From the Cover: Contrasting drivers of diversity in hosts and parasites across the tropical Andes

Geographic turnover in community composition is created and maintained by eco-evolutionary forces that limit the ranges of species. One such force may be antagonistic interactions among hosts and parasites, but its general importance is unknown. Understanding the processes that underpin turnover requires distinguishing the contributions of key abiotic and biotic drivers over a range of spatial and temporal scales. Here, we address these challenges using flexible, nonlinear models to identify the factors that underlie richness (alpha diversity) and turnover (beta diversity) patterns of interacting host and parasite communities in a global biodiversity hot spot. We sampled 18 communities in the Peruvian Andes, encompassing ∼1,350 bird species and ∼400 hemosporidian parasite lineages, and spanning broad ranges of elevation, climate, primary productivity, and species richness. Turnover in both parasite and host communities was most strongly predicted by variation in precipitation, but secondary predictors differed between parasites and hosts, and between contemporary and phylogenetic timescales. Host communities shaped parasite diversity patterns, but there was little evidence for reciprocal effects. The results for parasite communities contradicted the prevailing view that biotic interactions filter communities at local scales while environmental filtering and dispersal barriers shape regional communities. Rather, subtle differences in precipitation had strong, fine-scale effects on parasite turnover while host–community effects only manifested at broad scales. We used these models to map bird and parasite turnover onto the ecological gradients of the Andean landscape, illustrating beta-diversity hot spots and their mechanistic underpinnings.

Turnover in community composition across space, or “beta diversity,” reflects eco-evolutionary processes that determine range limits of species (1–3). These processes include adaptive specialization on particular habitats, barriers to dispersal, and interactions among species (4–6). Antagonistic interactions between hosts and parasites may have an underappreciated effect on turnover (7), as evidenced by the sensitivity of host populations to novel parasites. For example, introductions of avian malaria (Plasmodium relictum) and avian pox (Avipoxvirus) led to extinctions or range contractions for dozens of endemic Hawaiian honeycreeper species (8). Introduced parasites have also driven shifts in community composition when competing hosts differ in susceptibility to infection (9). While these cases highlight extreme impacts of parasites on host communities, it remains unclear whether host–parasite interactions generally drive turnover in continental faunas, whether such effects are reciprocal or unidirectional, and whether these interactions also impact diversity patterns at regional scales or over evolutionary time.A persistent challenge in studying the factors that underlie community assembly is that turnover is dynamic and exhibits nonlinear variation over space and time (10). As a result, different processes may underlie turnover, depending on the scale at which the community is defined (11–13). For instance, numerous studies have asserted that adaptive specialization on abiotic conditions and barriers to dispersal drive regional turnover patterns while biotic interactions filter communities locally (2, 14). Still, the spatial scales of these various processes are uncertain (11, 15, 16), and empirical tests are complicated by the fact that potential drivers of turnover tend to be spatially autocorrelated (17).To determine the drivers and scale of community turnover in complex systems, we need appropriate, nonlinear analytical tools. Generalized dissimilarity models (GDMs) are an extension of matrix regression that provides two notable innovations: 1) GDMs can incorporate various biotic and abiotic predictors into a single model, and 2) GDMs explicitly model the curvilinear relationship between community dissimilarity and ecological or geographic distance (4, 10, 18). This modeling framework is better suited than linear matrix regression to identifying key factors underlying turnover in complex environments (19–21). In addition, by incorporating phylogenetic measures of community diversity and similarity, we can use GDMs to test how drivers of turnover have varied over evolutionary time (22). Comparing “phylogenetic turnover” to species turnover allows us to distinguish deep-time processes that may restrict the ranges of clades from contemporary processes that may constrain the range limits of individual species (2). For example, evolutionary conservation of traits may exclude entire clades from certain habitats, leading to strong phylogenetic turnover over ecological gradients (3). Alternatively, if traits that underpin environmental associations are evolutionarily labile, species turnover will be higher than phylogenetic turnover and better predicted by ecological variation.The tropical Andes provide an ideal natural laboratory for investigating community turnover in response to biotic and abiotic changes in the environment. Habitable elevational gradients spanning more than 5,000 vertical meters encompass rapid changes in vegetation structure, temperature, atmospheric pressure, ultraviolet (UV) exposure, and precipitation (23, 24). The Andean cordillera generates broad orographic precipitation, but its complex topography also creates a patchwork of rain shadows. Rain-shadowed slopes and valleys fragment the ranges of humid and dry-adapted species, particularly those occurring at higher elevations (25–29). Environmental change across elevational gradients of the Andes is exceptionally rapid compared to change along axes parallel to the cordillera. As a result, spatial distance and environmental difference are decoupled. Pairs of communities separated by the same geographic distance may have similar or contrasting environments. In this way, this landscape provides the opportunity to pinpoint environmental effects on community turnover and distinguish them from the effects of dispersal limitation.The Andes are a global hot spot for species richness and turnover, evolutionary distinctness, and small-ranged species (30–33). Species interactions are thought to be particularly important in shaping Andean community turnover: For example, Andean birds are often highly specialized on particular habitats and resources (13, 34), and competitive exclusion is thought to further limit and reinforce range boundaries (7, 35–37). However, parasitism has received less attention as a driver of turnover compared to competition (35, 37) and bird–plant mutualisms (36, 38, 39). One important group that could affect bird turnover is the hemosporidians (Apicomplexa: Haemosporida), a diverse clade of vector-borne parasites in the genera Haemoproteus, Parahaemoproteus, Plasmodium, and Leucocytozoon (40, 41). These parasites can reduce the fitness of their hosts, even in low-level chronic infections (42), and are thought to have the potential to shape avian biogeographic patterns (40, 43). Hemosporidian communities in turn are thought to be influenced to varying degrees by host community, climate, and barriers to dispersal (44–51), but improved modeling frameworks with new data are needed to reciprocally test the causes of host and parasite turnover across biodiverse, tropical landscapes.In this study, we identified and compared the drivers of diversity in interacting bird and hemosporidian communities of the Peruvian Andes. First, we tested whether similar or different drivers affect host and parasite turnover; second, we tested how drivers of turnover vary with spatial scale; and third, we tested how drivers of turnover have changed over evolutionary time. Then, we used a complementary modeling approach to identify sources of variation in species richness among host and parasite communities, respectively. We used these models to map host and parasite turnover and richness to identify hot spots for faunal overlap and transition, critical zones for biodiversity study and protection.     

