Plant Breeding System and Primary Pollinator as a Proxy to Estimate Inbreeding and Inbreeding Depression

Cisternas Fuentes, Anita

doi:https://doi.org/10.21985/n2-3f0a-4655

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Plant Breeding System and Primary Pollinator as a Proxy to Estimate Inbreeding and Inbreeding Depression

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Genetic factors such as loss of genetic diversity, mutations, and inbreeding depression can increase a populations chances of extinction, therefore it is important to understand how these factors can contribute to populations decline. Among the genetic factors that can contribute to populations extinction, inbreeding depression is the only one that has direct consequences on the fitness of the individuals and therefore can contribute to fitness changes in the next generations. Inbreeding depression refers to the fitness decline of inbreed individuals compared to outcross individuals. Increased inbreeding can lead to inbreeding depression, however, this relationship is not always straightforward and multiple factors can contribute to differences in inbreeding and its impact on the expression of inbreeding depression. Species reproductive system and pollinators, can influence on the rates of inbreeding and outcrossing of a population and therefore should play an important role on the expression of inbreeding depression. In this dissertation I tested the influence that reproductive system and different pollinators have on inbreeding and inbreeding depression. In chapter 1, I performed two meta-analyses to test the role that plant breeding system and type of pollinators have on inbreeding levels (FIS) and inbreeding depression (F) across taxa. The results indicated that self-compatible taxa have an overall higher level of inbreeding within a population and reduced inbreeding depression compared to self-incompatible taxa, while the role of pollinators does not show a clear or significant pattern. Next, I focus on testing the relation between rates of inbreeding and inbreeding depression, using populations of three different species that differ on their reproductive system or in their pollinators to estimate inbreeding and inbreeding depression. In chapter 2 and 3, I focus on populations of Oenothera primiveris, which have variation on their reproductive system across their range of distribution. In chapter 2, I tested differences on the species reproductive system and how these differences associate with floral traits and with population genetic parameters. The results indicate a transition towards the a selfing syndrome in O. primiveris moving from west to east across its geographic range. This shift includes variation in the breeding system, reduction of floral traits (flower diameter, herkogamy, and scent production), and reduced genetic diversity with increased inbreeding. While, in chapter 3, I tested how variation on the breeding system and the inbreeding coefficient in Oenothera primiveris can impact the expression of inbreeding depression. The results of this chapter do not support the hypothesis that populations with self-incompatible individuals will have higher inbreeding depression than self-compatible populations, suggesting that not only the reproductive system can influence inbreeding depression and that knowing more about the history of the populations is necessary. Finally, in chapter 4, I tested differences on inbreeding depression in two sister species with contrasting pollinators. Clarkia breweri is mainly pollinated by hawkmoths, which are known to migrate long distances and be sporadic foragers, while Clarkia concinna subsp. concinna is mainly pollinated by bees and beeflies, which tend to be local pollinators. The results do not support the hypothesis that hawkmoth-pollinated population will lead to higher inbreeding depression under inbreeding compared to bee-pollinated populations. The results suggest that pollinators influence on the populations mating system might be more variable than expected based on the pollinators size and behavior. Overall my results show that inbreeding depression is population-specific and more variable than anticipated based on the populations reproductive system or their main pollinator. My results also suggest that knowing more about the populations history and demography is important to contextualize inbreeding depression in the populations.

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