Carbon-concentrating mechanisms are a key trait in lichen ecology and distribution.

Carbon-concentrating mechanisms (CCMs) are a widespread phenomenon in photosynthetic organisms. In vascular plants, the evolution of CCMs ([C44-carbon compound] and crassulacean acid metabolism [CAM]) is associated with significant shifts, most often to hot, dry and bright, or aquatic environments. If and how CCMs drive distributions of other terrestrial photosynthetic organisms, remains little studied. Lichens are ecologically important obligate symbioses between fungi and photosynthetic organisms. The primary photosynthetic partner in these symbioses can include CCM-presenting cyanobacteria (as carboxysomes), CCM-presenting green algae (as pyrenoids) or green algae lacking any CCM. We use an extensive dataset of lichen communities from eastern North America, spanning a wide climatic range, to test the importance of CCMs as predictors of lichen ecology and distribution. We show that the presence or absence of CCMs leads to opposite responses to temperature and precipitation in green algal lichens, and different responses in cyanobacterial lichens. These responses contrast with our understanding of lichen physiology, whereby CCMs mitigate carbon limitation by water saturation at the cost of efficient use of vapor hydration. This study demonstrates that CCM status is a key functional trait in obligate lichen symbioses, equivalent in importance to its role in vascular plants, and central for studying present and future climate responses.

Climate change and elevational range shifts in insects.

On mountains, unique in their steep and rapid climatic gradients, many insects are shifting their elevational range limits to track recent temperature change. In a review of the range shift literature to date, most of the 1478 montane insect populations tested so far are shifting to higher elevations, but there is conspicuous variation in the responses. We discuss the impact of study methodology as well as potential abiotic and biotic factors that may underlie this variation in climate change response. We encourage more empirical studies spanning greater insect biodiversity and directly testing how variation in species' traits, biogeography, and abiotic-biotic context shapes variation in range shift responses.

Unusually large upward shifts in cold-adapted, montane mammals as temperature warms.

The largest and tallest mountain range in the contiguous United States, the Southern Rocky Mountains, has warmed considerably in the past several decades due to anthropogenic climate change. Herein we examine how 47 mammal elevational ranges (27 rodent and 4 shrew species) have changed from their historical distributions (1886-1979) to their contemporary distributions (post 2005) along 2,400-m elevational gradients in the Front Range and San Juan Mountains of Colorado. Historical elevational ranges were based on more than 4,580 georeferenced museum specimen and publication records. Contemporary elevational ranges were based on 7,444 records from systematic sampling efforts and museum specimen records. We constructed Bayesian models to estimate the probability a species was present, but undetected, due to undersampling at each 50-m elevational bin for each time period and mountain range. These models leveraged individual-level detection probabilities, the number and patchiness of detections across 50-m bands of elevation, and a decaying likelihood of presence from last known detections. We compared 95% likelihood elevational ranges between historical and contemporary time periods to detect directional change. Responses were variable as 26 mammal ranges changed upward, 6 did not change, 11 changed downward, and 4 were extirpated locally. The average range shift was 131 m upward, while exclusively montane species shifted upward more often (75%) and displayed larger average range shifts (346 m). The best predictors of upper limit and total directional change were species with higher maximum latitude in their geographic range, montane affiliation, and the study mountain was at the southern edge of their geographic range. Thus, mammals in the Southern Rocky Mountains serve as harbingers of more changes to come, particularly for montane, cold-adapted species in the southern portion of their ranges.

Natural population variability may be masking the more-individuals hypothesis.

Species richness and productivity are correlated at global and regional scales, but the mechanisms linking them are inconclusive. The most commonly invoked mechanism, the more-individuals hypothesis (MIH), hypothesizes that increased productivity leads to increased food resource availability, which leads to an increased number of individuals supporting more species. Empirical evidence for the MIH remains mixed despite a substantial literature. Here we used simulations to determine whether interannual population variability could be masking a "true" MIH relationship. In each simulation, fixed linear relationships between productivity, richness, and 50-yr average abundance mimicked the MIH mechanism. Abundance was allowed to vary annually and sampled for 1-40 yr. Linear regressions of richness on sampled abundance assessed the probability of detecting the fixed MIH relationship. Medium to high population variability with short-term sampling (1-3 yr) led to poor detection of the fixed MIH relationship. Notably, this level of sampling and population variability describes nearly all MIH studies to date. Long-term sampling (5+ yr) led to improved detection of the fixed relationship; thus it is necessary to detect support for the MIH reliably. Such sampling duration is nonexistent in the MIH literature. Robust future studies of the MIH necessitate consideration of interannual population variability.

