Diversity and community biomass depend on dispersal and disturbance in microalgal communities

The evidence for species diversity effects on ecosystem functions is mainly based on studies not explicitly addressing local or regional processes regulating coexistence or the importance of community structure in terms of species evenness. In experimental communities of marine benthic microalgae, we altered the successional stages and thus the strength of local species interactions by manipulating rates of dispersal and disturbance. The treatments altered realized species richness, evenness and community biomass. For species richness, dispersal mattered only at high disturbance rates; when opening new space, dispersal led to maximized richness at intermediate dispersal rates. Evenness, in contrast, decreased with dispersal at low or no disturbance, i.e. at late successional stages. Community biomass showed a non-linear hump-shaped response to increasing dispersal at all disturbance levels. We found a positive correlation between richness and biomass at early succession, and a strong negative correlation between evenness and biomass at late succession. In early succession both community biomass and richness depend directly on dispersal from the regional pool, whereas the late successional pattern shows that if interactions allow the most productive species to become dominant, diverting resources from this species (i.e. higher evenness) reduces production. Our study emphasizes the difference in biodiversity–function relationships over time, as different mechanisms contribute to the regulation of richness and evenness in early and late successional stages.     

Temporal patterns in rates of community change during succession

While ecological dogma holds that rates of community change decrease over the course of succession, this idea has yet to be tested systematically across a wide variety of successional sequences. Here, I review and define several measures of community change rates for species presence-absence data and test for temporal patterns therein using data acquired from 16 studies comprising 62 successional sequences. Community types include plant secondary and primary succession as well as succession of arthropods on defaunated mangrove islands and carcasses. Rates of species gain generally decline through time, whereas rates of species loss display no systematic temporal trends. As a result, percent community turnover generally declines while species richness increases--both in a decelerating manner. Although communities with relatively minor abiotic and dispersal limitations (e.g., plant secondary successional communities) exhibit rapidly declining rates of change, limitations arising from harsh abiotic conditions or spatial isolation of the community appear to substantially alter temporal patterns in rates of successional change.     

Phyllostomid bat assemblages in different successional stages of tropical rain forest in Chiapas,Mexico

Due to their role in seed dispersal, changes in the community of phyllostomid bats have direct consequences on ecological succession. The objective of this work was to document changes in the structure of bat assemblages among secondary successional stages of tropical rain forest in Chiapas, Mexico. Bats were mist-netted at ground level during 18 months in 10 sites belonging to 3 successional stages: four sites represented early succession (2–8 years of abandonment), four intermediate succession (10–20 years of abandonment), and two late succession (mature old-growth forest).We captured 1,179 phyllostomids comprising 29 species. Phyllostomid species richness was 17 (58% of all species) in the early stage, 18 (62%) in the intermediate stage and 24 (83%) in the late stage. The late successional mature forest possessed nine species that were exclusively found there, whereas early and intermediate successional stages contained only one exclusive species. Sturnira lilium, Artibeus lituratus, Carollia perpicillata, Artibeus jamaicensis and Glossophaga soricina represented 88% of all captured phyllostomid bats. Frugivores made up more than 90% of the species captured in early and intermediate successional stages and 84% in late successional forest. The Bray–Curtis index of dissimilarity showed a replacement of species through successional stages with the largest dissimilarity between early and late stages, followed by intermediate and late, and the lowest dissimilarity between early and intermediate stages. The number of gleaning insectivore species increased during succession. The carnivorous guild was exclusively found in the late stage (three species). We conclude that the late successional mature forest was the main reservoir for the gleaning insectivore and carnivore guilds; however, early and intermediate successional stages possessed a great diversity of species including many frugivores.     

Study of community assembly patterns and interspecific interactions involved in insect succession on rat carcasses

Although many forensic entomological studies have described patterns of carrion insect succession and theoretical studies have explained interspecific interactions that drive succession, empirical studies on the quantitative and ecological aspects of carrion insect succession, such as the degree of historical contingency in community assembly and interspecific interactions during succession, are limited. In this study, I investigated variability in the successional pathways of carrion insect communities in rat carcasses and their decomposition processes, and examined the interspecific interactions involved in succession, such as the effects of carcass utilization by early‐arriving species on late‐arriving species. Members of the families Calliphoridae and Formicidae and the species Eusilpha japonica (Motschulsky) and Nicrophorus concolor Kraatz were chiefly observed. In almost all carcasses, formicid species arrived first, and calliphorid species and E. japonica arrived simultaneously or immediately after. Nicrophorus concolor arrived last, with its time of colonization occurring earlier in carcasses with greater E. japonica abundance. Meanwhile, the early‐arriving species decreased when N. concolor arrived. Nicrophorus concolor tended to reproduce on carcasses with lower cumulative abundance of early‐arriving species and tended to feed on carcasses with greater cumulative abundance of early‐arriving species. These results show that the successional pathways of the chief carrion insect species are highly consistent among carcasses. In contrast, early‐arriving species seem to influence the utilization patterns of carcasses by late‐arriving species, and therefore produce variability in the decomposition process. These results also show that succession could be driven by facilitation and interspecific competition between early‐arriving and late‐arriving species.     

