Recruitment and Feasibility of Hair Cortisol Collection in a Sample of Ethnically and Sexually Diverse, Low-Income Adults: A Qualitative Community-Partnered Participatory Research Study.

The current study describes how a community-partnered participatory research (CPPR) model was used to enhance hair cortisol research engagement among low-income adults of diverse ethnicities and sexual and gender identities. Participants' reported motivations and concerns surrounding providing a hair sample are also described. Participants from a larger longitudinal study were invited to provide a hair sample and/or complete acceptability interviews. Results indicated that 71% of all persons (N=133) contacted participated in the current study, of whom 82% provided hair samples. Several themes emerged from the interviews indicating that participants were motivated to provide a hair sample due to internal and external factors; however, concerns about mistrust of research remained. Thus, collecting biospecimens in research with underserved groups requires careful consideration of benefits and risks to the individual and their communities. Our results provide guidelines for engaging low-income racially/ethnically and sexually diverse community members in biospecimen research to understand stress-health relationships.

"I Don't Feel at Home in This World" Sexual and Gender Minority Emerging Adults' Self-Perceived Links Between Their Suicidal Thoughts and Sexual Orientation or Gender Identity.

OBJECTIVES: To examine whether sexual and gender minority (SGM) emerging adults perceived their SGM status was linked to suicidal ideation, and to explore if their responses fell within tenets of the minority stress framework. METHOD: Open text (survey) responses of Dutch and Flemish SGM emerging adults (n = 187) were thematically analysed using the constant comparative comparison method for qualitative analysis. RESULTS: We identified 8 themes in our qualitative analysis. Two themes fell within the scope of the minority stress framework that has received little attention: (1) concerns about relationships and family planning and (2) feeling different (internal stressor). Two additional themes emerged largely beyond the scope of existing minority stress framework studies on suicidality: (3) SGM-related questioning; (4) negativity in LGBT communities. Four established minority stress framework themes emerged: (5) gender identity stress; (6) victimization; (7) coming-out stress; (8) psychological difficulties linked to SGM status. CONCLUSION: Suicide prevention needs to focus on supporting SGM emerging adults who worry about feeling "different", or who have concerns over their romantic and family life, on reducing gender minority stress, as well as on caring for those who are victimized due to their sexual or gender identity.

Greater lifetime stressor exposure is associated with poorer mental health among sexual minority people of color.

BACKGROUND: Research has shown that sexual minority people of color experience pervasive and sometimes severe life stressors that increase their risk of experiencing mental health problems, and that can contribute to lifelong health disparities. However, no studies in this population have investigated stressor exposure occurring over the entire lifespan. Moreover, it remains unknown whether these stressor-health effects differ based on the timing or types of stressors experienced. PURPOSE: The purpose of this study is to examine how cumulative lifetime stressor exposure is associated with mental health among Black, Latinx, and biracial Black-Latinx sexual minority persons. METHOD: Participants were 285 ethnic/racial minority young adults (Mage = 25.18 years old, SD = 1.94, age range = 19-29 years), who completed the Stress and Adversity Inventory for Adults to assess for retrospective reports of lifetime stressor count and severity. The Brief Symptom Inventory was used to assess participants' symptoms of anxiety, depression, and somatization, which were the main outcomes. Most participants identified as cisgender male (94.7%) and gay (74.2%), with the remaining participants identifying as transgender or genderqueer/nonbinary for gender and bisexual/pansexual, queer, or another sexual orientation. RESULTS: Multiple regression analyses indicated that experiencing more-and more severe-stressors across the lifespan was related to greater anxiety, depressive, and somatization symptoms. These effects were robust while controlling for race/ethnicity, sexual orientation, education, and employment status, and they differed based on stressor exposure timing, type, primary life domain, and core social-psychological characteristic. CONCLUSION: Greater cumulative lifetime stressor exposure is related to poorer mental health among sexual minority people of color. Screening for lifetime stressors may thus help identify at-risk persons and provide an opportunity to intervene to help mitigate or prevent mental health disparities in multiply stigmatized adults.

