Low Species Turnover Research Articles

Caves’ environmental stability shaping subterranean biodiversity in the neotropics

Caves, once thought to be isolated ecosystems", are now understood to have intricate connections with surface environments, particularly evident at their entrances. These connections can significantly affect the microclimate within caves, leading to varying degrees of environmental stability. Our research explores the impact of microclimate conditions, specifically related to cave environmental stability, on biodiversity changes. We surveyed subterranean invertebrates during two different seasonal periods in 17 limestone caves in three karst regions in southeastern Brazil. Our analysis aimed to understand how environmental stability influences the overall richness of cave invertebrates and troglobitic species richness (restricted to subterranean habitats). We hypothesized that more stable caves would experience less fluctuation in relative species richness and lower turnover between seasons. Additionally, we anticipated that caves with greater environmental stability would harbor a higher richness of cave-restricted species in the function of their length. Our findings support these hypotheses, revealing a significant positive correlation between cave environmental stability and species richness. Caves with higher environmental stability demonstrated lower species turnover rates between seasons, indicating enhanced community stability. While environmental stability significantly affected species richness, its influence on cave-restricted species was comparatively less pronounced. This suggests a complex interplay of factors shaping the unique fauna of caves. Nonetheless, the implications of climate change underscore the importance of preserving the environmental stability of these ecosystems. Using environmental stability as a guide can help protect cave biodiversity from the adverse effects of climate change, contributing to broader conservation efforts for these unique habitats.

Trait–environment relationships depend on species life history

AbstractQuestionPredicting the functional response of vegetation to environmental variations remains highly challenging. A first reason is that trait–environment relationships result from joint intraspecific and interspecific responses. A second reason is that most plant communities host sets of species that are expected to display different environmental responses according to their ecophysiological strategies.LocationMediterranean rangeland, Larzac Plateau, France (“La Fage” INRAE experimental station: 43°55′ N, 3°05′ E).MethodsIn a Mediterranean rangeland, we tested whether changes in trait values in response to management intensification (increased resource availability and grazing intensity) differ between annuals and perennials that coexist locally. To capture the multiple facets of plant phenotypes, we studied nine traits related to carbon acquisition and conservation, plant size, water‐use efficiency, phenology and reproduction.ResultsFor most traits, we evidenced a significant interaction between environment and life history. In particular, changes in trait values were higher in perennials for leaf traits related to tissue density and growth. These differences were explained by: (a) a lower species turnover in annuals, and (b) the presence of species with more distinct trait values across environments in perennials. For most traits, these changes were not accompanied by differential intraspecific variations between annuals and perennials, which invalidates previous theoretical predictions. In addition, the contribution of intraspecific trait variation to among‐communities trait variance was higher for annuals than perennials for most traits.ConclusionAltogether, our findings highlight that changes in trait values with the environment can depend on functional groups (here, life history), which can further critically impact the assessment of the functional response of communities. They challenge the mean field approaches to communities in which trait aggregation is most often blindly applied, without considering potential different trajectories in response to environmental changes at various nested organizational levels.

Cover page

Diversity and DistributionsVolume 29, Issue 4 p. i-i COVER IMAGEOpen Access Cover page First published: 14 March 2023 https://doi.org/10.1111/ddi.13576AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract The cover image relates to the Research Article https://doi.org/10.1111/ddi.13662 “Low species turnover of upland Amazonian birds in the absence of physical barriers” by Rutt et al. Although the Black-faced Antthrush (Formicarius analis) is a widespread Neotropical species, this terrestrial insectivore was one of many forest birds detected less often at Reserva Ducke, suggesting that even a very large preserve is not insulated from anthropogenic degradation. Image credit: Cameron L. Rutt. Volume29, Issue4April 2023Pages i-i RelatedInformation

Low species turnover of upland Amazonian birds in the absence of physical barriers

