Genetic variability and social structure of colonies in Acromyrmex heyeri and A. striatus (Hymenoptera: Formicidae)

Abstract

The breeding structure of both colony and population of social insects can be examined by genetic analysis. Colonies of the leaf-cutting ants Acromyrmex heyeri and A. striatus (Myrmicinae, Attini) were thus analyzed for isoenzyme systems MDH, a-GPDH, and AMY to describe genotype variability and social structure. A total of five loci were investigated (three for amylase and one for each other system). Ninety-seven colonies of A. heyeri and 103 of A. striatus were sampled in different localities in Southern Brazil (State of Rio Grande do Sul). The genotypes found show the occurrence of monogyny and polygyny associated or not with polyandry, which indicates that the social organization is colony-specific. The polygyny and polyandry observed are likely to be responsible for the great genotypic diversity of the colonies. The average inbreeding coefficient per colony was higher in A. striatus than in A. heyeri, which may reflect the different patterns of production of sexual individuals and nuptial flight of those two species.Key words: Attini, genetic polymorphism, breeding structure, leaf-cutter ants. RESUMOVariabilidade genética e estrutura social das colônias de Acromyrmex heyeri e A. striatus (Hymenoptera, Formicidae)A estrutura de cruzamento de colônias e populações de insetos sociais pode ser observada por análise genética. Assim, colônias de formigas cortadeiras Acromyrmex heyeri e A. striatus (Myrmicinae, Attini) foram analisadas para os sistemas isoenzimáticos MDH, a-GPDH e AMY, a fim de descrever sua variabilidade genotípica e estrutura social. Foram investigados cinco locos (três para amilase e um para cada outro sistema), em 97 colônias de A. heyeri e 103 de A. striatus, amostradas em diversas localidades do Rio Grande do Sul. Os genótipos encontrados indicaram a ocorrência de monoginia e poliginia associadas ou não à poliandria, indicando que a organização social é colônia específica. Tanto a poliginia quanto a poliandria são responsáveis pela grande diversidade genotípica das colônias. O coeficiente de endocruzamento médio por colônia foi mais alto em A. striatus do que em A. heyeri e pode refletir os diferentes padrões de produção dos indivíduos sexuados e de vôo nupcial das duas espécies.Palavras-chave: Attini, polimorfismo genético, estrutura de cruzamento, formigas cortadeiras.Braz. J. Biol., 61(4): 667-678 668 DIEHL, E., ARAÚJO, A. M. de and CAVALLI-MOLINA, S.

Isoenzymatic polymorphism in the leaf-cutting ant Atta capiguara Gonçalves (hymenoptera: formicidae)

“…This fact may have occurred due to females restricting dispersion by secondary polygyny and, consequently, the new nests were dependent on the founder nest. Such characteristic may assume a strong genetic differentiation, as has been shown in several ant species (Diehl et al 2001, Gyllenstrand & Seppä, 2003, Mäki-Petäys et al 2005.…”

“…However, few isozymes were analyzed and the queen was not looked for in the nests. Atta nests are monogynic, just Atta texana found in Mexico, is described as polygynic (Diehl et al 2001). The fixation index (F IS ) for A. capiguara was high (0.7954) ( Table 3).…”

Acromyrmex charruanus: a new inquiline social parasite species of leaf-cutting ants

“…Polygyny, in particular, presents an opportunity for one queen to reproductively exploit the other queen(s) and can lead to the evolution of intraspecific parasitism (Buschinger 1986;Seifert 2010;. Interestingly, every host and parasite species of fungus-growing ants that has been investigated so far is at least facultatively polygynous (Della Lucia and Vilela 1986;Delabie 1989;Bekkevold et al 1999;Bekkevold and Boomsma 2000;Diehl et al 2001;De Souza et al 2004;Rabeling et al 2007b;Rabeling and Bacci 2010), which supports the hypothesis that the evolutionary origin of social parasitism is contingent on the presence of polygyny in a given species. A population survey of A. charruanus's host species, A. heyeri, in southern Brazil revealed that at least 17 % of the colonies were polygynous and polyandrous and that 68 % of the colonies for which monogyny was inferred had to be descendants of a necessarily heterozygous mother, suggesting that the frequency of polygyny in this population was likely higher (Diehl et al 2001).…”

“…Interestingly, every host and parasite species of fungus-growing ants that has been investigated so far is at least facultatively polygynous (Della Lucia and Vilela 1986;Delabie 1989;Bekkevold et al 1999;Bekkevold and Boomsma 2000;Diehl et al 2001;De Souza et al 2004;Rabeling et al 2007b;Rabeling and Bacci 2010), which supports the hypothesis that the evolutionary origin of social parasitism is contingent on the presence of polygyny in a given species. A population survey of A. charruanus's host species, A. heyeri, in southern Brazil revealed that at least 17 % of the colonies were polygynous and polyandrous and that 68 % of the colonies for which monogyny was inferred had to be descendants of a necessarily heterozygous mother, suggesting that the frequency of polygyny in this population was likely higher (Diehl et al 2001). The sexual strategies of the Uruguayan A. heyeri host colonies and of A. charruanus are currently unknown, and we are currently employing recently developed genetic markers to infer the mating strategies of this host-parasite pair (Rabeling et al 2014a).…”

Termitofauna (Insecta, Isoptera) em Remanescentes de Floresta Estacional Semidecidual em São Leopoldo, Rio Grande do Sul, Brasil

“…Por exemplo, a área em sucessão vegetal (Imperatriz Leopoldina), após seu desmatamento foi aterrada inúmeras vezes, de modo que colônias de térmitas provenientes de outros locais podem ter sido transportadas juntas, favorecendo a emigração (Fontes 1998b;Diehl et al 2001) e, por conseqüência, elevando-se a riqueza de espécies.…”