Explaining behavioral health differences in urban and rural sexual minority adolescents: A longitudinal investigation of minority stress in a diverse national sample of sexual minority adolescents: A longitudinal investigation of minority stress in a diverse national sample of sexual minority adolescents.

PURPOSE: Experiences of sexuality-based discrimination (ie, minority stressors) against youth who identify as nonheterosexual (ie, sexual minority) have been associated with increased symptoms of anxiety, depression, and post-traumatic stress disorder (PTSD) for sexual minority adolescents (SMA; ages 14-17). However, little is known about the experiences of SMA living in rural communities across the United States. Thus, the present study sought to examine differences in mental health patterns between urban and rural dwelling SMA, and to see whether these differences are, at least in part, explained by experiences of lifetime minority stress. METHODS: A nationwide sample of SMA residing in the United States (N = 2,558; aged 14-17, M = 15.90 years, SD = 0.98) was recruited through purposive social media and respondent-driven sampling methods to complete a cross-sectional survey online. Measures included those of minority stress, urbanicity, and symptoms of anxiety, depression, and PTSD. Parallel multiple mediation (PMM) analysis was employed to test whether urbanicity was associated with anxiety, depressive, and PTSD symptoms through reported lifetime minority stress. FINDINGS: On average, SMA living in rural areas significantly reported more lifetime minority stress, depressive, and PTSD symptoms than SMA living in urban settings. Results from our PMM analysis indicated that heightened experiences of lifetime minority stress indirectly linked the effects of living in rural areas on anxiety (b = -0.288, 95% CI = [-0.491, -0.085]), depressive (b = -0.158, 95% CI = [-0.270, -0.047), and PTSD symptoms PTSD (b = -0.349, 95% CI = [-0.596, -0.105]). The model accounted for 16.8%, 18%, and 24.1% of the variability in anxiety symptoms, depressive symptoms, and PTSD symptoms, respectively. CONCLUSIONS: SMA in our study who reside in rural areas reported elevated minority stress, depressive, and PTSD symptoms as compared to their urban dwelling peers. Our study found that lifetime experiences of minority stress fully mediated the relationship between urbanicity and both depressive and PTSD symptoms, and partially mediated the relationship between urbanicity and anxiety. These findings highlight the need to increase support for rural youth who are growing into adulthood and may find continuing challenges in their family, peer, and community relationships.

Agaricus macrochlamys, a New Species from the (Sub)tropical Cloud Forests of North America and the Caribbean, and Agaricus fiardii, a New Synonym of Agaricus subrufescens.

Agaricus is a genus of fungi in the family Agaricaceae, with several highly priced edible and medicinal species. Here we describe Agaricus macrochlamys, a new species, in A. sect. Arvenses, sympatric and morphologically cryptic with the edible and medicinally cultivated mushroom, A. subrufescens. Phylogenetic analyses showed that A. macrochlamys is closely related to A. subrufescens, and that A. fiardii is a new synonym of A. subrufescens. Despite being morphologically cryptic, A. macrochlamys can be distinguished from A. subrufescens by several ITS and tef1α species-specific markers and a 4-bp insertion in the tef1α sequence. Furthermore, A. subrufescens is a cosmopolitan species, while A. macrochlamys distribution is so far restricted to Mexico, the Dominican Republic, and the United States.

Adrenocortical responses of emerging adults in California in the two months following the Pulse night club massacre: Evidence for distal stress responses.

