Lower Beta Diversity Research Articles

Functional Ecology of Forest, Heath, and Shrub Savannah Alternate States in Eastern Canada

In eastern Canada, alternation of wildfire regime due to fire suppression creates alternate vegetation states converting black spruce forest to heath and shrub savannah (SS). We compared the taxonomic diversity (TD) and functional diversity (FD) of post-fire forest, heath, and SS alternate states to determine if community FD can explain their persistence. We hypothesized that (i) species diversity (TD and FD) would be the highest in forest followed by SS and heath due to decreased interspecific competition and niche differentiation, (ii) differences between TD and FD indices would be greater in communities with high TD in forest due to high trait differentiation and richness, and (iii) changes in community trait values would indicate niche limitations and resource availability. We conducted this study in Terra Nova National Park, Newfoundland, Canada. We calculated functional dispersion (alpha FD), functional pairwise dissimilarity (beta FD), Shannon’s diversity (alpha TD), and Bray–Curtis dissimilarity (beta TD) from species cover. We used five functional traits (specific root length, specific leaf area, leaf dry matter content, height, and seed mass) related to nutrient acquisition, productivity, and growth. We found lower beta diversity in forest than heath and SS; forest also had higher species diversity and greater breadth in niche space utilization. SS was functionally similar to heath but lower than forest in functional dispersion and functional divergence. It had the highest functional richness and evenness. There was no difference in functional evenness between forest and heath. Functional beta diversity was the highest in forest, and did not differ between heath and SS. Resource acquisition and availability was the greatest in forest and the lowest in heath. We suspect that this might be due to forest having the highest functional trait turnover and niche utilization. We conclude that alternate vegetation states originating from alterations to the natural fire regime negatively impact ecosystem function.

Wine Terroir and the Soil Bacteria: An Amplicon Sequencing-Based Assessment of the Barossa Valley and Its Sub-Regions.

A wines’ terroir, represented as wine traits with regional distinctiveness, is a reflection of both the biophysical and human-driven conditions in which the grapes were grown and wine made. Soil is an important factor contributing to the uniqueness of a wine produced by vines grown in specific conditions. Here, we evaluated the impact of environmental variables on the soil bacteria of 22 Barossa Valley vineyard sites based on the 16S rRNA gene hypervariable region 4. In this study, we report that both dispersal isolation by geographic distance and environmental heterogeneity (soil plant-available P content, elevation, rainfall, temperature, spacing between row and spacing between vine) contribute to microbial community dissimilarity between vineyards. Vineyards located in cooler and wetter regions showed lower beta diversity and a higher ratio of dominant taxa. Differences in soil bacterial community composition were significantly associated with differences in fruit and wine composition. Our results suggest that environmental factors affecting wine terroir, may be mediated by changes in microbial structure, thus providing a basic understanding of how growing conditions affect interactions between plants and their soil bacteria.

Partitioning the colonization and extinction components of beta diversity across disturbance gradients.

Changes in species diversity often result from species losses and gains. The dynamic nature of beta diversity (spatial variation in species composition) that derives from such temporal species turnover, however, has received relatively little attention. Here, we disentangled extinction and colonization components of beta diversity by using the sets of species that went locally extinct and that newly colonized the study sites. We applied this concept of extinction and colonization beta diversity to ground vegetation communities that have been repeatedly surveyed in forests where fire and harvesting were experimentally applied. We first found that fire and harvesting caused no effect on beta diversity 2 yr after the treatments. From this result, we might conclude that they did not alter the ways in which species assemble across space. However, when we analyzed the extinction and colonization beta diversity between pre-treatment and 2 yr after the treatments, both measures were found to be significantly lower in burned sites compared to unburned sites (i.e., the groups of excluded and newly colonized species both showed low beta diversity in the burned sites). These results indicate that the fire excluded similar subsets of species across space, making communities become more heterogeneous, but at the same time induced spatially uniform colonization of new species, causing communities to homogenize. Consequently, the effects of these two processes canceled each other out. The relative importance of extinction and colonization components per se also changed temporally after the treatments. Fire and harvesting showed synergetic negative impacts on extinction beta diversity between pre-treatment and 10 yr after the treatments. Overall, analyses using extinction and colonization beta diversity allowed us to detect nonrandom disassembly and reassembly dynamics in ground vegetation communities. Our results suggest that common practices of analyzing beta diversity at one point in time can mask significant variation driven by disturbance. Acknowledging the extinction-colonization dynamics behind beta diversity is essential for understanding the spatiotemporal organization of biodiversity.

