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1.
Trends Ecol Evol ; 39(3): 213-216, 2024 03.
Artigo em Inglês | MEDLINE | ID: mdl-38320928

RESUMO

Fieldwork is crucial for science but poses heightened risks of gender-based harassment and assault. Current practices prioritize post-incident reporting, despite the demonstrated potential of preventive approaches. We recommend proactive practices, training strategies, and systemic policy changes to build safe and inclusive fieldwork settings from the outset.


Assuntos
Assédio Sexual , Assédio Sexual/prevenção & controle
2.
Sci Rep ; 14(1): 523, 2024 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-38191560

RESUMO

Fieldwork is a critical tool for scientific research, particularly in applied disciplines. Yet fieldwork is often unsafe, especially for members of historically marginalized groups and people whose presence in scientific spaces threatens traditional hierarchies of power, authority, and legitimacy. Research is needed to identify interventions that prevent sexual harassment and assault from occurring in the first place. We conducted a quasi-experiment assessing the impacts of a 90-min interactive training on field-based staff in a United States state government agency. We hypothesized that the knowledge-based interventions, social modeling, and mastery experiences included in the training would increase participants' sexual harassment and assault prevention knowledge, self-efficacy, behavioural intention, and behaviour after the training compared to a control group of their peers. Treatment-control and pre-post training survey data indicate that the training increased participants' sexual harassment and assault prevention knowledge and prevention self-efficacy, and, to a lesser extent, behavioural intention. These increases persisted several months after the training for knowledge and self-efficacy. While we did not detect differences in the effect of the training for different groups, interestingly, post-hoc tests indicated that women and members of underrepresented racial groups generally scored lower compared to male and white respondents, suggesting that these groups self-assess their own capabilities differently. Finally, participants' likelihood to report incidents increased after the training but institutional reports remained low, emphasizing the importance of efforts to transform reporting systems and develop better methods to measure bystander actions. These results support the utility of a peer-led interactive intervention for improving workplace culture and safety in scientific fieldwork settings. PROTOCOL REGISTRATION: "The stage 1 protocol for this Registered Report was accepted in principle on August 24, 2022. The protocol, as accepted by the journal, can be found at: https://doi.org/10.6084/m9.figshare.21770165 .


Assuntos
Assédio Sexual , Humanos , Feminino , Masculino , Assédio Sexual/prevenção & controle , Processos Grupais , Instalações de Saúde , Intenção , Conhecimento
3.
Nat Ecol Evol ; 5(9): 1213-1223, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34373620

RESUMO

Racial and ethnic discrimination persist in science, technology, engineering and mathematics fields, including ecology, evolution and conservation biology (EECB) and related disciplines. Marginalization and oppression as a result of institutional and structural racism continue to create barriers to inclusion for Black people, Indigenous people and people of colour (BIPOC), and remnants of historic racist policies and pseudoscientific theories continue to plague these fields. Many academic EECB departments seek concrete ways to improve the climate and implement anti-racist policies in their teaching, training and research activities. We present a toolkit of evidence-based interventions for academic EECB departments to foster anti-racism in three areas: in the classroom; within research laboratories; and department wide. To spark restorative discussion and action in these areas, we summarize EECB's racist and ethnocentric histories, as well as current systemic problems that marginalize non-white groups. Finally, we present ways that EECB departments can collectively address shortcomings in equity and inclusion by implementing anti-racism, and provide a positive model for other departments and disciplines.


Assuntos
Racismo , Negro ou Afro-Americano , Ecologia , Engenharia , Humanos , Grupos Populacionais
4.
Integr Comp Biol ; 61(3): 926-933, 2021 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-34215879

RESUMO

This paper introduces the collection of manuscripts from the symposium, "Biology Beyond the Classroom: Experiential Learning through Authentic Research, Design, and Community Engagement," presented at the 2021 annual meeting of the Society for Integrative and Comparative Biology. The following papers showcase innovative approaches for engaging undergraduate students in experiential science learning experiences. Specifically, we focus on three high-impact practices that allow students to take their learning outside of the classroom for increased relevance and authenticity: (1) Course-Based Undergraduate Research, (2) Digital Fabrication in Makerspaces, and (3) Service or Community-based Learning Opportunities. Although each topic is unique, all provide an alternative approach to the traditional lecture and have proven effective at appealing to diverse groups of students who are traditionally underrepresented in the Science, Technology, Engineering, and Mathematics workforce.


