Diverse historical processes shape deep phylogeographical divergence in the pollinating seed parasite Greya politella

Abstract

Understanding the historical framework in which species interactions have diversified across landscapes may help to partition the effects of vicariance and geographically variable selection in shaping the geographical mosaic of coevolving species. We used phylogeographical analyses of the pollinating seed parasite Greya politella (Lepidoptera: Prodoxidae) to define the historical processes that may have structured interactions of this species with its host plants across major biogeographical breaks in western North America. Using 648 bp of cytochrome oxidase I and amplified fragment length polymorphisims, we identified deep genetic breaks among some populations consistent with some definitions of cryptic species. A combination of phylogenetic and population genetic approaches indicates that different historical processes may have structured G. politella genetic diversity in four regions: northern Pacific Northwest, southern Oregon, southern Sierra Nevada, and the remainder of California. The northern Pacific Northwest had high genetic diversity likely due to glacial refugia and subsequent spatial expansion, concordant with some other taxa. Populations in southern Oregon possessed unique, closely related haplotypes with restricted gene flow, possibly indicating a long-standing set of populations in this endemic-rich region. Analyses of California populations showed evidence of restricted gene flow and spatial expansion with many closely related haplotypes that occupy a broad geographical range. Southern Sierra Nevada populations were genetically distinct and highly diverse, possibly due to a localized glacial refugium. Together, these results suggest that vicariance and population expansion, possibly in combination with geographically variable selection, have shaped the diversification of G. politella and its interactions with its host plants.

Floral Scent Contributes to Interaction Specificity in Coevolving Plants and Their Insect Pollinators

“…These species are self-incompatible , and previous studies have shown that the moths are the dominant pollinator of these plants at the study sites (Rich et al 2008;Thompson and Cunningham 2002;. Two of the plant species were chosen because they emit very different floral scent bouquets: Lithophragma parviflorum from Turnbull Wildlife Refuge (47 24.0'N, 117 34.0'W) in eastern Washington, and L. cymbalaria from the UC Santa Barbara Sedgwick Reserve in California (34 42.871'N, 120 2.999'W) .…”

“…At least five of the nine species in the Lithophragma genus are involved in a mutualistic relationship with the G. politella moth species complex (Rich et al 2008;Thompson 2010;. These four cryptic moth taxa are defined by genetically distinct mitochondrial haplotype clusters (Rich et al 2008), and also show evidence of morphological divergence, albeit with partly overlapping morphological distributions . The plants and insects appear in different combinations at different sites.…”

“…The plants and insects appear in different combinations at different sites. Thereby, the interaction range includes sites with pairwise interactions (1 moth subspecies/1 plant species) as well as sites where up to three Lithophragma species are pollinated by the same subspecies of moth (Rich et al 2008;JNT unpublished data). To our knowledge, there are no sites that include multiple subspecies of G. politella.…”

Diversification through multitrait evolution in a coevolving interaction

“…In some communities, however, insects other than Greya moths, especially solitary bees or bombyliid flies, contribute importantly to the pollination of woodland stars (17)(18)(19)(20). Nevertheless, the interaction between woodland stars and Greya moths has persisted for millions of years as the plants and moths have diversified (18,21).…”

“…Woodland star species are pollinated by moths in the Greya politella species complex, which includes up to four geographically separated, and molecularly divergent, cryptic species (21). The study sites included all four lineages, hereafter labeled G. politella PNW, OR, CA, and SN for Pacific Northwest, southern Oregon, California, and southern Sierra Nevada, respectively.…”