A taxonomically broad metagenomic survey of 339 species spanning 57 families suggests cystobasidiomycete yeasts are not ubiquitous across all lichens.

PREMISE: Lichens are fungi that enter into obligate symbioses with photosynthesizing organisms (algae, cyanobacteria). Traditional narratives of lichens as binary symbiont pairs have given way to their recognition as dynamic metacommunities. Basidiomycete yeasts, particularly of the genus Cyphobasidium, have been inferred to be widespread and important components of lichen metacommunities. Yet, the presence of basidiomycete yeasts across a wide diversity of lichen lineages has not previously been tested. METHODS: We searched for lichen-associated cystobasidiomycete yeasts in newly generated metagenomic data from 413 samples of 339 lichen species spanning 57 families and 25 orders. The data set was generated as part of a large-scale project to study lichen biodiversity gradients in the southern Appalachian Mountains Biodiversity Hotspot of southeastern North America. RESULTS: Our efforts detected cystobasidiomycete yeasts in nine taxa (Bryoria nadvornikiana, Heterodermia leucomelos, Lecidea roseotincta, Opegrapha vulgata, Parmotrema hypotropum, P. subsumptum, Usnea cornuta, U. strigosa, and U. subgracilis), representing 2.7% of all species sampled. Seven of these taxa (78%) are foliose (leaf-like) or fruticose (shrubby) lichens that belong to families where basidiomycete yeasts have been previously detected. In several of the nine cases, cystobasidiomycete rDNA coverage was comparable to, or greater than, that of the primary lichen fungus single-copy nuclear genomic rDNA, suggesting sampling artifacts are unlikely to account for our results. CONCLUSIONS: Studies from diverse areas of the natural sciences have led to the need to reconceptualize lichens as dynamic metacommunities. However, our failure to detect cystobasidiomycetes in 97.3% (330 species) of the sampled species suggests that basidiomycete yeasts are not ubiquitous in lichens.

Habitat quality and disturbance drive lichen species richness in a temperate biodiversity hotspot.

The impacts of disturbance on biodiversity and distributions have been studied in many systems. Yet, comparatively less is known about how lichens-obligate symbiotic organisms-respond to disturbance. Successful establishment and development of lichens require a minimum of two compatible yet usually unrelated species to be present in an environment, suggesting disturbance might be particularly detrimental. To address this gap, we focused on lichens, which are obligate symbiotic organisms that function as hubs of trophic interactions. Our investigation was conducted in the southern Appalachian Mountains, USA. We conducted complete biodiversity inventories of lichens (all growth forms, reproductive modes, substrates) across 47, 1-ha plots to test classic models of responses to disturbance (e.g., linear, unimodal). Disturbance was quantified in each plot using a standardized suite of habitat quality variables. We additionally quantified woody plant diversity, forest density, rock density, as well as environmental factors (elevation, temperature, precipitation, net primary productivity, slope, aspect) and analyzed their impacts on lichen biodiversity. Our analyses recovered a strong, positive, linear relationship between lichen biodiversity and habitat quality: lower levels of disturbance correlate to higher species diversity. With few exceptions, additional variables failed to significantly explain variation in diversity among plots for the 509 total lichen species, but we caution that total variation in some of these variables was limited in our study area. Strong, detrimental impacts of disturbance on lichen biodiversity raises concerns about conservation and land management practices that fail to incorporate complete estimates of biodiversity, especially from ecologically important organisms such as lichens.

Systolic Hypertension, Preeclampsia-Related Mortality, and Stroke in California.

OBJECTIVE: To describe the clinical characteristics of stroke and opportunities to improve care in a cohort of preeclampsia-related maternal mortalities in California. METHODS: The California Pregnancy-Associated Mortality Review retrospectively examined a cohort of preeclampsia pregnancy-related deaths in California from 2002 to 2007. Stroke cases were identified among preeclampsia deaths, and case summaries were reviewed with attention to clinical variables, particularly hypertension. Health care provider- and patient-related contributing factors were also examined. RESULTS: Among 54 preeclampsia pregnancy-related deaths that occurred in California from 2002 to 2007, 33 were attributed to stroke. Systolic blood pressure exceeded 160 mm Hg in 96% of cases, and diastolic blood pressure was 110 or higher in 65% of cases. Hemolysis, elevated liver enzymes, and low platelet count syndrome was present in 38% (9/24) of cases with available laboratory data; eclampsia occurred in 36% of cases. Headache was the most frequent symptom (87%) preceding stroke. Elevated liver transaminases were the most common laboratory abnormality (71%). Only 48% of women received antihypertensive treatment. A good-to-strong chance to alter outcome was identified in stroke cases 66% (21/32), with delayed response to clinical warning signs in 91% (30/33) of cases and ineffective treatment in 76% (25/33) cases being the most common areas for improvement. CONCLUSION: Stroke is the major cause of maternal mortality associated with preeclampsia or eclampsia. All but one patient in this series of strokes demonstrated severe elevation of systolic blood pressure, whereas other variables were less consistently observed. Antihypertensive treatment was not implemented in the majority of cases. Opportunities for care improvement exist and may significantly affect maternal mortality.

