Seasonal fluctuation, phenology and turnover of chafer assemblages – insight to the structural plasticity of insect communities in tropical farmlands

1 Studies on chafer assemblages were conducted on two farmland sites in the Terai lowland of Nepal (200 m above sea level) using light traps. During the course of a 2-year field monitoring program, a total of 4503 specimens was captured and an unexpectedly high number of syntopically co-occurring species was found: 52 from Gunganagar (GN) and 36 from Gaindakot (GK), respectively. Highest species abundances and species numbers were found during April and May.
2 Species occurrence was strongly correlated with air temperature and the maximum soil temperature, at least during the pre-monsoon season. However, assemblage structure from the two sites showed significant qualitative and quantitative changes seasonally, as well as from 1 year to the next. Turnover rates between adjacent months were in the range 26–62% (GN) and 37–70% (GK), whereas the turnover from 2004 to 2005 was 25.8% (GN) and 21.4% (GK) respectively.
3 When only dominant and subdominant taxa are considered, the seasonal change in species composition was even more striking.
4 Strong fluctuation in chafer assemblage over time suggests: (i) a possible influence of patchy habitat types and soil working on seasonal assemblage structure and (ii) colonization of suitable habitats (fields) in great part by chance.     

Patterns of forest insect distribution within a large city: microlepidoptera in St Peterburg, Russia

Short-scale distribution patterns of eight species and one species-group of forest moths with low migratory abilities were studied within the city of St Peterburg, Russia. For species of native fauna which have either completely ( Micropterix calthella L.) or partly ( Eriocrania spp., Stigmella spp.) vanished, at least in downtown, the city is considered as a lacuna within the primary distribution range. The opposite pattern (city as an island outside the primary area) was recorded for two invaders, Caloptilia syringella F. and Coleophora sibiricella Flkv. The distribution of Parornix scoticella Stt. was not altered by the city. Habitat fragmentation affected survival of populations of small moths by decreasing colonization rate more than by decreasing patch size. For eurytopic species limited mostly by host plant range (like Eriocrania ), lacunae can disappear if host plants are planted over the city; extinction of stenotopic species (like Micropterix ) or species with very limited dispersal (like Stigmella ) is practically irreversible. Changes in moth distribution in the city have a strong historical background; they can be both reconstructed and predicted.     

A sediment-based history of medium altitude forest in central Africa: a record from Kabata Swamp, Ndale volcanic field, Uganda

1 Sedimentary data from a 6-m long core from Kabata Swamp, an in-filled crater in the Ndale volcanic field of western Uganda, provided evidence for a number of cycles of disturbance and recovery of medium altitude forest.
2 The date of formation of the crater was earlier than an Accelerator Mass Spectrometry (AMS) radiocarbon date of 11 460 ± 90  bp (11 699–11 209 bc cal.) and thus appears to predate volcanism farther north in the Fort Portal area.
3 A form of medium altitude forest was already present in western Uganda by the later stages of the last ice age. A more diverse form of medium altitude forest was present from 11 460 ± 90  bp .
4 Some phases of disturbance of this forest during the Holocene could be correlated with established political–economic changes in the study area. One dated c. 2500  bp (768–542 bc cal.) could be associated with the entry of Bantu-speaking people. A second at 400 ± 60  bp ( ad  1419–1648 cal.) coincides with significant shifts in the focus of settlement from drier grassland to wetter, more forested parts.
5 Levels of biodiversity in forests in western Uganda remain relatively high, even after substantial modifications of vegetation cover over an extended period of time. Many central African forest taxa may therefore be able to cope with environmental change, including prolonged human impact.     

Mortality of zebra mussel, Dreissena polymorpha, veligers during downstream transport

1. Streams flowing from lakes which contain zebra mussels, Dreissena polymorpha , provide apparently suitable habitats for mussel colonization and downstream range expansion, yet most such streams contain few adult mussels. We postulated that mussel veligers experience high mortality during dispersal via downstream transport. They tested this hypothesis in Christiana Creek, a lake-outlet stream in south-western Michigan, U.S.A., in which adult mussel density declined exponentially with distance downstream.
2. A staining technique using neutral red was developed and tested to distinguish quickly live and dead veligers. Live and dead veligers were distinguishable after an exposure of fresh samples to 13.3 mg L⁻⁻¹ of neutral red for 3 h.
3. Neutral red was used to determine the proportion of live veligers in samples taken longitudinally along Christiana Creek. The proportion of live veligers (mean ± SE) declined from 90 ± 3% at the lake outlet to 40 ± 8% 18 km downstream.
4. Veligers appear to be highly susceptible to damage by physical forces (e.g. shear), and therefore, mortality in turbulent streams could be an important mechanism limiting zebra mussel dispersal to downstream reaches. Predictions of zebra mussel spread and population growth should consider lake-stream linkages and high mortality in running waters.     

