Local Abiotic Conditions Research Articles

Environmental conditions in the Massif Central during the Upper Palaeolithic using stable isotope tracking (13C, 15N) of bone collagen from large herbivores

ABSTRACTThe environmental conditions experienced by hunter‐gatherers during the second part of the Upper Palaeolithic (ca. 28 000–15 000 cal bp) are poorly known in the mid‐elevation volcanic mountains of the Massif Central in southern France. The stable isotope ratios of carbon and nitrogen (13C/12C and 15N/14N expressed as δ13C and δ15N values) in bone collagen of large herbivores can track their diet and habitat, reflecting local abiotic conditions (temperature, aridity, altitude). Due to poor preservation of skeletal organic matter in the region, new radiocarbon dating was conducted on a limited number of quality‐controlled collagen samples, based on a minimum carbon content of 30%. They document three main phases of occupation corresponding to the Final Gravettian, the Badegoulian and the Magdalenian, each of which is represented in different regions of the Allier and Loire valleys. Over time, a decrease in horse δ15N values, the best documented species of large herbivores, is found between the Final Gravettian (ca. 26 700–25 600 cal bp), around the Last Glacial Maximum and the Badegoulian (ca. 21 900–19 200 cal bp), followed by an increase in δ15N and δ13C values during the Magdalenian (ca. 19 100–16 600 cal bp). During the Badegoulian, the δ15N values of the horses were lower than those of their counterparts in southwestern France, testifying to harsh climatic conditions favourable to a tundra‐like landscape, also reflected in the higher horse and reindeer δ13C values in the Allier valley compared to those in southwestern France. The relatively high δ13C and low δ15N values of a Final Gravettian wolf from the Allier valley suggests reindeer as a preferred prey, in line with their high abundance in the archaeological sites. Game access, rather than climatic conditions or lithic resources, seems to have motivated human groups to occupy the Massif Central during the Upper Palaeolithic.

Winter dry season reproductive phenology in Bahamian dry forest and implications for conservation

AbstractThe reproductive phenology of plants has profound influence on ecosystem dynamics including plant–animal interactions. Broad phenological patterns, especially the timing of reproduction, may result from long‐term climate trends and co‐evolution between plants and their pollinators, dispersers, and predators. Yet, interannual climate variation and local abiotic conditions may also affect the timing and magnitude of plant reproduction. Understanding the patterns of and controls on plant reproduction are crucial for conservation efforts under a changing global climate and rapidly expanding human development. However, phenology studies from the Neotropics are sparse. Here, we examine the relative timing and magnitude of fleshy‐fruited plant reproduction during the winter dry season in subtropical dry forest on Eleuthera, The Bahamas over a nine‐year period. At least 47 species were observed with some dry season reproductive activity, but only 17% showed evidence of a fruiting peak or continuous reproduction. Overall fruit abundance generally declined through the dry season, but flower production increased between mid and late dry season. Variation in fruit and flower abundance among years was related to temperature and rainfall, but local site conditions—particularly successional stage and groundwater availability—explained more variability in reproductive activity than climate variation. Groundwater availability had a particularly strong positive influence on flower and fruit abundance at the end of the dry season, a critical time for migrant frugivores preparing to return to their breeding grounds. This emphasizes the importance of protecting sites with accessible groundwater to conserve biodiversity in the archipelago and elsewhere.

Short-term influences of flow alteration on microbial community structure and putative metabolic functions in gravel bar hyporheic zones

Microbial communities in the hyporheic zone are important for self-purification as the riverbed is metabolically active and responsible for the retention, storage, and mineralisation of organic matter transported in the surface water. Studies exploring the response of the hyporheic microbial community to flow regime alterations remain scarce. Here, we characterised the microbial community structure over downwelling, upwelling and intermediate hyporheic zone areas within and among gravel bars at high and low discharge levels to determine flow-induced changes in a dam-regulated river using 16S rRNA gene sequencing. At low discharge, microbial composition varied across the different areas of gravel bars, reflecting heterogeneity in local abiotic conditions. However, high discharge lead to microbial community homogenisation across the three areas of the gravel bars. Microbial communities across adjacent gravel bars remained dissimilar regardless of discharge levels, likely reflecting differences in bar morphology. Our results can help better understand how anthropogenic changes in hydrologic conditions can affect microbial diversity and function in the hyporheic zone. This knowledge will help us to understand better how changes in hydrological conditions affect ecosystem functions and services in rivers affected by human impacts.