AbstractAimOne of the oldest and most powerful ways for ecologists to explain distinct biological communities is to invoke underlying environmental differences. But in hyper‐diverse systems, which often display high species richness and low species abundance, these sorts of community comparisons are especially challenging. The classic view for Amazonian birds posits that riverine barriers and habitat specialization determine local and regional community composition. We test the tacit, complementary assumption that similar bird communities should therefore permeate uniform habitat between major rivers, regardless of distance.LocationUpland (terra firme) rainforests of central Amazonia.MethodsWe conducted intensive whole‐community surveys of birds in three pairs of 100‐ha plots, separated by 40–60 km. We then used dissimilarity indices, cluster analysis, and ordination to characterize differences among the six avian communities.ResultsIn all, we detected 244 forest‐dependent birds, with an average of 190 species (78%) per plot. Species turnover was negligible, no unique indicator species were found among plot pairs, and all documented species were already known from a complete inventory at one of the three sites.Main ConclusionsOur study corroborates the classic biogeographical pattern and suggests that turnover contributes little to regional avian diversity within upland forests. Using a grain size of 100 ha, this implies that upland birds perceive the environment as uniform, at least over distances of ~60 km. Therefore, to maximize both local species richness and population persistence, our findings support the conservation of very large tracts of upland rainforest. Our analyses also revealed that the avifauna at Reserva Ducke, encroached by urban sprawl from the city of Manaus, shows the hallmarks of a disturbed community, with fewer vulnerable insectivores. This defaunation signals that even an enormous preserve (10 × 10 km) in lowland Amazonia is not insulated from anthropogenic degradation within the surrounding landscape.

Current street tree communities reflect race-based housing policy and modern attempts to remedy environmental injustice.

Humans promote and inhibit other species on the urban landscape, shaping biodiversity patterns. Institutional racism may underlie the distribution of urban species by creating disproportionate resources in space and time. Here, we examine whether present-day street tree occupancy, diversity, and composition in Baltimore, MD, USA, neighborhoods reflect their 1937 classification into grades of loan risk-from most desirable (A = green) to least desirable (D = "redlined")-using racially discriminatory criteria. We find that neighborhoods that were redlined have consistently lower street tree α-diversity and are nine times less likely to have large (old) trees occupying a viable planting site. Simultaneously, redlined neighborhoods were locations of recent tree planting activities, with a high occupancy rate of small (young) trees. However, the community composition of these young trees exhibited lower species turnover and reordering across neighborhoods compared to those in higher grades, due to heavy reliance on a single tree species. Overall, while the negative effects of redlining remain detectable in present-day street tree communities, there are clear signs of recent investment. A strategy of planting diverse tree cohorts paired with investments in site rehabilitation and maintenance may be necessary if cities wish to overcome ecological feedbacks associated with legacies of environmental injustice.

Long-term response of wetland plant communities to management intensity, grazing abandonment, and prescribed fire.

Isolated, seasonal wetlands within agricultural landscapes are important ecosystems. However, they are currently experiencing direct and indirect effects of agricultural management surrounding them. Because wetlands provide important ecosystem services, it is crucial to determine how these factors affect ecological communities. Here, we studied the long-term effects of land-use intensification, cattle grazing, prescribed fires, and their interactions on wetland plant diversity, community dynamics, and functional diversity. To do this, we used vegetation and trait data from a 14-year-old experiment on 40 seasonal wetlands located within seminatural and intensively managed pastures in Florida. These wetlands were allocated different grazing and prescribed fire treatments (grazed vs. ungrazed, burned vs. unburned). Our results showed that wetlands within intensively managed pastures have lower native plant diversity, floristic quality, evenness, and higher nonnative species diversity and exhibited the most resource-acquisitive traits. Wetlands embedded in intensively managed pastures were also characterized by lower species turnover over time. We found that 14 years of cattle exclusion reduced species diversity in both pasture management intensities and had no effect on floristic quality. Fenced wetlands exhibited lower functional diversity and experienced a higher rate of community change, both due to an increase in tall, clonal, and palatable grasses. The effects of prescribed fires were often dependent on grazing treatment. For instance, prescribed fires increased functional diversity in fenced wetlands but not in grazed wetlands. Our study suggests that cattle exclusion and prescribed fires are not enough to restore wetlands in intensively managed pastures and further highlights the importance of not converting seminatural pastures to intensively managed pastures. Our study also suggests that grazing levels applied in seminatural pastures maintained high plant diversity and prevented tree and shrub encroachment and that in the absence of grazing, prescribed fire became crucial to maintaining higher species evenness.

