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James, Patrick M. A.; Cooke, Barry; Brunet, Bryan; Lumley, Lisa; Sperling, Felix; Fortin, Marie-Josée; Quinn, Vanessa S.; Sturtevant, Brian R.; Brunet, Bryan M. T.; Lumley, Lisa M.; Sperling, Felix A. H. 2014-12-03 Dispersal determines the flux of individuals, energy, and information and is therefore a key determinant of ecological and evolutionary dynamics. Yet, it remains difficult to quantify its importance relative to other factors. This is particularly true in cyclic populations in which demography, drift, and dispersal contribute to spatio-temporal variability in genetic structure. Improved understanding of how dispersal influences spatial genetic structure is needed to disentangle the multiple processes that give rise to spatial synchrony in irruptive species. In this study, we examined spatial genetic structure in an economically important irruptive forest insect, the spruce budworm (Choristoneura fumiferana) to better characterize how dispersal, demography, and ecological context interact to influence spatial synchrony in a localized outbreak. We characterized spatial variation in microsatellite allele frequencies using 231 individuals and 7 geographic locations. We show that: (1) gene flow among populations is likely very high (Fst ≈ 0); (2) despite an overall low level of genetic structure, important differences exist between adult (moth) and juvenile (larvae) life-stages; and (3) the localized outbreak is the likely source of moths captured elsewhere in our study area. This study demonstrates the potential of using molecular methods to distinguish residents from migrants and for understanding how dispersal contributes to spatial synchronization. In irruptive populations, the strength of genetic structure depends on the timing of data collection (e.g., trough vs. peak), location, and dispersal. Taking into account this ecological context allows us to make more general characterizations of how dispersal can affect spatial synchrony in irruptive populations.
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Blackburn, Gwylim S.; Brunet, Bryan M. T.; Muirhead, Kevin; Cusson, Michel; Béliveau, Catherine; Levesque, Roger C.; Lumley, Lisa M.; Sperling, Felix A. H. 2017-10-27 Populations are often exposed to multiple sources of gene flow, but accounts are lacking of the population genetic dynamics that result from these interactions or their effects on local evolution. Using a genomic clines framework applied to 1195 SNPs, we documented genome-wide, locus-specific patterns of introgression between Choristoneura occidentalis biennis spruce budworms and two ecologically divergent relatives, C. o. occidentalis and C. fumiferana, that it interacts with at alternate boundaries of its range. We observe contrasting hybrid indexes between these hybrid zones, no overlap in ‘gene flow outliers’ (clines showing relatively extreme extents or rates of locus-specific introgression), and variable linkage disequilibrium among those outliers. At the same time, correlated genome-wide rates of introgression between zones suggest the presence of processes common to both boundaries. These findings highlight the contrasting population genetic dynamics that can occur at separate frontiers of a single population, while also suggesting that shared patterns may frequently accompany cases of divergence-with-gene-flow that involve a lineage in common. Our results point to potentially complex evolutionary outcomes for populations experiencing multiple sources of gene flow.
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Campbell, Erin O.; Brunet, Bryan M.T.; Dupuis, Julian R.; Sperling, Felix A.H.; Brunet, Bryan M. T.; Sperling, Felix A. H. 2019-06-11 1. Sampling markers throughout a genome with restriction enzymes emerged in the 2000s as reduced representation shotgun sequencing (RRS). Rapid advances in sequencing technology have since spurred modifications of RRS, giving rise to many derivatives with unique names, such as restriction site-associated DNA sequencing (RADseq). But naming conventions have often been more creative than consistent and criteria for recognizing unique methods have been unclear, resulting in a proliferation of names characterized by ambiguity. 2. We give an overview of methodological and etymological relationships among 36 restriction enzyme-based methods, and survey the consistency of references to five prominent methods in the literature. 3. We identified several instances of methodological convergence, and note that many published derivatives have modified only minor elements of parent protocols. Misattribution through ambiguous or inconsistent literature references was observed in 8.4% of journal articles citing the original one and two-enzyme RADseq and GBS, as well as SBG publications. 4. The rapid expansion of names associated with derivative protocols is confusing and, in many cases, unwarranted. We urge greater restraint in naming derivative methods and suggest general guidelines for naming that promote a balance between clarity, descriptiveness, and recognition of scientific innovation.

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