No abstract

The similarities in the theories of community ecology and population genetics suggest that species diversity within and between communities and genetic diversity within and between populations are driven by the same four general mechanisms: (1) drift, (2) dispersal, (3) selection, and (4) the formation of new variants (i.e. speciation and mutation). Since, for both species diversity and genetic diversity, the relative significances of each of the first three mechanisms are very much influenced by characteristics of the environment, correlations between species diversity and genetic diversity, i.e. species-genetic diversity correlations (SGDCs), are expected. Considering that practical conservation most often focuses on species diversity (or surrogates thereof), SGDCs could provide information on how conservation and management decisions influence genetic diversities of populations, and thus also their viabilities. Furthermore, teasing apart the drivers of the SGDCs can offer mechanistic explanations for diversity and therefore suggest a process-based approach to conservation. I studied the generalizability of SGDC and the role of environmental characteristics by means of a literary review and empirical studies on natural dragonfly and damselfly communities. I then conducted individual-based simulations to assess how inbreeding depression due to loss of genetic diversity can influence extinction rates in neutral multispecies metacommunities. My results suggest that SGDCs are highly variable in natural systems and that interactions between ecologically similar species can influence their genetic structures. Therefore, the results question the utility of using species diversity or genetic structures of ecologically similar species as surrogates for genetic diversity of species of conservation concern. Furthermore, my results suggest that if intraspecific genetic diversity is not explicitly considered, the extinction rates in multispecies metacommunities might be underestimated.

Eight polymorphic microsatellite loci were developed and characterized for the diploid Centaurea aspera L. and the tetraploid Centaurea seridis L., two species of the Seridia section of Asteraceae. We used 132 individuals collected from 5 locations. These markers provided high polymorphism ranging from 3 to 10 alleles per locus. These microsatellite loci will be useful tools to study polyploid complexes that include triploid individuals.

As species do not live in isolation from each other, they are faced with an elementary choice when searching for a mating partner: a choice between conand heterospecific individuals. Despite the remarkable research effort on hybridization and its avoidance, there are still some less well covered areas, e.g. what is the role of males in hybridization, what patterns are found in sympatric wild populations, what role do alternative reproductive tactics (ARTs) have on the likelihood of heterospecific matings, and what are the true costs of heterospecific interactions. In this thesis I first quantify the frequency of hybridization, backcrossing and heterospecific matings in sympatric wild populations of Calopteryx splendens and C. virgo damselflies in Finland. The possible influence of population densities, relative abundances of the species, and operational sex ratios on the frequency of heterospecific matings is also investigated. The second aim is to investigate how the intensity of territorial competition influences males' reproductive response to a heterospecific female. Finally, I dissect the importance of male ARTs on hybridization propensity and I attempt to quantify the reproductive costs that males' hybridization propensity inflicts among the tactics. The results imply a major role for C. splendens males in heterospecific reproductive interactions between the study species. Especially territorial males seem to be prone to hybridization, and the prevalence of hybridization is increased with a high availability of C. virgo females. Hybridization seems to be costly because there was high discordance between heterospecific mating frequency and observed numbers of hybrids. However, heterospecific courtship did not reduce conspecific mating success. The results also show that C. splendens males are able to adjust their level of heterospecific courtship according to the competitive environment as well as to the ART it follows. My thesis is a step towards understanding the causes of species reproductive interactions in wild populations.