An optimized RNA extraction method for diverse leaves of Hawaiian Metrosideros, a hypervariable tree species complex.

Premise: The isolation of RNA from trees is challenging due to the interference of polyphenols and polysaccharides with downstream processes. Furthermore, many RNA extraction protocols are time consuming and involve hazardous chemicals. To address these issues, we aimed to develop a safe protocol for high-quality RNA extraction from diverse Metrosideros taxa representing a broad range of leaf toughness, pubescence, and secondary metabolites. Methods and Results: We tested popular RNA isolation kits and protocols that were effective on other recalcitrant trees, including a broad range of optimization and purification steps. We optimized a protocol involving two silica-membrane column-based kits that yielded high-quantity RNA with an RNA integrity number >7 and without DNA contamination. All RNA samples were used successfully in a follow-on RNA-Seq experiment. Conclusions: We present an optimized high-throughput RNA extraction protocol that yielded high-quality and high-quantity RNA from three contrasting leaf phenotypes within a hyperdiverse woody species complex.

Phenotypic disruption of cuticular hydrocarbon production in hybrids between sympatric species of Hawaiian picture-wing Drosophila.

Interspecies hybrids can express phenotypic traits far outside the range of parental species. The atypical traits of hybrids provide insight into differences in the factors that regulate the expression of these traits in the parental species. In some cases, the unusual phenotypic traits of hybrids can lead to phenotypic dysfunction with hybrids experiencing reduced survival or reproduction. Cuticular hydrocarbons (CHCs) in insects are important phenotypic traits that serve several functions, including desiccation resistance and pheromones for mating. We used gas chromatography mass spectrometry to investigate the differences in CHC production between two closely related sympatric Hawaiian picture-wing Drosophila species, Drosophila heteroneura and D. silvestris, and their F1 and backcross hybrid offspring. CHC profiles differed between males of the two species, with substantial sexual dimorphism in D. silvestris but limited sexual dimorphism in D. heteroneura. Surprisingly, F1 hybrids did not produce three CHCs, and the abundances of several other CHCs occurred outside the ranges present in the two parental species. Backcross hybrids produced all CHCs with greater variation than observed in F1 or parental species. Overall, these results suggest that the production of CHCs was disrupted in F1 and backcross hybrids, which may have important consequences for their survival or reproduction.

Barriers and Facilitators to Accessing Digital Health Tools Faced by South Asian Canadians in Surrey, British Columbia: Community-Based Participatory Action Exploration Using Photovoice.

BACKGROUND: South Asian community members in Canada experience a higher burden of chronic disease than the general population. Digital health innovations provide a significant opportunity to address various health care challenges such as supporting patients in their disease self-management. However, South Asian community members are less likely to use digital tools for their health and face significant barriers in accessing them because of language or cultural factors. OBJECTIVE: The aim of this study is to understand the barriers to and facilitators of digital health tool uptake experienced by South Asian community members residing in Canada. METHODS: This study used a qualitative community-based participatory action research approach. Residents from Surrey, British Columbia, Canada, who spoke 1 of 4 South Asian languages (Hindi, Punjabi, Urdu, or Tamil) were invited to participate in focus group discussions. A subsample of the participants were invited to use photovoice methods in greater depth to explore the research topics. RESULTS: A total of 197 participants consented to the focus group discussions, with 12 (6.1%) participating in the photovoice phase. The findings revealed several key obstacles (older age, lack of education, and poor digital health literacy) and facilitators (social support from family or community members and positive attitudes toward technology) to using digital health tools. CONCLUSIONS: The results support the value of using a community-based participatory action research approach and photovoice methods to engage the South Asian community in Canada to better understand digital health competencies and needs. There were several important implications for policy makers and future research, such as continued engagement of community leaders by health care providers and administrators to learn about attitudes and preferences.

Ancestral polymorphisms shape the adaptive radiation of Metrosideros across the Hawaiian Islands.

