Summary
Trait‐based approaches are increasingly being used to test mechanisms underlying species assemblages and biotic interactions across a wide range of organisms including terrestrial arthropods ...and to investigate consequences for ecosystem processes. Such an approach relies on the standardized measurement of functional traits that can be applied across taxa and regions. Currently, however, unified methods of trait measurements are lacking for terrestrial arthropods and related macroinvertebrates (terrestrial invertebrates hereafter).
Here, we present a comprehensive review and detailed protocol for a set of 29 traits known to be sensitive to global stressors and to affect ecosystem processes and services. We give recommendations how to measure these traits under standardized conditions across various terrestrial invertebrate taxonomic groups.
We provide considerations and approaches that apply to almost all traits described, such as the selection of species and individuals needed for the measurements, the importance of intraspecific trait variability, how many populations or communities to sample and over which spatial scales.
The approaches outlined here provide a means to improve the reliability and predictive power of functional traits to explain community assembly, species diversity patterns and ecosystem processes and services within and across taxa and trophic levels, allowing comparison of studies and running meta‐analyses across regions and ecosystems.
This handbook is a crucial first step towards standardizing trait methodology across the most studied terrestrial invertebrate groups, and the protocols are aimed to balance general applicability and requirements for special cases or particular taxa. Therefore, we envision this handbook as a common platform to which researchers can further provide methodological input for additional special cases.
A lay summary is available for this article.
Lay Summary
The study of biodiversity spatial patterns along ecological gradients can serve to elucidate factors shaping biological community structure and predict ecosystem responses to global change. Ant ...assemblages are particularly interesting as study cases, because ant species play a key role in many ecosystem processes and have frequently been identified as useful bioindicators.
Here we analyzed the response of ant species richness and assemblage composition across elevational gradients in Mediterranean grasslands and subsequently tested whether these responses were stable spatially and temporally. We sampled ant assemblages in two years (2014, 2015) in two mountain ranges (Guadarrama, Serrota) in Central Spain, along an elevational gradient ranging from 685 to 2390 m a.s.l.
Jackknife estimates of ant species richness ranged from three to 18.5 species and exhibited a hump-shaped relationship with elevation that peaked at mid-range values (1100-1400 m). This pattern was transferable temporally and spatially. Elevation was related to ant assemblage composition and facilitated separation of higher elevation assemblages (> 1700 m) from the remaining lower elevation species groups. Ant assemblages were nested; therefore species assemblages with a decreased number of species were a subset of the richer assemblages, although species turnover was more important than pure nestedness in all surveys. The degree of nestedness changed non-linearly as a cubic polynomial with elevation. These assembly patterns coincided more clearly over time than between the two study regions.
We suggest double environmental stressors typical of Mediterranean mountains explained species richness patterns: drought at low elevations and cold temperatures at high elevations likely constrained richness at both extremes of elevational gradients. The fact that species turnover showed a dominant role over pure nestedness suggested current ant assemblages were context-dependent and highly vulnerable to global change, which threatens the conservation of present day native ant communities, particularly at high elevations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
1. Changes in livestock grazing regimes are among the most important drivers of species loss and decrease in functional diversity world-wide. However, taxonomic and functional diversities (TD and FD) ...can respond differently to changes in grazing regime or productivity. 2. We surveyed plant communities from 67 sites under different grazing regimes (from heavy grazing to grazing abandonment) in wet and dry habitats, in both wet and dry years. We tested the influence of grazing intensity, habitat type and rainfall on TD, FD and the relationship between them. We also partitioned diversity to examine the effects of grazing on TD and FD across scales (within communities, within grazing levels and between grazing levels). 3. The effect of grazing within and across communities was modulated by water availability, with grazing showing the strongest effects in dry habitats. The relationship between FD and TD varied between habitat types and years and revealed high functional similarity between species (i.e. redundancy) in dry habitats. TD was reduced in the driest conditions across all the observation levels, contrasting with the high temporal stability of FD, suggesting that FD was decoupled from TD, especially in dry habitats. However, despite the high temporal and spatial stability of FD, results show that under severely limited water availability, high grazing pressure can reduce FD, revealing a convergence in traits under the combined effect of grazing and drought conditions. 4. Synthesis and applications. Results highlight the dependence of functional diversity on the combined effect of water availability and grazing regime. Under severely limited water availability, grazing intensification reduced the functional diversity of these grasslands. Because of the foreseeable reduction in water availability in Mediterranean environments, we recommend the adoption of flexible grazing management schemes that take species and functional diversities into account simultaneously and adapt the level of grazing pressure to water availability.
Context
Drove roads are landscape corridors traditionally used for livestock movement in many regions of the world, including Spain, where they cover about 0.8% of the land. They have ecological ...importance due to their role in connectivity, seed dispersal, soil preservation, habitat and biodiversity conservation, and the provision of ecosystem services. Drove roads are experiencing deterioration due to the abandonment of extensive grazing and transhumance.
