Single introductions of soil biota and plants generate long‐term legacies in soil and plant community assembly

Recent demonstrations of the role of plant–soil biota interactions have challenged the conventional view that vegetation changes are mainly driven by changing abiotic conditions. However, while this concept has been validated under natural conditions, our understanding of the long‐term consequences of plant–soil interactions for above‐belowground community assembly is restricted to mathematical and conceptual model projections. Here, we demonstrate experimentally that one‐time additions of soil biota and plant seeds alter soil‐borne nematode and plant community composition in semi‐natural grassland for 20 years. Over time, aboveground and belowground community composition became increasingly correlated, suggesting an increasing connectedness of soil biota and plants. We conclude that the initial composition of not only plant communities, but also soil communities has a long‐lasting impact on the trajectory of community assembly.     

Biodiversity issues for the forthcoming tropical Mediterranean Sea

Present-day Mediterranean marine biodiversity is undergoing rapid alteration. Because of the increased occurrence of warm-water biota, it has been said that the Mediterranean is under a process of ‘tropicalization’. This paper analyses the main patterns of the Mediterranean Sea tropicalization and considers briefly its extent and consequences. As happened during previous interglacial phases of the Quaternary, Atlantic water, entering via the Straits of Gibraltar, carries into the Mediterranean species that are prevalently of (sub)tropical affinity. On the other side of the basin, Red Sea species penetrate through the Suez Canal, a phenomenon called lessepsian migration from the name of F. de Lesseps, the French engineer who promoted the cutting of the Canal. Also the many exotic species introduced by humans voluntarily or involuntarily are nearly always typical of warm waters. Climate change combines with Atlantic influx, lessepsian migration and the introduction of exotic species by humans to the establishment of tropical marine biota in the Mediterranean Sea. Present-day warming ultimately favours the spread of warm-water species through direct and indirect effects, and especially by changing water circulation. It is impossible at present to foresee to what extent the exuberance of warm-water species will affect the trophic web and the functioning of marine ecosystems in the Mediterranean Sea of tomorrow. While Mediterranean Sea communities are modifying their pattern of species composition, they do not seem to be acquiring a more marked tropical physiognomy: Mediterranean coastal marine ecosystems are still dominated by frondose algae (even if the species that are gaining ascendancy are of tropical origin) and not by corals as is normal in tropical seas.     

The co-evolution of phytoplankton and trace element cycles in the oceans

The composition of the oceans and of its biota have influenced each other through Earth's history. Of all the biologically essential elements, nitrogen is the only one whose seawater concentration is clearly controlled biologically; this is presumably the main reason why the stoichiometry of nitrogen (defined as its mol ratio to phosphorus), but not that of the trace nutrients manganese, iron, cobalt, nickel, copper, zinc and cadmium, is the same in seawater and in the plankton. Like the major nutrients, the trace nutrients are depleted in surface seawater as a result of quasi-complete utilization by the biota. This is made possible in part by the ability of marine phytoplankton to replace one trace metal by another in various biochemical functions. This replacement also results in an equalization of the availability of most essential trace metals in surface seawater. The difference in the stoichiometric composition of the plankton and of deep seawater, which is the dominant source of new nutrients to the surface, indicates that some nutrients are likely recycled with different efficiencies in the photic zone. The difference in the composition of the ocean and its biota provides insight into the coupling of biochemistry and biogeochemistry in seawater.     

Evolution on a shaky piece of Gondwana: is local endemism recent in New Caledonia?

New Caledonia is well known as a hot spot of biodiversity whose origin as a land mass can be traced back to the Gondwanan supercontinent. The local flora and fauna, in addition to being remarkably rich and endemic, comprise many supposedly relictual groups. Does the New Caledonian biota date back to Gondwanan times, building up its richness and endemism over 100 Myr or does it result from recent diversifications after Tertiary geological catastrophic events? Here we use a molecular phylogenetic approach to answer this question with the study of the Neocaledonian cockroach genus Angustonicus belonging to the subfamily Tryonicinae from Australia and New Caledonia. Both geological and molecular dating show that the diversification of this group is less than two million years old, whatever the date of its origin itself. This dating is not consistent with hypotheses of Gondwanan richness and endemism in New Caledonian biota. In other terms, local richness and endemism at the specific level are not necessarily related to an old Gondwanan origin of the Neocaledonian groups. © The Willi Hennig Society 2005.     