Positive effects of plant diversity on dry matter yield while maintaining a high level of forage digestibility in intensively managed grasslands across two contrasting environments

AbstractThe local abiotic and environmental conditions of a grass‐based farming system may influence the agricultural benefits of mixtures in comparison to pure stands. We investigated the effects of species identities and interactions between grass, legume, and herb species on dry matter yield and sward digestibility and explored how contrasting environments may affect these relationships. We established experimental plots across 11 mixtures and 4 monocultures of perennial ryegrass (Lolium perenne L.), chicory (Cichorium intybus L.), white clover (Trifolium repens L.), and red clover (Trifolium pratense L.) established at two seeding densities in two sites Brody and Szelejewo (Poland) and managed them over a 3‐year period. The two sites were close geographically and had similar climates, but differed in soil types (Luvisols and Cambisols, respectively). We confirmed that the annual DM yields were generally higher on Cambisols soil as compared to Luvisols soil; both individual species effects and species interaction strengths differed across the two contrasting environments. The predicted annual DM yield for the 4‐species mixtures in general gave comparable or higher yields compared to monocultures across the 3 years, with the mixtures giving around 10%–30% higher yields than the weighted average of the monocultures of the constituent species. Analysing the transgressive overyielding it turned out that there was no significant difference between the 4‐species mixtures and best performing monoculture. The benefits of species diversity in our study was greater on less productive site because we found larger overyielding of the 4‐species sward on the Luvisols soil than on the Cambisols soil. Additionally, the effect of mixtures composed by 4‐species increased the yield stability compared to monocultures in the 3‐year period of our study, particularly on Cambisols soil. Sward digestibility applied to average values did not differ much between sites with mixtures performing similarly to monocultures. The reason for that could have been the dynamics of sward botanical composition during study years shifted towards increased perennial ryegrass and decreased proportions of chicory in the sward as well as the observed phenomenon that the species in mixed swards progressed to successive growth stages more slowly than in pure sowing.

Vegetation-rainfall coupling as an indicator of ecosystem state in a heterogeneous landscape

Coexisting vegetation types in tropical landscapes can respond in contrasting ways to rainfall, despite being in the same climatic envelope. Understanding such heterogeneity in vegetation-rainfall interactions is key for predicting how ecosystems might respond to future environmental changes. Here we test whether temporal coupling between vegetation greenness and rainfall is a good indicator of ecosystem state in the landscape. For this, we study a well-preserved landscape of the Brazilian Cerrado that is formed by mosaics of contrasting ecosystems, including savannas, dry forests and gallery forests. First, we correlate the time-series of rainfall and vegetation greenness to quantify their coupling for each vegetation type. We then compare vegetation-rainfall coupling with other state variables, such as local-scale vegetation structural and functional traits, as well as differences in environmental conditions in which these vegetation types exist. Coexisting vegetation types are set in contrasting local-scale environmental conditions and have distinct responsiveness to rainfall. Commonly used structural and functional state variables, such as tree cover and tree height, do not depict such marked differences between the vegetation types, particularly for gallery and dry forests. Dry forests have the strongest coupling and decrease their greenness during dry seasons, reflecting vegetation deciduousness on nutrient-richer soils. In contrast, gallery forests increase their greenness during the dry season, when direct radiation peaks, likely due to perennial access to groundwater. Savannas are less responsive to rainfall and have a more stable greenness throughout the year. Our findings suggest that heterogeneity in local abiotic conditions contribute to determining both vegetation distribution and ecosystem states in these tropical savanna landscapes. Changes in these conditions as a result of climate and land-use changes will likely alter the distribution of vegetation types in the future. Our functional metric may thus be useful for assessing future responses of tropical ecosystems to changes in precipitation.