Changes in the ecological diversity of the forest population of ground beetles (Coleoptera,Carabidae) after deforestation and during the initial period of reforestation

The ecological structure of ground beetles was studied. Its dynamics during the migration of ground beetles from one habitat to another as a result of severe ecological disturbances caused by tree felling and subsequent reforestation was considered. Some regularities in the formation and development of a ground beetle community in the early stage of secondary succession at the felling site were determined. Further trends were revealed using the simplest indices of diversity, species, abundance, distribution, and dominance of species. The species richness of ground beetles at the site one year after felling increased from 28 to 41 species. It decreased to 36 species in four years. According to the ecological preference, the basis of the complex of ground beetles at the forest site before felling was formed by spring-breeding species. Four years after felling, the proportion of forest species decreased (from 73.4 to 65.7%) and the significance of forestmarsh and meadow-field species increased. The proportion of summer- and autumn-breeding species also increased. The species and quantitative composition of ground beetles at the site during the first year after felling was mostly determined by neighboring forests. As reforestation proceeded, a separate biocenosis developed at the felling site and the influence of the forests became lower. The proportion of summer- and autumnbreeding species increased. The species and quantitative composition of ground beetles at the felling site was mostly determined by the neighboring forest during the first year. A separate biocenosis developed at the felling site in the following years, and the influence exercised by the forest diminished.     

Rate of succession in restored wetlands and the role of site context

Question: Are changes in plant species composition, functional group composition and rates of species turnover consistent among early successional wetlands, and what is the role of landscape context in determining the rate of succession? Location: Twenty‐four restored wetlands in Illinois, USA. Methods: We use 4 years of vegetation sampling data from each site to describe successional trends and rates of species turnover in wetlands. We quantify: (1) the rate at which composition changes from early‐successional to late‐successional species and functional groups, as indicated by site movement in ordination space over time, and (2) the rate of change in the colonization and local extinction of individual species. We correlate the pace of succession to site area, isolation and surrounding land cover. Results: Some commonalities in successional trends were evident among sites. Annual species were replaced by clonal perennials, and colonization rates declined over time. However, differences among sites outweighed site age in determining species composition, and the pace of succession was influenced by a site's landscape setting. Rates of species turnover were higher in smaller wetlands. In addition, wetlands in agricultural landscapes underwent succession more rapidly, as indicated by a rapid increase in dominance by late‐successional plants. Conclusions: Although the outcome of plant community succession in restored wetlands was somewhat predictable, species composition and the pace of succession varied among sites. The ability of restoration practitioners to accelerate succession through active manipulation may be contingent upon landscape context.     

Richness, diversity, and rate of primary succession over 20?year in tropical coastal dunes

The tropical coastal dunes in central Gulf of Mexico have been stabilizing over the last decades resulting in reduced substrate mobility, and promoting primary succession. We describe changes in species richness and diversity in dune vegetation during 20?years. Our questions: (a) Do species richness and diversity increase over time as predicted by models of ecological succession or do they show a hump-backed manner similar to the observations in temperate coastal dunes?, (b) What is the interaction between vegetation cover and diversity and species richness?, (c) Is there a relationship between species diversity and succession rate and does succession rate change over time?, and (d) How do plant functional types change during succession? In order to answer these questions, we set 140 4?×?4?m permanent plots in a mobile dune area and monitored vegetation cover and species richness from 1991 to 2011. In time, diversity increased in a logistic manner toward an asymptotic value once vegetation cover surpassed 60?%. Species richness increased in a humped-back shape, also reaching a maximum peak at 60?% vegetation cover. The succession rate of diversity was measured by the Euclidean distance, and showed a significant humped-back relation, meaning that it was slower in early and late successional stages. The study supports the intermediate disturbance theory. The conservation of coastal dunes vegetation should focus on all, species-poor and species-rich habitats that help to maintain the ecological integrity of these ecosystems. The understanding of community dynamics and diversity patterns becomes an essential component of coastal dune management and conservation.     

