Response of ant communities and ant–seed interactions to bush regeneration

Summary Bush regeneration programmes aim to restore native plant communities by interventions designed to assist natural recovery, supplemented by planting or direct seeding where necessary. The present study compared ground-dwelling ant communities and rates of seed removal by ants in weed-infested, regenerating and undamaged urban bushland in northern Sydney. Three replicate dry sclerophyll sites on sandstone were studied, each containing zones of weed-infested, regenerating and undamaged bushland. Canopy cover, midstorey cover, ground cover and litter depth were measured at each site. Each zone type showed distinctive vegetation and cover characteristics, particularly at the ground level. Ground foraging ants were sampled with pitfall traps, sorted to morphospecies and placed in functional groups. There were no significant differences in ant abundance, number of genera or number of morphospecies between site types. Ant diversity and equitability was highest in the undamaged zones, followed by regenerating zones, then weedy zones. There was a significant difference between zone types in the proportion of ant species in different functional groups. Weedy zones were dominated by Opportunist species whereas regenerating zones had a high proportion of Dominant Dolichoderinae. At undamaged zones, the distribution of ants across functional groups was more even. Differences in the ant communities between the three zone types were reflected by differences in interactions between ants and seeds. Seed removal rates of both native and exotic seeds were significantly lower at weedy zones than at undamaged zones, with the regenerating zones having intermediate rates. Sites subject to regeneration 4–10 years previously were intermediate between undamaged and weedy zones for ground cover, litter depth, ant species diversity and equitability, proportion of Opportunist ant species, and seed removal rates. Thus, the regeneration techniques used have been at least partially successful in restoring some aspects of the invertebrate fauna and ecological interactions typical of undamaged dry sclerophyll bushland.     

Subcaste‐specific evolution of head size in the ant genus Pheidole

An organism's morphology is constrained by its evolutionary history and the need to meet a variety of potentially competing functions. The ant genus Pheidole is the most species‐rich ant genus and almost every species has a dimorphic worker caste (a few are trimorphic). This separation of workers into two developmentally distinct subcastes (smaller minors and larger majors with distinctively large heads) may partially release individuals from functional constraints on morphology, making Pheidole an ideal genus for addressing questions on the evolution of morphology in relation to ecological specialization. Major workers can perform a variety of tasks, although they are usually specialized for defence, as well as food retrieval and processing. Pheidole species vary in their diet, although many species gather seeds. The major workers mill the seeds using large jaws powered by mandible closer muscles that occupy a large proportion of the head cavity. In the present study, we examined the relationship between seed‐harvesting and morphology in Pheidole, hypothesizing that majors of seed‐harvesting species would have larger heads relative to non‐seed‐harvesters to accommodate the powerful mandibular muscles needed to mill seeds. By taking a phylogenetically controlled comparative approach, we found that majors of seed‐associated Pheidole did not have larger heads (width and length) than majors of non‐seed‐harvesting species. However, the head length of minors (and to a lesser extent head width) was smaller in seed‐harvesters. Additionally, we found the difference in head size between majors and minors was greater in seed‐harvesting species. These morphological differences in diet, however, were not related to changes in the rate of evolution in either seed‐harvesting or non‐seed‐harvesting lineages. These findings suggest that the morphologies of worker subcastes can evolve independently of each other, allowing colonies with polymorphic workers to specialize on new resources or tasks in ways not possible in monomorphic species.     