Midpoint attractors and species richness: Modelling the interaction between environmental drivers and geometric constraints.

We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor - a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon-specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness.

A Systematic Review of Global Drivers of Ant Elevational Diversity.

Ant diversity shows a variety of patterns across elevational gradients, though the patterns and drivers have not been evaluated comprehensively. In this systematic review and reanalysis, we use published data on ant elevational diversity to detail the observed patterns and to test the predictions and interactions of four major diversity hypotheses: thermal energy, the mid-domain effect, area, and the elevational climate model. Of sixty-seven published datasets from the literature, only those with standardized, comprehensive sampling were used. Datasets included both local and regional ant diversity and spanned 80° in latitude across six biogeographical provinces. We used a combination of simulations, linear regressions, and non-parametric statistics to test multiple quantitative predictions of each hypothesis. We used an environmentally and geometrically constrained model as well as multiple regression to test their interactions. Ant diversity showed three distinct patterns across elevations: most common were hump-shaped mid-elevation peaks in diversity, followed by low-elevation plateaus and monotonic decreases in the number of ant species. The elevational climate model, which proposes that temperature and precipitation jointly drive diversity, and area were partially supported as independent drivers. Thermal energy and the mid-domain effect were not supported as primary drivers of ant diversity globally. The interaction models supported the influence of multiple drivers, though not a consistent set. In contrast to many vertebrate taxa, global ant elevational diversity patterns appear more complex, with the best environmental model contingent on precipitation levels. Differences in ecology and natural history among taxa may be crucial to the processes influencing broad-scale diversity patterns.

Population variability complicates the accurate detection of climate change responses.

The rush to assess species' responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre- and post-CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species' range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate 'canaries in the coal mine' for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses.

Pregnancy-related cardiovascular deaths in California: beyond peripartum cardiomyopathy.

OBJECTIVE: Maternal mortality rates rose markedly from 2002 to 2006 in California, prompting an in-depth maternal mortality review in a state that comprises one twelfth of the US birth cohort. Cardiovascular disease has emerged as the leading cause of pregnancy-related death in the United States. The primary aim of this analysis was to describe the incidence and type of cardiovascular disease as a cause of pregnancy-related mortality in California. The secondary aims were to describe racial/ethnic and socioeconomic disparities, risk factors, birth outcomes, timing of death and diagnosis, and signs and symptoms of cardiovascular disease and identify contributing factors. STUDY DESIGN: The California Pregnancy-Associated Mortality Review retrospectively examined a case series of 64 cardiovascular pregnancy-related deaths from 2002 through 2006. Two cardiologists independently reviewed complete inpatient and outpatient medical records including laboratory, radiology, electrocardiogram, chest X-ray, echocardiograms, and autopsy findings for each cardiovascular death and classified cause of death by type of cardiovascular disease. Demographic data, racial disparities, risk factors, signs and symptoms, timing of diagnosis and death, birth outcomes, and contributing factors were analyzed using bivariate comparisons with noncardiovascular pregnancy-related deaths and population-based data. RESULTS: Among 2,741,220 California women who gave birth, 864 died while pregnant or within 1 year of pregnancy; 257 of the deaths were deemed pregnancy related, and of these, 64 (25%) were attributed to cardiovascular disease. There were 42 deaths caused by cardiomyopathy, and the pregnancy-related mortality rate from cardiomyopathy was 1.54 per 100,000 births. Dilated cardiomyopathy existed in 29 cases, of which 15 met the definition of peripartum cardiomyopathy. Women with cardiovascular disease were more likely than women who died from noncardiovascular causes to be African-American (39.1% vs 16.1%; P < .01) and more likely to use illicit substances (23.7% vs 9.4%; P < .01). Thirty-seven percent were obese and 20% had a concomitant diagnosis of hypertension or preeclampsia during pregnancy. Health care decisions in the diagnosis or treatment of cardiovascular disease during and after pregnancy contributed to the fatal outcomes. CONCLUSION: African-American race, substance use, and obesity were risk factors for pregnancy-related cardiovascular disease mortality. Chronic disease prevention and better recognition and response to cardiovascular disease during pregnancy are needed to reduce maternal mortality.