This study examined adrenocortical responses in the days following the Pulse nightclub massacre on June 12, 2016, among emerging adults in Northern California (N = 202; M = 23.18 years, SD = 2.56; 25% LGBQ-Latinx, 25% LGBQ-White, 25% Straight-Latinx, and 25% Straight-White) between June 13-August 12, 2016. As predicted, participants tested more proximally to the massacre had higher waking cortisol (intercepts) and flatter diurnal cortisol output (slopes), indicative of time-dependent adrenocortical arousal across the day. The effect of days post-massacre on waking cortisol was moderated by daily distress, with days since the Pulse massacre predicting waking cortisol significant only for participants reporting lower distress; participants who reported feeling higher daily distress had elevated waking cortisol across the testing period. These findings were independent of weekly personal stressors, and consistent across participants' demographic and identity characteristics. The violent attack at the Pulse nightclub was connected to increased waking cortisol and diurnal cortisol production for several days after the massacre, in a distal population exposed to the massacre vicariously, and especially for individuals not experiencing other, personal stressors. Heightened physiological responses to violent crimes support policy efforts to protect vulnerable communities, including violence prevention, gun control, and community-based trauma response services for those directly and indirectly affected by gun violence.

Conceptualizing the Influence of Social and Structural Determinants of Neurobiology and Mental Health: Why and How Biological Psychiatry Can Do Better at Addressing the Consequences of Inequity.

Psychiatry and allied disciplines have recognized the potency of structural and social determinants of mental health, yet there has been scant attention given to the roles of neurobiology in the links between structural and social determinants and mental health. In this article, we make the case for why greater attention must be given to structural and social determinants of biological psychiatry by researchers, practitioners, and policy-makers. After defining these terms and theoretical frameworks for considering their relevance in biological psychiatry, we review empirical research with marginalized and minoritized racial, ethnic, gender, sexual, and economic communities that reveals the ways in which structural and social determinants affect neurobiological functioning with implications for mental health. We give particular emphasis to developmental science and developmentally informed research, because structural and social determinants influence neurobiological adaptation and maturation across the lifespan. We conclude with recommendations for advancing research, practice, and policy that connect biological psychiatry with structural and social determinants of health. Foremost among these is diversifying the ranks of biological psychiatry, from classrooms through laboratories, hospitals, and community health centers. Transforming and advancing the understanding of the structural and social determinants of neurobiology and mental health is most likely to come through transforming the discipline itself.

Access to health services among sexual minority people in the United States.

Sexual minority people in the United States are less likely to have access to health services when compared to their heterosexual counterparts. Less is known about the within-group sociodemographic memberships among sexual minority people regarding access to health services. Using data from a nationally representative sample, a series of univariate and bivariate analyses were used to determine associations between sociodemographic group membership and access to health services. Results suggest there are significant differences in access to health services within the sexual minority population. Differences in access to health services when considering sex-at-birth, sexual identity, age, race/ethnicity, urbanicity, education level and income status were found. These findings offer insight into the role sociodemographic group membership has on the equity of access to health services. Specifically, results indicated that disproportionate access to health services among sexual minority people were more pronounced among those with group membership who experience social marginalisation. This was particularly true for sexual minority people who were bisexual, younger, Black and Latinx, lower-income earners and sexual minority people with less education attainment. Results from this study may be used to inform policies and practices aimed at improving access to health services including, but not limited to, the expansion of the Affordable Care Act and continued development of Federally Qualified Health Centers, while acknowledging the role of within-group differences among sexual minority people.

Consistency among social groups in judging emotions across time.

