THE ROLE OF FACTORS PROMOTING GENETIC DIVERSITY WITHIN SOCIAL INSECT COLONIES, ACTA UNIVERSITATIS OULUENSIS A Sci e n t i a e Rerum Nat u r a l i u m 555

The evolution of sociality is often associated with close relatedness and genetic similarity of\ninteracting individuals. However, colonies of advanced social insects (e.g. ants, bees and wasps)\ncharacterized by large colony size and division of tasks, are also shaped by acquisition of genetic\ndiversity by polyandry, polygyny, recombination and even by hybridization. The balance between\nforces selecting for high relatedness on one hand and for improved colony performance though\nincreased genetic diversity on the other hand forms an intriguing area of research.\nMy study has produced the first genetic linkage maps for ants (Acromyrmex echinatior and\nPogonomyrmex rugosus) and social wasps (Vespula vulgaris). Together with the findings of\nearlier honeybee research, it is shown that advanced eusocial insects have higher recombination\nrates than any other insect (or animal) studied so far. The estimates obtained here were 14 cM/Mb\nfor P. rugosus, 9.7 cM/Mb for V. vulgaris and 6.2 cM/Mb for A. echinatior.\nPogonomyrmex harvester ants have a genetic caste determination system in which workers\narise from mating between two hybridizing lineages whereas sexuals are produced by withinlineage\nmating. I evaluated the origin of the lineages and the caste determination system by using\n751 variable nuclear genetic markers. Fertile hybrids would lead to introgression, particularly in\ngenomic regions characterized by a high recombination rate and lack of strongly selected loci. The\nhybridizing lineages (lineage pairs J1/J2 and H1/H2) showed many fixed differences. Nineteen of\nthem were in the constructed linkage map, scattered in different linkage groups. The results\nsuggest that there has been no recent introgression. As the hybrids are viable (as workers), caste\ndifferentiation can be affected by many loci scattered throughout the ant genome or by a small\nnumber of very strongly selected loci.\nGenetic diversity in colonies of the ant Formica cinerea is affected by varying levels of\npolygyny. I tested the hypotheses that the prevalence of endosymbiotic bacteria can vary in\npolygynous colonies but be either very low or very high in monogynous colonies. However, I\nfound no association between the level of polygyny and endosymbiont prevalence. In addition to\nWolbachia, I found two other endosymbiotic bacteria Cardinium and Candidatus Serratia\nsymbiotica which have not been earlier reported from ants.\nGenetic diversity in insect colonies is affected by polyandry and polygyny. My results indicate\nthat high a recombination rate is also an important factor influencing diversity. Genotypically\ndiverse progenies can enhance colony success, e.g. through effects on division of labour or\ndefence against pathogens. Recombination differs from the other factors in its effects on genetic\nrelatedness among colony members.

ISBN-10:
978-951-42-6206-7
Kieli:
eng.
Sivumäärä:
172 s.
Tekijät:
Sirviö Anu
Tuotekoodi 013983
20,00 €