Some of the most spectacular adaptive radiations begin with founder populations on remote islands. How genetically limited founder populations give rise to the striking phenotypic and ecological diversity characteristic of adaptive radiations is a paradox of evolutionary biology. We conducted an evolutionary genomics analysis of genus Metrosideros, a landscape-dominant, incipient adaptive radiation of woody plants that spans a striking range of phenotypes and environments across the Hawaiian Islands. Using nanopore-sequencing, we created a chromosome-level genome assembly for Metrosideros polymorpha var. incana and analyzed whole-genome sequences of 131 individuals from 11 taxa sampled across the islands. Demographic modeling and population genomics analyses suggested that Hawaiian Metrosideros originated from a single colonization event and subsequently spread across the archipelago following the formation of new islands. The evolutionary history of Hawaiian Metrosideros shows evidence of extensive reticulation associated with significant sharing of ancestral variation between taxa and secondarily with admixture. Taking advantage of the highly contiguous genome assembly, we investigated the genomic architecture underlying the adaptive radiation and discovered that divergent selection drove the formation of differentiation outliers in paired taxa representing early stages of speciation/divergence. Analysis of the evolutionary origins of the outlier single nucleotide polymorphisms (SNPs) showed enrichment for ancestral variations under divergent selection. Our findings suggest that Hawaiian Metrosideros possesses an unexpectedly rich pool of ancestral genetic variation, and the reassortment of these variations has fueled the island adaptive radiation.

Sustained Virologic Response of Patients Hospitalized Compared With Those Not Hospitalized During Treatment for Hepatitis C Virus With Direct-Acting Antivirals.

BACKGROUND: Direct-acting antivirals (DAAs) for treatment of hepatitis C virus (HCV) have resulted in great success through high attainment of sustained virologic response (SVR). Risk factors for DAA treatment failure are important to identify because of worsened outcomes with failure and high treatment cost. OBJECTIVE: We sought to identify whether hospitalization during treatment affects SVR. The primary outcome was the difference in SVR at 12 weeks after treatment. METHODS: This multicenter, single health system retrospective cohort review compared achievement of SVR between patients hospitalized during DAA treatment for HCV with those not hospitalized during treatment. RESULTS: Patients in the hospitalized cohort (n = 94) had more severe disease at baseline than nonhospitalized patients (n = 167) as indicated through higher Model for End-Stage Liver Disease (MELD) scores, Fibrosis-4 scores, and imaging-suggested or biopsy-confirmed cirrhosis. Patients hospitalized during treatment had lower SVR rates compared with those not hospitalized (87.2% vs 95.2%; P = 0.043) but failed to reach significance when inpatient mortality was excluded on secondary analysis (91.1% vs 95.2%; P = 0.195). Patients who were hospitalized and did not achieve SVR had higher MELD scores, were more likely to have intensive care unit stay, and had longer hospital stay compared with those who achieved SVR. Of 94 patients, 93 provided home supply of DAAs during hospitalization. CONCLUSION AND RELEVANCE: Patients hospitalized during DAA treatment for HCV had reduced rates of SVR. This reduced SVR rate may be driven by inpatient mortality and severity of liver disease. Patient education to bring home supply of medication for use during admission is an effective intervention.

Testing a school-based program to promote digital health literacy and healthy lifestyle behaviours in intermediate elementary students: The Learning for Life program.