Objectives
We aim to characterize the conservation status and main predictors of deterioration of the drove roads in the Community of Madrid, a region in Spain with a high presence of these corridors.
Methods
We considered all the network of the region, with the main analyses based on a sample of 160 segments of 200 m-long, which were evaluated using GIS and fieldwork.
Results
Nearly one third of the network surface is occupied by crops, communication infrastructure, and urban or industrial surfaces. Natural habitats make up 60% of the network and are affected by soil degradation and grazing abandonment. Landscape matrix was the main predictor of drove road status, with urban and cropland matrices leading to a reduction in spatial integrity and availability for natural habitats. Grazing was most preserved in grassland matrices. Eco-district, drove road width, and distance to city center also had influence on conservation status.
Conclusions
Despite their concerning state, the network is restorable in many areas of the region. Restoration should focus on intensified and simplified landscapes, where the network plays a more decisive role, and should consider the reintroduction of livestock.
Aim
Many aspects of vegetation response to increased drought remain uncertain but it is expected that phenotypic plasticity may be key to early adaptation of plants to environmental stress. In this ...work we observe the response of specific leaf area (SLA) of woody shrub vegetation to the summer drought typical of the Mediterranean climate. In addition, to observe the possible interaction between the impact of drought and the environmental characteristics of the ecosystems, communities from different edaphic and structural contexts distributed along the double stress gradient of the Mediterranean mountains (high temperature and low precipitation at low elevation; low temperature and high irradiation at high elevation) have been analysed.
Location
Central Mountain range of the Iberian Peninsula.
Methods
Along the entire altitudinal gradient, 33 shrub communities belonging to different habitat typologies (shrublands, rocky areas, hedgerows, understorey) were sampled before and after the passage of summer, both in 2017 and 2019. A total of 1724 individuals and 15,516 leaves were collected and measured to estimate the mean values and diversity of SLA of each community.
Results
The community‐weighted mean and functional divergence have inverse quadratic relationships with the environmental gradient. Shrub communities at both ends of the gradient have low mean SLA values and high functional divergence of this trait. Summer drought implies a generalised decrease in the mean SLA of the communities throughout the gradient, as well as an alteration in functional richness and uniformity. However, the effect of summer drought on the plant community is mediated by the microenvironmental characteristics of its habitat.
Conclusions
Drought acclimatisation of shrub communities through phenotypic plasticity leads to rapid changes in their functional leaf structure. In the long term, our results point to an increase in plant conservative strategies, reduced ecosystem productivity, slower nutrient recycling and the reduction of communities of specific habitats as drought increases.
Assessing the effect of drought on vegetation under different environmental conditions could improve our understanding of climate change impacts. We have found that summer drought produces rapid changes in the diversity and mean SLA of Mediterranean shrub communities distributed along an altitudinal gradient. This functional response differs between habitats but generally implies a shift towards a more conservative strategy.
Insects play a key role in the regulation and dynamics of many ecosystem services (ES). However, this role is often assumed, with limited or no experimental quantification of its real value. We ...examined publication trends in the research on ES provided by insects, ascertaining which ES and taxa have been more intensively investigated, and which methodologies have been used, with particular emphasis on experimental approaches. We first performed a systematic literature search to identify which ES have been attributed to insects. Then we classified the references retrieved according to the ES, taxonomic group and ecosystem studied, as well as to the method applied to quantify each ES (in four categories: no quantification, proxies, direct quantification and experiments). Pollination, biological control, food provisioning, and recycling organic matter are the most studied ES. However, the majority of papers do not specify the ES under consideration, and from those that do, most do not quantify the ES provided. From the rest, a large number of publications use proxies as indicators for ES, assuming or inferring their provision through indirect measurements such as species abundances, species density, species richness, diversity indices, or the number of functional groups. Pollinators, predators, parasitoids, herbivores, and decomposers are the most commonly studied functional groups, while Hymenoptera, Coleoptera, and Diptera are the most studied taxa. Experimental studies are relatively scarce and they mainly focus on biological control, pollination, and decomposition performed in agroecosystems. These results suggest that our current knowledge on the ES provided by insects is relatively scarce and biased, and show gaps in the least-studied functional and taxonomic groups. An ambitious research agenda to improve the empirical and experimental evidence of the role played by insects in ES provision is essential to fully assess synergies between functional ecology, community ecology, and biodiversity conservation under current global changes.
Both intra‐ and interspecific differences in traits may modulate interactions between plants. Two mechanisms are hypothesized to regulate these effects: competitive hierarchies and trait ...dissimilarities, but it is unclear how the prevalence of each might depend on environmental conditions and on intra and interspecific differences.