Virulence and Reproduction of Entomopathogenic Nematodes Isolated from a Single Mexican Locality

Abstract Entomopathogenic nematodes (EPNs) are important biological control agents of insect pests. Strains or isolates obtained in specific regions and utilized in situ might contribute to the success of EPNs, since they are adapted to local abiotic conditions. We isolated and identified three isolates each of Heterorhabditis bacteriophora Poinar and Steinernema carpocapsae (Weiser) from soils at Saltillo, Coahuila State, Mexico. These six isolates were bioassayed against larvae of Tenebrio molitor L., using six concentrations of infective juveniles (IJs) per larva (0, 10, 25, 50, 100, 200). EPN-induced mortality of the isolates ranged from 15.2% to 100%. The designated M5 isolate of S. carpocapsae caused 100% mortality after 72 h at concentrations ≥25 IJs/larva with a median lethal concentration of 4.99 IJs/larva. Comparison of mortality levels induced at the same concentration of the six EPN isolates indicated that the Steinernema isolates, in general, induced higher mortality levels than the Heterorhabditis isolates. IJ production in T. molitor larvae also was greatest with the M5 isolate of S. carpocapsae following exposure of larvae to a concentration of 100 IJs/larva with a mean of 17,320 IJs/larva. Based on induced mortality and IJ production, the S. carpocapsae M5 isolate appears to be a viable candidate for further study and possible development for use in insect pest management programs. This study indicates that naturally coexisting local nematode isolates possess different attributes critical for their use as biocontrol agents.

Exploring intraspecific variability – biochemical and morphological traits of the sugar kelp Saccharina latissima along latitudinal and salinity gradients in Europe

Broadly distributed seaweeds, such as the boreal-temperate kelp species Saccharina latissima, contain a multitude of metabolites supporting acclimation to environmental changes, such as temperature and salinity. In Europe, S. latissima occurs along the coasts from Spitsbergen to Portugal, including the Baltic Sea, exhibiting great morphological plasticity. We investigated the morphological and biochemical traits of field-collected sporophytes from 16 different locations across the species entire distributional range in relation to local abiotic conditions (sea surface temperature, salinity). By statistically linking morphological and biochemical data to geographic information that also took into account the respective sampling depth, we aimed to obtain first insights into the site-specific adaptive features of this species. Frond length and width, mannitol and phlorotannin contents, and molar C:N ratio showed strong intraspecific variability among S. latissima sporophytes dependent on individual local abiotic drivers. Despite the conspicuous impact of local abiotic factors on specimens’ morphology, we could not determine habitat-specific signatures in the biochemical phenotypes. Even though our findings are based on a relative small sample size per site, they cover a broad biogeographical range and support a high plasticity of S. latissima sporophytes. The study provides a first base for studying separation processes of populations across latitudes and conservation ecology.

Invasion‐mediated mutualism disruption is evident across heterogeneous environmental conditions and varying invasion intensities

The impact of a biological invasion on native communities is expected to be uneven across invaded landscapes due to differences in local abiotic conditions, invader abundance, and traits and composition of the native community. One way to improve predictive ability about the impact of an invasive species given variable conditions is to exploit known mechanisms driving invasive species' success. Invasive plants frequently exhibit allelopathic traits, which can be directly toxic to plants or indirectly impact them via disruption of root symbionts, including mycorrhizal fungi. The indirect mechanism – mutualism disruption – is predicted to impact plants that rely on mycorrhizas but not affect non‐mycorrhizal plant species. To assess whether invader‐driven mutualism disruption explains observed changes in native plant communities, we analyzed long‐term (1998–2018) plant cover data from forest plots across the state of Illinois. We evaluated native plant communities experiencing a range of abundance of invasive allelopathic garlic mustard Alliaria petiolata and varying environmental conditions. Consistent with the mutualism disruption hypothesis, we showed that as garlic mustard abundance increased over time in 0.25 m2 sampling quadrats, the abundance of mycorrhizal plant species decreased, but non‐mycorrhizal plant species did not. Over space and time, garlic mustard abundance predicted plant abundances and diversity at the quadrat level, but this relationship was not present at a larger scale when quadrats were aggregated within sites. Garlic mustard's impact on the plant community was highly localized, yet it was as important as abiotic variables for predicting local plant diversity. We showed that garlic mustard abundance was a key predictor of patterns of plant diversity across invasion intensity and environmental heterogeneity in a way that is consistent with mutualism disruption. Our work indicates that the mutualism disruption hypothesis can provide generalizable predictions of the impacts of allelopathic invasive plants that are evident at a broad spatial scale.