Promoting digital health literacy and healthy lifestyle behaviours in children can lead to positive long-term health outcomes and prevent chronic diseases. However, there are few school-based interventions promoting this education to intermediate elementary students. The objective of this study was to test the effectiveness of a novel intervention to increase students' digital health literacy and health knowledge. Learning for Life is a classroom-based education program, developed for grade 4-7 students and delivered by teachers over six weeks. Three Canadian schools were recruited to deliver the intervention in 2018. This study had a pre-post design and no control group. Students' self-reported digital health literacy and healthy lifestyle behaviours were measured at pre-intervention (n = 126), post-intervention (n = 119), and two-month follow-up (n = 104). Students at pre-intervention had a mean (SD) age of 10.98 (0.56) years (57.1% females). Almost all (97%) students had unsupervised access to the Internet through a computer or smartphone. From pre- to post-intervention, students' digital health literacy increased (p = 0.009), but decreased from post-intervention to follow-up (p < 0.001). Post-intervention, the majority of students could identify at least one healthy behaviour (e.g., exercising one hour/day) and reported making at least one healthy change in their lives (e.g., eating more fruits/vegetables). This study demonstrated that the Learning for Life intervention can improve intermediate elementary students' digital health literacy over the short-term and help them learn and retain healthy lifestyle knowledge and behaviours. These findings affirm the need for interventions promoting digital healthy literacy and healthy lifestyle behaviours for this age group.

Comparing Adaptive Radiations Across Space, Time, and Taxa.

Adaptive radiation plays a fundamental role in our understanding of the evolutionary process. However, the concept has provoked strong and differing opinions concerning its definition and nature among researchers studying a wide diversity of systems. Here, we take a broad view of what constitutes an adaptive radiation, and seek to find commonalities among disparate examples, ranging from plants to invertebrate and vertebrate animals, and remote islands to lakes and continents, to better understand processes shared across adaptive radiations. We surveyed many groups to evaluate factors considered important in a large variety of species radiations. In each of these studies, ecological opportunity of some form is identified as a prerequisite for adaptive radiation. However, evolvability, which can be enhanced by hybridization between distantly related species, may play a role in seeding entire radiations. Within radiations, the processes that lead to speciation depend largely on (1) whether the primary drivers of ecological shifts are (a) external to the membership of the radiation itself (mostly divergent or disruptive ecological selection) or (b) due to competition within the radiation membership (interactions among members) subsequent to reproductive isolation in similar environments, and (2) the extent and timing of admixture. These differences translate into different patterns of species accumulation and subsequent patterns of diversity across an adaptive radiation. Adaptive radiations occur in an extraordinary diversity of different ways, and continue to provide rich data for a better understanding of the diversification of life.

Isolation of Metrosideros ('Ohi'a) Taxa on O'ahu Increases with Elevation and Extreme Environments.

Species radiations should be facilitated by short generation times and limited dispersal among discontinuous populations. Hawaii's hyper-diverse, landscape-dominant tree, Metrosideros, is unique among the islands' radiations for its massive populations that occur continuously over space and time within islands, its exceptional capacity for gene flow by both pollen and seed, and its extended life span (ca. >650 years). Metrosideros shows the greatest phenotypic and microsatellite DNA diversity on O'ahu, where taxa occur in tight sympatry or parapatry in mesic and montane wet forest on 2 volcanoes. We document the nonrandom distributions of 12 taxa (including unnamed morphotypes) along elevation gradients, measure phenotypes of ~6-year-old common-garden plants of 8 taxa to verify heritability of phenotypes, and examine genotypes of 476 wild adults at 9 microsatellite loci to compare the strengths of isolation across taxa, volcanoes, and distance. All 8 taxa retained their diagnostic phenotypes in the common garden. Populations were isolated by taxon to a range of degrees (pairwise FST between taxa: 0.004-0.267), and there was no pattern of isolation by distance or by elevation; however, significant isolation between volcanoes was observed within monotypic species, suggesting limited gene flow between volcanoes. Among the infraspecific taxa of Metrosideros polymorpha, genetic diversity and isolation significantly decreased and increased, respectively, with elevation. Overall, 5 of the 6 most isolated taxa were associated with highest elevations or otherwise extreme environments. These findings suggest a principal role for selection in the origin and maintenance of the exceptional diversity that occurs within continuous Metrosideros stands on O'ahu.