Biogeography and evolution of the Galapagos: integration of the biological and geological evidence

Biogeographic tracks are mapped for Galapagos endemics representing 25 plant and animal taxa and including organisms with good and poor means of dispersal. These patterns confirm standard biogeographic tracks linking Galapagos with Central America, western North and South America, the Caribbean, Asia and Australasia. Discovery of the Galapagos Gore in the 1970s corroborates the biogeographic prediction for a major tectonic centre associated with the Galapagos. The biogeographic model developed by Croizat in 1958 of Galapagos colonization involving an ancestral biota inhabiting eastern Pacific geosynclinal forelands is congruent with plate tectonic models supporting a Pacific island arc origin for western American terranes. American relatives of Galapagos endemics may have originated within an eastern Pacific paleogeography rather than representing centres of origin for dispersal to the Galapagos. Galapagos colonization by an eastern Pacific biota between late Cretaceous and mid-Tertiary has significant implications for understanding the tempo and mode for both the origins of island biota and general models of evolutionary differentiation. Popular assertions that overwater dispersal represents the only viable origin for the entire Galapagos biota is no longer biogeographically or geologically tenable.     

The ecogeographical differentiation of Amazonian inundation forests

Due to the considerable annual fluctuations of water level of the Amazonian rivers, their river banks are fringed with periodically flooded forests of vast extension. The biota of these communities are adapted to annual inundations that can last for more than half a year. Water chemistry is most important for the floristic differentiation of these flooded forests. White water rivers, which carry a rich load of suspended material originating from the erosion of the Andes, have a floristic composition related to that of the noninundatable Amazonian forest. Clear water and black water rivers, which originate in the Amazon Basin or its adjacent crystalline shields, are nutrient-poor and more or less acidic; their flora is related to that of peculiar woodland and savannah vegetation on oligotrophic white sand. The distribution patterns of floodplain species of nutrient-poor waters point to a centre of diversity in the Upper Rio Negro region, and another one in the Guayana lowland. These coincide with diversity centres for species of non-flooded habitats. Hence it seems unlikely that species diversity is directly influenced by pluviosity. The flooded forests have developed biotic interactions with the fish fauna of the Amazon Basin, which are vital for their continued existence. It is assumed that the origin of these habitats, their biota and their interactions dates back long into the Tertiary.     

Biogeographic differences in plant–soil biota relationships contribute to the exotic range expansion of Verbascum thapsus

1. Exotic plant species can evolve adaptations to environmental conditions in the exotic range. Furthermore, soil biota can foster exotic spread in the absence of negative soil pathogen–plant interactions or because of increased positive soil biota–plant feedbacks in the exotic range. Little is known, however, about the evolutionary dimension of plant–soil biota interactions when comparing native and introduced ranges.
2. To assess the role of soil microbes for rapid evolution in plant invasion, we subjected Verbascum thapsus, a species native to Europe, to a reciprocal transplant experiment with soil and seed material originating from Germany (native) and New Zealand (exotic). Soil samples were treated with biocides to distinguish between effects of soil fungi and bacteria. Seedlings from each of five native and exotic populations were transplanted into soil biota communities originating from all populations and subjected to treatments of soil biota reduction: application of (a) fungicide, (b) biocide, (c) a combination of the two, and (d) control.
3. For most of the investigated traits, native populations showed higher performance than exotic populations; there was no effect of soil biota origin. However, plants developed longer leaves and larger rosettes when treated with their respective home soil communities, indicating that native and exotic plant populations differed in their interaction with soil biota origin. The absence of fungi and bacteria resulted in a higher specific root length, suggesting that V. thapsus may compensate the absence of mutualistic microbes by increasing its root–soil surface contact.
4. Synthesis. Introduced plants can evolve adaptations to soil biota in their new distribution range. This demonstrates the importance of biogeographic differences in plant–soil biota relationships and suggests that future studies addressing evolutionary divergence should account for differential effects of soil biota from the home and exotic range on native and exotic populations of successful plant invaders.

     

The ecology of ostracodes (Ostracoda,Crustacea) in western Mongolia

Aquatic biota in Central Asia witnesses and faces a changing environment. Because ostracodes contribute to both extant and fossil lacustrine diversity, they can be used to track evolution in water quality. Living ostracode communities in a variety of aquatic habitats of western Mongolia were analyzed in relation to environmental and hydrochemical variables of those habitats, based on presence/absence data from net samples. The sampled water bodies represent broad gradients in ionic concentration and composition. Ostracode community composition of springs differed from all other sampled habitats, which was also reflected in CCA analyses. Our data indicated that the ostracode fauna of western Mongolia shows a high response to calcium content, alkalinity, salinity, temperature, nutrients, and altitude. Species composition and diversity seem to be determined by solute evolution dominated by Ca-depletion. In general, this seems to be an important regulator of lacustrine ostracode species composition in several semi-arid regions. Binary logistic regression was used to predict the occurrence of the most common species with a minimal set of environmental variables. The resulting models showed on average low performance, and mainly demonstrated the potential of such modeling to predict the distribution of typical bio-indicator species.     