Coastal squeeze on temperate reefs: Long-term shifts in salinity, water quality, and oyster-associated communities.

Foundation species, such as mangroves, saltmarshes, kelps, seagrasses, and oysters, thrive within suitable environmental envelopes as narrow ribbons along the land-sea margin. Therefore, these habitat-forming species and resident fauna are sensitive to modified environmental gradients. For oysters, many estuaries impacted by sea-level rise, channelization, and municipal infrastructure are experiencing saltwater intrusion and water-quality degradation that may alter reef distributions, functions, and services. To explore decadal-scale oyster-reef community patterns across a temperate estuary in response to environmental change, we resampled reefs in the Newport RiverEstuary (NRE) during 2013-2015 that had previously been studied during 1955-1956. We also coalesced historical NRE reef distribution (1880s-2015), salinity (1913-2015), and water-quality-driven shellfish closure boundary (1970s-2015) data to document environmental trends that could influence reef ecology and service delivery. Over the last 60-120 years, the entire NRE has shifted toward higher salinities. Consequently, oyster-reef communities have become less distinct across the estuary, manifest by 20%-27% lower species turnover and decreased faunal richness among NRE reefs in the 2010s relative to the 1950s. During the 2010s, NRE oyster-reef communities tended to cluster around a euhaline, intertidal-reef type more so than during the 1950s. This followed faunal expansions farther up estuary and biological degradation of subtidal reefs as NRE conditions became more marine and favorable for aggressive, reef-destroying taxa. In addition to these biological shifts, the area of suitable bottom on which subtidal reefs persist (contracting due to up-estuary intrusion of marine waters) and support human harvest (driven by water quality, eroding from up-estuary) has decreased by >75% since the natural history of NRE reefs was first explored. This "coastal squeeze" on harvestable subtidal oysters (reduced from a 4.5-km to a 0.75-km envelope along the NRE's main axis) will likely have consequences regarding the economic incentives for future oyster conservation, as well as the suite of services delivered by remaining shellfish reefs (e.g., biodiversity maintenance, seafood supply). More broadly, these findings exemplify how "squeeze" may be a pervasive concern for biogenic habitats along terrestrial or marine ecotones during an era of intense global change.

Diversity of Deep-Sea Scale-Worms (Annelida, Polynoidae) in the Clarion-Clipperton Fracture Zone

The polymetallic nodules lying on the seafloor of the Clarion-Clipperton Fracture Zone (CCFZ) represent over 30 billion metric tons of manganese. A single mining operation has potential to directly impact approximately 200 km2 of the seabed per year. Yet, the biodiversity and functioning of the bentho-demersal ecosystem in the CCFZ remain poorly understood. Recent studies indicate a high species diversity in a food-poor environment, although the area remains poorly sampled. Undersampling is aggravated by a combination of low densities of fauna and high habitat heterogeneity at multiple spatial scales. This study examines the Polynoidae, a diverse family of mobile polychaetes. Sampling with an epibenthic sledge and a remotely operated vehicle was performed during the cruise SO239 within the eastern CCFZ. Five areas under the influence of a sea surface productivity gradient were visited. Specimens were identified using morphology and DNA: (i) to provide a more comprehensive account of polynoid diversity within the CCFZ, (ii) to infer factors potentially driving alpha and beta diversity, and (iii) to test the hypothesis that epibenthic polychaetes have low species turnover and large species range. Patterns of species turnover across the eastern CCFZ were correlated with organic carbon fluxes to the seafloor but there was also a differentiation in the composition of assemblages north and south of the Clarion fracture. In contrast to the previous studies, patterns of alpha taxonomic and phylogenetic diversity both suggest that polynoid assemblages are the most diverse at Area of Particular Environmental Interest no. 3, the most oligotrophic study site, located north of the Clarion fracture. Without ruling out the possibility of sampling bias, the main hypothesis explaining such high diversity is the diversification of polynoid subfamily Macellicephalinae, in response to oligotrophy. We propose that macellicephalins evolved under extremely low food supply conditions through adoption of a semi-pelagic mode of life, which enabled them to colonise new niches at the benthic boundary layer and foster their radiation at great depths.