Divergent Selection and Primary Gene Flow Shape Incipient Speciation of a Riparian Tree on Hawaii Island.

A long-standing goal of evolutionary biology is to understand the mechanisms underlying the formation of species. Of particular interest is whether or not speciation can occur in the presence of gene flow and without a period of physical isolation. Here, we investigated this process within Hawaiian Metrosideros, a hypervariable and highly dispersible woody species complex that dominates the Hawaiian Islands in continuous stands. Specifically, we investigated the origin of Metrosideros polymorpha var. newellii (newellii), a riparian ecotype endemic to Hawaii Island that is purportedly derived from the archipelago-wide M. polymorpha var. glaberrima (glaberrima). Disruptive selection across a sharp forest-riparian ecotone contributes to the isolation of these varieties and is a likely driver of newellii's origin. We examined genome-wide variation of 42 trees from Hawaii Island and older islands. Results revealed a split between glaberrima and newellii within the past 0.3-1.2 My. Admixture was extensive between lineages within Hawaii Island and between islands, but introgression from populations on older islands (i.e., secondary gene flow) did not appear to contribute to the emergence of newellii. In contrast, recurrent gene flow (i.e., primary gene flow) between glaberrima and newellii contributed to the formation of genomic islands of elevated absolute and relative divergence. These regions were enriched for genes with regulatory functions as well as for signals of positive selection, especially in newellii, consistent with divergent selection underlying their formation. In sum, our results support riparian newellii as a rare case of incipient ecological speciation with primary gene flow in trees.

Varieties of the highly dispersible and hypervariable tree, Metrosideros polymorpha, differ in response to mechanical stress and light across a sharp ecotone.

PREMISE: The drivers of isolation between sympatric populations of long-lived and highly dispersible conspecific plants are not well understood. In the Hawaiian Islands, the landscape-dominant tree, Metrosideros polymorpha, displays extraordinary phenotypic differences among sympatric varieties despite high dispersibility of its pollen and seeds, thereby presenting a unique opportunity to investigate how disruptive selection alone can maintain incipient forms. Stenophyllous M. polymorpha var. newellii is a recently evolved tree endemic to the waterways of eastern Hawai'i Island that shows striking neutral genetic differentiation from its ancestor, wet-forest M. polymorpha var. glaberrima, despite sympatry of these forms. We looked for evidence for, and drivers of, differential local adaptation of these varieties across the range of M. polymorpha var. newellii. METHODS: For paired populations of these varieties, we compared seedling performance under contrasting light conditions and a strong water current characteristic of the riparian zone. We also conducted a reciprocal transplant experiment and contrasted adult leaf anatomy. RESULTS: Results suggest that the riparian zone is harsh and that selection involving the mechanical stress of rushing water, and secondarily, light, led to significant reciprocal immigrant inviability in adjacent forest and riparian environments. The strongest adaptive divergence between varieties was seen in leaves and seedlings from the site with the sharpest ecotone, coincident with the strongest genetic isolation of M. polymorpha var. newellii observed previously. CONCLUSIONS: These findings suggest that disruptive selection across a sharp ecotone contributes to the maintenance of an incipient riparian ecotype from within a continuous population of a long-lived and highly dispersible tree species.

Incipient ecological speciation between successional varieties of a dominant tree involves intrinsic postzygotic isolating barriers.