New Caledonia: a very old Darwinian island?

New Caledonia has generally been considered a continental island, the biota of which largely dates back to Gondwanan times owing to its geological origin and the presence of phylogenetic relicts. This view is contradicted by geological evidence indicating long Palaeocene and Eocene submersions and by recent biogeographic and phylogenetic studies, with molecular or geophysical dating placing the biota no older than the Oligocene. Phylogenetic relicts do not provide conclusive information in this respect, as their presence cannot be explained by simple hypotheses but requires assumption of many ad hoc extinction events. The implication of this new scenario is that all the New Caledonian biota colonized the island since 37 Ma Local richness can be explained by local radiation and adaptation after colonization but also by many dispersal events, often repeated within the same groups of organisms. Local microendemism is another remarkable feature of the biota. It seems to be related to recent speciation mediated by climate, orography, soil type and perhaps unbalanced biotic interactions created by colonization disharmonies. New Caledonia must be considered as a very old Darwinian island, a concept that offers many more fascinating opportunities of study.     

Responses of Terrestrial Antarctic Ecosystems to Climate Change

Antarctic terrestrial biota are generally limited by the inexorably linked environmental factors of low summer temperature and lack of available water. However, in parts of the Antarctic, both these factors are changing rapidly on contemporary timescales. Terrestrial biota have concurrently been faced with changes in the timing of UV-B maxima associated with spring ozone depletion. The region of the Antarctic Peninsula and Scotia Arc has experienced one of the most rapid rates of environmental warming seen worldwide over the last 30–50 years. Together with local changes in precipitation, this has resulted in a rapid reduction in extent and thinning of many ice-fields and glaciers, exposing new terrain for colonisation while, at the same time, altering patterns of water availability in terrestrial habitats. The rapid development of communities on newly-exposed ground is also facilitated by the existence of soil propagule banks, which contain propagules of both local and exotic origin. In this paper we collate and review evidence from a range of observational and manipulative studies that investigate the effect of climate change, especially increased temperature, on the processes of colonisation and subsequent community development by plants in the Antarctic. Biological changes that have been associated with climate change are visible in the form of expansions in range and local population numbers amongst elements of the flora. Environmental manipulation experiments further demonstrate the possibility of large and rapid species and community responses to climate amelioration, with many resident biota responding positively, at least in the absence of increased competition from exotic colonists. Manipulation studies are also starting to elucidate more subtle responses to climate changes, at levels ranging from cell biochemistry to habitat and food web structure. Integrating such subtle responses is vital to improving our ability to understand the consequences of climate change, as these may lead to much greater consequential impacts on communities and ecosystems.      

Do interactions between plant and soil biota change with elevation? A study on Fagus sylvatica

Theoretical models predict weakening of negative biotic interactions and strengthening of positive interactions with increasing abiotic stress. However, most empirical tests have been restricted to plant-plant interactions. No empirical study has examined theoretical predictions of interactions between plants and below-ground micro-organisms, although soil biota strongly regulates plant community composition and dynamics. We examined variability in soil biota effects on tree regeneration across an abiotic gradient. Our candidate tree species was European beech (Fagus sylvatica L.), whose regeneration is extremely responsive to soil biota activity. In a greenhouse experiment, we measured tree survival in sterilized and non-sterilized soils collected across an elevation gradient in the French Alps. Negative effects of soil biota on tree survival decreased with elevation, similar to shifts observed in plant-plant interactions. Hence, soil biota effects must be included in theoretical models of plant biotic interactions to accurately represent and predict the effects of abiotic gradient on plant communities.     

Taurine. Effect on exotrophia and metabolism in mammals and fish

Data have been presented on the taurine content in various mammalian and fish tissues as well as on pathways of its formation, turnover, and numerous functions. Based on comparison of the character of the taurine effects on various animal functions as well as of the fact of the presence of taurine in the more ancient by origin potential objects of the mammalian and fish nutrition, it is suggested that the taurine polyfunctionality has appeared at different stages of the biota.     