Local habitat is a strong determinant of spatial and temporal patterns of macrophyte diversity and composition in boreal lakes

Abstract Macrophyte species and trait assemblages from 104 minimally disturbed boreal forest lakes, covering broad environmental and geographic gradients were analysed to identify associations with environmental variables at different spatial scales: geographic context (GEO) and catchment (CATCH) and lake (LOCAL) characteristics. Constrained ordination and variation partitioning were used to quantify variation in species (canonical correspondence analysis [CCA] and pCCA) and trait (redundancy analysis [RDA] and pRDA) compositions that could be explained by environmental variables, and to rank the main environmental factors associated with spatial and temporal patterns. Diversity and assemblage composition correlated with spatial context and variables related to the length of the growing season, catchment forest type and with lake characteristics such as ecosystem size, lake productivity and alkalinity. Variation partitioning showed that lake characteristics alone explained 53% (species) and 73.5% (traits) of the variability in macrophyte assemblages. Contrary to predictions, the shared variance component between latitude and catchment forest type (GEO&CATCH < 0.1% for both species and traits) and between latitude and lake characteristics (GEO&LOCAL = 6.7% for species and 3.9% for traits) was low. Temporal variability, measured as changes in species richness, diversity and a pollution‐specific index (the Trophic Macrophyte Index), using a subset of the lakes sampled on two occasions (19 lakes sampled in 2012 and 2018 and five lakes sampled in 2013 and 2019) did not differ (p > 0.05, paired t‐test). Ordination showed that among‐year variability in macrophyte assemblage composition was also negligible (0.3%) compared to the variability explained by GEO, CATCH and LOCAL variables. Combined, these findings indicate low species turnover in the boreal lakes of our study. Responses of macrophyte species and trait assemblages and the TMI index were predictable and significantly correlated with lake characteristics associated with nutrient enrichment (Chl a, nutrients) and alkalinity supporting their use in monitoring eutrophication of boreal lakes.

Tree species richness, tree identity and non-native tree proportion affect arboreal spider diversity, abundance and biomass

Sustainable forest management increasingly favors mixtures, but effects on many ecosystem characteristics, such as biocontrol by predators and their biodiversity, are still not well understood. This knowledge gap can be particularly problematic when these mixtures include non-native tree species, such as Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), which are planted because of their high growth rates and climatic suitability but might have negative effects on forest biota. Available studies have mostly focused on epigeic communities, even though tree-associated predator communities can be assumed to make an important contribution to biocontrol that differs significantly from conditions on the forest floor.Here, we analyzed the responses of spiders, as generalist arboreal predators, along a tree species richness gradient in a young tree diversity experiment in Thuringia, Germany, utilizing four of the most economically important deciduous and coniferous tree species in Europe: European beech (Fagus sylvatica L.), Norway spruce (Picea abies (L.) H. Karst.), Douglas fir and sessile oak (Quercus petraea Liebl.), planted in stands of 1–4 tree species. We tested for effects of tree species richness, tree identity and composition (tree species proportion and position of individual trees) on arboreal spider species richness, functional diversity, abundance, biomass and community structure at both the tree and plot level.Tree species richness promoted arboreal spider species richness and functional richness at the plot level and community-weighted mean spider biomass at the tree level. Tree identity and composition had a stronger influence than tree species richness on structuring spider communities, with arboreal spiders having higher numbers per tree on conifers, especially on Douglas fir. However, at the plot level spider species richness, abundance and biomass decreased with an increasing proportion of conifers due to lower species turnover among coniferous trees. The observed effects of tree species richness, tree identity and tree species proportions early in the establishment of forest stands might influence the strength of top-down control of herbivores in critical stages of development of forest stands. Tree species selection and the proportion in which these trees are mixed with other species should be determined with care in order to concomitantly promote biodiversity and biocontrol. In this context, an important finding of our analyses is that potentially negative effects of non-native Douglas fir on arboreal arthropods were not more severe than effects of native conifers that are planted outside of their natural habitats.