Plant species composition and local habitat conditions as primary determinants of terrestrial arthropod assemblages

Arthropods respond to vegetation in multiple ways since plants provide habitat and food resources and indicate local abiotic conditions. However, the relative importance of these factors for arthropod assemblages is less well understood. We aimed to disentangle the effects of plant species composition and environmental drivers on arthropod taxonomic composition and to assess which aspects of vegetation contribute to the relationships between plant and arthropod assemblages. In a multi-scale field study in Southern Germany, we sampled vascular plants and terrestrial arthropods in typical habitats of temperate landscapes. We compared independent and shared effects of vegetation and abiotic predictors on arthropod composition distinguishing between four large orders (Lepidoptera, Coleoptera, Hymenoptera, Diptera), and five functional groups (herbivores, pollinators, predators, parasitoids, detritivores). Across all investigated groups, plant species composition explained the major fraction of variation in arthropod composition, while land-cover composition was another important predictor. Moreover, the local habitat conditions depicted by the indicator values of the plant communities were more important for arthropod composition than trophic relationships between certain plant and arthropod species. Among trophic groups, predators showed the strongest response to plant species composition, while responses of herbivores and pollinators were stronger than those of parasitoids and detritivores. Our results highlight the relevance of plant community composition for terrestrial arthropod assemblages across multiple taxa and trophic levels and emphasize the value of plants as a proxy for characterizing habitat conditions that are hardly accessible to direct environmental measurements.

Breeding stage and tissue isotopic consistency suggests colony-level flexibility in niche breadth of an Arctic marine bird.

Organisms must overcome environmental limitations to optimize their investment in life history stages to maximize fitness. Human-induced climate change is generating increasingly variable environmental conditions, impacting the demography of prey items and, therefore, the ability of consumers to successfully access resources to fuel reproduction. While climate change effects are especially pronounced in the Arctic, it is unknown whether organisms can adjust foraging decisions to match such changes. We used a 9-year blood plasma δ13C and δ15N data set from over 700 pre-breeding Arctic common eiders (Somateria mollissima) to assess breeding-stage and inter-annual variation in isotopic niche, and whether inferred trophic flexibility was related to colony-level breeding parameters and environmental variation. Eider blood isotope values varied both across years and breeding stages, and combined with only weak relationships between isotopic metrics and environmental conditions suggests that pre-breeding eiders can make flexible foraging decisions to overcome constraints imposed by local abiotic conditions. From an investment perspective, an inshore, smaller isotopic niche predicted a greater probability to invest in reproduction, but was not related to laying phenology. Proximately, our results provide evidence that eiders breeding in the Arctic can alter their diet at the onset of reproductive investment to overcome increases in the energetic demand of egg production. Ultimately, Arctic pre-breeding common eiders may have the stage- and year-related foraging flexibility to respond to abiotic variation to reproduce successfully.

A role for the local environment in driving species‐specific parasitism in a multi‐host parasite system

Abstract The extent and magnitude of parasitism often vary among closely related host species and across populations within species. Determining the ecological basis for this species and population‐level variation in parasitism is critical for understanding infection dynamics in multi‐host–parasite systems. To investigate such ecological underpinnings of variation in parasitism, we studied Enallagma damselfly host species and their water mite (Arrenurus spp.) ectoparasites in lakes. We first evaluated how host identity and density could shape parasitism. To test the effects of con‐ and heterospecific host density on parasitism, we used a field experiment with Enallagma basidens and E. signatum. We found that parasitism did not vary with con‐ or heterospecific density and was determined by host identity alone, with no spillover effects. We also evaluated the potential role of local adaptation and resource availability in shaping parasitism. To do so, we used E. signatum in a reciprocal transplant experiment crossed with a prey resource‐level manipulation. This experiment revealed that parasitism declined sharply for one host population in its non‐local lake, but not the other source population, with no effects of prey levels. This asymmetry implies that damselflies express enhanced defences against parasitism that are neither population‐specific nor dependent on resource abundance, or that mites developed heightened local host specificity. The results of multivariate modeling from an observational study generally supported these experimental findings: neither host density nor resource abundance strongly explained among‐population variation in parasitism. Instead, local abiotic conditions (pH) had the strongest relationship with parasitism, with minimal associations with predator density, temperature and a measure of immune function. Collectively, our findings suggest a crucial role for the local environment in shaping host–parasite interactions within multi‐host–parasite systems. More generally, these results show that research at the intersection of community ecology and disease ecology is critical for understanding host–parasite dynamics within natural communities.