Assuntos
Biologia/educação , Aprendizagem , Aprendizagem Baseada em Problemas , Humanos , Estudantes , Universidades
5.
Proc Natl Acad Sci U S A ; 118(26)2021 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-34162704

RESUMO

Biodiversity losses are a major driver of global changes in ecosystem functioning. While most studies of the relationship between biodiversity and ecosystem functioning have examined randomized species losses, trait-based filtering associated with species-specific vulnerability to drivers of diversity loss can strongly influence how ecosystem functioning responds to declining biodiversity. Moreover, the responses of ecosystem functioning to diversity loss may be mediated by environmental variability interacting with the suite of traits remaining in depauperate communities. We do not yet understand how communities resulting from realistic diversity losses (filtered by response traits) influence ecosystem functioning (via effect traits of the remaining community), especially under variable environmental conditions. Here, we directly test how realistic and randomized plant diversity losses influence productivity and invasion resistance across multiple years in a California grassland. Compared with communities based on randomized diversity losses, communities resulting from realistic (drought-driven) species losses had higher invasion resistance under climatic conditions that matched the trait-based filtering they experienced. However, productivity declined more with realistic than with randomized species losses across all years, regardless of climatic conditions. Functional response traits aligned with effect traits for productivity but not for invasion resistance. Our findings illustrate that the effects of biodiversity losses depend not only on the identities of lost species but also on how the traits of remaining species interact with varying environmental conditions. Understanding the consequences of biodiversity change requires studies that evaluate trait-mediated effects of species losses and incorporate the increasingly variable climatic conditions that future communities are expected to experience.


Assuntos
Biodiversidade , Biomassa , California , Análise de Componente Principal , Especificidade da Espécie
6.
Integr Comp Biol ; 61(3): 957-968, 2021 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-34089317

RESUMO

Field courses have been identified as powerful tools for student success in science, but the potential for field courses to address demographic disparities and the mechanisms behind these benefits are not well understood. To address these knowledge gaps, we studied students in a nonmajors Ecology and Evolutionary Biology course, Introduction to Field Research and Conservation, at the University of California Santa Cruz, a large Hispanic-Serving Institution. We examined (a) the effects of participation on students' perception of their scientific competencies and (b) how the field course shaped student experiences and built their sense of community, confidence and belonging in science. Our mixed-methods approach included the Persistence in the Sciences (PITS) survey with field course students and a control group; interviews, focus groups, and prompted student journal entries with a subset of field course students; and participant-observation. We found that field course participants scored higher on all science identity items of the PITS instrument than students in the control (lecture course) group. Field course students from underrepresented minority groups also scored similarly to or higher than their well-represented peers on each of the six PITS survey components. From our qualitative data, themes of growth in peer community, relationships with mentors, confidence living and working outdoors, team-based science experiences, and a sense of contributing to knowledge and discovery interacted throughout the course-especially from the initial overnight field trip to the final one-to assist these gains and strengthen interest in science and support persistence. These findings highlight the importance of holistic support and community building as necessary driving factors in inclusive course design, especially as a way to begin to dismantle structures of exclusion in the sciences.


Assuntos
Biologia/educação , Ecologia/educação , Aprendizagem , Mentores , Estudantes , Evolução Biológica , Humanos , Grupos Minoritários
7.
Sci Adv ; 7(22)2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-34039595

RESUMO

Globally, cold-limited trees and forests are expected to experience growth acceleration as a direct response to warming temperatures. However, thresholds of temperature limitation may vary substantially with local environmental conditions, leading to heterogeneous responses in tree ecophysiology. We used dendroecological and isotopic methods to quantify shifting tree growth and resource use over the past 143 years across topographic aspects in a high-elevation forest of central Mexico. Trees on south-facing slopes (SFS) grew faster than those on north-facing slopes (NFS) until the mid-20th century, when this pattern reversed notably with marked growth rate declines on SFS and increases on NFS. Stable isotopes of carbon, oxygen, and carbon-to-nitrogen ratios suggest that this reversal is linked to interactions between CO2 stimulation of photosynthesis and water or nitrogen limitation. Our findings highlight the importance of incorporating landscape processes and habitat heterogeneity in predictions of tree growth responses to global environmental change.