Serine and threonine residues of plant STN7 kinase are differentially phosphorylated upon changing light conditions and specifically influence the activity and stability of the kinase

STN7 kinase catalyzes the phosphorylation of the globally most common membrane proteins, the light‐harvesting complex II (LHCII) in plant chloroplasts. STN7 itself possesses one serine (Ser) and two threonine (Thr) phosphosites. We show that phosphorylation of the Thr residues protects STN7 against degradation in darkness, low light and red light, whereas increasing light intensity and far red illumination decrease phosphorylation and induce STN7 degradation. Ser phosphorylation, in turn, occurs under red and low intensity white light, coinciding with the client protein (LHCII) phosphorylation. Through analysis of the counteracting LHCII phosphatase mutant tap38/pph1, we show that Ser phosphorylation and activation of the STN7 kinase for subsequent LHCII phosphorylation are heavily affected by pre‐illumination conditions. Transitions between the three activity states of the STN7 kinase (deactivated in darkness and far red light, activated in low and red light, inhibited in high light) are shown to modulate the phosphorylation of the STN7 Ser and Thr residues independently of each other. Such dynamic regulation of STN7 kinase phosphorylation is crucial for plant growth and environmental acclimation.     

A Water‐Proof Triboelectric–Electromagnetic Hybrid Generator for Energy Harvesting in Harsh Environments

Packaging is a critical aspect of triboelectric nanogenerators (TENG) toward practical applications, since the performance of TENG is greatly affected by environmental conditions such as humidity. A waterproof triboelectric–electromagnetic hybrid generator (WPHG) for harvesting mechanical energy in harsh environments is reported. Since the mechanical transmission from the external mechanical source to the TENG is through a noncontact force between the paired magnets, a fully isolated packaging of TENG part can be easily achieved. At the same time, combining with metal coils, these magnets can be fabricated to be electromagnetic generators (EMG). The characteristics and advantages of outputs from both TENG and EMG are systematically studied and compared to each other. By using transformers and full‐wave rectifiers, 2.3 mA for total short‐circuit current and 5 V for open‐circuit voltage are obtained for WPHG under a rotation speed of 1600 rpm, and it can charge a supercapacitor (20 mF) to 1 V in 22s. Finally, the WPHG is demonstrated to harvest wind energy in the rainy condition and water‐flow energy under water. The reported WPHG renders an effective and sustainable technology for ambient mechanical energy harvesting in harsh environments. Solid progress in both the packaging of TENG and the practical applications of the hybrid generator toward practical power source and self‐powered systems is presented.     

Measuring potential negative effects of traditional harvesting practices on waterbirds: a case study with migrating curlews

Because of potential conflicts between commercial and conservation interests, one challenge in coastal-area management is how to regulate harvesting practices in coastal areas without adversely affecting the survival of migratory waterbirds. In most Spanish intertidal areas of importance for shorebirds, managers have concentrated only on stock management of the shellfish species. Here, we studied aspects of the foraging behaviour of Eurasian curlews Numenius arquata migrating through a Ramsar area in north Spain in the presence and absence of hand harvesters. We aimed to assess potential negative effects on curlews with a view to making coastal management recommendations that would help reduce conflict between local people and waterbirds. The average density of hand harvesters and foraging curlews at low tide was 0.56±0.09 persons per 10 ha and 16.47±0.73 birds per 10 ha, respectively. The presence of harvesters had a significant effect on foraging activity (no harvesting: 86.47±1.01%; harvesting: 82.70±1.00%). However, the absence of significant differences in all other foraging variables, between days with and without harvesting, indicated that curlews were able to compensate for the impact of harvesters on their foraging activity. We recommend, as a point of departure, that intertidal coastal managers of this Spanish site and similar areas of importance for shorebirds limit the harvesting load to <0.56 persons per 10 ha⁻¹ at least during autumn migration.     

Harvesting surface vegetation does not impede self‐recovery of Sphagnum peatlands