Invasion impacts and dynamics of a European-wide introduced species.

Globalization has led to the introduction of thousands of alien species worldwide. With growing impacts by invasive species, understanding the invasion process remains critical for predicting adverse effects and informing efficient management. Theoretically, invasion dynamics have been assumed to follow an "invasion curve" (S-shaped curve of available area invaded over time), but this dynamic has lacked empirical testing using large-scale data and neglects to consider invader abundances. We propose an "impact curve" describing the impacts generated by invasive species over time based on cumulative abundances. To test this curve's large-scale applicability, we used the data-rich New Zealand mud snail Potamopyrgus antipodarum, one of the most damaging freshwater invaders that has invaded almost all of Europe. Using long-term (1979-2020) abundance and environmental data collected across 306 European sites, we observed that P. antipodarum abundance generally increased through time, with slower population growth at higher latitudes and with lower runoff depth. Fifty-nine percent of these populations followed the impact curve, characterized by first occurrence, exponential growth, then long-term saturation. This behaviour is consistent with boom-bust dynamics, as saturation occurs due to a rapid decline in abundance over time. Across sites, we estimated that impact peaked approximately two decades after first detection, but the rate of progression along the invasion process was influenced by local abiotic conditions. The S-shaped impact curve may be common among many invasive species that undergo complex invasion dynamics. This provides a potentially unifying approach to advance understanding of large-scale invasion dynamics and could inform timely management actions to mitigate impacts on ecosystems and economies.

Species provenance and traits mediate establishment and performance in an invaded grassland

Abstract In many invaded grasslands, dominant exotic species can produce large amounts of litter that modify local abiotic conditions and species' interactions. These novel conditions can reduce native species abundance and promote the persistence of exotic species, yet the strength of this disparity may be influenced by how consumer pressure interacts with litter accumulation. Consumers may exacerbate this disparity by preferentially targeting native species or by promoting heterogeneity in microhabitats due to their movement and small‐scale ground disturbances that favours fast growing exotic species. How species respond to litter accumulation and consumer pressure may depend on either evolutionary differences, whereby exotics species may benefit from a lack natural predators, or by functional differences, in which species' physiological traits may confer fitness advantages to low‐light conditions or herbivory or granivory pressure. We examined the impact of litter presence and small mammal herbivory on the establishment and reproduction of functionally diverse exotic versus native species seeded across sites that naturally vary in resource availability in an annual invaded California grassland. We assessed whether seed mass and leaf nitrogen content (LNC) were predictive of successful establishment and reproduction. Litter accumulation affected exotic and native species differently, with litter significantly decreasing native recruitment and reproduction, while exotics were largely unaffected. Small mammals had a slight positive effect on the establishment of native species when litter was present but did not influence exotic species. Regardless of species provenance, larger seeded species established at a higher density while species with lower leaf nitrogen content had a higher density of reproductive individuals. Native species that successfully established and reproduced were functionally different in LNC than the resident community, while successful exotic species were functionally more similar to the resident community in LNC. Our study demonstrates that exotic species outperformed native species regardless of the presence of litter or herbivory pressure. Without the removal or thinning of litter, it is likely that exotic species will continue to dominate, resulting in positive feedback that further favours the persistence of exotic species within this invaded grassland system. Read the free Plain Language Summary for this article on the Journal blog.

Exposure to lysed bacteria can promote or inhibit growth of neighboring live bacteria depending on local abiotic conditions.

Microbial death is extremely common in nature, yet the ecological role of dead bacteria is unclear. Dead cells are assumed to provide nutrients to surrounding microbes, but may also affect them in other ways. We found that adding lysate prepared from dead bacteria to cultures of Escherichia coli in nutrient-rich conditions suppressed their final population density. This is in stark contrast with the notion that the primary role of dead cells is nutritional, although we also observed this type of effect when we added dead bacteria to cultures that were not supplied with other nutrients. We only observed the growth-suppressive effect of our dead-bacteria treatment after they had undergone significant lysis, suggesting a key role for cellular contents released during lysis. Transcriptomic analysis indicated changes in gene expression in response to dead cells in growing populations, particularly in genes involved in motility. This was supported by experiments with genetic knockouts and copy-number manipulation. Because lysis is commonplace in natural and clinical settings, the growth-suppressive effect of dead cells we describe here may be a widespread and previously unrecognized constraint on bacterial population growth.