8.
Ecol Evol ; 11(8): 3625-3635, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33898015

RESUMO

The COVID-19 pandemic has disrupted many standard approaches to STEM education. Particularly impacted were field courses, which rely on specific natural spaces often accessed through shared vehicles. As in-person field courses have been found to be particularly impactful for undergraduate student success in the sciences, we aimed to compare and understand what factors may have been lost or gained during the conversion of an introductory field course to an online format. Using a mixed methods approach comparing data from online and in-person field-course offerings, we found that while community building was lost in the online format, online participants reported increased self-efficacy in research and observation skills and connection to their local space. The online field course additionally provided positive mental health breaks for students who described the time outside as a much-needed respite. We maintain that through intentional design, online field courses can provide participants with similar outcomes to in-person field courses.

9.
Syst Biol ; 70(3): 527-541, 2021 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-32941630

RESUMO

Understanding how gene flow affects population divergence and speciation remains challenging. Differentiating one evolutionary process from another can be difficult because multiple processes can produce similar patterns, and more than one process can occur simultaneously. Although simple population models produce predictable results, how these processes balance in taxa with patchy distributions and complicated natural histories is less certain. These types of populations might be highly connected through migration (gene flow), but can experience stronger effects of genetic drift and inbreeding, or localized selection. Although different signals can be difficult to separate, the application of high-throughput sequence data can provide the resolution necessary to distinguish many of these processes. We present whole-genome sequence data for an avian species group with an alpine and arctic tundra distribution to examine the role that different population genetic processes have played in their evolutionary history. Rosy-finches inhabit high elevation mountaintop sky islands and high-latitude island and continental tundra. They exhibit extensive plumage variation coupled with low levels of genetic variation. Additionally, the number of species within the complex is debated, making them excellent for studying the forces involved in the process of diversification, as well as an important species group in which to investigate species boundaries. Total genomic variation suggests a broadly continuous pattern of allele frequency changes across the mainland taxa of this group in North America. However, phylogenomic analyses recover multiple distinct, well supported, groups that coincide with previously described morphological variation and current species-level taxonomy. Tests of introgression using D-statistics and approximate Bayesian computation reveal significant levels of introgression between multiple North American taxa. These results provide insight into the balance between divergent and homogenizing population genetic processes and highlight remaining challenges in interpreting conflict between different types of analytical approaches with whole-genome sequence data. [ABBA-BABA; approximate Bayesian computation; gene flow; phylogenomics; speciation; whole-genome sequencing.].


Assuntos
Tentilhões/genética , Fluxo Gênico , Genoma , Animais , Regiões Árticas , Teorema de Bayes , Evolução Biológica , Genoma/genética , Filogenia
10.
Trends Ecol Evol ; 35(11): 953-956, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32919797

RESUMO

Field courses have been identified as powerful tools for inclusion and student success in science. However, not all students are equally likely to take field courses. How do we remove barriers to equity in field courses, to make them engines for inclusion, diversity, and collective excellence in ecology and evolution?


