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Data from: Population structure of mountain pine beetle symbiont Leptographium longiclavatum and the implication on the multipartite beetle-fungi relationships
Tsui, Clement Kin-Ming; Farfan, Lina; Roe, Amanda D.; Rice, Adrianne V.; Cooke, Janice E. K.; El-Kassaby, Yousry A.; Hamelin, Richard C. — 2015-06-17 Over 18 million ha of forests have been destroyed in the past decade in Canada by the mountain pine beetle (MPB) and its fungal symbionts. Understanding their population dynamics is critical to improving modeling of beetle epidemics and providing potential clues to predict population expansion. Leptographium longiclavatum and Grosmannia clavigera are fungal symbionts of MPB that aid the beetle to colonize and kill their pine hosts. We investigated the genetic structure and demographic expansion of L. longiclavatum in populations established within the historic distribution range and in the newly colonized regions. We identified three genetic clusters/populations that coincide with independent geographic locations. The genetic profiles of the recently established populations in northern British Columbia (BC) and Alberta suggest that they originated from central and southern BC. Approximate Bayesian Computation supports the scenario that this recent expansion represents an admixture of individuals originating from BC and the Rocky Mountains. Highly significant correlations were found among genetic distance matrices of L. longiclavatum, G. clavigera, and MPB. This highlights the concordance of demographic processes in these interacting organisms sharing a highly specialized niche and supports the hypothesis of long-term multipartite beetle-fungus co-evolutionary history and mutualistic relationships.
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Data from: Spatial genetic structure of the mountain pine beetle (Dendroctonus ponderosae) outbreak in western Canada: historical patterns and contemporary dispersal
Samarasekera, G. D. N. Gayathri; Bartell, Nicholas V.; Lindgren, B. Staffan; Cooke, Janice E. K.; Davis, Corey S.; James, Patrick M. A.; Coltman, David W.; Mock, Karen E.; Murray, Brent W. — 2011-10-17 Environmental change has a wide range of ecological consequences, including species extinction and range expansion. Many studies have shown that insect species respond rapidly to climatic change. A mountain pine beetle epidemic of record size in North America has led to unprecedented mortality of lodgepole pine, and a significant range expansion to the northeast of its historic range. Our goal was to determine the spatial genetic variation found among outbreak population from which genetic structure, and dispersal patterns may be inferred. Beetles from 49 sampling locations throughout the outbreak area in western Canada were analysed at 13 microsatellite loci. We found significant north-south population structure as evidenced by: (i) Bayesian-based analyses, (ii) north-south genetic relationships and diversity gradients; and (iii) a lack of isolation-by-distance in the northernmost cluster. The north-south structure is proposed to have arisen from the processes of postglacial colonization as well as recent climate-driven changes in population dynamics. Our data support the hypothesis of multiple sources of origin for the outbreak and point to the need for population specific information to improve our understanding and management of outbreaks. The recent range expansion across the Rocky Mountains into the jack/lodgepole hybrid and pure jack pine zones of northern Alberta is consistent with a northern British Columbia origin. We detected no loss of genetic variability in these populations, indicating that the evolutionary potential of mountain pine beetle to adapt has not been reduced by founder events. This study illustrates a rapid range-wide response to the removal of climatic constraints, and the potential for range expansion of a regional population.
