Archerfish are renowned for dislodging aerial prey using well-aimed shots of water. Recently it has been shown that these fish can shape their aerial jets by adjusting the dynamics of their mouth ...opening and closing. This allows the fish to adjust their jet to target distance so that they can forcefully hit prey over considerable distances. Here, we suggest that archerfish use the same technique to also actively control jets under water. Fired from close range, the underwater jets are powerful enough to lift up buried food particles, which the fish then can pick up. We trained fish so that we could monitor their mouth opening and closing maneuvers during underwater shooting and compare them with those employed in aerial shooting. Our analysis suggests that the fish use the same dynamic mechanism to produce aerial and underwater jets and that they employ the same basic technique to adjust their jets in both conditions. When food is buried in substrate that consists of large particles, the fish use a brief pulse, but they use a longer one when the substrate is more fine-grained. These findings extend the notion that archerfish can flexibly shape their jets to be appropriate in different contexts and suggest that archerfish shooting might have been shaped both by constraints in aerial and underwater shooting.
Ecology aims to comprehend species distribution and its interaction with environmental factors, from global to local scales. While global environmental changes affect marine biodiversity, ...understanding the drivers at smaller scales remains crucial. Tidal flats can be found on most of the world's coastlines and are particularly vulnerable to anthropogenic disturbances. They are important transient ecosystems between terrestrial and marine ecosystems, and their biodiversity provides important ecosystem services. Owing to this unique, terrestrial–marine transition, strong environmental gradients of elevation, sediment composition and food availability prevail. Here, we investigated which regional and local environmental factors drive the spatio‐temporal dynamics of macrozoobenthos communities on back‐barrier tidal flats in the East Frisian Wadden Sea. On the regional level, we found that species composition changed significantly from west to east on the East Frisian islands and that total abundance and species richness decreased from west to east. On the local abiotic level, we found that macrozoobenthos biomass decreased with higher elevation towards the salt marsh and that the total abundance of organisms in the sediment significantly increased with increasing mud content, while biodiversity and biomass were not changing significantly. In contrast to expectations, increasing Chl a availability as a measure of primary productivity did not result in changes in abundance, biomass or biodiversity, but extremely high total organic carbon (TOC) content was associated with a decrease in biomass and biodiversity. In conclusion, we found regional and local relationships that are similar to those observed in previous studies on macrozoobenthos in the Wadden Sea. Macrozoobenthos biomass, abundance and biodiversity are interrelated in a complex way with the physical, abiotic and biotic processes in and above the sediment.
This study investigates the spatio‐temporal dynamics of macrozoobenthos communities on back‐barrier tidal flats in the East Frisian Wadden Sea. They found significant changes in species composition and a decrease in abundance and species richness from west to east on the East Frisian Islands, while extremely high total organic carbon content was associated with a decrease in biomass and biodiversity, suggesting potential negative effects of nutrient inputs in tidal flat areas.
Microphytobenthos (MPBs) are the main primary producers in shallow marine ecosystems, such as the Wadden Sea. We investigated the spatial and temporal dynamics of MPB communities across the ...marine-terrestrial boundary over three seasons (spring, summer, and fall) on three East Frisian Islands (Norderney, Spiekeroog, and Wangerooge) in the German Wadden Sea. Natural transects were compared with 12 experimental islands (salt marsh vegetated vs. initially bare islands) established on the tidal flats of Spiekeroog for studying dispersal-mediated community assembly. Sediment cores were taken along triplicate transects and on three elevation levels of the experimental islands, corresponding to the pioneer (pio) zone, the lower salt (LS) marsh, and the upper salt (US) marsh. On both the natural transects and the experimental islands, the highest MPB biomass was observed in the pio zone, where vegetation-driven sediment stabilization and high-mud content could have promoted MPB biomass in this marine-terrestrial transition zone. On the experimental islands, MPB biomass and diversity significantly decreased with elevation regardless of the season, indicating that the rarely submerged upper salt marsh level supported minimal MPB growth. The MPB biomass was also higher on initially vegetated than on bare islands, which was the most pronounced on the US level. On the tidal flat transects, the MPB biomass significantly increased with elevation up to the pio zone before decreasing again in the LS marsh. Temperature, sediment water content, and grain size significantly affected transect MPB biomass. MPB diversity, on the other hand, was not related to elevation but was rather determined by temperature, mean grain size, and mud content. Our study suggests that extending MPB studies into the “terrestrial” domain of salt marshes enhances our understanding of the microalgae–plant interaction in this important boundary zone.
