UC Riverside

Conservation of natural species requires an understanding of organisms' geographic ranges and existential threats that occur within these ranges. A species’ rarity or commonness is ultimately determined by taxonomy which defines boundaries between closely related species. As rare species tend to be at inherently greater extinction risk than widespread ones, taxonomy interacts heavily with conservation. Similarly, hybridization strongly interacts with taxonomy because it points to limitations in species boundaries. Hybridization also interacts directly with conservation in that hybrid individuals are difficult to classify in terms of legal conservation status, and outbreeding may be beneficial or harmful to species’ persistence depending on context. Thus, the topics of conservation, taxonomy, and hybridization are heavily intertwined, but they have not been expressly studied together as a conceptual framework. To develop this conceptual framework, I use the study system of manzanitas to investigate how these topics interact at three scales of observation. At the population level, I show that detecting hybridization led to the discovery of a new species of manzanita and ongoing hybridization poses a threat to its persistence. At higher scales of observation, hybridization could only be inferred indirectly but remained a prominent consideration. At the subregion scale, I show that the genetic distinctiveness of federally endangered Del Mar manzanita could only be observed after broad sampling and considering all neighboring manzanita species because they appear to be linked by hybridization. The study defines the range of Del Mar manzanita which is limited to the Coast of San Diego County. At the bioregional scale, I evaluate the phylogenetic relationships of 88% of species in the genus of manzanitas and find at least partial support for the majority investigated species. I can identify which taxa seem well-understood and which taxa require further study such as several widespread tetraploid species. Overall, the study suggests that for diverse systems with frequent hybridization, higher scales of observation are useful for identifying general patterns and complications such as cryptic hybridization, but taxonomic revision is better reserved until cases can be evaluated at small or intermediate scales, especially at the population scale where it is easier to directly observe hybridization.