We measured judgments about emotions across time. In Study 1 (N = 254) and Study 2 (N = 162), LGBTQ-Latinx, straight-Latinx, LGBTQ-White, and straight-White emerging adults rated how they would feel if a perpetrator acted positively (P) or negatively (N) toward them in single, isolated events. In Study 2, participants also responded to a new emotions across time task where they judged how they would feel interacting with a hypothetical perpetrator across three timepoints: (1) an initial past event, (2) a recent past event, and (3) an uncertain future-oriented event (e.g., seeing the perpetrator again). Participants further predicted their thoughts and decisions in the uncertain future-oriented event. The past emotional events appeared in various sequences (PP, NN, NP, PN). Results indicated that participants judged events as emotionally unambiguous when occurring first in a sequence or in isolation (positive events feel better than negative events). In contrast, initial events shaped emotional reactions to subsequent events: Participants responded more intensely to episodes that were preceded by events of the same valence. In addition to this augmenting effect, initial negative events were especially sticky: Participants rated a positive event following a negative event as feeling less good than when a positive event appeared first or in isolation, but they judged negative events to feel equivalently bad regardless of order. When evaluating future-oriented affective states, participants drew from the prior experiences and prioritized the recent past (more positive emotions, thoughts, and decisions for PP > NP > PN > NN). Effects replicated across all social groups. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Subtle and Intersectional Minority Stress and Depressive Symptoms Among Sexual and Gender Minority Adolescents of Color: Mediating Role of Self-Esteem and Sense of Mastery.

Little research has examined subtle, intersectional, and everyday minority stress, such as microaggressions specific to being a queer person of color, and its associations with depressive symptoms among sexual and gender minority adolescents (SGMA) of color. Moreover, research is needed to identify mechanisms that might explain the associations between minority stress and depression. This study examined the associations between subtle and intersectional minority stress (i.e., SGMA of color-specific microaggressions) and depressive symptoms among SGMA of color and tested self-concept factors (i.e., self-esteem and sense of mastery) as mediators of these associations. A large national US sample of SGMA of color (N = 3398; 31.8% transgender; 55.7% plurisexual) ages 13 to 17 years (M = 15.56, SD = 1.27) were recruited online. Participants' race/ethnicity were Asian/Pacific Islander (12.2%), Black/African American (13.2%), Hispanic/Latina(o)/x (30%), Native American/Alaska Native (1.2%), Middle Eastern (1.9%), Biracial or Multiracial (40%), and other racial/ethnic minority groups (1.7%). Over and above the effects of racism and SGM-based victimization, subtle intersectional minority stressors were associated with greater depressive symptoms and lower self-esteem and sense of mastery. Mediation analyses indicated that subtle intersectional minority stressors had indirect effects on depressive symptoms through lower self-esteem and sense of mastery for the aggregate sample of SGMA of color and most racial/ethnic groups in the sample. The results demonstrate that subtle and intersectional minority stress is a unique and significant form of minority stress that is a risk factor for depressive symptoms for SGMA of color. Moreover, our findings underscore self-concept mechanisms as targets for prevention and intervention.

Patterns of poverty across adolescence predict salivary cortisol stress responses in Mexican-origin youths.

Poverty is a chronic stressor associated with disruptions in psychophysiological development during adolescence. This study examined associations of chronic poverty and income changes experienced from pre- to mid-adolescence with hypothalamic-pituitary-adrenal (HPA) axis stress responses in late adolescence. Participants (N = 229) were adolescents of Mexican-origin (48.7% female). Household income (converted to income-to-needs ratios) was assessed annually when children were 10-16 years old. At 17 years, adolescents completed Cyberball, a social exclusion simulation task while undergoing a functional magnetic resonance imaging scan. Saliva samples were collected prior to and five times over a 50-minute period following the scan, from which salivary cortisol was assayed. Results showed that differential trajectories of poverty from ages 10-16 predicted HPA axis activity at age 17. Relative to others, distinct HPA suppression (hyporeactivity) was demonstrated by youth who started adolescence in deep poverty and were still living in poverty at age 16 despite experiencing some income gains. Youth from more economically secure families evinced typical cortisol increases following the lab stressor. These results suggest that subsequent HPA functioning varies as a function of economic status throughout adolescence, and that efforts to increase family income may promote healthy HPA functioning for youths in the most impoverished circumstances.

"Trying My Best": Sexual Minority Adolescents' Self-Care During the COVID-19 Pandemic.