Pregnancy-related mortality in California: causes, characteristics, and improvement opportunities.

OBJECTIVE: To compare specific maternal and clinical characteristics and contributing factors among the five leading causes of pregnancy-related mortality to develop focused clinical and public health prevention programs. METHODS: California pregnancy-related deaths from 2002-2005 were identified with enhanced surveillance using linked birth and death certificates. A multidisciplinary committee reviewed medical records, autopsy reports, and coroner reports to determine cause of death, clinical and demographic characteristics, chance to alter outcome, contributing factors (at health care provider, facility, and patient levels), and quality improvement opportunities. The five leading causes of death were compared with each other and with the overall California birth population. RESULTS: Among the 207 pregnancy-related deaths, the five leading causes were cardiovascular disease, preeclampsia or eclampsia, hemorrhage, venous thromboembolism, and amniotic fluid embolism. Among the leading causes of death, we identified differing patterns for race, maternal age, body mass index, timing of death, and method of delivery. Overall, there was a good-to-strong chance to alter the outcome in 41% of deaths, with the highest rates of preventability among hemorrhage (70%) and preeclampsia (60%) deaths. Health care provider, facility, and patient contributing factors also varied by cause of death. CONCLUSION: Pregnancy-related mortality should not be considered a single clinical entity. Reducing mortality requires in-depth examination of individual causes of death. The five leading causes exhibit different characteristics, degrees of preventability, and contributing factors, with the greatest improvement opportunities identified for hemorrhage and preeclampsia. These findings provide additional support for hospital, state, and national maternal safety programs.

Body size and activity times mediate mammalian responses to climate change.

Model predictions of extinction risks from anthropogenic climate change are dire, but still overly simplistic. To reliably predict at-risk species we need to know which species are currently responding, which are not, and what traits are mediating the responses. For mammals, we have yet to identify overarching physiological, behavioral, or biogeographic traits determining species' responses to climate change, but they must exist. To date, 73 mammal species in North America and eight additional species worldwide have been assessed for responses to climate change, including local extirpations, range contractions and shifts, decreased abundance, phenological shifts, morphological or genetic changes. Only 52% of those species have responded as expected, 7% responded opposite to expectations, and the remaining 41% have not responded. Which mammals are and are not responding to climate change is mediated predominantly by body size and activity times (phylogenetic multivariate logistic regressions, P < 0.0001). Large mammals respond more, for example, an elk is 27 times more likely to respond to climate change than a shrew. Obligate diurnal and nocturnal mammals are more than twice as likely to respond as mammals with flexible activity times (P < 0.0001). Among the other traits examined, species with higher latitudinal and elevational ranges were more likely to respond to climate change in some analyses, whereas hibernation, heterothermy, burrowing, nesting, and study location did not influence responses. These results indicate that some mammal species can behaviorally escape climate change whereas others cannot, analogous to paleontology's climate sheltering hypothesis. Including body size and activity flexibility traits into future extinction risk forecasts should substantially improve their predictive utility for conservation and management.

California Pregnancy-Associated Mortality Review: mixed methods approach for improved case identification, cause of death analyses and translation of findings.

After several decades of declining rates, maternal mortality climbed in California from a three-year moving average of 9.4 deaths per 100,000 live births in 1999-2001 to a high of 14.0 deaths per 100,000 live births in 2006-2008 (p < 0.001). The Maternal, Child and Adolescent Health Division of the California Department of Public Health developed a mixed method approach to identify and investigate maternal deaths to inform prevention strategies. This paper describes the methodology of the California Pregnancy-Associated Mortality Review (CA-PAMR) and its advantages for improved surveillance, cause of death analysis, and translation of findings. From 2002 to 2004, 1,598,792 live births occurred in California and 555 women died while pregnant or within one year of pregnancy. A screening algorithm identified cases for review that were likely to be pregnancy-related. Medical records were then abstracted and reviewed by a multidisciplinary committee to determine cause of death, contributing factors, and opportunities for quality improvement. Mixed methods were used to analyze, synthesize and translate Committee recommendations for improved care. Of 211 cases selected for review, 145 deaths were determined to be pregnancy-related. CA-PAMR methods corrected misclassification of cases and more accurately identified the leading causes of death. Cardiovascular disease emerged as the leading cause of pregnancy-related deaths (20%), and African-American women were disproportionately represented among cardiovascular deaths. Overall, the chance to prevent the fatal outcome appeared good or strong in 40% of cases reviewed. The CA-PAMR methodology resulted in additional case finding, improved accuracy of the causes of pregnancy-related deaths, and evidence to guide development of prevention and quality improvement efforts.

