Phylogeographic insights into an irruptive pest outbreak

Abstract

Irruptive forest insect pests cause considerable ecological and economic damage, and their outbreaks have been increasing in frequency and severity. We use a phylogeographic approach to understand the location and progression of an outbreak by the MPB (Dendroctonus ponderosae Hopkins), an irruptive bark beetle that has caused unprecedented damage to lodgepole pine forests in western North America and is poised to expand its range across the boreal forest. We sampled MPB populations across British Columbia and Alberta and used phylogeographic methods to describe lineage diversification, characterize population structure, investigate expansion dynamics, and identify source populations of the outbreak. Using 1181 bp of mitochondrial DNA sequence from 267 individuals, we found high haplotype diversity, low nucleotide diversity, and limited lineage diversification. The overall pattern was consistent with isolation by distance at a continental scale, and with reduced diversity and population structure in the northerly, outbreak regions. Post-Pleistocene expansion was detected, however more recent expansion signals were not detected, potentially due to the size and rapid rate of range expansion. Based on the limited genetic structure, there were likely multiple source populations in southern British Columbia, although the magnitude of the demographic expansion and rate of spread have obscured the signature of these source populations. Our data highlight the need for caution in interpreting phylogeographic results for species with similar demographics.

Population Structure of Mountain Pine Beetle Symbiont Leptographium longiclavatum and the Implication on the Multipartite Beetle-Fungi Relationships

“…The genetic diversity of L. longiclavatum in northern and central BC is comparable. If colonization/expansion had only originated from a southern population following the end of the glacial period, we would have observed a decreasing diversity from south to north with increasing latitude [78] as observed in G. clavigera and MPB [8], [38], [72]. This contrasting diversity pattern might suggest a centre of diversity for L. longiclavatum in central BC or the presence of glacial refugia [79], where the historical gene pool was maintained during the ice age.…”

Repurposing population genetics data to discern genomic architecture: A case study of linkage cohort detection in mountain pine beetle (Dendroctonus ponderosae)

“…These speciation events are driven by rapid degradation of the neo‐Y chromosome proceeding independently between populations. In addition to rapid changes in sex chromosomes, changes in climate have expanded MPB's Canadian range northward and eastward into naive landscapes and host plants, providing an opportunity for adaptive radiation (Carroll, Taylor, Regniere, & Safranyik, ; Cullingham, Roe, Sperling, & Coltman, ; Fauria & Johnson, ; Janes et al, ). Within the beetle's Canadian range, MPB population genetic structure has a well‐defined north–south division (Batista et al, ; Cullingham et al, ; Janes et al, ; Mock et al, ; Samarasekera et al, ), but lacks fine‐scale population structure (Janes et al, ).…”

Genetic diversity of Thaumetopoea pityocampa in Greece: the role of Quaternary changes in Aegean Sea

“…This has already been done for parts of southern Europe like the Iberian Peninsula, France and Italy [22], as well as for T. wilkinsoni in Turkey [24]. An analysis of populations in the glacial refuges in Greece, however, [16], has yet to be undertaken.…”

“…To better understand and investigate the range expansions and possible control measures for a pest, a phylogenetic analysis can be used [22,23]. This has already been done for parts of southern Europe like the Iberian Peninsula, France and Italy [22], as well as for T. wilkinsoni in Turkey [24].…”