Global diversity of true and pygmy grasshoppers (Acridomorpha,Orthoptera) in freshwater

A small percentage of Orthoptera Acridomorpha is comprised species dependant on continental water ecosystems. However, as phytophagous insects, they are important at the basis of the trophic chain, mainly in regions with large permanent biota resulting from the pulses of the rivers. An assessment of the composition and origin of the populations from different biogeographical regions is attempted, and the state of our current knowledge is given in Tables 1, 2 and 3. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Cretaceous-Tertiary diversification among select Scolopendrid centipedes of South India

Given that peninsular India was part of the Gondwanan super continent, part of its current biota has Gondwanan origin. To determine the Gondwanan component of the peninsular Indian biota, a large number of species spanning diverse taxonomic groups need to be sampled from multiple, if not all, of the former Gondwanan fragments. Such a large scale phylogenetic approach will be time consuming and resource intensive. Here, we explore the utility of a limited sampling approach, wherein sampling is confined to one of the Gondwanan fragments (peninsular India), in identifying putative Gondwanan elements. To this end, samples of Scolopendrid centipedes from Western Ghats region of peninsular India were subjected to molecular phylogenetic and dating analyses. The resulting phylogenetic tree supported monophyly of the family Scolopendridae which was in turn split into two clades constituting tribes Otostigmini and Scolopendrini-Asanadini. Bayesian divergence date estimates suggested that the earliest diversifications within various genera were between 86 and 73mya, indicating that these genera might have Gondwanan origin. In particular, at least four genera of Scolopendrid centipedes, Scolopendra, Cormocephalus, Rhysida and Digitipes, might have undergone diversification on the drifting peninsular India during the Late Cretaceous. These putative Gondwanan taxa can be subjected to more extensive sampling to confirm their Gondwanan origin.     

Tree diversity and species identity effects on soil fungi,protists and animals are context dependent

Plant species richness and the presence of certain influential species (sampling effect) drive the stability and functionality of ecosystems as well as primary production and biomass of consumers. However, little is known about these floristic effects on richness and community composition of soil biota in forest habitats owing to methodological constraints. We developed a DNA metabarcoding approach to identify the major eukaryote groups directly from soil with roughly species-level resolution. Using this method, we examined the effects of tree diversity and individual tree species on soil microbial biomass and taxonomic richness of soil biota in two experimental study systems in Finland and Estonia and accounted for edaphic variables and spatial autocorrelation. Our analyses revealed that the effects of tree diversity and individual species on soil biota are largely context dependent. Multiple regression and structural equation modelling suggested that biomass, soil pH, nutrients and tree species directly affect richness of different taxonomic groups. The community composition of most soil organisms was strongly correlated due to similar response to environmental predictors rather than causal relationships. On a local scale, soil resources and tree species have stronger effect on diversity of soil biota than tree species richness per se.     

Ecohydrology as a new tool for sustainable management of estuaries and coastal waters

Throughout the world, estuaries and coastal waters have experienced degradation. Present proposed remedial measures based on engineering and technological fix are not likely to restore the ecological processes of a healthy, robust estuary and, as such, will not reinstate the full beneficial functions of the estuary ecosystem. The successful management of estuaries and coastal waters requires an ecohydrologybased, basin-wide approach. This necessitates changing present practices by official institutions based on municipalities or counties as an administrative unit, or the narrowly focused approaches of managers of specific activities (e.g., farming and fisheries, water resources, urban and economic developments, wetlands management and nature conservationists). Without this change in thinking and management concept, estuaries and coastal waters will continue to degrade, whatever integrated coastal management plans are implemented. To help in this process of change there is a need to (1) develop a profound understanding of the effects of biota and biotic processes on mediating estuary response to changing hydrology, sediment and nutrient flux and of the biota on hydrology at the river basin scale, and (2) to develop science-based remediation measures at the river basin scale, with elements of ecohydrology and phytotechnology at their core, to strengthen the ability of the biota to sustain and adapt to human-induced stresses.This revised version wa published online in March 2005 with corrections to the issue cover date.     

Altitudinal patterns of diversity and functional traits of metabolically active microorganisms in stream biofilms

Resources structure ecological communities and potentially link biodiversity to energy flow. It is commonly believed that functional traits (generalists versus specialists) involved in the exploitation of resources depend on resource availability and environmental fluctuations. The longitudinal nature of stream ecosystems provides changing resources to stream biota with yet unknown effects on microbial functional traits and community structure. We investigated the impact of autochthonous (algal extract) and allochthonous (spruce extract) resources, as they change along alpine streams from above to below the treeline, on microbial diversity, community composition and functions of benthic biofilms. Combining bromodeoxyuridine labelling and 454 pyrosequencing, we showed that diversity was lower upstream than downstream of the treeline and that community composition changed along the altitudinal gradient. We also found that, especially for allochthonous resources, specialisation by biofilm bacteria increased along that same gradient. Our results suggest that in streams below the treeline biofilm diversity, specialisation and functioning are associated with increasing niche differentiation as potentially modulated by divers allochthonous and autochthonous constituents contributing to resources. These findings expand our current understanding on biofilm structure and function in alpine streams.     