Temporal segregations in the surface community of an ephemeral habitat: Time separates the potential competitors of coprophilous Diptera

Temporal separations among species greatly enhance the species' coexistence, especially in insect communities inhabiting temporally unstable, yet resource‐rich, ephemeral habitats like dung or carrion. The insect communities inhabiting ephemeral habitats consist of two components, the internal community dwelling within the substrate (mostly Coleoptera), and the surface community inhabiting the habitat's outer rim (mostly adult Diptera). In contrast to the internal community, the surface community is very rarely studied. We present here the first quantitative study of temporal trends in the surface community of coprophilous dipteran adults. Using artificially created 1.5 L cow dung pats, we studied the succession and seasonality in the surface community during six sampling periods in 2011 and 2012. In total, we sampled 13579 adults of dung‐visiting Diptera. Both the abundance and species richness decreased rapidly throughout the succession, and were highest during summer. Along the successional gradient, the community was separated into two main groups (early and late) and four subgroups: (i) species occurring during the first few hours (mainly Calyptratae: Diptera); (ii) species occurring between the first and second days; (iii) species occurring between the second and third days (mainly Acalyptratae: Diptera); and (iv) species with optima after the third day of dung pat existence (mainly Nematocera). The earliest and latest successional groups, occurring mainly during spring–autumn, were seasonally separated from the two mid‐successional groups, occurring during summer. The ecologically similar species displayed detectable seasonal micro‐optima, which likely facilitate their coexistence. There was a high overall similarity in temporal patterns between dung and carrion surface communities.     

Diversity and community composition of herbaceous plants in different habitat types in south‐east Cameroon

The composition of herbaceous vegetation was evaluated with the aim of characterizing forests at various ages of stand development. Herb stems were sampled in 250 4‐m² square plots distributed within six habitat types. A total of 36 herb species belonging to 15 families were recorded. Species richness did not significantly differ between habitat types. Most herb species occurred in all habitat types and were therefore generalists. However, a few indicator herb species were detected, and the results roughly suggested that herb species of the families Poaceae and Araceae were indicative of late successional forests; Zingiberaceae are indicative of early successional forests; and Commelinaceae, Costaceae, Cyperaceae and Marantaceae are indicators of flooded habitats. Species diversity and stem density of herbaceous plants did not change with forest succession as a decrease in abundance and frequency of occurrence of pioneer species in late successional forests was counterbalanced by the presence of generalist and late successional species. However, increasing proportions of dwarf stems in late successional forests translated to changes in the vertical structure of herbaceous plant communities. Herbivory pressure by gorillas did not have a notable effect on herbaceous plant community development. This study contributes to the definition of herbaceous ecological indicators of forest succession in different settings.     

Marine invertebrates in an algal succession. I. Variations in abundance and diversity with succession

This is a study of the effects of successional algal changes on the community of small invertebrate animals living in the algae at a marine intertidal boulder field. At each of 14 sampling times over a 2-yr period, replicate samples were taken from all stages of succession. By sampling all successional stages simultaneously at each date over an extended period, we could analyze spatial and temporal variations within and among stages. Species richness, diversity, and abundance of the whole invertebrate community increased from early to middle successional stages, while remaining similar from middle to late stages. Evenness remained about constant throughout succession. The increases occur primarily through the addition of species to the community. Some taxonomic groups in this study showed different patterns. Unlike patterns seen in birds, insects, and spiders associated with terrestrial plant succession, species replacements are rare, and there are few early and middle successional specialists. Trophic structure changed markedly during succession. Spatial variation did not change with succession but temporal variation declined. Many of these results are different from the predictions of equilibrium-based theory. Succession in this marine animal community is very different from that in terrestrial animal groups, probably because of the higher rate of exchange of matter in this open coast system.     

Microbial community composition but not diversity changes along succession in arctic sand dunes

The generality of increasing diversity of fungi and bacteria across arctic sand dune succession was tested. Microbial communities were examined by high‐throughput sequencing of 16S rRNA genes (bacteria) and internal transcribed spacer (ITS) regions (fungi). We studied four microbial compartments (inside leaf, inside root, rhizosphere and bulk soil) and characterized microbes associated with a single plant species (Deschampsia flexuosa) across two sand dune successional stages (early and late). Bacterial richness increased across succession in bulk soil and leaf endosphere. In contrast, soil fungal richness remained constant while root endosphere fungal richness increased across succession. There was, however, no significant difference in Shannon diversity indices between early and late successional stage in any compartment. There was a significant difference in the composition of microbial communities between early and late successional stage in all compartments, although the major microbial OTUs were shared between early and late successional stage. Co‐occurrence network analysis revealed successional stage‐specific microbial groups. There were more co‐occurring modules in early successional stage than in late stage. Altogether, these results emphasize that succession strongly affects distribution of microbial species, but not microbial diversity in arctic sand dune ecosystem and that fungi and bacteria may not follow the same successional trajectories.     