Whereas disruptive selection imposed by heterogeneous environments can lead to the evolution of extrinsic isolating barriers between diverging populations, the evolution of intrinsic postzygotic barriers through divergent selection is less certain. Long-lived species such as trees may be especially slow to evolve intrinsic isolating barriers. We examined postpollination reproductive isolating barriers below the species boundary, in an ephemeral hybrid zone between two successional varieties of the landscape-dominant Hawaiian tree, Metrosideros polymorpha, on volcanically active Hawai'i Island. These archipelago-wide sympatric varieties show the weakest neutral genetic divergence of any taxon pair on Hawai'i Island but significant morphological and ecological differentiation consistent with adaptation to new and old lava flows. Cross-fertility between varieties was high and included heterosis of F1 hybrids at the seed germination stage, consistent with a substantial genetic load apparent within varieties through low self-fertility and a lack of self-pollen discrimination. However, a partial, but significant, barrier was observed in the form of reduced female and male fertility of hybrids, especially backcross hybrids, consistent with the accumulation of genetic incompatibilities between varieties. These results suggest that partial intrinsic postzygotic barriers can arise through disruptive selection acting on large, hybridizing populations of a long-lived species.

Facilitators of and barriers to accessing clinical prevention services for the South Asian population in Surrey, British Columbia: a qualitative study.

BACKGROUND: British Columbia falls short in uptake of recommended clinical prevention services, with even lower rates among immigrant populations. This study explored facilitators of and barriers to uptake of clinical prevention services among people from South Asia, who represent 31% of the population in Surrey, British Columbia. METHODS: We used a qualitative descriptive approach and employed vignettes in a focus group setting to elicit perspectives of South Asian people on accessing clinical prevention services. Participants aged 40 years or more were recruited between October 2014 and February 2015 from health care and community settings such as older-adult housing, day programs and health education events. Letters of introduction to the study were provided in English or Punjabi or both to all potential participants. We conducted qualitative content analysis of the results. RESULTS: Sixty-two South Asian adults (36 women and 26 men) aged 40-87 years participated in 1 of 8 focus groups in health care or community settings. Facilitators of and barriers to accessing clinical prevention services were noted at the patient, primary care provider and health care system levels. Facilitators at the patient level included taking ownership over one's health, health literacy and respecting the provider's advice; barriers included fear of the diagnosis, death and/or procedures, perceived low risk of disease or utility of the intervention, and side effects of procedures. Provider factors centred on a trust-based patient-provider relationship, strong communication and adequate time during visits. Health care system factors included such facilitators as processes to routinely offer prevention services as part of other health care or social services, systems that encourage prevention-oriented family practice and services at low or no cost to the patient. INTERPRETATION: Our findings validate previously identified facilitators of and barriers to accessing preventive care for immigrant populations. However, the results suggest that system-level factors influencing the duration of primary care visits may have a more salient impact on uptake of clinical prevention services in this population.

Genomic Signatures of Speciation in Sympatric and Allopatric Hawaiian Picture-Winged Drosophila.

The Hawaiian archipelago provides a natural arena for understanding adaptive radiation and speciation. The Hawaiian Drosophila are one of the most diverse endemic groups in Hawaiì with up to 1,000 species. We sequenced and analyzed entire genomes of recently diverged species of Hawaiian picture-winged Drosophila, Drosophila silvestris and Drosophila heteroneura from Hawaiì Island, in comparison with Drosophila planitibia, their sister species from Maui, a neighboring island where a common ancestor of all three had likely occurred. Genome-wide single nucleotide polymorphism patterns suggest the more recent origin of D. silvestris and D. heteroneura, as well as a pervasive influence of positive selection on divergence of the three species, with the signatures of positive selection more prominent in sympatry than allopatry. Positively selected genes were significantly enriched for functional terms related to sensory detection and mating, suggesting that sexual selection played an important role in speciation of these species. In particular, sequence variation in Olfactory receptor and Gustatory receptor genes seems to play a major role in adaptive radiation in Hawaiian pictured-winged Drosophila.

Postzygotic barriers isolate sympatric species of Cyrtandra (Gesneriaceae) in Hawaiian montane forest understories.