Juvenile queen conch are primarily associated with native seagrass such as Thalassia testudinum in large parts of their range in the Caribbean and the southern Gulf of Mexico. Here, a number of ...non-native seagrass species have been introduced including Halophila stipulacea, which is natural to the Red Sea and the Indo-Pacific. In the Caribbean, H. stipulacea often creates dense continuous mats with little or no sediment exposed, compared to native seagrass, which grows much less dense. We examined the diet and growth of juvenile conch in both native, mixed, and invasive seagrass beds using stable isotope analysis and an in situ growth enclosure experiment. Organic material in the sediment (i.e. benthic diatoms and particulate organic matter) was found to be the most important source of carbon and nitrogen for juvenile queen conch in all 3 habitats investigated, and there was a significantly higher probability of positive growth in the native seagrass compared to the invasive seagrass. Due to the importance of the organic material in the sediment as a source of nutrition for juvenile conch, limited access to the sediment in the invasive seagrass can potentially cause inadequate nutritional conditions to sustain high growth rates. Thus, it is likely that there is a negative effect on juvenile queen conch growth currently inhabiting invasive seagrass beds, compared to native seagrass beds, when other potential sources of nutrition are not available.
Abstract
Recently reported insect declines have raised both political and social concern. Although the declines have been attributed to land use and climate change, supporting evidence suffers from ...low taxonomic resolution, short time series, a focus on local scales, and the collinearity of the identified drivers. In this study, we conducted a systematic assessment of insect populations in southern Germany, which showed that differences in insect biomass and richness are highly context dependent. We found the largest difference in biomass between semi-natural and urban environments (−42%), whereas differences in total richness (−29%) and the richness of threatened species (−56%) were largest from semi-natural to agricultural environments. These results point to urbanization and agriculture as major drivers of decline. We also found that richness and biomass increase monotonously with increasing temperature, independent of habitat. The contrasting patterns of insect biomass and richness question the use of these indicators as mutual surrogates. Our study provides support for the implementation of more comprehensive measures aimed at habitat restoration in order to halt insect declines.
Climate and land use are major determinants of biodiversity, and declines in species richness in cold and human exploited landscapes can be caused by lower rates of biotic interactions. Deadwood ...fungi and bacteria interact strongly with their hosts due to long‐lasting evolutionary trajectories. However, how rates of biotic interactions (specialization) change with temperature and land‐use intensity are unknown for both microbial groups. We hypothesize a decrease in species richness and specialization of communities with decreasing temperature and increasing land use intensity while controlling for precipitation. We used a full‐factorial nested design to disentangle land use at habitat and landscape scale and temperature spanning an area of 300 × 300 km in Germany. We exposed four deadwood objects representing the main tree species in Central Europe (beech, oak, spruce, pine) in 175 study plots. Overall, we found that fungal and bacterial richness, community composition and specialization were weakly related to temperature and land use. Fungal richness was slightly higher in near‐natural than in urban landscapes. Bacterial richness was positively associated with mean annual temperature, negatively associated with local temperature and highest in grassland habitats. Bacterial richness was positively related to the covariate mean annual precipitation. We found strong effects of host‐tree identity on species richness and community composition. A generally high level of fungal host‐tree specialization might explain the weak response to temperature and land use. Effects of host‐tree identity and specialization were more pronounced in fungi. We suggest that host tree changes caused by land use and climate change will be more important for fungal communities, while changes in climate will affect bacterial communities more directly. Contrasting responses of the two taxonomic groups suggest a reorganization of deadwood microbial communities, which might have further consequences on diversity and decomposition in the Anthropocene.
Local and landscape-scale agricultural intensification is a major driver of global biodiversity loss. Controversially discussed solutions include wildlife-friendly farming or combining high-intensity ...farming with land-sparing for nature. Here, we integrate biodiversity and crop productivity data for smallholder cacao in Indonesia to exemplify for tropical agroforests that there is little relationship between yield and biodiversity under current management, opening substantial opportunities for wildlife-friendly management. Species richness of trees, fungi, invertebrates, and vertebrates did not decrease with yield. Moderate shade, adequate labor, and input level can be combined with a complex habitat structure to provide high biodiversity as well as high yields. Although livelihood impacts are held up as a major obstacle for wildlife-friendly farming in the tropics, our results suggest that in some situations, agroforests can be designed to optimize both biodiversity and crop production benefits without adding pressure to convert natural habitat to farmland.
Global warming can increase insect pest pressure by enhancing reproductive rates. Whether this translates into yield losses depends on phenological synchronisation of pests with their host plants and ...natural enemies. Simultaneously, landscape composition may mitigate climate effects by shaping the resource availability for pests and their antagonists. Here, we study the combined effects of temperature and landscape composition on pest abundances, larval parasitism, crop damage and yield, while also considering crop phenology, to identify strategies for sustainable management of oilseed rape (OSR) pests under warming climates.
In all, 29 winter OSR crop fields were investigated in different climates (defined by multi‐annual mean temperature, MAT) and landscape contexts in Bavaria, Germany. We measured abundances of adult pollen beetles and stem weevil larvae, pollen beetle larval parasitism, bud loss, stem damage and seed yield, and calculated the flowering date from growth stage observations. Landscape parameters (proportion of non‐crop and OSR area, change in OSR area relative to the previous year) were calculated at six spatial scales (0.6–5 km).