We sowed six replicates of all possible pairwise combinations across eight annual species (including conspecific competition and individuals without competitors), in pots under two levels of fertilization. We measured above‐ and below‐ground traits and total biomass of the focal individuals. We expressed competition as the decrease in biomass of focal individuals relative to biomass without competition, and modelled competition using directional (hierarchy) or non‐directional (dissimilarity) trait differences, with or without intraspecific variability (ITV).
We found evidence of different trait hierarchies operating under different fertilization conditions but little support for trait dissimilarities. The negative effect of competition on focal plants increased with the height of the competitors in both of fertilization levels. Further, in unfertilized conditions, plants with lower specific leaf area (SLA) and larger root systems experienced less competition. Including ITV in trait hierarchies substantially improved our ability to predict the intensity of competition. This was partly due to ITV reducing competitive hierarchies.
Synthesis. Our results underscore the importance of traits in driving interactions among plants. Competitive relationships between species depend on complex interactions between trait intra and interspecific differences and resource availability. ITV appears to be a mechanism capable of reducing trait hierarchies, and hence the intensity of competition between coexisting plants.
in Spanish
Las diferencias intra‐ e interespecíficas en atributos funcionales pueden afectar a las interacciones entre plantas. En teoría, dos mecanismos pueden regular estos efectos: las jerarquías competitivas y la disimilitud en atributos, pero no esta claro como la prevalencia de cada uno de estos mecanismos depende tanto de las condiciones ambientales como de las diferencias intra e interespecíficas.
Seis réplicas de todas las posibles combinaciones de parejas de ocho especies anuales típicas de pastizales mediterráneos (además de competición entre individuos de una misma especie e individuos aislados sin competidores) fueron sembradas en macetas con dos niveles de fertilización. Se midieron atributos funcionales de la parte aérea y de las raíces de los individuos focales. Para expresar el grado de competición, se consideró la reducción de biomasa en los individuos focales en relación con la de los individuos sin competición, y se modelizó la competición utilizando diferencias en los atributos tanto direccionales (jerarquías) como no direccionales (disimilitud), con y sin consideración de la variabilidad intraespecífica (ITV).
Nuestros resultados muestran que las jerarquías de atributos que determinan la competencia entre especies dependieron de los niveles de fertilización, mientras que la disimilitud entre atributos no parece un determinante de importancia en estas relaciones. El efecto negativo de la competición sobre las plantas focales fue directamente proporcional a la altura de las plantas competidoras en ambos niveles de fertilización. Además, en condiciones de alta fertilidad, las plantas con un área foliar especifica (SLA) más baja y raíces más grandes sufrieron menos la competición. Considerar la ITV en las estimaciones de las jerarquías de atributos funcionales mejoró sustancialmente la capacidad predictiva de los modelos. Esta mejora se debió en parte a que la ITV redujo las jerarquías competitivas.
Síntesis: Nuestros resultados resaltan la importancia de los atributos funcionales como determinantes de las interacciones entre plantas. Las relaciones de competición entre especies dependen de interacciones complejas entre las diferencias intra e interespecificas en atributos y la disponibilidad de recursos. La ITV aparece como un mecanismo que permite reducir las jerarquías competitivas y por tanto la intensidad de la competición entre plantas.
Our results underscore the importance of traits in driving interactions among plants. Competitive relationships between species depend on complex interactions between trait intra and interspecific differences and resource availability. ITV appears to be a mechanism capable of reducing trait hierarchies, and hence the intensity of competition between coexisting plants.
More for less Carmona, Carlos P.; Rota, Cristina; Azcárate, Francisco M. ...
Functional ecology,
04/2015, Letnik:
29, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Summary
Ecologists use approaches based on plant functional traits to tackle several fundamental and applied questions. Although a perfect characterization of functional trait structure requires the ...measurement of all the individuals in communities, this is prohibitively resource‐consuming. Consequently, the general practice is to average the trait values of a reduced number of individuals per species. However, there are different alternatives regarding the number, identity and spatial location of the individuals chosen to calculate species‐averaged trait values.
In this study, we compared different strategies for sampling functional traits, using community‐weighted mean trait values (CWM) and the Rao index of functional diversity (FD). We intensively sampled the functional trait structure along a topographical gradient in a Mediterranean grassland, obtaining accurate estimations of the ‘real’ values of these indices (CWMI and FDI) for three traits (height, leaf area and specific leaf area).
We simulated three different sampling strategies differing in the spatial location of the individuals used to estimate species‐mean trait: (i) average of the whole gradient (GLO), (ii) average of the sampling unit in which the abundances of species maximize (MAX) and (iii) average of a reduced number of individuals per species and sampling unit (LOC). For each strategy, we simulated different sampling intensities (number of individuals sampled).
For each trait, we examined the ability of each strategy and sampling intensity to accurately estimate CWMI and FDI, as well as their ability to detect changes in functional trait structure along the topographical gradient.