PREMISE OF THE STUDY: Recent reviews of reproductive isolation (RI) in plants propose that boundaries between closely related species are maintained predominantly through prezygotic mechanisms. However, few experimental studies have explored how boundaries are maintained in long-lived species. Hawaiian Cyrtandra presents an intriguing challenge to our understanding of RI, as it comprises 60 shrub or small tree species that are almost exclusively restricted to wet forests, where sympatry of multiple species is common. METHODS: We assessed the relative strengths of pre- and postzygotic barriers among four species of Cyrtandra occurring at the extremes of the main Hawaiian Island's natural island-age gradient, Kaua'i (4.7 Myr) and Hawai'i Island (0.6 Myr), to contrast the strengths and stages of reproductive isolation among species at different stages of divergence. KEY RESULTS: A combination of F1 seed germination, F1 seedling survival, and F1 seedling growth isolated (61-91%) three of the species from sympatric relatives. In contrast, the fourth species was isolated (59%) from its sympatric relative through phenological differences alone. Significant postzygotic barriers in between-island crosses were also observed in one species. CONCLUSIONS: Results suggest that boundaries between sympatric Cyrtandra species in Hawaii are maintained predominantly through postzygotic barriers. Observations from between-island crosses indicate that postzygotic barriers can arise in allopatry, which may be important in the initial divergence of populations. Future studies of RI in Cyrtandra should include a broader range of species to determine if postzygotic isolating barriers are foremost in the maintenance of species boundaries in this large genus.

Note-taking and Handouts in The Digital Age.

Most educators consider note-taking a critical component of formal classroom learning. Advancements in technology such as tablet computers, mobile applications, and recorded lectures are altering classroom dynamics and affecting the way students compose and review class notes. These tools may improve a student's ability to take notes, but they also may hinder learning. In an era of dynamic technology developments, it is important for educators to routinely examine and evaluate influences on formal and informal learning environments. This paper discusses key background literature on student note-taking, identifies recent trends and potential implications of mobile technologies on classroom note-taking and student learning, and discusses future directions for note-taking in the context of digitally enabled lifelong learning.

Community-based research in action: tales from the Ktunaxa community learning centres project.

BACKGROUND: Rural communities, particularly Aboriginal communities, often have limited access to health information, a situation that can have significant negative consequences. To address the lack of culturally and geographically relevant health information, a community-university partnership was formed to develop, implement, and evaluate Aboriginal Community Learning Centres (CLCs). OBJECTIVES: The objective of this paper is to evaluate the community-based research process used in the development of the CLCs. It focuses on the process of building relationships among partners and the CLC's value and sustainability. METHODS: Semistructured interviews were conducted with key stakeholders, including principal investigators, community research leads, and supervisors. The interview transcripts were analyzed using an open-coding process to identify themes. RESULTS: Key challenges included enacting shared project governance, negotiating different working styles, and hiring practices based on commitment to project objectives rather than skill set. Technological access provided by the CLCs increased capacity for learning and collective community initiatives, as well as building community leads' skills, knowledge, and self-efficacy. An important lesson was to meet all partners "where they are" in building trusting relationships and adapting research methods to fit the project's context and strengths. CONCLUSIONS: Successful results were dependent upon persistence and patience in working through differences, and breaking the project into achievable goals, which collectively contributed to trust and capacity building. The process of building these partnerships resulted in increased capacity of communities to facilitate learning and change initiatives, and the capacity of the university to engage in successful research partnerships with Aboriginal communities in the future.

Primers for low-copy nuclear genes in Metrosideros and cross-amplification in Myrtaceae.

PREMISE OF THE STUDY: Primers were developed to amplify low-copy nuclear genes in Hawaiian Metrosideros (Myrtaceae). • METHODS AND RESULTS: Data from a pooled 454 Titanium run of the partial transcriptomes of four Metrosideros taxa were used to identify the loci of interest. Ten exon-primed intron-crossing (EPIC) markers were amplified and sequenced directly with success in Metrosideros, as well as in a representative selection of Myrtaceae, including Syzygium, Psidium, and Melaleuca for most of the markers. The loci amplified ranged between 500 and 1100 bp, and up to 117 polymorphic sites were observed within an individual gene alignment. Two introns contained microsatellites in some of the species. • CONCLUSIONS: These novel primer pairs should be useful for phylogenetic analysis and population genetics of a broad range of Myrtaceae, particularly the diverse fleshy-fruited tribes Syzygieae and Myrteae.