PURPOSE: The COVID-19 pandemic has resulted in major life disruptions for sexual minority adolescents (SMAs), who already face and cope with pervasive and disproportionate rates of social, behavioral, and mental health challenges. Current research suggests that SMAs are struggling with COVID-19-related shelter in place orders navigating family proximity and dynamics and experiencing isolation from SMA-specific supports. Given identified challenges that may exacerbate known mental health disparities in SMAs, this work explores self-care practices among SMAs during the COVID-19 pandemic. METHODS: The present study uses data from open-ended questions to understand SMA experiences of self-care within a nationwide sample of SMAs (N = 770; M = 17.48 years, SD = 1.00) who are part of an ongoing prospective study. Data were collected via online questionnaire between May 13 and 31, 2020. Thematic analysis guided data exploration. RESULTS: Thematic analysis revealed five self-care practices among SMAs: (1) relationships, (2) routines, (3) body and mind, (4) rest and reset, and (5) tuning out. SMAs engaged in many positive coping strategies (i.e., exercise, establishing routine) and often linked these activities to positive well-being. Other SMAs engaged in activities to distract or disengage from stressors (i.e., excessive TV and alcohol and drug use). CONCLUSIONS: These findings highlight the resiliency of SMAs during the current pandemic, opportunities for providers to emphasize adaptive coping skills with youths, and the need for more research on adolescent self-care practices.

Four new species of Agaricus subgenus Spissicaules from China.

Agaricus subgenus Spissicaules is widely distributed in the world. In this study, 114 specimens were included in multigene phylogenetic analyses that allowed a better circumscription of the four sections in A. subg. Spissicaules. Three new species from China, A. brunneovariabilis, A. beijingensis, and A. planiceps, are described and placed in different sections. The invalidly described A. catenariocystidiosus is validated here as an additional new species. Comparisons between the sequences of the three closely related species A. thiersii, A. parasubrutilescens, and A. linzhiensis support the distinction between these three species despite the paraphyly of A. linzhiensis, which results from its high intraspecific variability with numerous heteromorphisms.

Family Belongingness Attenuates Entrapment and Buffers Its Association with Suicidal Ideation in a Sample of Dutch Sexual Minority Emerging Adults.

Sexual minority emerging adults are more likely to engage in suicidal ideation than their heterosexual counterparts. Experiences of homophobic violence are associated with suicidal ideation. Yet, the specific mechanisms linking homophobic violence to suicidal ideation remain unclear. Entrapment and social belongingness were tested to determine their relevance for understanding the link between homophobic violence and suicidal ideation. A sample of sexual minority Dutch emerging adults (N = 675; ages 18-29, M = 21.93 years, SD = 3.20) were recruited through online platforms and flyers. Homophobic violence was expected to be positively associated with suicidal ideation and entrapment. The association between homophobic violence and suicidal ideation was expected to be indirectly linked through entrapment. We explored whether various sources of social belongingness moderated the path between entrapment and suicidal ideation and whether those sources of social belongingness moderated the indirect effect of homophobic violence on suicidal ideation through entrapment. Results showed that homophobic violence and entrapment were positively associated with suicidal ideation and that family belongingness was negatively associated with suicidal ideation. Homophobic violence and suicidal ideation were not indirectly linked through entrapment. The interaction effect between entrapment and family belongingness was significant, suggesting that, on average, the effect of entrapment on suicidal ideation decreased when family belongingness was high. These results suggest that family belongingness may reduce the association between entrapment and suicidal ideation while adjusting for homophonic violence. Reducing entrapment and improving family belongingness may be useful targets for programs aimed at preventing suicidal ideation among sexual minority emerging adults.

Integrating the Neurobiology of Minority Stress with an Intersectionality Framework for LGBTQ-Latinx Populations.