Macroecology of macrophytes in the freshwater realm: Patterns, mechanisms and implications

• Few broad-scale patterns are well-studied for aquatic macrophytes. • Local environmental predictors were important for freshwater plants at broad-scales. • Several knowledge gaps on macroecology of freshwater plants were identified. • Lack of lotic studies and databases of species traits and phylogeny were found. • Additional macroecological investigations on freshwater plants are clearly needed. Broad-scale studies of species distributions and diversity have contributed to the emergence of general macroecological rules. These rules are typically founded on research using well-known terrestrial taxa as models and it is thus uncertain whether aquatic macrophytes follow these macroecological rules. Our purpose is to draw together available information from broad-scale research on aquatic macrophytes growing in lakes, ponds, wetlands, rivers and streams. We summarize how different macroecological rules fit the patterns shown by freshwater plants at various spatial scales. Finally, we outline future actions which should be taken to advance macroecological research on freshwater plants. Our review suggested that some macroecological patterns are relatively well-evidenced for aquatic macrophytes, whereas little information exists for others. We found, for example, that the species richness-latitude relationship follows a unimodal pattern, and species turnover prevails over species nestedness, whereas higher nestedness-related richness differences are found in low beta diversity regions. Contrary to terrestrial plants, climate or history seem not to be dominant determinants explaining these broad-scale patterns; instead local explanatory variables (e.g., water quality, such as alkalinity and nutrients, and hydromorphology) are often important for freshwater plants. We identified several knowledge gaps related, for example, to a smaller number of studies in lotic habitats, compared with lentic habitats, lack of spatially-adequate aquatic plant studies, deficiency of comprehensive species traits databases for aquatic macrophytes, and absence of a true phylogeny comprising most freshwater plant lineages. We hope this review will encourage the undertaking of additional macroecological investigations on freshwater plants across broad spatial and temporal scales.

Temperature but not nutrient addition affects abundance and assemblage structure of colonizing aquatic insects

Abiotic conditions are important considerations in the species sorting process, which ultimately determines the distribution and abundance of species. Freshwater ecosystems will be impacted by ongoing temperature rise and other anthropogenically induced changes, such as nutrient enrichment and eutrophication. Changing characteristics of freshwater habitats will likely impact organisms in numerous ways, including through effects on colonization dynamics. Species are expected to colonize habitat patches where fitness will be the highest for themselves and their offspring, and how habitat selection interacts with changing environments remains an important question. We conducted a warming experiment to test the habitat selection preferences of aquatic beetles and hemipterans between habitat patches (mesocosms) of varying temperatures (via heaters), nutrient addition, and their interaction. Overall, insect abundance and richness were higher in unheated patches, with taxon-specific variation in response to heating. Although nutrients had limited effects on environmental conditions in mesocosms, their addition had no significant effects on insects. Insect assemblages had unique structures across heating treatments, with lower beta diversity and higher effective numbers of species in the warmest mesocosms. Our data support the importance of spatial variation in abiotic factors during the habitat selection process, and in determining species distributions and abundances as shallow lentic ecosystems are impacted by rising global temperatures.

Are vascular epiphytes in urban green areas subject to the homogenization of biodiversity? A case study in the Brazilian Atlantic Forest

Urbanization is a disturbance process that can select species and result in biodiversity homogenization. Despite this, urban green areas shelter nature and are also important to human welfare. Epiphytes are an important functional group present in such areas, that are rarely studied. We evaluated the vascular epiphytic component in 26 urban green areas in the Brazilian Atlantic Forest and tested hypotheses related to the anthropogenic disturbances: 1) the community of epiphytes in urban green areas presents low richness and diversity of species; 2) there is low beta diversity due to flora homogenization represented by a reduced set of more tolerant species to disturbance. A total of 2288 trees (1563 representing phorophytes) and 110 epiphytic species were sampled. Six species were dominant, resulting in low diversity values, but some green areas had relatively high richness. The similarity found between the majority of the sampled areas suggests that epiphytic flora is subject to homogenization due to environmental filters. We found a high richness of species without adaptations to the epiphytic lifeform (accidental epiphytes) (42% of total sampled). Some results suggest that more comprehensive ecological and/or floristic studies about the epiphytes in the urban environment are necessary, such as Orchidaceae as the second richest family (since it is often poor in urban areas). More information about the species distribution patterns are necessary, both regarding the anthropized environments and the relationships with exotic or native phorophytes, as well as to enhance the knowledge of the ecological functions played by the epiphytes in these places.