Ecosystem restoration frequently involves the reintroduction of plant material in the degraded ecosystem. When there are no plant nurseries or seeds available on the market, the plant material has to be harvested in the wild, in a “donor ecosystem.” A comprehensive assessment of donor ecosystem recovery is lacking, especially for Sphagnum‐dominated donor peatlands, where all top vegetation is harvested mechanically with different practices. We aimed to evaluate (1) the regeneration of vegetation, especially of Sphagnum mosses, to determine which harvesting practices are best to enhance recovery and (2) the influence of the site hydrological conditions and meteorological variables of the first complete growing season postharvesting on peat moss regeneration. Twenty‐five donor sites covering a 17‐year chronosequence (harvested 1–17 years ago) were inventoried along with 15 associated natural reference sites located in Quebec, New Brunswick, and Alberta, Canada. All donor sites aged 10 years or more were dominated by Sphagnum mosses, though plant composition varied between donor and their associated reference sites because of the wetter conditions at harvested donor sites. Harvesting practices strongly influenced donor site recovery, showing that the skills of the practitioner are an essential ingredient. Harvesting practices minimizing donor site disturbances are recommended, such as the choice of the adequate donor site (localization, hydrologic conditions, vegetation), the use of less disruptive methods, and harvesting when the soil is deeply frozen. This study demonstrated that harvesting surface plant material for peatland restoration is not detrimental towards the recovery of near‐natural peatland ecosystems.     

Fragmentation and separation analysis of the photosynthetic membrane from spinach

Membrane vesicles, originating from grana, grana core (appressed grana regions), grana margins and stroma lamellae/end membranes, were analysed by counter current distribution (CCD) using aqueous dextran-polyethylene glycol two-phase systems. Each vesicle population gave rise to distinct peaks in the CCD diagram representing different vesicle subpopulations. The grana vesicles and grana core vesicles each separated into 3 different subpopulations having different chlorophyll a/b ratios and PSI/PSII ratios. Two of the grana core subpopulations had a chlorophyll a/b ratio of 2.0 and PSI/PSII ratio of 0.10 and are among the most PSII enriched thylakoid vesicle preparation obtained so far by a non detergent method. The margin vesicles separated into 3 different populations, with about the same chlorophyll a/b ratios, but different fluorescence emission spectra. The stroma lamellae/end membrane vesicles separated into 4 subpopulations. Plastoglobules, connected to membrane vesicles, were highly enriched in 2 of these subpopulations and it is proposed that these 2 subpopulations originate from stroma lamellae while the 2 others originate from end membranes. Fragmentation and separation analysis shows that the margins of grana constitute a distinct domain of the thylakoid and also allows the estimation of the chlorophyll antenna sizes of PSI and PSII in different thylakoid domains.     

Collection strategies for quantifying protist assemblages in temperate headwater streams

We aimed at indicating some regularities of a constructed wetland treating agricultural runoff in China. The regularities, including the nitrogen removal capacity all year round, the nitrogen distribution pathways, and the nitrogen species removal kinetics, of a free water surface constructed wetland (2,800 m²) in the Dianchi Valley, which has been in operation for 27 months, were studied. The planted Phragmites australis and Zizania caduciflora were harvested biannually. The average inflow rate was recorded by an ultrasonic flow instrument, and then the hydraulic loading rate (HLR) and hydraulic retention time (HRT) were calculated. The average inflow and outflow concentrations of total nitrogen (TN), ammonia, and nitrate were measured, while the corresponding removal rates were calculated, showing better results than other constructed wetlands. Then the distribution pathways of nitrogen were analyzed, which indicated that plant harvesting was more important in wetland-treated agricultural runoff than in domestic wastewater. The reason for a good nitrogen removal capability and the obvious function of plants in the present wetland is the sound climate and intermittent inflow in the wetland. Results showed that inflow load had significant correction with both TN and ammonia removal efficiency. HLR, inflow rate, inflow nitrogen concentration, and temperature had significant and positive correction with both TN and ammonia removal. However, HRT had negative correction with both TN and ammonia removal, and the nitrate removal efficiency and parameters mentioned earlier were not significantly correlated. The rate constant values for nitrate and ammonia in summer were obviously larger than in winter. It is possible that bacterial and microbial activities were more active in summer than winter, and more conducive to bacterial and vegetative growth in summer than winter. Since this study was a pioneer for the implementation of constructed wetlands in China treating agricultural runoff, it has proved that this eco-technology could be used effectively for water quality enhancement in China and other areas with a similar climate.