Assuntos
Estudantes , Humanos
11.
Ecol Evol ; 10(12): 5184-5196, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32607142

RESUMO

Disparities remain in the representation of marginalized students in STEM. Classroom-based experiential learning opportunities can increase student confidence and academic success; however, the effectiveness of extending learning to outdoor settings is unknown. Our objectives were to examine (a) demographic gaps in ecology and evolutionary biology (EEB) major completion, college graduation, and GPAs for students who did and did not enroll in field courses, (b) whether under-represented demographic groups were less likely to enroll in field courses, and (c) whether under-represented demographic groups were more likely to feel increased competency in science-related tasks (hereafter, self-efficacy) after participating in field courses. We compared the relationships among academic success measures and demographic data (race/ethnicity, socioeconomic status, first-generation, and gender) for UC Santa Cruz undergraduate students admitted between 2008 and 2019 who participated in field courses (N = 941 students) and who did not (N = 28,215 students). Additionally, we administered longitudinal surveys to evaluate self-efficacy gains during field-based versus classroom-based courses (N = 570 students). We found no differences in the proportion of students matriculating at the university as undecided, proposed EEB, or proposed other majors across demographic groups. However, five years later, under-represented students were significantly less likely to graduate with EEB degrees, indicating retention rather than recruitment drives disparities in representation. This retention gap is partly due to a lower rate of college completion and partly through attrition to other majors. Although under-represented students were less likely to enroll in field courses, field courses were associated with higher self-efficacy gains, higher college graduation rates, higher EEB major retention, and higher GPAs at graduation. All demographic groups experienced significant increases in self-efficacy during field-based but not lecture-based courses. Together, our findings suggest that increasing the number of field courses and actively facilitating access to students from under-represented groups can be a powerful tool for increasing STEM diversity.

12.
PLoS One ; 15(5): e0233005, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32469978

RESUMO

Helping the world's coastal communities adapt to climate change impacts requires evaluating the vulnerability of coastal communities and assessing adaptation options. This includes understanding the potential for 'natural' infrastructure (ecosystems and the biodiversity that underpins them) to reduce communities' vulnerability, alongside more traditional 'hard' infrastructure approaches. Here we present a spatially explicit global evaluation of the vulnerability of coastal-dwelling human populations to key climate change exposures and explore the potential for coastal ecosystems to help people adapt to climate change (ecosystem-based adaptation (EbA)). We find that mangroves and coral reefs are particularly well situated to help people cope with current weather extremes, a function that will only increase in importance as people adapt to climate change now and in coming decades. We find that around 30.9 million people living within 2km of the coast are highly vulnerable to tropical storms and sea-level rise (SLR). Mangroves and coral reefs overlap these threats to at least 5.3 and 3.4 million people, respectively, with substantial potential to dissipate storm surges and improve resilience against SLR effects. Significant co-benefits from mangroves also accrue, with 896 million metric tons of carbon stored in their soils and above- and below-ground biomass. Our framework offers a tool for prioritizing 'hotspots' of coastal EbA potential for further, national and local analyses to quantify risk reduction and, thereby, guide investment in coastal ecosystems to help people adapt to climate change. In doing so, it underscores the global role that conserving and restoring ecosystems can play in protecting human lives and livelihoods, as well as biodiversity, in the face of climate change.


Assuntos
Aclimatação , Mudança Climática , Ecossistema , Animais , Biodiversidade , Sequestro de Carbono , Conservação dos Recursos Naturais , Recifes de Corais , Tempestades Ciclônicas , Aquecimento Global , Humanos , Elevação do Nível do Mar , Áreas Alagadas
13.
Conserv Biol ; 33(2): 351-360, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30004134

RESUMO

Unpredictable or variable ecosystem recovery from disturbance presents a challenge to conservation, particularly as the scale of human disturbance continues to increase. Theory suggests land-cover and disturbance characteristics affect recovery, but individual studies of disturbance and recovery frequently struggle to uncover generalizable patterns because of high levels of site-specific variation. To understand how land-cover, disturbance type, and disturbance duration influence ecosystem recovery, we used studies documenting recovery of 50 streams to perform a global meta-analysis of stream recovery from disturbances that affect water quality (e.g., oil spill, fire, wastewater). We extracted upstream natural and urban land-cover percentages for each site and performed model selection and averaging to identify influences on recovery completeness. Most streams improved following the end of a disturbance (median 240% of disturbed condition) but did not recover fully to baseline predisturbance condition within the studied period (median study period 2 years; median recovery 60% of baseline). Scale of disturbance in time and space did not predict recovery, but sites with higher percentages of upstream natural land cover had less complete recovery relative to sites with more urban or agricultural cover, possibly due to higher baseline conditions in these streams. Our findings suggest impacts to systems with low anthropogenic stress may be more irreversible than impacts to already modified systems. We call for more long-term evaluations of ecosystem response to disturbance and the inclusion of regional references and predisturbance reference conditions for comparison. A more thorough understanding of the role of the surrounding landscape in shaping stream response to disturbance can help managers calibrate expectations for recovery and prioritize protection.