Effects of mining and reduced turnover of Ephemeroptera (Insecta) in streams of the Eastern Brazilian Amazon

Mining operations can cause environmental alterations that have a major impact on aquatic organisms. In the present study, we analyzed the effects of mining operations on the environmental heterogeneity of streams in the eastern Brazilian Amazon, and the beta diversity (and components) of the local communities of the order Ephemeroptera. We tested three hypotheses: (a) mining activities reduce the environmental variation of streams; (b) altered streams have lower beta diversity, and (c) environmental variables influence the genus richness and abundance of ephemeropterans. The ephemeropterans were sampled in the Carajas National Forest in the dry season over 3 years. Streams were sampled in areas near the extraction of iron ore (16) and in pristine environments (8). The beta diversity was estimated based on the occurrence and abundance approaches. We recorded 2259 individuals and 32 genera. The comparative assessment of environmental variables indicated that environments altered by mining have higher total manganese and iron concentrations than preserved environments. Environmental variables influenced ephemeropteran communities, and the analysis of the components of the beta diversity indicated a higher turnover of ephemeropterans in preserved streams, which implies that species substitution rates are higher in preserved streams than in altered streams. These results indicate that the substitution of species in preserved streams is limited spatially, probably linked to the sensitivity of the organisms to oscillations in the environmental variables occurring in impacted environments. IMPLICATIONS FOR INSECT CONSERVATION: The results indicated that possibly the changes brought about by mining activities restrict the turnover of species between the preserved and altered areas, and only species tolerant to these changes were established. Over time and with the advancement of mining activities may occur the local exclusion of the most sensitive species and homogenization of the composition formed by more tolerant and less relevant conservation species.

Drivers of beta diversity in modern and ancient reef-associated soft-bottom environments.

Beta diversity, the compositional variation among communities, is often associated with environmental gradients. Other drivers of beta diversity include stochastic processes, priority effects, predation, or competitive exclusion. Temporal turnover may also explain differences in faunal composition between fossil assemblages. To assess the drivers of beta diversity in reef-associated soft-bottom environments, we investigate community patterns in a Middle to Late Triassic reef basin assemblage from the Cassian Formation in the Dolomites, Northern Italy, and compare results with a Recent reef basin assemblage from the Northern Bay of Safaga, Red Sea, Egypt. We evaluate beta diversity with regard to age, water depth, and spatial distance, and compare the results with a null model to evaluate the stochasticity of these differences. Using pairwise proportional dissimilarity, we find very high beta diversity for the Cassian Formation (0.91 ± 0.02) and slightly lower beta diversity for the Bay of Safaga (0.89 ± 0.04). Null models show that stochasticity only plays a minor role in determining faunal differences. Spatial distance is also irrelevant. Contrary to expectations, there is no tendency of beta diversity to decrease with water depth. Although water depth has frequently been found to be a key factor in determining beta diversity, we find that it is not the major driver in these reef-associated soft-bottom environments. We postulate that priority effects and the biotic structuring of the sediment may be key determinants of beta diversity.

High water flow velocity reduces beta diversity and leads to a distinct composition of Oligochaeta in Neotropical lotic ecosystems

Water flow velocity is a strong environmental filter structuring benthic communities in lotic ecosystems. While many studies have determined its effect on the distribution and diversity patterns of insects, the role of water flow velocity on other groups of aquatic invertebrates (i.e., Oligochaeta) has remained unexplored. We sampled five lotic ecosystems to investigate the influence of water flow velocity on the species composition of Oligochaeta assemblages in a Neotropical floodplain. Our first hypothesis was that higher water flow velocity decreases Oligochaeta assemblages variability. Consequently, we expected a lower beta diversity among the mid-channels of the ecosystems (i.e., sites with higher water velocity) relative to channel margins (i.e., sites with lower water velocity). Our second hypothesis was that water flow velocity determines species composition of Oligochaeta. Consequently, we expected a different species composition between the mid-channel and the channel margins of lotic ecosystems. We found 19 Oligochaeta species across the five lotic ecosystems. We corroborated both hypotheses because we found lower Oligochaeta beta diversity among the mid-channels of the lotic ecosystems as well as a different species composition. Haplotaxis aedeochaeta and Narapa bonettoi were the taxa strongly associated with the mid-channel, because they are adapted to live among the sand grains in the bottom of the rivers with high depth and water velocity. Overall, water flow velocity should be considered as a strong driver of Oligochaeta species composition.