Impervious surface and local abiotic conditions influence arthropod communities within urban greenspaces.

The abundance of arthropods is declining globally, and human-modification of natural habitat is a primary driver of these declines. Arthropod declines are concerning because arthropods mediate critical ecosystem functions, and sustained declines may lead to cascading trophic effects. There is growing evidence that properly managed urban environments can provide refugium to arthropods, but few cities have examined arthropods within urban greenspaces to evaluate their management efforts. In this study, we surveyed arthropod communities within a medium-sized, growing city. We investigated arthropod communities (abundance, richness, diversity, community composition) within 16 urban greenspaces across metropolitan Grand Rapids, Michigan (USA). We focused our efforts on urban gardens and pocket prairies, and measured environmental variables at each site. We collected 5,468 individual arthropods that spanned 14 taxonomic orders and 66 morphospecies. The results showed that community composition was influenced by impervious surface, white flower abundance, and humidity. Total arthropod abundance and diversity were positively associated with humidity. For specific orders, Hymenoptera (bees, ants, wasps) abundance was negatively associated with temperature, and positively associated with site perimeter-area ratio. Hemiptera (true bugs) were negatively associated with impervious surface and positively associated with humidity. These findings show that impervious surfaces impact arthropod communities, but many of the observed changes were driven by local abiotic conditions like temperature and humidity. This suggests that management decisions within urban greenspaces are important in determining the structure of arthropod communities. Future studies on arthropods in cities should determine whether manipulating the abiotic conditions of urban greenspaces influences the composition of arthropod communities. These results should inform city planners and homeowners of the need to properly manage urban greenspaces in cities to maintain diverse arthropod assemblages.

Collateral Sensitivity Interactions between Antibiotics Depend on Local Abiotic Conditions.

ABSTRACTMutations conferring resistance to one antibiotic can increase (cross-resistance) or decrease (collateral sensitivity) resistance to others. Antibiotic combinations displaying collateral sensitivity could be used in treatments that slow resistance evolution. However, lab-to-clinic translation requires understanding whether collateral effects are robust across different environmental conditions. Here, we isolated and characterized resistant mutants of Escherichia coli using five antibiotics, before measuring collateral effects on resistance to other paired antibiotics. During both isolation and phenotyping, we varied conditions in ways relevant in nature (pH, temperature, and bile). This revealed that local abiotic conditions modified expression of resistance against both the antibiotic used during isolation and other antibiotics. Consequently, local conditions influenced collateral sensitivity in two ways: by favoring different sets of mutants (with different collateral sensitivities) and by modifying expression of collateral effects for individual mutants. These results place collateral sensitivity in the context of environmental variation, with important implications for translation to real-world applications.IMPORTANCE When bacteria become resistant to an antibiotic, the genetic changes involved sometimes increase (cross-resistance) or decrease (collateral sensitivity) their resistance to other antibiotics. Antibiotic combinations showing repeatable collateral sensitivity could be used in treatment to slow resistance evolution. However, collateral sensitivity interactions may depend on the local environmental conditions that bacteria experience, potentially reducing repeatability and clinical application. Here, we show that variation in local conditions (pH, temperature, and bile salts) can influence collateral sensitivity in two ways: by favoring different sets of mutants during bacterial resistance evolution (with different collateral sensitivities to other antibiotics) and by modifying expression of collateral effects for individual mutants. This suggests that translation from the lab to the clinic of new approaches exploiting collateral sensitivity will be influenced by local abiotic conditions.

Microbial “hotspots” of organic matter decomposition in temperate peatlands are driven by local spatial heterogeneity in abiotic conditions and not by vegetation structure