Meta-Análisis de los Efectos de la Cobertura Río-Arriba sobre la Restauración de Arroyos Resumen La restauración impredecible o variable de un ecosistema después de una perturbación presenta un reto para la conservación, particularmente conforme la escala de perturbaciones humanas continúa incrementando. La teoría sugiere que la cobertura de suelo y las características de la perturbación afectan a la restauración pero los estudios individuales sobre las perturbaciones y las restauraciones constantemente luchan por descubrir patrones generalizables debido a los niveles altos de variación específica en el sitio. Usamos estudios que documentan la restauración de 50 arroyos para realizar un meta-análisis global de la restauración de arroyos después de perturbaciones que afectaron la calidad del agua (p. ej.: derrames de petróleo, incendios, aguas negras) y así entender cómo la cobertura de suelo, el tipo de perturbación, y la duración de la perturbación influyen sobre la restauración del ecosistema. Extrajimos porcentajes de la cobertura natural y urbana de suelo río-arriba para cada sitio y realizamos una selección y promedio de modelos para identificar las influencias sobre la completitud de la restauración. La mayoría de los arroyos mejoraron después de que terminó la perturbación (mediana del 240% de la condición perturbada) pero no se recuperó completamente hasta la línea base de condiciones previas a la perturbación dentro del periodo estudiado (mediana del periodo de estudio: dos años; mediana de la restauración 60% de la línea base). La escala de perturbación en el tiempo y en el espacio no pronosticó la restauración, pero los sitios con porcentajes más altos de cobertura natural de suelo río-arriba tuvieron una restauración menos completa en relación con los sitios con una cobertura más urbana o agrícola, posiblemente debido a las condiciones más altas de línea base en estos arroyos. Nuestros hallazgos sugieren que los impactos sobre los sistemas con un bajo estrés antropogénico pueden ser más irreversibles que los impactos sobre sistemas que ya han sido modificados. Hacemos un llamado por más evaluaciones a largo plazo de la respuesta de los ecosistemas ante las perturbaciones y por la inclusión de referencias regionales y condiciones previas a la perturbación como referencia para realizar comparaciones. Un entendimiento más a fondo del papel del paisaje circundante en la formación de la respuesta de los arroyos ante las perturbaciones puede ayudar a los administradores a calibrar expectativas para la restauración y a priorizar la protección.


Assuntos
Ecossistema , Rios , Agricultura , Conservação dos Recursos Naturais , Humanos , Qualidade da Água
14.
Sci Total Environ ; 625: 909-919, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29996462

RESUMO

We provide updated spatial distribution and inventory data for on-road NH3 emissions for the continental United States (U.S.) On-road NH3 emissions were determined from on-road CO2 emissions data and empirical NH3:CO2 vehicle emissions ratios. Emissions of NH3 from on-road sources in urbanized regions are typically 0.1-1.3tkm-2yr-1 while NH3 emissions in agricultural regions generally range from 0.4-5.5tkm-2yr-1, with a few hotspots as high as 5.5-11.2tkm-2yr-1. Counties with higher vehicle NH3 emissions than from agriculture include 40% of the U.S. POPULATION: The amount of wet inorganic N deposition as NH4+ from the National Atmospheric Deposition Program (NADP) network ranged from 37 to 83% with a mean of 58.7%. Only 4% of the NADP sites across the U.S. had <45% of the N deposition as NH4+ based on data from 2014 to 2016, illustrating the near-universal elevated proportions of NH4+ in deposition across the U.S. Case studies of on-road NH3 emissions in relation to N deposition include four urban sites in Oregon and Washington where the average NH4-N:NO3-N ratio in bulk deposition was 2.3. At urban sites in the greater Los Angeles Basin, bulk deposition of NH4-N and NO3-N were equivalent, while NH4-N:NO3-N in throughfall under shrubs ranged from 0.6 to 1.7. The NH4-N:NO3-N ratio at 7-10 sites in the Lake Tahoe Basin averaged 1.4 and 1.6 in bulk deposition and throughfall, and deposition of NH4-N was strongly correlated with summertime NH3 concentrations. On-road emissions of NH3 should not be ignored as an important source of atmospheric NH3, as a major contributor to particulate air pollution, and as a driver of N deposition in urban and urban-affected regions.