Variability in Environmental Conditions Strongly Impacts Ostracod Assemblages of Lowland Springs in a Heavily Anthropized Area

The Po river plain (Northern Italy) hosts artificial, lowland springs locally known as fontanili, which provide important ecosystem services in an area dominated by intensive agricultural activities. Here we present a study carried out in 50 springs. Each spring was visited once from October 2015 to January 2016. The sampled sites were selected to include springs studied in 2001 and 2004, to evaluate changes in water quality and ostracod assemblages that possibly occurred over a period of 10–15 years, and explore the relationships between ostracod community composition and water physical and chemical variables. Our results showed a decrease in the chemical water quality especially, in springs south of the Po river, evidenced by high nitrate levels. Most of the studied springs showed a relevant decrease in dissolved reactive silica, probably related to recent transformations of either agricultural practices or crop typology. Ostracods were mostly represented by common and tolerant species, and communities were characterized by low alpha diversity and high species turnover. Water temperature and mineralization level were the most influential variables in structuring the ostracod communities. We stress the need to implement conservation and restoration measures for these threatened ecosystems, to regain their role as ecosystem services providers.

Mangrove responses to droughts since the little ice age in the Colombian Caribbean

Mangroves are ecosystems that are seriously threatened by climate change, particularly sea level rise and an increase of droughts. They are resilient to short droughts but their response to longer ones remains arguable. In this work, we studied the responses of R. mangle dominated forests on a carbonate island (El Rosario Island) to climate anomalies and their drivers at inter-annual, decadal and inter-decadal scales during the last centuries. Palynological analysis of a sediment core retrieved from an R. mangle dominated forest was used to reconstruct vegetation changes during the last 400 years. Time series, Multi-taper spectral, Fourier and correlation analyses of PDO, AMO and ENSO series were performed to identify the matches between these series and mangrove changes during this time. The pollen record showed the influence of coastal dynamics on mangrove vegetation changes on a local scale and the influence of climate on a regional one. Changes in coastal vegetation and mangroves were influenced by beach ridge formations and lagoon closing, which were, in turn, determined by shifts in wave and wind intensity. The simultaneous diminution of both types of vegetation were related to both natural (earthquake and extreme droughts) and anthropogenic disturbances. Our results also showed the replacement of the Rhizophora dominated forest by an Avicennia dominated forest when droughts became longer. The peaks of Rhizophora pollen percentages identified along the pollen record showed a 64 year recurrence cycle that dominated during the Little Ice Age (1610–1862) and a 32 year cycle during the Current Warm Period (1866–1954). While the first cycle was positively correlated with the warm phase of PDO and AMO time series, the second cycle showed a negative significant correlation with PDO, AMO and ENSO time series. During warm periods, mangroves were stressed by droughts, but as these cycles became shorter, mangroves could recover more rapidly. From 1954 to the present, no significant correlations were observed between vegetation changes and climate drivers, which is likely related to the increased anthropogenic disturbance beyond that period of time. Our results show the high resilience of mangroves to cyclic climate changes that involve droughts, winds and sea level rises but low recovery and species turnover with extreme and longer droughts and strong anthropogenic disturbances.