Long-term effects of copper exposure to agricultural soil function and microbial community structure at a controlled and experimental field site

The long-term effect of heavy metals on soil microbial communities and their function is relatively unknown and little work has been done in field settings. To address this gap, we revisited a field-based experiment, 12 years after the application of copper (Cu) to agricultural soils, with treatment concentrations ranging from 0 to 3310 mg Cu kg−1 soil. We measured the long-term effects of Cu exposure to soils using multiple functionality assessments and environmental DNA-based community analyses. The assessment results revealed that soils that received moderate to high Cu doses had still not recovered functionality 12-years post exposure. However, plots that received doses of 200 mg kg−1 Cu or less appeared to have a functionality index not dissimilar to control plots. Environmental DNA analyses of the microbial communities revealed a high level of beta diversity in low Cu treatment plots, whereas communities within high Cu treatment plots had similar community structures to one another (low beta diversity), indicating that specific Cu-tolerant or dormant taxa are selected for in high-Cu environments. Interestingly, high Cu plots had higher within-sample taxa counts (alpha diversity) compared with controls and low Cu plots. We hypothesise that taxa in high Cu plots activated dormancy mechanisms, such that their genetic signal remained present, whilst the functionality of the soil was reduced. Many species identified in high Cu plots are known to have associated dormancy mechanisms and survive in high stress environments. Understanding how these mechanisms collectively contribute to contaminant outcomes is of great importance for the goals of predicting and managing microbial communities and their function. As we found that Cu concentrations above 200 mg kg−1 can cause significant functionality loss and a selective pressure on microbial communities, it is recommended that Cu concentrations above 200 mg kg−1are avoided in agricultural soils.

Invasive Saltcedar and Drought Impact Ant Communities and Isopods in South-Central Nebraska.

The establishment and spread of non-native species often results in negative impacts on biodiversity and ecosystem function. Several species of saltcedar, Tamarix spp. L., have been recently naturalized in large portions of the United States where they have altered plant and animal communities. To test the prediction that saltcedar negatively affects invertebrates, we measured ant genera diversity and the activity density of the exotic isopod Armadillidium vulgare Latrielle (Isopoda: Oniscoidea) for 2 yr using pitfall traps located within 30 5-m2 plots with or without saltcedar at a south-central Nebraska reservoir. From 2005 to 2006, we collected 10,837 ants representing 17 genera and 4,953 A. vulgare. Per plot, the average number of ant genera was not different between saltcedar (x̅ = 3.9) and non-saltcedar areas ( x̅ = 3.9); however, saltcedar plots were compositionally different and more similar from plot to plot (i.e., they had lower beta diversity than control plots) in 2005, but not in 2006. Isopods were likewise temporally affected with higher activity density (+89%) in control plots in 2005, but higher activity density (+27%) in saltcedar plots in 2006. The observed temporal differences occurred as the drought that initially enabled the saltcedar invasion became less severe in 2006. Combined, our results suggest that invertebrate groups like ants, which are generally omnivorous, may be better equipped than more specialized taxa like detritivores to withstand habitat changes due to invasions by non-native species, especially during extreme weather events such as prolonged droughts.