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Data from: Characterizing the physical and genetic structure of the lodgepole pine × jack pine hybrid zone: mosaic structure and differential introgression
Cullingham, Catherine I.; James, Patrick M. A.; Cooke, Janice E. K.; Coltman, David W. — 2012-04-10 Understanding the physical and genetic structure of hybrid zones can illuminate factors affecting their formation and stability. In north central Alberta, lodgepole pine (P. contorta Dougl. ex Loud. var. latifolia) and jack pine (P. banksiana Lamb) form a complex and poorly defined hybrid zone. Better knowledge of this zone is relevant, given the recent host expansion of mountain pine beetle into jack pine. We characterized the zone by genotyping 1998 lodgepole, jack pine and hybrids from British Columbia, Alberta, Saskatchewan, Ontario and Minnesota at 11 microsatellites. Using Bayesian algorithms, we calculated genetic ancestry and used this to model the relationship between species occurrence and environment. In addition, we analyzed the ancestry of hybrids to calculate the genetic contribution of lodgepole and jack pine. Finally we measured the amount of gene flow between the pure species. We found the distribution of the pine classes is explained by environmental variables, and these distributions differ from classic distribution maps. Hybrid ancestry was biased towards lodgepole pine; however gene flow between the two species was equal. The results of this study suggest that the hybrid zone is complex and influenced by environmental constraints. As a result of this analysis, range limits should be redefined. https://creativecommons.org/publicdomain/zero/1.0/
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Data from: Comparative phylogeography, genetic differentiation, and contrasting reproductive modes in three fungal symbionts of a multipartite bark beetle symbiosis
Roe, Amanda D.; Rice, Adrianne V.; Coltman, David W.; Cooke, Janice E. K.; Sperling, Felix A. H. — 2010-11-08 Multipartite symbioses are complex symbiotic relationships involving multiple interacting partners. These types of partnerships provide excellent opportunities in which to apply a comparative approach to identify common historical patterns of population differentiation and species-specific life history traits. Using three symbiotic blue stain fungal species (Ophiostomatacea) associated with outbreaking populations of the mountain pine beetle (Dendroctonus ponderosae Hopkins) in western Canada, we applied phylogenetic, population genetic, and demographic approaches to clarify phylogeographic patterns among the three fungal species. Broadly, the three species showed significant population differentiation, forming northern and southern populations, despite dramatic differences in haplotype diversity. Finer scale structuring and population demographic patterns were less consistent, showing some interspecific incongruence. By contrasting these species simultaneously, we were able to identify differences in recombination rate and ecological traits that can explain the observed patterns of incongruence among the fungal species. By applying a comparative approach to partners of a multipartite symbiosis we were able to distinguish congruent population structuring and species-specific differences that help us to understand the complexity and evolution of this symbiotic system.
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Data from: Population structure and migration pattern of a conifer pathogen, Grosmannia clavigera, as influenced by its symbiont the mountain pine beetle
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Tsui, Clement Kin Ming; Roe, Amanda D.; El-Kassaby, Yousry A.; Rice, Adrianne V.; Massoumi Alamouti, Sepideh; Sperling, Felix A. H.; Cooke, Janice E. K.; Bohlmann, Jörg; Hamelin, Richard C. — 2011-09-13 We investigated the population structure of Grosmannia clavigera (Gc), a fungal symbiont of the mountain pine beetle (MPB) that plays a crucial role in the establishment and reproductive success of this pathogen. This insect–fungal complex has destroyed over 16 million ha of lodgepole pine forests in Canada, the largest MPB epidemic in recorded history. During this current epidemic, MPB has expanded its range beyond historically recorded boundaries, both northward and eastward, and has now reached the jack pine of Alberta, potentially threatening the Canadian boreal forest. To better understand the dynamics between the beetle and its fungal symbiont, we sampled 19 populations in western North America and genotyped individuals from these populations with eight microsatellite markers. The fungus displayed high haplotype diversity, with over 250 unique haplotypes observed in 335 single spore isolates. Linkage equilibria in 13 of the 19 populations suggested that the fungus reproduces sexually. Bayesian clustering and distance analyses identified four genetic clusters that corresponded to four major geographical regions, which suggested that the epidemic arose from multiple geographical sources. A genetic cluster north of the Rocky Mountains, where the MPB has recently become established, experienced a population bottleneck, probably as a result of the recent range expansion. The two genetic clusters located north and west of the Rocky Mountains contained many fungal isolates admixed from all populations, possibly due to the massive movement of MPB during the epidemic. The general agreement in north–south differentiation of MPB and G. clavigera populations points to the fungal pathogen’s dependence on the movement of its insect vector. In addition, the patterns of diversity and the individual assignment tests of the fungal associate suggest that migration across the Rocky Mountains occurred via a northeastern corridor, in accordance with meteorological patterns and observation of MPB movement data. Our results highlight the potential of this pathogen for both expansion and sexual reproduction, and also identify some possible barriers to gene flow. Understanding the ecological and evolutionary dynamics of this fungus–beetle association is important for the modelling and prediction of MPB epidemics.

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(auteur : Cooke, Janice E. K.)

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