16.
Proc Natl Acad Sci U S A ; 114(13): 3463-3468, 2017 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-28289231

RESUMO

Observational studies and experimental evidence agree that rising global temperatures have altered plant phenology-the timing of life events, such as flowering, germination, and leaf-out. Other large-scale global environmental changes, such as nitrogen deposition and altered precipitation regimes, have also been linked to changes in flowering times. Despite our increased understanding of how abiotic factors influence plant phenology, we know very little about how biotic interactions can affect flowering times, a significant knowledge gap given ongoing human-caused alteration of biodiversity and plant community structure at the global scale. We experimentally manipulated plant diversity in a California serpentine grassland and found that many plant species flowered earlier in response to reductions in diversity, with peak flowering date advancing an average of 0.6 days per species lost. These changes in phenology were mediated by the effects of plant diversity on soil surface temperature, available soil N, and soil moisture. Peak flowering dates were also more dispersed among species in high-diversity plots than expected based on monocultures. Our findings illustrate that shifts in plant species composition and diversity can alter the timing and distribution of flowering events, and that these changes to phenology are similar in magnitude to effects induced by climate change. Declining diversity could thus contribute to or exacerbate phenological changes attributed to rising global temperatures.


Assuntos
Biodiversidade , Flores/crescimento & desenvolvimento , California , Mudança Climática , Ecossistema , Fenótipo , Desenvolvimento Vegetal , Estações do Ano , Temperatura , Fatores de Tempo
17.
Ecol Appl ; 25(5): 1259-70, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26485954

RESUMO

Maintaining native biodiversity in grasslands requires management and mitigation of anthropogenic changes that have altered resource availability, grazing regimes, and community composition. In California (USA), high levels of atmospheric nitrogen (N) deposition have facilitated the invasion of exotic grasses, posing a threat to the diverse plant and insect communities endemic to serpentine grasslands. Cattle grazing has been employed to mitigate the consequences of exotic grass invasion, but the ecological effects of grazing in this system are not fully understood. To characterize the effects of realistic N deposition on serpentine plant communities and to evaluate the efficacy of grazing as a management tool, we performed a factorial experiment adding N and excluding large herbivores in California's largest serpentine grassland. Although we observed significant interannual variation in community composition related to climate in our six-year study, exotic cover was consistently and negatively correlated with native plant richness. Sustained low-level N addition did not influence plant community composition, but grazing reduced grass abundance while maintaining greater native forb cover, native plant diversity, and species richness in comparison to plots excluding large herbivores. Furthermore, grazing increased the temporal stability of plant communities by decreasing year-to-year variation in native forb cover, native plant diversity, and native species richness. Taken together, our findings demonstrate that moderate-intensity cattle grazing can be used to restrict the invasive potential of exotic grasses and maintain native plant communities in serpentine grasslands. We hypothesize that the reduced temporal variability in serpentine plant communities managed by grazing may directly benefit populations of the threatened Edith's Bay checkerspot butterfly (Euphydryas editha bayensis).


