Intranidal mating, gyne polymorphism, polygyny, and supercoloniality as factors for sympatric and parapatric speciation in ants

Abstract

Abstract. 1. The syndrome of intranidal mating, morpho-ethological gyne polymorphism, and polygyny is found in less than 5% of European ant species, but is considered as an important precondition for sympatric and parapatric speciation.2. This idea is discussed in three cases that represent example of evolution below the species level: (1) the polygynous-polydomous form of Lasius turcicus as a model of how speciation of the supercolonial Lasius neglectus could have taken place; (2) the microgyne form of Myrmica rubra as a model for sympatric speciation of socially parasitic species; and (3) hybridisation and rapid genotype selection in supercolonial wood ants of the Formica rufa group as a model for hybrid speciation.3. The first step of the evolutionary scenario is transition to polygyny followed by development of morpho-ethological gyne polymorphism: smaller gynes with weaker wing muscles and body reserves shift to intranidal mating and reduce dispersal flight, while larger gynes with bigger wing muscles and body reserves retain nuptial and dispersal flight. This scenario leads to mating place separation and facilitates further genotype divergence.4. There is much less gene flow between conspecific supercolonies of Formica rufa group ants with dominance of intranidal or intracolonial mating than between conspecific monogynous colonies performing a nuptial flight. If two supercolonial species occasionally hybridise and if landscape structure provides some isolation of the resulting hybrid supercolony, very strong selection for genotypes takes place within this cohesive system of thousands of reproductive females eventually leading to novel genotypes and new species.Key words. Distorted selection, hybridogenous speciation, social parasites, supercoloniality. IntroductionThe formation of eusocial, perennial colonies in ants represents a major evolutionary transition and provided the basis for their overwhelming presence in many boreal, temperate, and tropical ecosystems (Wilson, 1989). This ecological aspect tends to make us forget that eusociality in ants has also offered novel pathways of speciation unprecedented in other insects. This paper aims to direct attention to a syndrome of biological traits which is expressed only in a minority of extant ant species, but nevertheless is of evolutionary interest since it provides the basis for rather rare, yet exemplaric speciation scenarios. Components of this scenario are: (1) reduction of nuptial and dispersal flight; (2) morpho-ethological polymorphism of sexual castes; and (3) polygynous-polydomous colonies culminating in supercoloniality. Within the European ant fauna, less than 5% of the species-belonging to the genera Formica, Lasius, Myrmica, Messor, and Tetramorium -are known to show this syndrome, or to be in a precursory stage (Rosengren et al

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.…”

Hybridization and speciation

“…If gene flow within taxon A (or B) is limited, for example in a patchy environment, a second outcome of reinforcement may be the evolution of reproductive traits in overlap populations that are so divergent from those outside the area of contact that individuals with the alternative trait types are less likely to reproduce (Howard, 1993; see also reviews, discussion, and references therein by Pfennig & Pfennig, 2009, 2010Ortiz-Barrientos et al, 2009;Hoskin & Higgie, 2010). Consequently, this can lead to the initiation of reproductive isolation between sympatric and allopatric populations of taxon A (or B), which can ultimately lead to speciation (Howard, 1993;Pfennig & Pfennig, 2009, 2010Ortiz-Barrientos et al, 2009;Hoskin & Higgie, 2010; for theoretical treatments see Pfennig & Ryan, 2006;McPeek & Gavrilets, 2006). For example, Jaenike et al (2006) showed that, between two sympatric species of Drosophila, strong hybrid inviability not only selected for discrimination against heterospecifics but also, as a side product, led to discrimination against conspecifics from allopatric populations.…”

“…Trade-offs in fitness between assortative mating and sexual selection within populations may enhance the divergence between populations (e.g. Pfennig & Pfennig, 2005; for further discussion, see Pfennig & Pfennig, 2009, 2010Ortiz-Barrientos et al, 2009;Hoskin & Higgie, 2010). These trade-offs may be emphasized when a stepwise change in environmental conditions coincides with the boundary of the region of range overlap.…”

Genetic diversity and colony structure of Tapinoma melanocephalum on the islands and mainland of South China

“…This result suggests that the clusters are not completely distinct. It may be attributed to long-distance dispersal of the ghost ant that frequently occurs due to human activities (Seifert, 2010). Therefore, newly introduced populations may mix with earlier arrivals to form a single more genetically diverse unicolonial society, thus promoting gene flow at large scales among island and mainland populations.…”