Pollen beetle abundance increased with MAT but to different degrees depending on the landscape context, that is, increased less strongly when OSR proportions were high (1‐km scale), interannually constant (5‐km scale) or both. In contrast, stem weevil abundance and stem damage did not respond to landscape composition nor MAT. Pollen beetle larval parasitism was overall low, but occasionally exceeded 30% under both low and high MAT and with reduced OSR area (0.6‐km scale).
Despite high pollen beetle abundance in warm climates, yields were high when OSR flowered early. Thereby, higher temperatures favoured early flowering. Only among late‐flowering OSR crop fields yield was higher in cooler than warmer climates. Bud loss responded analogously. Landscape composition did not substantially affect bud loss and yield.
Synthesis and applications: Earlier flowering of winter OSR compensates for higher pollen beetle abundance in warmer climates, while interannual continuity of OSR area prevents high pollen beetle abundance in the first place. Thus, regional coordination of crop rotation and crop management promoting early flowering may contribute to sustainable pest management in OSR under current and future climatic conditions.
Earlier flowering of winter OSR compensates for higher pollen beetle abundance in warmer climates, while interannual continuity of OSR area prevents high pollen beetle abundance in the first place. Thus, regional coordination of crop rotation and crop management promoting early flowering may contribute to sustainable pest management in OSR under current and future climatic conditions.
Climate and land‐use change are key drivers of environmental degradation in the Anthropocene, but too little is known about their interactive effects on biodiversity and ecosystem services. Long‐term ...data on biodiversity trends are currently lacking. Furthermore, previous ecological studies have rarely considered climate and land use in a joint design, did not achieve variable independence or lost statistical power by not covering the full range of environmental gradients.
Here, we introduce a multi‐scale space‐for‐time study design to disentangle effects of climate and land use on biodiversity and ecosystem services. The site selection approach coupled extensive GIS‐based exploration (i.e. using a Geographic information system) and correlation heatmaps with a crossed and nested design covering regional, landscape and local scales. Its implementation in Bavaria (Germany) resulted in a set of study plots that maximise the potential range and independence of environmental variables at different spatial scales.
Stratifying the state of Bavaria into five climate zones (reference period 1981–2010) and three prevailing land‐use types, that is, near‐natural, agriculture and urban, resulted in 60 study regions (5.8 × 5.8 km quadrants) covering a mean annual temperature gradient of 5.6–9.8°C and a spatial extent of ~310 × 310 km. Within these regions, we nested 180 study plots located in contrasting local land‐use types, that is, forests, grasslands, arable land or settlement (local climate gradient 4.5–10°C). This approach achieved low correlations between climate and land use (proportional cover) at the regional and landscape scale with |r ≤ 0.33| and |r ≤ 0.29| respectively. Furthermore, using correlation heatmaps for local plot selection reduced potentially confounding relationships between landscape composition and configuration for plots located in forests, arable land and settlements.
The suggested design expands upon previous research in covering a significant range of environmental gradients and including a diversity of dominant land‐use types at different scales within different climatic contexts. It allows independent assessment of the relative contribution of multi‐scale climate and land use on biodiversity and ecosystem services. Understanding potential interdependencies among global change drivers is essential to develop effective restoration and mitigation strategies against biodiversity decline, especially in expectation of future climatic changes. Importantly, this study also provides a baseline for long‐term ecological monitoring programs.
Arthropod predators are important for ecosystem functioning by providing top-down regulation of insect herbivores. As predator communities and activity are influenced by biotic and abiotic factors on ...different spatial scales, the strength of top-down regulation ('arthropod predation') is also likely to vary. Understanding the combined effects of potential drivers on arthropod predation is urgently needed with regard to anthropogenic climate and land-use change. In a large-scale study, we recorded arthropod predation rates using artificial caterpillars on 113 plots of open herbaceous vegetation embedded in contrasting habitat types (forest, grassland, arable field, settlement) along climate and land-use gradients in Bavaria, Germany. As potential drivers we included habitat characteristics (habitat type, plant species richness, local mean temperature and mean relative humidity during artificial caterpillar exposure), landscape diversity (0.5-3.0-km, six scales), climate (multi-annual mean temperature, 'MAT') and interactive effects of habitat type with other drivers. We observed no substantial differences in arthropod predation rates between the studied habitat types, related to plant species richness and across the Bavarian-wide climatic gradient, but predation was limited when local mean temperatures were low and tended to decrease towards higher relative humidity. Arthropod predation rates increased towards more diverse landscapes at a 2-km scale. Interactive effects of habitat type with local weather conditions, plant species richness, landscape diversity and MAT were not observed. We conclude that landscape diversity favours high arthropod predation rates in open herbaceous vegetation independent of the dominant habitat in the vicinity. This finding may be harnessed to improve top-down control of herbivores, e.g. agricultural pests, but further research is needed for more specific recommendations on landscape management. The absence of MAT effects suggests that high predation rates may occur independent of moderate increases of MAT in the near future.
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