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

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.