Assessments of population genetic structure have become an increasing focus as they can provide valuable insight into patterns of migration and gene flow. STRUC-TURE, the most highly cited of several clustering-based methods, was developed to provide robust estimates without the need for populations to be determined a priori. STRUCTURE introduces the problem of selecting the optimal number of clusters, and as a result, the DK method was proposed to assist in the identification of the "true" number of clusters. In our review of 1,264 studies using STRUCTURE to explore population subdivision, studies that used DK were more likely to identify K = 2 (54%, 443/822) than studies that did not use DK (21%, 82/386). A troubling finding was that very few studies performed the hierarchical analysis recommended by the authors of both DK and STRUCTURE to fully explore population subdivision. Furthermore, extensions of earlier simulations indicate that, with a representative number of markers, DK frequently identifies K = 2 as the top level of hierarchical structure, even when more subpopulations are present. This review suggests that many studies may have been over-or underestimating population genetic structure; both scenarios have serious consequences, particularly with respect to conservation and management. We recommend publication standards for population structure results so that readers can assess the implications of the results given their own understanding of the species biology.

Despite taxonomy's 250-year history, the past 20 years have borne witness to remarkable advances in technology and techniques, as well as debate. DNA barcoding has generated a substantial proportion of this debate, with its proposition that a single mitochondrial sequence will consistently identify and delimit species, replacing more evidence-rich and time-intensive methods. Although mitochondrial DNA (mtDNA) has since been the focus of voluminous discussion and case studies, little effort has been made to comprehensively evaluate its success in delimiting closely related species. We have conducted the first broadly comparative literature review addressing the efficacy of molecular markers for delimiting such species over a broad taxonomic range. By considering only closely related species, we sought to avoid confusion of success rates with those due to deeply divergent taxa. We also address whether increased populationlevel or geographic sampling affects delimitation success. Based on the results from 101 studies, we found that all marker groups had approximately equal success rates ( 70%) in delimiting closely related species and that the use of additional loci increased average delimitation success. We also found no relationship between increased sampling of intraspecific variability and delimitation success. Ultimately, our results support a multilocus integrative approach to species delimitation and taxonomy.

A new species, Contarinia brassicola Sinclair (Diptera: Cecidomyiidae), which induces flower galls on canola (Brassica napus Linnaeus and Brassica rapa Linnaeus (Brassicaceae)), is described from Saskatchewan and Alberta, Canada. Larvae develop in the flowers of canola, which causes swelling and prevents opening, pod formation, and seed set. Mature larvae exit the galls, fall to the soil, and form cocoons. Depending on conditions, larvae will either pupate and eclose in the same calendar year or enter facultative diapause and emerge the following year. At least two generations of C. brassicola occur each year. Adults emerge from overwintering cocoons in the spring and lay eggs on developing canola flower buds. The galls produced by C. brassicola were previously attributed to the swede midge, Contarinia nasturtii (Kieffer) in Saskatchewan; here, we compare and list several characters to differentiate the two species.

Populations delineated based on genetic data are commonly used for wildlife conservation and management. Many studies use the program structure combined with the ΔK method to identify the most probable number of populations (K). We recently found K = 2 was identified more often when studies used ΔK compared to studies that did not. We suggested two reasons for this: hierarchical population structure leads to underestimation, or the ΔK method does not evaluate K = 1 causing an overestimation. The present contribution aims to develop a better understanding of the limits of the method using one, two and three population simulations across migration scenarios. From these simulations we identified the “best K” using model likelihood and ΔK. Our findings show that mean probability plots and ΔK are unable to resolve the correct number of populations once migration rate exceeds 0.005. We also found a strong bias towards selecting K = 2 using the ΔK method. We used these data to identify the range of values where the ΔK statistic identifies a value of K that is not well supported. Finally, using the simulations and a review of empirical data, we found that the magnitude of ΔK corresponds to the level of divergence between populations. Based on our findings, we suggest researchers should use the ΔK method cautiously; they need to report all relevant data, including the magnitude of ΔK, and an estimate of connectivity for the research community to assess whether meaningful genetic structure exists within the context of management and conservation.

Swallowtail butterflies (Lepidoptera: Papilionidae) have been instrumental in understanding many foundational concepts in biology; despite this, a resolved and robust phylogeny of the group has been a major impediment to elucidating patterns and processes of their ecological and evolutionary history. This study presents a mitogenomic, time‐calibrated phylogeny for all swallowtail genera. A shotgun sequencing approach was performed to obtain 32 complete mitogenomes that were added to available butterfly mitogenomes, resulting in a dataset including 142 butterfly taxa (and four outgroups) representing all butterfly families. Phylogenetic analyses were carried out under maximum likelihood (ML) and Bayesian inferences (BIs) with alternative partitioning strategies and the mixture (CAT) model. To test competing hypotheses about the systematics of Papilionidae, such as the enigmatic position of Baronia brevicornis or the status of the tribe Teinopalpini, we estimated the marginal likelihood of alternative topologies and computed Bayes factors. Estimates of divergence times were assessed using a Bayesian relaxed‐clock approach calibrated with six fossils while testing for the number of clocks. The results recovered a well‐resolved and supported phylogeny confirming that Baroniinae is sister to Parnassiinae + Papilioninae, both recovered as monophyletic. It also laid the foundations for classification at tribe and genus level, suggesting that the tribe Teinopalpini only contains the genus Teinopalpus (Meandrusa being sister to Papilio). The number of molecular clocks in dating analyses had a significant impact on divergence times. A single clock recovered an origin of butterflies in the Cretaceous (98, 66–188 Ma) and also for swallowtails (85, 55–163 Ma), while partitioning the clocks yielded an origin of Papilionoidea in the very Late Cretaceous (71, 64–86 Ma), and all butterfly families originated in the aftermath of the Cretaceous–Paleogene extinction. These results challenge previous studies suggesting that butterflies appeared in the Early Cretaceous, 110 Ma, concurrently with the rise of angiosperms.

Mayr, 1963; Nosil, 2012). When genetic divergence has a strong spatial component, causes are generally attributed to spatial variation in evolutionary processes, such as gene flow, genetic drift,

Local adaptation can be a fundamental component of speciation, but its dynamics in relation to gene flow are not necessarily straightforward. Herbivorous taxa with localized host plant or habitat specialization across their geographic range are ideal models for investigating the patterns and constraints of local adaptation and its impact on diversification. The charismatic, day‐flying moths of the Hemileuca maia species complex (Lepidoptera: Saturniidae) are such taxa, as they are geographically widespread, exhibit considerable ecological and morphological variability and host and habitat specificity, but apparently lack genetic differentiation across their range. Here, we use genomewide single nucleotide polymorphisms to assess relationships and population structure of this group across North America and investigate the scales where genomic divergence correlates with adaptive ecological characteristics. In contrast to previous genetic studies of the group, we find broad‐ and fine‐scale genetic differentiation between lineages, which is at odds with various levels of taxonomic description and recognition of conservation units. Furthermore, ecological specialization only explains some fine‐scale genetic differentiation, and across much of the group's range, local adaptation is apparently occurring in the face of strong gene flow. These results provide unprecedented insight into drivers of speciation in this group, the relationship between taxonomy and genomics‐informed species boundaries and conservation management of internationally protected entities. Broadly, this system provides a model for understanding how local adaptation in an herbivore can arise and be maintained in the face of apparently strong gene flow, and the importance of geographic isolation in generating genomic divergence, despite a lack of ecological divergence.

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