fernández-Marín et al 2005;Rabeling et al 2007), suggesting M. smithii may be parthenogenetic (Fernández-Marín et al 2005; see electronic supplementary material).…”

Section: Introductionmentioning

confidence: 99%

No sex in fungus-farming ants or their crops

et al. 2009

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Asexual reproduction imposes evolutionary handicaps on asexual species, rendering them prone to extinction, because asexual reproduction generates novel genotypes and purges deleterious mutations at lower rates than sexual reproduction. Here, we report the first case of complete asexuality in ants, the fungusgrowing ant Mycocepurus smithii, where queens reproduce asexually but workers are sterile, which is doubly enigmatic because the clonal colonies of M. smithii also depend on clonal fungi for food. Degenerate female mating anatomy, extensive field and laboratory surveys, and DNA fingerprinting implicate complete asexuality in this widespread ant species. Maternally inherited bacteria (e.g. Wolbachia, Cardinium) and the fungal cultivars can be ruled out as agents inducing asexuality. M. smithii societies of clonal females provide a unique system to test theories of parent-offspring conflict and reproductive policing in social insects. Asexuality of both ant farmer and fungal crop challenges traditional views proposing that sexual farmer ants outpace coevolving sexual crop pathogens, and thus compensate for vulnerabilities of their asexual crops. Either the double asexuality of both farmer and crop may permit the host to fully exploit advantages of asexuality for unknown reasons or frequent switching between crops (symbiont reassociation) generates novel ant-fungus combinations, which may compensate for any evolutionary handicaps of asexuality in M. smithii.

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“…The fungus of lower and higher Attini colonies is reared mainly with insect carcasses, feces, dead plant parts, and to a lesser extent with living plant tissue [Weber, 1972;Hölldobler and Wilson, 1990;Mueller and Wcislo, 1998;Mackay et al, 2004]. The small body size and the small mandibles of lower and of most higher Attini workers are unsuited to cut fresh leaves [Wilson, 1980a, b].…”

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The Antennal Lobes of Fungus-Growing Ants (Attini): Neuroanatomical Traits and Evolutionary Trends

et al. 2009

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Ants of the tribe Attini are characterized by their obligate cultivation of symbiotic fungi. In addition to the complex chemical communication system of ants in general, substrate selection and fungus cultivation pose high demands on the olfactory system of the Attini. Indeed, behavioral studies have shown a rich diversity of olfactory-guided behaviors and tremendous odor sensitivity has been demonstrated. To allow fine-tuned behavioral responses, adaptations within the olfactory system of the Attini are expected. We compared the number, volumes and position of the glomeruli (functional units) of the antennal lobe of 25 different species from all three major Attini groups (lower, higher and leaf-cutting Attini). The antennal lobes of all investigated Attini comprise a high number of glomeruli (>257). The highest number (630) was found in Apterostigma cf. mayri. This species is at a basal position within the Attini phylogeny, and we suggest that a high number of glomeruli might have been advantageous in the evolution of the advanced olfactory systems of the Attini. In the leaf-cutting Attini, an extremely large glomerulus (macroglomerulus) near the antennal nerve entrance was recently described in two species. Preliminary results show that this macroglomerulus is involved in processing of trail-pheromone information. In our comparative study, we find this macroglomerulus in all investigated leaf-cutting Attini, but in none of the lower and higher Attini species. It is found only in large workers, and for all investigated species it is located close to the entrance of the antennal nerve. Our results indicate that the presence of a macroglomerulus in large workers of leaf-cutting Attini is a derived over-expression of a trait in the polymorphic leaf-cutting species. It presumably represents an olfactory adaptation to elaborate foraging and mass recruitment systems, and adds to the complexity of division of labor and social organization known for this group.

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The ants of North and Central America: the genus Mycocepurus (Hymenoptera: Formicidae)

Cited by 21 publications

References 10 publications

Cryptic sexual populations account for genetic diversity and ecological success in a widely distributed, asexual fungus-growing ant

Cryptic sexual populations account for genetic diversity and ecological success in a widely distributed, asexual fungus-growing ant

No sex in fungus-farming ants or their crops

The Antennal Lobes of Fungus-Growing Ants (Attini): Neuroanatomical Traits and Evolutionary Trends

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