Changes in movement, range and habitat preferences of adult grayling from late summer to early winter

Radio‐tagged adult grayling Thymallus thymallus ( n  = 22), monitored from mid August to mid December 1999 in the River Kuusinkijoki, Finland, shifted by the end of September (water temperature 10·0–14·5° C) from riffle sites to deeper and slower pool sites 0·7–1·6 km up‐ or downstream. In early winter ( c . 0° C water temperature), eight of 13 fish still under study made a further shift into new pool sites, possibly triggered by ice formation. The summer range of grayling in the riffles was smaller (mean ±  s . d . length: 75 ± 146 m) than the autumn range (99 ± 46 m) in the pools, but gross daily movements were equally short in both the seasons (18 ± 34 m and 15 ± 7 m, respectively). In late summer, adult grayling preferred water depths 80–120 cm and mean velocities >40 cm s⁻¹. In autumn, the preferred ranges were 100–240 cm and <30 cm s⁻¹, respectively. Substratum was mainly boulders in the summer sites, and gravel or pebbles in the autumn sites.     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.     

Elevation gradients of diversity for rodents and bats in Oaxaca, Mexico

1  This study documents patterns of rodent and bat diversity related to abiotic and biotic factors along elevational gradients in the Sierra Mazateca (640–2600 m a.s.l.) and Sierra Mixteca (700–3000 m a.s.l.) in Oaxaca, Mexico.
2  The two transects share similar faunas: 17 and 23 rodent species were captured in the sierras Mazateca and Mixteca, respectively, 14 of which occurred on both transects. Rodent species richness was similar in the wet season and the dry season along both transects. Rodent species richness peaked at 1025–1050 m in tropical semi-deciduous forest on both transects. Endemic species were restricted to high-elevation habitats.
3  Sixteen and 17 bat species were captured in the sierras Mazateca and Mixteca, respectively; 11 occurred on both transects. Bat species richness was higher in the wet season than in the dry season in the Sierra Mazateca. Bat species richness peaked at 1850 m in pine–oak forest in the Sierra Mazateca, and at 750 m and 1050 m in tropical semi-deciduous forest in the Sierra Mixteca, decreasing abruptly at higher elevations on both transects.
4  Patterns of trophic diversity of rodents and bats coincided with those of species richness on each transect. Species richness increased with increasing habitat diversity; increased with increasing rainfall and productivity; increased with increasing resource diversity; and increased in areas with high rates of speciation (rodents only).
5  The need for conservation action in Oaxaca is urgent and proponents should promote establishment of protected areas linking lowland habitats with high species richness to high-elevation habitats harbouring large numbers of endemic forms.     

Seasonal spatial dynamics and causes of nest movement in colonies of the invasive Argentine ant (Linepithema humile)

Abstract.  1. Colony organisation and movement behaviour of the Argentine ant ( Linepithema humile ) was studied over 3 years in field populations in California and in captive colonies in the laboratory. This invasive species is highly polydomous and unicolonial; colonies consist of expansive and fluid networks of nests and trails. The spatial and temporal organisation of colonies may contribute to ecological dominance.
2. Argentine ant nests and inter-nest trails shift in size, abundance, and location, so that colony networks are spatially contracted in the winter and expanded spring to autumn. Colonies occupy permanent sites; ants migrated to and from the same winter nest locations year after year, and occupied 30% of the same nests repeatedly during seasonal migrations.
3. Nests were moved on average 2–3 m. Forty-two per cent were occupied less than 1 month, 4% the entire study, and the other 54% lasted 3.9 ± 2.3 months (mean ± SD).
4. Nests were located within 2–4 m of woody plants, in warm sites in the winter and cool sites in the summer. Both humidity and food availability influenced nest-site choice in laboratory colonies. However, when faced with a trade-off between factors, the ants chose humid nest boxes over nest boxes near food, and ants moved nests only in response to changes in humidity and not distance to food.
5. The results indicate that L. humile colonies are seasonally polydomous, and that nest movements are driven by changes in microclimate. Colony organisation maintains high local density and increases food supply, which may improve the competitive ability of L. humile colonies and reduce opportunities for species coexistence.     

The effect of hind-tibial spurs on digging rate in female eastern cicada killers

Abstract.  1. The function of the large hind-tibial spurs of female eastern cicada killer wasps ( Sphecius speciosus ), thought to be adaptations to digging, was examined by measuring the effect of spurs on digging rate.
2. Spurs were removed from one group of wasps and left intact in control specimens.
3. Wasps with intact spurs removed soil from the burrow at a rate of 0.98 ± 0.11 (16) g dry mass min⁻¹ [mean ± SEM ( N )]. Removal of spurs results in an average digging rate just over one-half that, 0.54 ± 0.13 (9) g min⁻¹.
4. The difference in digging rate was primarily because of a twofold greater mass of soil unloaded by intact wasps each time they exited the burrow, rather than the rate at which such loads were delivered.
5. Such inefficiency results in an estimated additional 8.2 h requirement to fully excavate an average burrow, or a 1–4% reduction in time available for foraging in spur-ablated wasps.
6. Calculations suggest that the time lost to digging would result in a 3.9–19.5% reduction in foraging success for spurless females.
7. These temporal and resulting foraging advantages of hind-tibial spurs presumably provided selection pressure for their evolution from smaller, pre-existing setae.     