PTSD in Latino Patients: Illness Beliefs, Treatment Preferences, and Implications for Care

Background  Little is known about how Latinos with post-traumatic stress disorder (PTSD) understand their illness and their preferences for mental health treatment. Objective  To understand the illness beliefs and treatment preferences of Latino immigrants with PTSD. Design  Semi-structured, face-to-face interviews. Participants  Sixty foreign-born, Latino adults recruited from five primary care centers in New York and New Jersey and screened for PTSD. Approach  Content analytic methods identified common themes, their range, and most frequent or typical responses. Results  Participants identified their primary feelings as sadness, anxiety, nervousness, and fear. The most common feeling was “sad” (triste). Other words frequently volunteered were “angry” (enojada), “nervous” (nerviosa), and “scared” (miedo). Participants viewed their PTSD as impairing health and functioning. They ascribed their somatic symptoms and their general medical problems to the “stress” from the trauma and its consequences on their lives. The most common reason participants volunteered for their work and school functioning being impaired was their poor concentration, often due to intrusive thoughts. Most expressed their desire to receive mental health treatment, to receive it within their primary care center, and preferred psychotherapy over psychotropic medications. Among participants who did not report wanting treatment, most said it was because the trauma was “in the past.” Conclusions  Clinicians may consider enquiring about PTSD in Latino patients who report feeling sad, anxious, nervous, or fearful. Our study suggests topics clinicians may include in the psychoeducation of patients with PTSD.     

Validation of the Social Appearance Anxiety Scale in Patients With Systemic Sclerosis: A Scleroderma Patient‐Centered Intervention Network Cohort Study

Objective

Systemic sclerosis (SSc) is an autoimmune disease that can cause disfiguring changes in appearance. This study examined the structural validity, internal consistency reliability, convergent validity, and measurement equivalence of the Social Appearance Anxiety Scale (SAAS) across SSc disease subtypes.

Methods

Patients enrolled in the Scleroderma Patient‐centered Intervention Network Cohort completed the SAAS and measures of appearance‐related concerns and psychological distress. Confirmatory factor analysis (CFA) was used to examine the structural validity of the SAAS. Multiple‐group CFA was used to determine whether SAAS scores can be compared across patients with limited and diffuse disease subtypes. Cronbach's alpha was used to examine internal consistency reliability. Correlations of SAAS scores with measures of body image dissatisfaction, fear of negative evaluation, social anxiety, and depression were used to examine convergent validity. SAAS scores were hypothesized to be positively associated with all convergent validity measures, with correlations significant and moderate to large in size.

Results

A total of 938 patients with SSc were included. CFA supported a 1‐factor structure (Comparative Fit Index 0.92, Standardized Root Mean Residual 0.04, and Root Mean Square Error of Approximation 0.08), and multiple‐group CFA indicated that the scalar invariance model best fit the data. Internal consistency reliability was good in the total sample (α = 0.96) and in disease subgroups. Overall, evidence of convergent validity was found with measures of body image dissatisfaction, fear of negative evaluation, social anxiety, and depression.

Conclusion

The SAAS can be reliably and validly used to assess fear of appearance evaluation in patients with SSc, and SAAS scores can be meaningfully compared across disease subtypes.