Pathways, mechanisms and predictability of vegetation change during tropical dry forest succession

The development of forest succession theory has been based on studies in temperate and tropical wet forests. As rates and pathways of succession vary with the environment, advances in successional theory and study approaches are challenged by controversies derived from such variation and by the scarcity of studies in other ecosystems. During five years, we studied development pathways and dynamics in a chronosequence spanning from very early to late successional stages (ca. 1–60 years) in a tropical dry forest of Mexico. We (1) contrasted dynamic pathways of change in structure, diversity, and species composition with static, chronosequence-based trends, (2) examined how structure and successional dynamics of guilds of trees shape community change, and (3) assessed the predictability of succession in this system. Forest diversity and structure increased with time but tree density stabilized early in succession. Dynamic pathways matched chronosequence trends. Succession consisted of two tree-dominated phases characterized by the development and dynamics of a pioneer and a mature forest species guild, respectively. Pioneer species dominated early recruitment (until ca. 10 years after abandonment), and declined before slower growing mature-forest species became dominant or reached maximum development rates (after 40–45 years). Pioneers promoted their replacement early in succession, while mature-forest species recruited and grew constantly throughout the process, with their lowest mortality coinciding with the peak of pioneer abundance. In contrast to prevailing stochastic views, we observed an orderly, community driven series of changes in this dry forest secondary succession. Chronosequences thus represent a valuable approach for revealing system-specific successional pathways, formulating hypotheses on causes and mechanisms and, in combination with repeated sampling, evaluating the effects of vegetation dynamics in pathway variation.     

Temporal changes in native-exotic richness correlations during early post-fire succession

The relationship between native and exotic richness has mostly been studied with respect to space (i.e., positive at larger scales, but negative or more variable at smaller scales) and its temporal patterns have rarely been investigated. Although some studies have monitored the temporal trends of both native and exotic richness, how these two groups of species might be related to each other and how their relative proportions vary through time in a local community remains unclear. Re-analysis of early post-fire successional data for a California chaparral community shows that, in the same communities and at small spatial scales, the native-exotic correlations varied through time. Both exotic richness and exotic fraction (i.e., the proportion of exotic species in the flora) quickly increased and then gradually declined, during the initial stages of succession following fire disturbance. This result sheds new light on habitat invasibility and has implications for timing the implementation of effective management actions to prevent and/or mitigate species invasions.     

Influence of late season fire on early successional vegetation of an Oklahoma prairie

Abstract. The study of vegetation dynamics in tallgrass prairie in response to fire has focused on dormant season fire in late successional prairies. Our objective was to determine if late season fire of varying frequency results in divergent successional patterns in an early successional tallgrass prairie disturbed by grazing and cultivation. Specifically, we evaluated the influence of late‐summer fires of varying frequency on community composition and species richness. We collected vegetation and environmental data on two sites burned in the late growing‐season at varying frequencies. These communities differed in composition depending primarily on edaphic factors, time since the last burn, and year‐to‐year variation. We interpret the time effect as related to changes in species composition accompanying plant succession that followed disturbance either from cropping and heavy grazing on the loamy site or heavy grazing on the shallow site. Other unidentified factors also have a role in vegetation dynamics on this prairie. Community composition and species richness were not consistently responsive to frequency of growing‐season fires.     

Long‐term development of species richness in a central European beech (Fagus sylvatica) forest affected by windthrow—Support for the intermediate disturbance hypothesis?