The comprehensive lived experiences of lesbian, gay, bisexual, transgender, and queer (LGBTQ) individuals of color remain invisible in neurobiological studies of LGBTQ populations. Models of minority stress posit that LGBTQ and Latinx individuals experience and internalize sexual, ethnic, racial, and gender discrimination, which may adversely impact mental and physical health. However, the current minority stress models predominantly focus on single categorical social identities and do not account for interlocking systems and processes of oppression based on features of sexuality, race, ethnicity, sex, and gender, as explained by an intersectionality framework in feminist theory. Thus, it remains unclear how LGBTQ people of color internalize and navigate multiple cultural, institutional, and societal stressors, and, furthermore, how these sources of stress may affect health and well-being. A potential mechanism for this adverse internalization process is through the effects of stress on neurobiological regulation. This review will apply an intersectionality framework to the examination of how heterosexism, racism, and cissexism, as systems of oppression, create LGBTQ and Latinx lived experiences, and the differential impacts of these inequalities on neurobiological stress regulation. The overarching goal of this manuscript is to advocate for the application of intersectionality theory to advance the ecological validity of biopsychosocial models of multiple-minority stress.

Agaricus section Arvenses: three new species in highland subtropical Southwest China.

Agaricus is a genus of saprobic basidiomycetes with more than 400 species recognized worldwide, with about 50 species known in China. Our objective was to investigate three new species of section Arvenses in highland subtropical Southwest China. Agaricus guizhouensis is a new species characterized by a white pileus with yellowish squamules, small ellipsoid spores and cheilocystidia with yellowish-brown pigments; another new species, Agaricus longistipes is recognized by its slender stipe, and its elongate-ellipsoid basidiospores; the third new one, Agaricus megalocarpus is remarkable by its large size and its pileus surface covered with fine brown squamules. It is firstly reported for Guizhou Province that Agaricus abruptibulbus, Agaricus flocculosipes, and Agaricus subrufescens are illustrated. Two probable new species require further studying. A phylogenetic analyses of rDNA-ITS sequence data belonging to section Arvenses showed that the section Arvenses is monophyletic and can be subdivided in five branches, the branch of A. subrufescens and four clades (A-D). The eight species from highland subtropical Southwest China were distributed in all five branches, indicating that this highland is at the climatic crossroads. The white pileus trait and the potential interest are discussed. These data suggest a potential species richness that remains to be discovered.

Morphological and molecular characterization of three Agaricus species from tropical Asia (Pakistan, Thailand) reveals a new group in section Xanthodermatei.

The genus Agaricus is known for its medicinal and edible species but also includes toxic species that belong to section Xanthodermatei. Previous phylogenetic reconstruction for temperate species, based on sequence data of nuc rRNA gene (rDNA) internal transcribed spacers (ITS), has revealed two major groups in this section and a possible third lineage for A. pseudopratensis. Recent research in Agaricus has shown that classifications need improving with the addition of tropical taxa. In this study we add new tropical collections to section Xanthodermatei. We describe three species from collections made in Pakistan and Thailand and include them in a larger analysis using all available ITS data for section Xanthodermatei. Agaricus bisporiticus sp. nov. and A. fuscopunctatus sp. nov. are introduced based on molecular and morphological studies, whereas A. microvolvatulus is recorded for the first time in Asia. Specimens from Thailand however have a much larger pileus than the type specimens from Congo. In maximum likelihood (ML) and maximum parsimony (MP) phylogenetic analyses these three species cluster with A. pseudopratensis from the Mediterranean area and A. murinocephalus recently described from Thailand. In Agaricus section Xanthodermatei this new group is monophyletic and receives low bootstrap support whereas the two previously known groups receive strong support. Within the new group, the most closely related species share some traits, but we did not find any unifying morphological character; however the five species of the group share a unique short nucleotide sequence. Two putatively toxic species of section Xanthodermatei are now recognized in Pakistan and six in Thailand.

New and rare taxa in Agaricus section Bivelares (Duploannulati).