LOC outperformed the other strategies in terms of accuracy and bias, and was much more efficient to describe changes along the gradient, regardless of the traits and indicators considered. Furthermore, LOC was the only strategy that improved consistently as sampling intensity increased, especially at low levels of intensity.
Our results indicate that the impact of considering intraspecific variability in trait values can be greater than commonly assumed. Strategies that neglect this source of variability can result in inaccurate or biased estimations of the functional trait structure of plant communities. Most importantly, we show that intraspecific variability can be taken into consideration without any increases in the total number of individuals measured.
Lay Summary
•PPM showed higher incidences in stands dominated by P. pinaster and P. nigra and lower for P. sylvestris and P. pinea.•Pine stands with higher grazing pressure were more vulnerable to pine ...processionary moth.•PPM incidence is lower in structurally complex forests, with more cover of non-host trees and higher diversity of tree sizes.•Clearings occupied by bushes or rocks reduced PPM incidence, but clearings with a more simplified structure increased it.
The occurrence of the pine processionary moth (Thaumetopoea pityocampa, hereafter PPM) in Mediterranean pine forests and plantations is of increasing concern as processes such as global warming and forest cover expansion have amplified the frequency and virulence of outbreaks. This study attempts to provide as complete an overview as possible of the different factors involved in pine forest susceptibility to PPM in 98 pine stands in Central Spain. A large study area (∼3,000 km2) was considered, including three different spatial scales (<1 ha, 1 ha, 10 ha) and four different pine tree species (Pinus pinaster, P. nigra, P. sylvestris, P. pinea), monitored over a 4-year period. Models were fitted for each of the three spatial scales, as well as for a combination of them (multiscale model). Pine species had a strong influence on vulnerability to PPM, with higher incidences in stands dominated by P. pinaster and P. nigra and lower for those dominated by P. sylvestris and P. pinea. Grazing pressure, a factor thus far disregarded, was also determining, with a prominent role at both the multiscale and the stand-scale levels. Other variables were highly influential at some of the spatial scales, showing a greater resistance in pine forests or plantations with a higher diversity of pine sizes, greater tree density, and a larger cover of non-host tree species. Open habitats also played a role in PPM incidence: we detected that, both at the locality and the plot scale, the presence of clearings occupied by bushes or rocky outcrops reduced vulnerability to PPM, while the clearings with a more simplified structure produced the opposite effect. We conclude that PPM incidence is greater in structurally simple pine forests, with strong grazing pressure and abundant open spaces without woody vegetation that may favour PPM pupation. To reduce damage by PPM, pine forest and plantations should be managed to avoid oversimplified forest structures. Patches of non-host tree species should be promoted, as well as some presence of shrubs in open areas. This implies avoiding overgrazing and other management models leading to an excessive increase in bare soil. Nevertheless, it should be noted that the implementation of these recommendations should consider the remaining challenges that need to be addressed in the current context of global change, such as the increased risk of wildfires and the emergence of other pests and diseases.
•Studies evaluating the role of arthropods as grassland indicators are increasing.•Macro-arthropods were used more than micro-arthropods (91% vs 15%).•Among macro-arthropods, Coleoptera were the ...preferred group (49% of the studies).•Species richness and abundance were the preferred indices to evaluate the response.•Arthropods were used to assess grazing, restoration and land use in 72% of studies.
Temperate grasslands are part of one of the biggest biomes on earth, sustaining high levels of biodiversity and providing multiple ecosystem services. However, the area covered by this open ecosystem is decreasing worldwide, due to several threats like land use change or climate change. Ground-dwelling arthropods are an important group of the community of grassland soil invertebrates, and they play a key role within this ecosystem, while at the same time being sensitive to the changes caused by management practices like grazing, mowing, prescribed fire, etc. Using the Web of Science database, we conducted a systematic review to identify which groups of arthropods are being used as indicators to evaluate the ecological condition of grasslands in temperate regions, and which indices are being measured. As grasslands have been traditionally managed by humans for centuries, their ecological condition is intrinsically linked to the development of different management practices like grazing, mowing or restoration strategies, which usually affect soil and vegetation structure. We found that macro-arthropods were used in a greater number of studies than micro-arthropods (91% vs 15%), and within that size group, beetles were the preferred indicator in most of the temperate grassland types (49% of the studies), followed by spiders and ants. Few studies used grasshoppers to monitor grasslands changes. The indices more frequently assessed were species richness and abundance, and we identified that the response to the different management practices was quite heterogeneous. Restoration and grazing effects were the two factors more frequently evaluated for macro-arthropods, while micro-arthropods (Acari and Collembola) were dominant to assess land use type. Overall, our findings highlight the need to increase the number of studies in some temperate regions, to explore the potential of overlooked groups of arthropods, and to include indices that measure functional diversity or community composition.
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