Inferring predator–prey interactions in food webs

AbstractFood webs are a powerful way to represent the diversity, structure, and function of ecological systems. However, the accurate description of food webs requires significant effort in time and resources, limiting their widespread use in ecological studies. Newly published methods allow for the inference of feeding interactions using proxy variables. Here, we compare the accuracy of two recently described methods, as well as describe a composite model of the two, for the inference of feeding interactions using a large, well‐described dataset.Both niche and neutral processes are involved in determining whether or not two species will form a feeding link in communities. Three different models for determining niche constraints of feeding interactions are compared, and all three models are extended by incorporating neutral processes, based on relative abundances. The three models compared here infer niche processes through (a) phylogenetic relationships, (b) local species trait distributions (e.g., body size), and (c) a composite of phylogeny and local traits.We show that all three methods perform well at predicting individual species interactions, and that these individual predictions scale up to the network level, resulting in food web structure of inferred networks being similar to their empirical counterparts.Our results indicate that inferring food web structure using phylogenies can be an efficient way of getting summary webs with minimal data, and offers a conservative test of changes in food web structure, particularly when there is low species turnover between sites. Inferences made using traits require more data, but allows for greater understanding of the mechanisms underlying trophic interactions. A composite model of the two methods provides a framework for investigating the importance of how phylogeny, trait distributions, and relative abundances, affect species interactions, and network structure.

Fish assemblage responses to flow seasonality and predictability in a tropical flood pulse system

AbstractHydropower dams are looming in the Mekong Basin, affecting river flows that structure aquatic communities. Here, we quantitatively assessed flow seasonality and predictability in three sites located in three rivers displaying a gradient in flow alterations caused by upstream dams and investigated how fish assemblages responded seasonally and inter‐annually to this gradient. By analyzing 7‐yr daily fish and water monitoring data, we found that dams disturbed the natural flow seasonality and predictability. While the river displaying the lower seasonality–predictability was characterized by a distinct seasonal variation in assemblage composition with high species turnover, rivers with stronger flow seasonality–predictability exhibited broadly similar seasonal patterns in fish assemblage composition with low species turnover and regular annual peaks of fish migration. These results challenge the expectation of higher species turnover in systems displaying higher flow seasonality and predictability and may be partly due to the strong adaptation of fish assemblages to these specific systems. By enhancing our understanding of biological systems in the highly seasonal–predictable and aseasonal–unpredictable environments of the lower Mekong system, these findings suggest that hydropower‐related pulsed flows that can mimic as far as possible natural pulsed flows are critical to reduce downstream effects on aquatic organisms.

Influence of Habitat Heterogeneity on Structure and Composition of a Chrysomelidae (Coleoptera) Assemblage in a Temperate Forest in Northeast Mexico

Disturbance in natural areas occurs as a result of various processes on various spatio-temporal scales, generating a heterogeneous mosaic of environmental characteristics. The effect of such change on diversity patterns has been explained by the hypothesis of habitat heterogeneity. Modifications in abiotic and biotic factors such as plant density influence the composition and structure of assemblages of phytophagous insects. Response of the leaf beetle (Coleoptera: Chrysomelidae) assemblage to such changes was evaluated in an oak (Quercus spp.) forest in the Altas Cumbres Natural Protected Area, Victoria, Tamaulipas, Mexico. The delimited mosaic was classified into four categories according to the length of time since the last disturbance: 1 year, 10 years, 30 years, and 40 years. Disturbance time categories were delimited using remote sensing techniques from LANDSAT satellite scenes. Leaf beetles were sampled each month from February to April 2016 in 10 plots per category. The numbers of herbaceous and shrubby plants in each plot were counted with the aim of estimating the plant density of each category and relating values with differences among communities of Chrysomelidae. In total, 1,056 individuals of six subfamilies and 37 species were obtained, with Centralaphthona sp. 1 the most abundant. Thirteen species were specialists, while Helocassis crucipennis (Boheman, 1855) occurred in the most niches. Leaf beetles preferred high plant densities and were most abundant and had most species richness in the category of 10 years since the last disturbance. The community had aggregate spatial distribution that might reflect significant biological patterns. Alpha diversity indices indicated the 10-year category was most even, with Hypolampsis sp. 1 the dominant species. In contrast, least evenness was in the 1-year category where Centralaphthona sp. 1 was dominant; the species might indicate permanent disturbance. The community had low species turnover among the categories of disturbance and is therefore expected to have high gamma diversity. Inventory of the study area had 82.4% completeness; however, categories of 10 and 30 years required more sampling effort. Results supported the hypothesis of habitat heterogeneity, because observed community patterns did not occur by chance. This suggested that environmental heterogeneity because of disturbance positively influenced composition and community structure of Chrysomelidae, and observed patterns responded to intra- and interspecific interactions.