Environmental harshness is positively correlated with intraspecific divergence in mammals and birds.

Life on Earth is conspicuously more diverse in the tropics. Although this intriguing geographical pattern has been linked to many biotic and abiotic factors, their relative importance and potential interactions are still poorly understood. The way in which latitudinal changes in ecological conditions influence evolutionary processes is particularly controversial, as there is evidence for both a positive and a negative latitudinal gradient in speciation rates. Here, we identify and address some methodological issues (how patterns are analysed and how latitude is quantified) that could lead to such conflicting results. To address these issues, we assemble a comprehensive data set of the environmental correlates of latitude (including climate, net primary productivity and habitat heterogeneity) and combine it with biological, historical and molecular data to explore global patterns in recent divergence events (subspeciation). Surprisingly, we find that the harsher conditions that typify temperate habitats (lower primary productivity, decreased rainfall and more variable and unpredictable temperatures) are positively correlated with greater subspecies richness in terrestrial mammals and birds. Thus, our findings indicate that intraspecific divergence is greater in regions with lower biodiversity, a pattern that is robust to both sampling variation and latitudinal biases in taxonomic knowledge. We discuss possible causal mechanisms for the link between environmental harshness and subspecies richness (faster rates of evolution, greater likelihood of range discontinuities and more opportunities for divergence) and conclude that this pattern supports recent indications that latitudinal gradients of diversity are maintained by simultaneously higher potentials for both speciation and extinction in temperate than tropical regions.

Willingness to have unprotected sex.

Little is known about people's willingness to engage in sex without protection from unwanted pregnancy. This study surveyed 1,497 women and men at 75 clinics and physician offices across California after their reproductive health care visits in late 2007 and early 2008. When asked if they would have sex without contraception, 30% said definitively that yes, they would have unprotected sex, and 20% indicated they would "sometimes" or "maybe" engage in unprotected sex. In multivariate models, compared to non-Latino White respondents, Latinos who responded to the survey in English were 52% more likely and African Americans were 75% more likely to report willingness to have unprotected intercourse. Wanting a child within the next three years was associated with increased willingness to have unprotected sex. Age, gender, parity, and relationship status were not significant in multivariate models. A considerable proportion of women and men may be willing to have unprotected sex, even with access to subsidized contraceptive services and even when recently counseled about birth control. The dominant behavioral models of contraceptive use need to acknowledge the widespread likelihood of occasional unprotected sex, even among people motivated to usually use contraceptives. Findings underscore the need to make contraceptive methods accessible, easy to use, and even pleasurable.

Latitude, elevational climatic zonation and speciation in New World vertebrates.

Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions.

Assessing the threat to montane biodiversity from discordant shifts in temperature and precipitation in a changing climate.

Mountains are centres of global biodiversity, endemism and threatened species. Elevational gradients present opportunities for species currently living near their upper thermal limits to track cooler temperatures upslope in warming climates, but only if changes in precipitation are sufficiently in step with temperature. We model local population extirpation risk for a range of temperature and precipitation scenarios over the next 100 years for 16 848 vertebrate species populations distributed along 156 elevational gradients. Average population extirpation risks due to warming alone were < 5%, but increased 10-fold, on average, when changes in precipitation were also considered. Under the driest scenarios (minimum predicted precipitation), local extirpation risks increased sharply (50-60%) and were especially worrisome for hydrophilic amphibians and montane Latin America (c. 80%). Realistic assessment of risks urgently requires improved monitoring of precipitation, better regional precipitation models and more research on the effects of changes in precipitation on montane distributions.

Microbes do not follow the elevational diversity patterns of plants and animals.

The elevational gradient in plant and animal diversity is one of the most widely documented patterns in ecology and, although no consensus explanation exists, many hypotheses have been proposed over the past century to explain these patterns. Historically, research on elevational diversity gradients has focused almost exclusively on plant and animal taxa. As a result, we do not know whether microbes exhibit elevational gradients in diversity that parallel those observed for macroscopic taxa. This represents a key knowledge gap in ecology, especially given the ubiquity, abundance, and functional importance of microbes. Here we show that, across a montane elevational gradient in eastern Peru, bacteria living in three distinct habitats (organic soil, mineral soil, and leaf surfaces) exhibit no significant elevational gradient in diversity (r2<0.17, P>0.1 in all cases), in direct contrast to the significant diversity changes observed for plant and animal taxa across the same montane gradient (r2>0.75, P<0.001 in all cases). This finding suggests that the biogeographical patterns exhibited by bacteria are fundamentally different from those of plants and animals, highlighting the need for the development of more inclusive concepts and theories in biogeography to explain these disparities.