The impacts of bioenergy pine plantation management practices on bee communities

AbstractCultivation of bioenergy feedstocks is a growing land‐use world‐wide, yet we have a poor understanding of how bioenergy crop management practices affect biodiversity. This knowledge gap is particularly acute for candidate cellulosic bioenergy feedstocks, such as tree plantations, and for organisms that provide important ecosystem services, such as pollinators.We examined bee communities in 83 sites across three states in the southeastern United States—Alabama, Florida and Georgia. We compared bee abundance and diversity in 66 pine plantation sites that reflect management with and without potential bioenergy feedstock production. At least three bioenergy feedstock production methods have been proposed for this region: (a) converting conventional timber stands to short‐rotation bioenergy plantations; (b) harvesting feedstock by thinning conventional plantations; and (c) harvesting of woody debris residues after plantations have been clear‐cut.We found that bioenergy‐associated management practices including younger plantations (relative to older) and woody debris removal (relative to debris unremoved) in clear‐cut plantations were associated with reduced bee diversity. Removing ground debris in clear‐cut plantations also drastically increased bee abundance, though this effect was largely driven by strong dominance of just two bee species. Clear‐cut plantations had lower beta diversity than standing plantations.Synthesis and applications. Management practices associated with bioenergy feedstock production can have negative effects on bee community diversity. In particular, harvesting of debris in clear‐cut plantations dramatically reduces bee diversity. Large‐scale bioenergy feedstock production that increases the prevalence of young and clear‐cut stands may cause landscape‐level beta diversity to decline. Nevertheless, bioenergy pine plantations likely support higher bee diversity than corn fields, an alternative bioenergy feedstock.

Land use change causes environmental homogeneity and low beta-diversity in Heteroptera of streams

Although species distribution pattern is a widely discussed topic, understanding the mechanisms that drive it in time and space is still one of the central goals of ecology. Moreover, it is of the most importance to discuss the maintenance of this biodiversity and the services it provides. Therefore, our aim is to test the following hypotheses: 1) Preserved environments have higher beta-diversity than environments with lower preservation values, since beta-diversity is determined by environmental variations between habitats; 2) Beta-diversity will be better than species richness to detect changes in community regarding environmental integrity gradients. This will occur because richness is not sensitive to changes in composition and this might mask results when sensitive species are lost and generalist species are introduced into the altered environments. In order to test these hypotheses, 20 points were sampled in five streams of the Brazilian Cerrado with different integrity conditions. Environmental change did not affect Heteroptera richness; however, it affected the beta-diversity of the group as a whole and of Nepomorpha, also negatively affecting both Gerromorpha beta-diversity and richness. Moreover, there was difference in variation of Gerromorpha composition in altered and degraded sites, but there was no effect on Nepomorpha. These results show that Gerromorpha is more sensitive to physical changes in streams caused by the loss of environmental integrity. Therefore, environmental changes with no regard to riparian vegetation boundaries causes shifts in stream conditions and changes aquatic communities, which places at risk the ecosystems services provided by these communities.

Resilience of zooplankton communities in temperate reservoirs with extreme water level fluctuations

ABSTRACT The importance of zooplankton as a food resource for higher trophic levels, including threatened and endangered salmon species, highlights the need to improve our understanding of the mechanisms that structure reservoir food webs. Pelagic plankton are the dominant primary and secondary producers in reservoirs experiencing extreme water level fluctuations (WLFs). In these systems, we might expect WLFs to promote predictable and homogenized biotic communities. Here we explored whether spring and summer zooplankton communities are homogenized in Pacific Northwest (USA) flood-control reservoirs managed with annual extreme WLFs. In addition, we evaluated whether community resilience is present in a reservoir that has been drained annually since 2011 for salmon passage. We sampled 4 reservoirs during spring and summer, including 1 that was fully drained, resulting in a lotic riverine environment, for 1 week each fall from 2012 to 2016. We found low beta diversity across reservoirs, indicating homogenized communities. Additionally, we did not observe changes across sample years or increased differences in species composition compared to historical data. Instead, we observed strong seasonal transitions that were predictably repeated each year. Our findings support the hypothesis that extreme WLFs, under which these reservoirs have been managed for >50 years, may have structured reservoir zooplankton communities such that they are resilient to even more dramatic draining. Understanding how WLFs and reservoir draining may impact zooplankton will be critical to minimizing unintended consequences of reservoir management on aquatic food webs.