     

Parallel analysis of genetic selections using whole genome oligonucleotide arrays

Thousands of genes have recently been sequenced in organisms ranging from Escherichia coli to human. For the majority of these genes, however, available sequence does not define a biological role. Efficient functional characterization of these genes requires strategies for scaling genetic analyses to the whole genome level. Plasmid-based library selections are an established approach to the functional analysis of uncharacterized genes and can help elucidate biological function by identifying, for example, physical interactors for a gene and genetic enhancers and suppressors of mutant phenotypes. The application of these selections to every gene in a eukaryotic genome, however, is generally limited by the need to manipulate and sequence hundreds of DNA plasmids. We present an alternative approach in which identification of nucleic acids is accomplished by direct hybridization to high-density oligonucleotide arrays. Based on the complete sequence of Saccharomyces cerevisiae, high-density arrays containing oligonucleotides complementary to every gene in the yeast genome have been designed and synthesized. Two-hybrid protein–protein interaction screens were carried out for S. cerevisiae genes implicated in mRNA splicing and microtubule assembly. Hybridization of labeled DNA derived from positive clones is sufficient to characterize the results of a screen in a single experiment, allowing rapid determination of both established and previously unknown biological interactions. These results demonstrate the use of oligonucleotide arrays for the analysis of two-hybrid screens. This approach should be generally applicable to the analysis of a range of genetic selections.     

Defective DNA mismatch repair in long-term (> or =3 years) survivors with pancreatic cancer.

BACKGROUND/AIMS: Defective DNA mismatch repair (MMR) in pancreatic cancer, reported in up to 13% of sporadic pancreatic cancers, may predict a good prognosis. To determine if long-term survival in pancreatic cancer could be attributed to defective DNA MMR, we ascertained its prevalence in 35 pancreatic cancer patients who survived > or =3 years after surgery. METHODS: We performed immunohistochemistry (IHC) for MMR proteins hMLH1, hMSH2, and hMSH6 in all 35 tumors and microsatellite instability (MSI) studies in 34/35 tumors using 10 microsatellite markers in paired normal and tumor DNA. Defective DNA MMR was defined as absence of protein expression on IHC and/or MSI in > or =30% of markers studied. RESULTS: On IHC, 3/35 (8.6%) tumors had defective DNA MMR. All 3 had absent expression of a DNA MMR protein (hMLH1 in 2 and hMSH2) and 2/3 also had MSI; the third could not be tested. Definitely 2, and probably all 3 patients had hereditary nonpolyposis colon cancer as determined by clinical and genetic profiles. CONCLUSION: Defective DNA MMR is uncommon in long-term survivors of pancreatic cancer and does not account for the survival benefit in those with sporadic pancreatic cancer.     

Type and intensity of activity and risk of mobility limitation: the mediating role of muscle parameters

OBJECTIVES: To investigate the association between different types of physical activity behavior and incident mobility limitation in older men and women and to examine whether muscle parameters mediate these associations. DESIGN: Cohort study with 4.5-year follow-up. SETTING: Metropolitan areas surrounding Pittsburgh, Pennsylvania, and Memphis, Tennessee. A random sample of white Medicare beneficiaries and all age-eligible blacks. PARTICIPANTS: Three thousand seventy-five black and white men and women aged 70 to 79 with no self-reported difficulty walking one-quarter of a mile or climbing 10 steps, enrolled in the Health, Aging and Body Composition (Health ABC) Study. MEASUREMENTS: Participants were classified as exercisers (reporting > or = 1,000 kcal/wk of exercise activity), lifestyle active (reporting < 1,000 kcal/wk of exercise activity and > or = 2,719 kcal/wk of total physical activity), or inactive (reporting < 1,000 kcal/wk of exercise activity and < 2,719 kcal/wk of total physical activity). The study outcome, incident mobility limitation, was defined as two consecutive, semiannual self-reports of any difficulty walking one quarter of a mile or climbing 10 steps. Thigh muscle area, thigh muscle attenuation (a marker of fat infiltration in muscle), appendicular lean soft tissue mass, and isokinetic knee extensor strength were examined as potential mediators. RESULTS: Over 4.5 years, 34.3% of men and 47.4% of women developed mobility limitation. Inactive persons had twice the risk of incident mobility limitation as exercisers (hazard ratio (HR)=2.08, 95% confidence interval (CI)=1.60-2.70, for men, HR=1.98, 95% CI=1.51-2.60, for women). Lifestyle-active men and women had an intermediate risk (HR=1.47 and 1.44, respectively). For the lifestyle active and inactive, absence of walking activity conferred an additional risk of mobility limitation. Muscle parameters did not mediate the relationship between physical activity and mobility limitation, except for knee extensor strength in men. CONCLUSION: Exercise and an active lifestyle that includes walking protect against mobility loss in older men and women. Activity effects on muscle parameters do not explain this association.