Ongoing field and laboratory studies have led to our recognition of new taxa in Agaricus section Bivelares, a recent combination and now the earliest synonym and correct name of section Duploannulati. Agaricus cupressophilus and A. tlaxcalensis, in the new Agaricus subsection Cupressorum, and A. agrinferus, A. devoniensis subsp. bridghamii, and A. subsubensis in Agaricus subsection Hortenses, are described. Agaricus subfloccosus is lectotypified. Phylogeny reconstruction methods with ITS1+2 DNA sequences were used to determine appropriate placements of the new taxa. Collectively these new taxa and phylogenetic associations represent a substantial augmentation and clarification of our knowledge of section Bivelares; described, sequenced species-level taxa in the northern hemisphere are increased from six to 10, a distinct subsectional lineage is revealed and infraspecific resolution within A. devoniensis is improved. An anomalous ITS1+2 sequence is documented in one collection of A. subsubensis. Preliminary data on another novel member of Bivelares from France also are provided. Several of these taxa are rare, highlighting opportunities and challenges for documenting biodiversity in this group. Additional comments on related taxa treated in recent publications are also provided.

Film formation from aqueous polyurethane dispersions of reactive hydrophobic and hydrophilic components; spectroscopic studies and Monte Carlo simulations.

Film formation of waterborne two-component polyurethanes is exceedingly complex due to the heterogeneous nature along with simultaneous progression of several parallel physicochemical processes which include water evaporation, cross-linking reactions, phase separation, and droplet coalescence, to name a few. While internal reflection infrared imaging (IRIRI) spectroscopy clearly facilitates analysis of chemical changes resulting from film formation, the complexity of processes leading to formation of specific surface/interfacial entities is a major experimental challenge. For this reason, we combined a spectrum of surface/interfacial analytical approaches including IRIRI, atomic force microscopy, and attenuated total reflectance Fourier transform infrared spectroscopy with Monte Carlo computer simulations to advance the limited knowledge of how temperature, stoichiometry, concentration levels, and reactivities of individual components affect the development of surface morphologies and compositional gradients across the film thickness. These studies show that in heterogeneous systems having both hydrophobic and hydrophilic components stratification of individual components to the film-air (F-A) interface is ultimately responsible for formation of rough surface topographies. These studies show that simultaneous stratification of hydrophobic components along with water evaporation to the F-A interface results in metastable interfacial layers, leading to surface dewetting. Subsequently, surface roughness is enhanced by higher concentrations of water in the cross-linking film.

Agaricus section Xanthodermatei: a phylogenetic reconstruction with commentary on taxa.

Agaricus section Xanthodermatei comprises a group of species allied to A. xanthodermus and generally characterized by basidiomata having phenolic odors, transiently yellowing discolorations in some parts of the basidiome, Schaeffer's reaction negative, and mild to substantial toxicity. The section has a global distribution, while most included species have distributions restricted to regions of single continents. Using specimens and cultures from Europe, North America, and Hawaii, we analyzed DNA sequences from the ITS1+2 region of the nuclear rDNA to identify and characterize phylogenetically distinct entities and to construct a hypothesis of relationships, both among members of the section and with representative taxa from other sections of the genus. 61 sequences from affiliated taxa, plus 20 from six (or seven) other sections of Agaricus, and one Micropsalliota sequence, were evaluated under distance, maximum parsimony and maximum likelihood methods. We recognized 21 discrete entities in Xanthodermatei, including 14 established species and 7 new ones, three of which are described elsewhere. Four species from California, New Mexico, and France deserve further study before they are described. Type studies of American taxa are particularly emphasized, and a lectotype is designated for A. californicus. Section Xanthodermatei formed a single clade in most analyses, indicating that the traditional sectional characters noted above are good unifying characters that appear to have arisen only once within Agaricus. Deep divisions within the sequence-derived structure of the section could be interpreted as subsections in Xanthodermatei; however, various considerations led us to refrain from proposing new supraspecific taxa. The nearest neighbors of section Xanthodermatei are putatively in section Duploannulati.