Spontaneous restoration of epiphytic lichen biota in managed forests planted on habitats typical for temperate deciduous forest

The study examines the changes of epiphytic lichen diversity in differently aged stands developing after clear cutting and pine planting on fertile habitats typical for deciduous forests. The study was conducted within one large complex consisting of pine, mixed pine-hornbeam and typical old oak-linden-hornbeam forests in northern Poland. Epiphytic lichens were recorded in 50 study plots randomly selected within 5 forest stand classes of a different structure and age, ranging from 80 to over 220 years. Altogether 143 lichen species were recorded, of which only 41 were entirely nonspecific, and were occurring in all the studied forest stand classes. Significant differences in lichen species richness between stand classes were found and the number of species increases with the forest age. Lichen species composition also differs and its changes progress towards restoration of lichen biota typical for deciduous forest consistent with the habitat. The age of the forest has the most significant effect on the biodiversity of lichen biota. Microhabitat space provided by oaks is highly desirable since it greatly enriches lichen biota in forests. Phorophyte specificity of particular lichens were assessed. Hornbeam and oak have the greatest number of species mostly confined to them and constitute a main refuge for lichens with a high conservation value. The changes of lichen biota are basically parallel with the changes of the forest stand structure. The selection of some parts within managed pine forests that should not be assigned for cutting in the future can be a simple procedure which helps to restore and preserve forest biodiversity.     

Microbiota within the perennial ice cover of Lake Vida, Antarctica

Lake Vida, located in the McMurdo Dry Valleys, Antarctica, is an 'ice-sealed' lake with approximately 19 m of ice covering a highly saline water column (approximately 245 ppt). The lower portions of the ice cover and the lake beneath have been isolated from the atmosphere and land for circa 2800 years. Analysis of microbial assemblages within the perennial ice cover of the lake revealed a diverse array of bacteria and eukarya. Bacterial and eukaryal denaturing gradient gel electrophoresis phylotype profile similarities were low (<59%) between all of the depths compared (five depths spanning 11 m of the ice cover), with the greatest differences occurring between surface and deep ice. The majority of bacterial 16S rRNA gene sequences in the surface ice were related to Actinobacteria (42%) while Gammaproteobacteria (52%) dominated the deep ice community. Comparisons of assemblage composition suggest differences in ice habitability and organismal origin in the upper and lower portions of ice cover. Specifically, the upper ice cover microbiota likely reflect the modern day transport and colonization of biota from the terrestrial landscape, whereas assemblages in the deeper ice are more likely to be persistent remnant biota that originated from the ancient liquid water column of the lake that froze.     

Soil arthropod composition differs between old-fields dominated by exotic plant species and remnant native grasslands

Secondary succession after agriculture abandonment (old-fields) is mostly dominated by exotic grass species. Non-native plant invasions may alter soil fauna, potentially inducing plant-soil feedbacks. Despite their importance in nutrient cycling and plant-soil interactions, meso and macrofauna received less attention than bacteria or fungi. Here we compared the composition of the soil arthropod community in native remnants and plant exotic-dominated old-fields grasslands in the Inland Pampa, Argentina. We sampled independent remnants and old-field grassland plots within a 100 km² agricultural landscape to test the hypothesis that the abundance of soil arthropod organisms is related to the quality of the plant biomass, whereas the diversity of the soil biota is related to plant species richness, resulting in a different soil biota composition because of differing plant communities. When compared to non-invaded remnant grasslands, soil activity and soil food-web characteristics of the old-fields sites included: 1. Higher total arthropod abundance, particularly of Isopoda, Pseudoescorpionida and Blattaria; 2. Lower abundance of Hymenoptera and Enthomobryomorpha (Collembola); 3. Lower diversity, and evenness, but similar richness of soil organisms orders; 4. Higher soil respiration rates and soil temperature; and 5. Higher total soil N and K⁺content, but lower soil P content. These results illustrate that soil arthropod composition can vary widely within grasslands patches depending on plant species composition. Also, the more diverse plant community of remnant grasslands supports a more diverse soil biota, although soil activity is slower. Our results support the strong linkage between plant community and soil arthropod composition and suggest that changes in soil biota composition might promote plant-soil feedback interactions inducing the persistence of these alternative grassland states in new agricultural human-modified landscapes.