title: Genetic divergence between the sympatric queen morphs of the ant Myrmica rubra.
abstract: Pairs of obligate social parasites and their hosts, where some of the parasites have recently diverged from their host through intraspecific social parasitism, provide intriguing systems for studying the modes and processes of speciation. Such speciation, probably in sympatry, has also been propounded in the ant Myrmica rubra and its intraspecific social parasite. In this species, parasitism is associated with queen size dimorphism, and the small microgyne has become a social parasite of the large macrogyne. Here, we investigated the genetic divergence of the host and the parasite queen morphs in 11 localities in southern Finland, using nuclear and mitochondrial markers of queens and workers. We formulated and tested four speciation-related hypotheses that differed in the degree of genetic divergence between the morphs. The queen morphs were genetically distinct from each other with little hybridization. In the nuclear data, when localities were nested within queen morphs in the hierarchical amova, 39% of the genetic variation was explained by the queen morph (standardized F'CT = 0.63, uncorrected FCT = 0.39), whereas 18% was explained by the locality (F'SC = 0.39, FSC = 0.29). This result corroborated the hypothesis of advanced sympatric speciation. In contrast, the mitochondrial DNA could not settle between the hierarchical levels of locality and queen morph, thus substantiating equally the hypotheses of incipient and advanced sympatric speciation. Together, our results support the view that the microgynous parasite has genetically diverged from its macrogynous host to the level of a nascent species.
authors: Department of Biosciences, University of Helsinki, P.O. Box 65, Helsinki, 00014, Finland.
authors: Jenni
authors: J
authors: Leppänen
authors: Perttu
authors: P
authors: Seppä
authors: Kari
authors: K
authors: Vepsäläinen
authors: Riitta
authors: R
authors: Savolainen
mesh_terms: D000483:Alleles; D000818:Animals; D001000:Ants / Q000235:genetics*; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D005260:Female; D005387:Finland; D049810:Genetic Speciation; D014644:Genetic Variation; D005838:Genotype; D017422:Sequence Analysis, DNA; D061350:Sympatry
chemical_list: D004272:DNA, Mitochondrial
keywords: Myrmica microrubra; hymenoptera; inquilinism; size dimorphism; social parasitism; sympatric speciation