Assuntos
Biodiversidade , Bovinos , Comportamento Alimentar/fisiologia , Pradaria , Animais , Monitoramento Ambiental , Estações do Ano , Fatores de Tempo
18.
Ecology ; 96(1): 90-8, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26236894

RESUMO

While most studies of the relationship between biodiversity and ecosystem functioning have examined randomized diversity losses, several recent experiments have employed nested, realistic designs and found that realistic species losses had larger consequences than random losses for ecosystem functioning. Progressive, realistic, biodiversity losses are generally strongly nested, but this nestedness is a potentially confounding effect. Here, we address whether nonrandom trait loss or degree of nestedness drives the relationship between diversity and productivity in a realistic biodiversity-loss experiment. We isolated the effect of nestedness through post hoc analyses of data from an experimental biodiversity manipulation in a California serpentine grassland. We found that the order in which plant traits are lost as diversity declines influences the diversity-productivity relationship more than the degree of nestedness does. Understanding the relationship between the expected order of species loss and functional traits is becoming increasingly important in the face of ongoing biodiversity loss worldwide. Our findings illustrate the importance of species composition and the order of species loss, rather than nestedness per se, for understanding the mechanisms underlying the effects of realistic species losses on ecosystem functioning.


Assuntos
Biodiversidade , Biomassa , California , Plantas , Estatística como Assunto
19.
Ecology ; 95(1): 88-97, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24649649

RESUMO

Numerous experiments have demonstrated that diverse plant communities use nitrogen (N) more completely and efficiently, with implications for how species conservation efforts might influence N cycling and retention in terrestrial ecosystems. However, most such experiments have randomly manipulated species richness and minimized environmental heterogeneity, two design aspects that may reduce applicability to real ecosystems. Here we present results from an experiment directly comparing how realistic and randomized plant species losses affect plant N use across a gradient of soil depth in a native-dominated serpentine grassland in California. We found that the strength of the species richness effect on plant N use did not increase with soil depth in either the realistic or randomized species loss scenarios, indicating that the increased vertical heterogeneity conferred by deeper soils did not lead to greater complementarity among species in this ecosystem. Realistic species losses significantly reduced plant N uptake and altered N-use efficiency, while randomized species losses had no effect on plant N use. Increasing soil depth positively affected plant N uptake in both loss order scenarios but had a weaker effect on plant N use than did realistic species losses. Our results illustrate that realistic species losses can have functional consequences that differ distinctly from randomized losses, and that species diversity effects can be independent of and outweigh those of environmental heterogeneity on ecosystem functioning. Our findings also support the value of conservation efforts aimed at maintaining biodiversity to help buffer ecosystems against increasing anthropogenic N loading.


Assuntos
Biodiversidade , Nitrogênio/metabolismo , Plantas/metabolismo , Solo , Biomassa
20.
Conserv Biol ; 28(2): 478-88, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24372761

RESUMO

Native plant species that have lost their mutualist partners may require non-native pollinators or seed dispersers to maintain reproduction. When natives are highly specialized, however, it appears doubtful that introduced generalists will partner effectively with them. We used visitation observations and pollination treatments (experimental manipulations of pollen transfer) to examine relationships between the introduced, generalist Japanese White-eye (Zosterops japonicus) and 3 endemic Hawaiian plant species (Clermontia parviflora, C. montis-loa, and C. hawaiiensis). These plants are characterized by curved, tubular flowers, apparently adapted for pollination by curve-billed Hawaiian honeycreepers. Z. japonicus were responsible for over 80% of visits to flowers of the small-flowered C. parviflora and the midsize-flowered C. montis-loa. Z. japonicus-visited flowers set significantly more seed than did bagged flowers. Z. japonicus also demonstrated the potential to act as an occasional Clermontia seed disperser, although ground-based frugivory by non-native mammals likely dominates seed dispersal. The large-flowered C. hawaiiensis received no visitation by any birds during observations. Unmanipulated and bagged C. hawaiiensis flowers set similar numbers of seeds. Direct examination of Z. japonicus and Clermontia morphologies suggests a mismatch between Z. japonicus bill morphology and C. hawaiiensis flower morphology. In combination, our results suggest that Z. japonicus has established an effective pollination relationship with C. parviflora and C. montis-loa and that the large flowers of C. hawaiiensis preclude effective visitation by Z. japonicus.


Assuntos
Comportamento Apetitivo , Campanulaceae/fisiologia , Espécies Introduzidas , Polinização , Dispersão de Sementes , Aves Canoras/fisiologia , Animais , Cadeia Alimentar , Havaí
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