Urbanization increases biotic homogenization of zooplankton communities in tropical reservoirs

Abstract Under rapid urbanization, many reservoirs built in rural areas are being embraced into by nearby expanding cities. Anthropogenic activities in urban areas can strongly affect aquatic biodiversity by modifying aquatic landscape and reduce habitat heterogeneity. As one of the key components in reservoir ecosystems, zooplankton is sensitive to such habitat changes. Within the metacommunity framework, we predict that in an urbanized landscape: (1) species sorting becomes the most important process in determining the variation of zooplankton communities; (2) urbanization will result in low beta-diversity and biotic homogenization of zooplankton communities and such homogenization will not significantly vary across time. To test these predictions, we investigated twenty five permanent reservoirs over three hydrological seasons in a well-developed and rapidly expanding city in tropical China. The reservoirs were grouped into two location classes and three storage size classes. Our results suggested that the structure of zooplankton communities were strongly homogenized in the studied urban reservoirs as being reflected in the low beta-diversity between the two location classes. However, high beta-diversity was found within each storage size class, mainly derived from species turnover (βsim). The high beta-diversity indicated that the variation of zooplankton community is a consequence of environmental heterogeneity within each storage size class. Variation partitioning revealed a weak spatial structure for zooplankton communities at the large scale, while only Chla as an indicator of food supply significantly explained high community variation among reservoirs in the dry season, but not in wet and transition seasons despite apparent species seasonal succession.

Seed dispersal as an ecosystem service by a keystone avian frugivore in New Zealand

ABSTRACTSeed dispersal service is the proportion of plant species dispersed by a given disperser. It is important since seed dispersal enables colonisation of new habitats, and because movement of seeds even short distances away from trees can reduce vulnerability of seeds and seedlings to disease, predation and density-dependent effects that occur in the immediate vicinity of parent trees. In New Zealand, indigenous large-fruited canopy tree species are susceptible to recruitment failure because Hemiphaga novaeseelandiae (kererū; Columbidae) is the only widespread avian frugivore capable of swallowing large fruit and dispersing their seeds, and its survival relies on ongoing predator control. In view of the critical nature of this mutualism, seed dispersal service was assessed by measuring the difference in composition of seeds of indigenous large-fruited canopy tree species that were dispersed by H. novaeseelandiae to under the canopies of co-fruiting large-fruited canopy tree species across the Auckland region in New Zealand. If seed dispersal were effective, seeds of all species should be found under the canopies of all tree species, i.e. low beta diversity of seed rain. Beta diversity was higher than expected at two locations, suggesting incomplete seed dispersal service; this pattern was attributed to interactions between frugivore behaviour and the local distribution of fruit. The third location had lower than expected beta diversity, reflecting dispersal of a complete array of tree species’ seeds to sampling sites, plus long-distance dispersal of nonlocal indigenous species of large seeds. Hemiphaga novaeseelandiae appears to be dispersing an array of species of large seeds between co-fruiting tree species at some Auckland locations. However, incomplete seed dispersal service at two of the locations, together with evidence of low recruitment of some species of seeds, could eventually reduce tree species diversity.

Increase in non-native species richness leads to biotic homogenization in vacant lots of a highly urbanized landscape

Vacant lots, unused lands covered by spontaneous vegetation, are widespread in urban landscapes. Although they are of less conservation value than natural ecosystems, they can provide important ecological services, such as maintaining air quality and mental health, and offering recreational space. Nevertheless, the effects of urbanization on the plant species richness and beta diversity of such lots remain poorly understood. We evaluated how plant species richness and beta diversity differ in vacant herbaceous lots 1) between two urban areas (Montreal and Quebec, Canada) characterized by contrasting urbanization intensity, and 2) along a rural-urban gradient within both landscapes. We inventoried 69 vacant lots in Montreal and 62 in Quebec distributed along three local levels of urbanization (established using NDVI values in a 500 m buffer zone around each lot). We found a lower beta diversity for plant communities in vacant lots in the most urbanized landscape (Montreal) compared to the least urbanized one (Quebec), but no effect of local level of urbanization intensity in either of the landscapes. Montreal was richer than Quebec in regard to non-native species, while native richness was similar between the two landscapes. Non-native richness was higher than that of natives at each local level of urbanization intensity, and the highest at moderate urbanization intensity. Finally, non-native species were functionally more homogenous than natives both within and between landscapes. Overall, our results suggest that biotic homogenization occurr only in very urbanized landscapes and that this homogenization results from non-native species invasion without local native extirpation.

Beta diversity of stream fish communities along anthropogenic environmental gradients at multiple spatial scales.