Monitoring fruit-feeding butterfly assemblages in two vertical strata in seasonal Atlantic Forest: temporal species turnover is lower in the canopy

Abstract:To address how seasonality affects the richness and abundance of tropical insects, we compared the canopy and understorey communities of fruit-feeding butterflies in a seasonal Atlantic forest in south-eastern Brazil. Butterflies were sampled over 1 y using a standardized design with baited traps. A total of 2047 individuals in 69 species were recorded (1415 in the canopy, 632 in the understorey). Clear differences were found between canopy and understorey, with significantly higher butterfly abundances in the canopy. We observed two marked peaks of abundance and richness in both strata; one at the transition from dry to the wet seasons, and the other at the transition from wet to dry seasons. We found lower species turnover throughout the year in the canopy. We interpret this as evidence that temperature is more important than rainfall in explaining the yearly variation of abundance in vertical strata. The higher temperatures found in the canopy may allow butterflies to maintain activity in this stratum all year round, whereas the understorey is subject to colder temperatures, thus presenting a higher species turnover. These results improve our understanding of diversity gradients between evergreen and seasonal tropical forests, allowing insights into how climate and beta diversity gradients interact.

Temporal changes in vegetation of a virgin beech woodland remnant: stand-scale stability with intensive fine-scale dynamics governed by stand dynamic events

The aim of this resurvey study is to check if herbaceous vegetation on the forest floor exhibits overall stability at the stand-scale in spite of intensive dynamics at the scale of individual plots and stand dynamic events (driven by natural fine scale canopy gap dynamics). In 1996, we sampled a 1.5 ha patch using 0.25 m² plots placed along a 5 m × 5 m grid in the best remnant of central European montane beech woods in Hungary. All species in the herbaceous layer and their cover estimates were recorded. Five patches representing different stand developmental situations (SDS) were selected for resurvey. In 2013, 306 plots were resurveyed by using blocks of four 0.25 m² plots to test the effects of imperfect relocation. We found very intensive fine-scale dynamics in the herbaceous layer with high species turnover and sharp changes in ground layer cover at the local-scale (< 1 m2). A decrease in species richness and herbaceous layer cover, as well as high species turnover, characterized the closing gaps. Colonization events and increasing species richness and herbaceous layer cover prevailed in the two newly created gaps. A pronounced decrease in the total cover, but low species turnover and survival of the majority of the closed forest specialists was detected by the resurvey at the stand-scale. The test aiming at assessing the effect of relocation showed a higher time effect than the effect of imprecise relocation. The very intensive fine-scale dynamics of the studied beech forest are profoundly determined by natural stand dynamics. Extinction and colonisation episodes even out at the stand-scale, implying an overall compositional stability of the herbaceous vegetation at the given spatial and temporal scale. We argue that fine-scale gap dynamics, driven by natural processes or applied as a management method, can warrant the survival of many closed forest specialist species in the long-run. Nomenclature: Flora Europaea (Tutin et al. 2010) for vascular plants; Soo 1968–1980 for syntaxa

The Impact of Tropical Peat Fire on Termite Assemblage in Sumatra, Indonesia: Reduced Complexity of Community Structure and Survival Strategies.