Climate change is triggering rapid shifts in plant communities and alterations in soil abiotic conditions in peatlands, with cascading effects on belowground decomposers and ecosystem C turnover. However, elucidating the dominant causal relationships between plant communities, soil biota and C fluxes in these vulnerable ecosystems requires a better understanding of the spatio-temporal variability of abiotic and biotic drivers. In this study we investigated the effects of biotic (plant functional types, PFTs) and abiotic factors (soil temperature and soil moisture) in determining dynamic patterns of soil microbial community structure and C cycling. Four representative temperate peatland habitats were selected based on their peat forming vegetation – an Atlantic wet heathland, two active blanket bogs with herbaceous plants (Molinia caerulea and Eriophorum angustifolium), and a transition mire dominated by Sphagnum mosses located along an altitudinal gradient to include the natural variations in soil temperature and water content regimes. We found that peat microbial communities were more strongly linked to local abiotic conditions than to the dominant above-ground vegetation. Aerobic conditions and warmer temperatures accelerated fungal driven decomposition and CO2 emissions under shrubs, whereas decreases in Gram−negative bacteria promoted increased C losses under Molinia. These findings suggest that small spatial differences in abiotic conditions can create local “hotspots” of organic matter decomposition. We propose that temperate peatlands should be considered as ‘ecosystem sentinels’ for climate change, acting as early-warning indicators of climate-carbon feedbacks.

Cryptic diversity within the Poecilochirus carabi mite species complex phoretic on Nicrophorus burying beetles: Phylogeny, biogeography, and host specificity.

Coevolution is often considered a major driver of speciation, but evidence for this claim is not always found because diversity might be cryptic. When morphological divergence is low, molecular data are needed to uncover diversity. This is often the case in mites, which are known for their extensive and often cryptic diversity. We studied mites of the genus Poecilochirus that are phoretic on burying beetles (Silphidae: Nicrophorus). Poecilochirus taxonomy is poorly understood. Most studies on this genus focus on the evolutionary ecology of Poecilochirus carabi sensu lato, a complex of at least two biological species. Based on molecular data of 230specimens from 43locations worldwide, we identified 24genetic clusters that may represent species. We estimate that these mites began to diversify during the Paleogene, when the clade containing P. subterraneus branched off and the remaining mites diverged into two further clades. One clade resembles P. monospinosus. The other clade contains 17genetic clusters resembling P. carabi s.l.. Among these are P. carabi sensu stricto, P. necrophori, and potentially many additional cryptic species. Our analyses suggest that these clades were formed in the Miocene by large-scale geographic separation; co-speciation of mites with the host beetles can be largely ruled out. Diversification also seems to have happened on a smaller scale, potentially due to adaptation to specific hosts or local abiotic conditions, causing some clusters to specialize on certain beetle species. Our results suggest that biodiversity in this genus was generated by multiple interacting forces shaping the tangled webs of life.

Invasive ant establishment, spread, and management with changing climate.

Ant invasions and climate change both pose globally widespread threats to the environment and economy. I highlight our current knowledge of how climate change will affect invasive ant distributions, population growth, spread, impact, and invasive ant management. Invasive ants often have traits that enable rapid colony growth in a range of habitats. Consequently, many invasive ant species will continue to have large global distributions as environmental conditions change. Distributions and impacts at community scales will depend on how resident ant communities respond to local abiotic conditions as well as availability of plant-based carbohydrate resources. Though target species may change under an altered climate, invasive ant impacts are unlikely to diminish, and novel control methods will be necessary.

Soil microbial communities are driven by the declining availability of cations and phosphorus during ecosystem retrogression

Development of soil microbial communities is driven by local abiotic and biotic conditions, yet our current understanding of their ecology is limited to studies in modified or young and relatively fertile ecosystems. In nutrient-impoverished soils, microbial communities may be predominantly structured by availability of key elements such as phosphorus (P) or nitrogen, regardless of the taxa (bacteria, archaea or fungi). Here, we determined if shifts in bacterial communities and biomass occurred along a long-term soil chronosequence in south-western Australia, and whether such shifts were related to changes in soil nutrient availability along the retrogressive phase of this chronosequence. We quantified shifts in the biomass and abundance of major soil microbial groups using phospholipid fatty acids and quantitative polymerase chain reaction. We found that declining soil P availability limited microbial growth and community structure. Common cations, notably magnesium, showed strong relationships with the abundance of most bacterial and archaeal taxa. In the oldest most severely impoverished soils, the fungal to bacteria ratio was higher than in the young soils, indicating fungi are better adapted to such environments. Finally, archaeal copy numbers decreased more strongly than bacterial copy numbers with increasing nutrient-impoverishment of soils. The study enhances our understanding of the ecology of soil bacteria, archaea, and fungi during ecosystem development and retrogression.