On the basis of long‐term surveys of permanent plots and traps, we examined the communities of saproxylic beetles, fungi, herbs, and trees on an untreated 22 ha large beech forest windthrow and asked whether the results lend support to the intermediate disturbance hypothesis (IDH). We studied species richness and the similarity of community composition. Additionally, we grouped species by their frequency trend over time to successional model types to examine whether, corresponding to the IDH, the diversity of these groups explained peak richness at intermediate intervals after the disturbance. In line with the IDH, species richness showed a hump‐backed temporal course for alpha and gamma diversity. We found evidence for a linear succession directly after the disturbance. This, however, did not continue, and in all species groups, a partial recovery of the initial community was observed. In the case of fungi, herbs, and trees, but not for saproxylic beetles, alpha diversity was driven by the diversity of the successional model types. Our results underline that the mechanisms driving species richness after disturbances are more complex than the IDH suggests and that these mechanisms vary with species group. We assumed that, besides competition, legacy effects, facilitation, habitat heterogeneity, and random saturation of the species pool are important. In case of trees and herbs, we found indications for strong legacy and competition effects. For fungi and beetles, substrate heterogeneity and microclimate were assumed to be important. We concluded that disturbances contribute to increasing species richness not only by reducing the effectiveness of competitors but also by increasing the amount and diversity of resources, as well as their rate of change over time.     

Environmental Heterogeneity Influences Successional Trajectories in Colombian Seasonally Dry Tropical Forests

Environmental characteristics have a major effect on the species composition of seasonally dry tropical forest. However, this effect has been little considered when describing secondary succession of this ecosystem. We tested the hypothesis that local environmental heterogeneity influences successional trajectories when high species richness is available. Changes in species composition and structure were described in 126 vegetation plots differing in successional stage and located along a topographical and soil nutrient gradient. Variation in community composition was partitioned between successional stage, environmental characteristics, and spatial structure using redundancy analyses. In addition, relationships between plot distance matrices for these factors were analysed by means of Mantel tests. High species turnover was observed during succession and species composition similarity was higher among late successional forest than among early and intermediate forests. A higher portion of variation in species composition was explained by environmental characteristics compared to successional stage, whereas the spatial structure of the data was weak. Our results suggest that in the region of study, variation in the successional trajectories is occurring owing to environmental heterogeneity, as well as to human disturbance and other unmeasured processes.     

Species and functional trait re-assembly of ground beetle communities in restored grasslands

Ecosystem restoration provides unique opportunities to study community dynamics under succession and can reveal how consumer communities re-assemble and respond to successional changes. Studying community dynamics from both taxonomic and functional trait perspectives also may provide more robust assessments of restoration progress or success and allow cross-system comparisons. We studied ground beetle (Coleoptera: Carabidae) communities for three years in a restored grassland chronosequence with sites from 0 to 28 years old. We measured traditional community metrics (abundance, richness, Shannon diversity) and functional trait metrics based on species’ body length, wing morphology, activity time, phenology, and diet. Communities had high species richness and abundance in early successional stages, but these declined in later stages to low levels comparable to an adjacent grassland remnant. Species composition also shifted with time, converging with the remnant. Although functional richness, like species richness, declined as succession progressed, functional divergence quickly increased and was maintained over time, suggesting niche differentiation in established communities. Young sites were typified by small, macropterous, phytophagous species, while older sites contained larger species more likely to be flightless and carnivorous. Prescribed burns also affected traits, decreasing prevalence of larger species. This study demonstrates that functionally diverse consumer communities can self-assemble under restoration practices. In a relatively short amount of time both morphological and trophic level diversity are established. However, prescribed fire intended to control non-desirable plants may also shape beetle community functional composition, and restoration managers should consider if plant community benefits of fire outweigh potential declines in consumer function.     

Average body length of arboreal and aerial beetle (Coleoptera) assemblages from remnant and plantation Eucalyptus forests in southwestern Australia

We examined body length differences between the beetle fauna of Eucalyptus plantation forests and remnant Eucalyptus forest in the same region using aerial and arboreal sampling. Mean body length of plantation-using species was greater than for remnant forest species, and the same pattern was apparent in the mean of all individuals collected regardless of species. This pattern was true for both Malaise-trap-collected beetles (aerial) and canopy-collected (arboreal) beetles. The tendency for plantation-restricted species to have longer bodies is significant even if clade is treated as a random factor in the analysis. Greater body length among plantation-using species is consistent with a few other studies that have found body size of insect species in early successional environments is typically greater than in late successional environments. Some studies suggest that larger species are better dispersers, which can rapidly colonise early successional habitats. In this study, however, there was little relationship between body length and the number of sites occupied; suggesting dispersal was not a major determinant of community membership. Two different patterns in this study support the hypothesis that body size differences are linked to trophic structure of the communities. First, the body length shift comparing remnant users to plantation users was greater among phytophages than for predators or saprophages. Second, saprophages were typically smaller than phytophages, and constituted a larger fraction of the remnant forest using fauna, driving down the mean body length in the saprophage-rich remnant forest community.