Cryptic adaptive radiation in tropical forest trees in New Caledonia.

The causes of the species richness of tropical trees are poorly understood, in particular the roles of ecological factors such as soil composition. The nickel(Ni)-hyperaccumulating tree genus Geissois (Cunoniaceae) from the South-west Pacific was chosen as a model of diversification on different substrates. Here, we investigated the leaf element compositions, spatial distributions and phylogeny of all species of Geissois occurring on New Caledonia. We found that New Caledonian Geissois descended from a single colonist and diversified relatively quickly into 13 species. Species on ultramafic and nonultramafic substrates showed contrasting patterns of leaf element composition and range overlap. Those on nonultramafic substrates were largely sympatric but had distinct leaf element compositions. By contrast, species on ultramafic substrates showed similar leaf element composition, but occurred in many cases exclusively in allopatry. Further, earlier work showed that at least three out of these seven species use different molecules to bind Ni. Geissois qualifies as a cryptic adaptive radiation, and may be the first such example in a lineage of tropical forest trees. Variation in biochemical strategies for coping with both typical and adverse soil conditions may help to explain the diversification and coexistence of tropical forest trees on similar soil types.

Divergence within and among 3 varieties of the endemic tree, 'Ohi'a Lehua (Metrosideros polymorpha) on the eastern slope of Hawai'i Island.

Examination of neutral genetic structure within young, hypervariable tree species over heterogeneous landscapes can yield insight into the causes of divergence within trees. Three varieties of the Hawaiian-forest-dominant, Metrosideros polymorpha, occur across the main islands and partition 2 striking environmental gradients on young Hawai'i Island. In an examination of 6 nuclear microsatellite loci across 10 populations on east Hawai'i, we found differentiation among varieties (mean F ST = 0.065; max = 0.081) that exceeded that observed among populations of some continental tree species over much broader spatial scales. High-elevation var. polymorpha exhibited the strongest average differentiation (F ST = 0.071). Weaker differentiation between the early- and late-successional varieties was consistent with previous records of high hybridization between these varieties coupled with differential selection favoring var. incana in early-successional or dry environments, and var. glaberrima in late-successional environments. A comparison of within-variety F ST values suggests that active volcanoes shape the genetic structure of early- and late-successional varieties differently. Examination of genetic structure of these same varieties on older islands is required to assess the degree to which the differentiation observed on Hawai'i Island is attributable to multiple colonizations of this young island by partially diverged forms versus divergence in situ.

Gene discordance in phylogenomics of recent plant radiations, an example from Hawaiian Cyrtandra (Gesneriaceae).

Resolving species relationships within recent radiations requires analysis at the interface of phylogenetics and population genetics, where coalescence and hybridization may confound our understanding of relationships. We developed 18 new primer pairs for nuclear loci in Cyrtandra (Gesneriaceae), one of the largest plant radiations in the Pacific Islands, and tested the concordance of 14 loci in establishing the phylogenetic relationships of a small number of Hawaiian species. Four genes yielded tree topologies conflicting with the primary concordance tree, suggesting plastid capture and horizontal transfer via hybridization. Combining all concordant genes yielded a tree with stronger support and a different topology from the total-evidence tree. We conclude that a small number of genes may be insufficient for accurate reconstruction of the phylogenetic relationships among closely related species. Further, the combination of genes for phylogenetic analysis without preliminary concordance tests can yield an erroneous tree topology. It seems that the number of genes needed for phylogenetic analysis of closely related species is significantly greater than the small numbers commonly used, which fail to isolate coalescence, introgression and hybridization.