Tropical peat swamp forests in Southeast Asia account for approximately 72% of global peatland. However, extensive forest exploitation following peat drainage for agricultural expansion has been leading to catastrophic peat fires. In this study, we compared the termite assemblage in burnt and unburnt peats in Sumatra, Indonesia. We also identified which taxonomic group is particularly resistant to fire disturbance and the traits that correlate with its persistence in fire-impacted peatlands. Overall, the termite species richness in fire-impacted peats was up to 40% lower than that of the total species found in peat swamp forests. Although the estimated species richness values in fire-impacted peats and peat swamp forests were not significantly different, fire changed termite community structure significantly. Only termites of the family Rhinotermitidae survived in the fire event, whereas members of the Termitidae that were reportedly resilient to fire and open habitats elsewhere disappeared during the fire events. The rhinotermitids found in the burnt sites were exclusively wood nesters. This suggests that the desiccation tolerance of termites in open habitat is not the simple underlying survival strategy, but tree branches and barks might have provided a refuge from heat during fire. The result also suggests that the high similarity in species composition in recently burnt peats and long burnt peats implies low species turnover. Thus, regardless of how much time had passed since the fire-impacted peats were abandoned or cultivated, the increase in habitat complexity did not favor colonization by the forest-dependent group.

Effects of land use on larval Odonata assemblages in cloud forest streams in central Veracruz, Mexico

This study analyzes the effect of stream water quality and its relationship with habitat characteristics on larval Odonata assemblages in streams found in tropical montane cloud forests, pastures, and coffee plantations in the upper La Antigua River watershed. The main factors that influenced larval Odonata assemblages in forest streams were low temperatures and high oxygen levels in water, coupled with a high diversity of the substrate and riparian vegetation; in pasture streams and coffee plantation streams, sedimentation strongly affected the composition of larval Odonata assemblages. In all the streams, species richness (0D) was higher during the dry season. The highest Shannon α diversity (1D) values were found in forest streams during the rainy season; however, in pasture and coffee plantation streams, 1D values were higher during the dry season. The low species turnover in forest streams suggests that these streams provide highly stable conditions for Odonata assemblages; however, in pasture and coffee plantation streams, the higher turnover was related to the more variable water and habitat conditions. Thus, the persistence of Odonata assemblages in the upper La Antigua River watershed is closely related to the conservation status of the tropical montane cloud forests.

Temporal fluctuations in oribatid mites indicate that density-independent factors favour parthenogenetic reproduction

We investigated the oribatid mite density, community structure and the percentage of parthenogenetic individuals in four different forest types across three regions in Germany in 2008 and once again in 2011. We compared temporal (inter-annual) fluctuations in population densities between sexually and parthenogenetically reproducing species of oribatid mites. We hypothesized that population densities in parthenogenetic oribatid mite species fluctuate more than in sexual ones. Further, we expected species composition and dominance of parthenogenetic species to differ between forest types and regions. Oribatid mite community structure did not differ between years but varied with forest type and region, indicating low species turnover in time. As hypothesized, temporal fluctuations were more pronounced in parthenogenetic as compared to sexual species. The percentage of parthenogenetic individuals was significantly higher in coniferous than in beech forests and significantly higher in Schorfheide-Chorin than in Hainich-Dün and Schwäbische Alb. The results indicate that parthenogenetic species flourish if populations are controlled by density-independent factors and dominate at sites were resources are plentiful and easily available, such as coniferous forests, and in regions with more acidic soils and thick organic layers, such as Schorfheide-Chorin. However, historical factors also may have contributed to the increased dominance of parthenogenetic species in the Schorfheide-Chorin, as this region was more heavily glaciated and this may have favoured parthenogenetic species. Overall, our study supports the hypothesis that parthenogenetic species benefit from the lack of density-dependent population control whereas the opposite is true for sexual species.