Despite the importance of assessing beta diversity to understand the effects of human modifications on biological communities, there are almost no studies that properly addressed how beta diversity varies along anthropogenic gradients. We developed an algorithm to calculate beta diversity among a set of sites included in a moving window along any given environmental gradient. This allowed us to assess beta diversity among sites with similar conditions in terms of human modifications (e.g., land use or instream degradation). We investigated beta diversity using stream fish community data and indicators of human modification quantified at four spatial scales (whole catchment, riparian, local, and instream). Variation in beta diversity was dependent on the scale of human modifications (catchment, riparian, local, instream, and all four scales combined) and on the type of diversity considered (taxonomic or functional). We also found evidence for non-linear responses of both taxonomic and functional beta diversity to human-induced environmental alterations. Therefore, the response of beta diversity was more complex than expected, as it depended on the scale used to quantify human impact and exhibited opposite responses depending on the location along the environmental impact gradient and on whether the response was taxonomic or functional diversity. Anthropogenic modifications can introduce unexpected variability among stream communities, which means that low beta diversity may not necessarily indicate a degraded environmental condition and high beta diversity may not always indicate a reference environmental condition. This has implications for how we should consider beta diversity in environmental assessments.

Microbial ecological processes in MBBR biofilms for biological phosphorus removal from wastewater.

Phosphorus is both a major environmental pollutant and a limiting resource. Although enhanced biological phosphorus removal (EBPR) is used worldwide for phosphorus removal, the standard activated sludge-based EBPR process shows limitations with stability and efficiency. Recently, a new EBPR moving bed biofilm reactor (MBBR) process has been developed at HIAS (Hamar, Norway), enabling a phosphorus removal stability above 90% during a whole year cycle. To increase the knowledge of the HIAS (MBBR) process the aim of the current work was to characterize the MBBR microbiota and operational performance weekly for the operational year. Surprisingly, we found a major succession of the microbiota, with a five-fold increase in phosphorus accumulating organisms (PAOs), and major shifts in eukaryote composition, despite a stable phosphorus removal. Temperature was the only factor that significantly affected both phosphorus removal and the microbiota. There was a lower phosphor removal during the winter, coinciding with a higher microbiota alpha diversity, and a lower beta diversity. This differs from what is observed for activated sludge based EBPR. Taken together, the knowledge gained from the current microbiota study supports the efficiency and stability of MBBR-based systems, and that knowledge from activated sludge-based EBPR approaches cannot be translated to MBBR systems.

Species sorting and mass effect along forest succession: Evidence from taxonomic, functional, and phylogenetic diversity of amphibian communities.

Species recovery after forest disturbance is a highly studied topic in the tropics, but considerable debate remains on the role of secondary forests as biodiversity repositories, especially regarding the functional and phylogenetic dimensions of biodiversity. Also, studies generally overlook how alpha and beta diversities interact to produce gamma diversity along successional gradients.We used a metacommunity approach to assess how species sorting (i.e., environmental filtering) and mass effect (i.e., source‐sink dynamics) affect 14 complementary metrics of amphibian taxonomic, functional, and phylogenetic diversity along a successional gradient in southern Mexico. As amphibians have narrow environmental tolerances and low dispersal capabilities, we expected that species sorting may be relatively more important than mass effect in structuring amphibian communities.Between 2010 and 2012, we sampled frogs, salamanders, and caecilians in 23 communities distributed in four successional stages: young (2–5 years old) and intermediate (13–28 years old) secondary forests, old‐growth forest fragments, and old‐growth continuous forest. We assessed 15 ecologically relevant functional traits per species and used a time‐calibrated molecular phylogeny.We recorded 1,672 individuals belonging to 30 species and 11 families. Supporting our expectations from the species sorting perspective, from the poorest (younger forests) to the best quality (continuous forest) scenarios, we observed (a) an increase in alpha diversity regardless of species abundances; (b) a clear taxonomic segregation across successional stages; (c) an increase in functional richness and dispersion; (d) an increase in mean phylogenetic distance and nearest taxon index; and (e) a reduction in mean nearest taxon distance. However, 10 species occurred in all successional stages, resulting in relatively low beta diversity. This supports a mass effect, where interpatch migrations contribute to prevent local extinctions and increase compositional similarity at the regional scale.Our findings indicate that amphibian metacommunities along forest successional gradients are mainly structured by species sorting, but mass effects may also play a role if high levels of forest cover are conserved in the region. In fact, secondary forests and forest fragments can potentially safeguard different aspects of amphibian diversity, but their long‐term conservation value requires preventing additional deforestation.