Coastal–marine discontinuities, critical patch size and isolation: implications for marine otter conservation

The consequences of habitat fragmentation include reduced habitat availability, increased isolation and patch extinction. This study investigates the occupancy patterns of Lontra felina , a little known and endangered marine otter, on naturally discontinuous habitat and the relationship between otter occupancy and rocky seashore patches, patch size and isolation and human influences. Marine otter occupancy was determined through direct sightings and the presence/absence of spraints, and measured by logistic regression and general linear models. The study was conducted in Chile between 28°S and 40°S, and consisted of eight study sites. Within these sites, a total of 23 rocky seashore patches, 2.3–63.8 km long, were surveyed from January 2005 to March 2006. The strongest predictors of marine otter occurrence were rocky seashore patches larger than 5 km long and <6 km apart. These networks should be no farther than 20 km from contiguous (without sandy beaches) rocky seashore patches over 15 km long.     

Floristics of the Dunbar Valley serpentinite site, Songimvelo Game Reserve, South Africa

The Dunbar Valley serpentinite outcrop has a flora comprising 254 taxa (species and below) in 172 genera and 63 families. Dunbar Valley has more species than other studied serpentinite sites in the Barberton Greenstone Belt (BGB). The genus Senecio is the most speciose genus in the BGB. The level of species endemism at Dunbar Valley is 2.0%. Most of the serpentinite endemics in the BGB show phytogeographical affinities with the Sudano-Zambezian Region. Six modified-Whittaker plots, three on serpentinite and three on non-serpentinite soils, were sampled. Sørenson's index was 0.312, indicating low similarity in species between serpentinite and non-serpentinite sites (β-diversity) at Dunbar Valley, as at other sites in the BGB. α-diversity (using the Shannon–Wiener index) for the serpentinite was 2.631 ± 0.901 and for the non-serpentinite, 2.886 ± 0.130. However, a Student's t -test showed no significant difference in α-diversity between the two habitats. There was also no significant difference in species richness between serpentinite and non-serpentinite sites. Total species showed negative correlations with total nickel, altitude and serpentinite outcrop size (area) for six sites in the BGB. Number of endemic taxa showed no correlation with environmental variables.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 271–285.     

Foraging trip duration of bumblebees in relation to landscape-wide resource availability

Abstract.  1. The study tested the hypotheses that bumblebees have shorter foraging trips in environments that provide abundant resources than in environments that provide sparse resources, and that shorter foraging trips translate into greater colony growth.
2. Six even-aged Bombus terrestris colonies were established in contrasting resource environments. Three colonies had access to abundant resources ( Phacelia tanacetifolia fields with high flower densities), and three colonies were placed in an environment with sparse resources (scattered semi-natural habitats with food plants at lower densities).
3. A total of 870 foraging trips of 220 marked B. terrestris foragers were observed using automated camcorder recordings.
4. The duration of foraging trips was shorter in environments with abundant resources (66 ± 4.6 min) than in environments with sparse resources (82 ± 3.7 min). Within 34 days colonies that had access to abundant resources gained significantly more weight (129 ± 40 g) than colonies foraging on sparse resources (19 ± 7 g).
5. Thus, the spatial distribution and quality of resources at landscape level affected the duration of foraging trips and the colony growth. It was concluded that future conservation schemes need to improve the spatial and temporal availability of resources in agricultural landscapes to counteract the ongoing decline of bumblebees.     

Bacterial diversity associated with the Brazilian endemic reef coral Mussismilia braziliensis

Aims:  We performed the first characterization of the microbiota associated with the reef coral Mussismilia braziliensis by means of a culture-independent approach.
Methods and Results:  The main groups were Proteobacteria , Cyanobacteria and unclassified bacteria according to the 16S rDNA libraries. Most of the sequences of the mucus of healthy and diseased M. braziliensis did not find close matches in GenBank (i.e. >97% 16S rDNA similarity). Most of the sequences of seawater and mucus of healthy coral fell into tight clusters (17 and 15 clusters respectively). In contrast, most of the sequences of mucus of diseased coral did not form clusters. The rarefaction curves indicate saturation in the recovery of higher taxa (approximately 40 phyla). However, the number of species in the coral mucus ( n  = 130–170) and seawater ( n  = 170) did not reach a plateau.
Conclusions:  The coral microbiota encompasses several potentially novel species and higher taxa. The microbiota of M. braziliensis appears to be species-specific. Diseased coral may have provided a suitable place for colonization by opportunistic bacteria, resulting in a greater bacterial diversity.
Significance and Impact of the Study:  The first study on the diversity of the microbiota of the endemic and endangered of extinction coral M. braziliensis .     

Uptake and persistence of human associated Enterococcus in the mussel Mytilus edulis: relevance for faecal pollution source tracking

Aims:  Micro-organisms and molecular markers for microbial source tracking (MST) in coastal waters are often present at low numbers, and often exhibit significant variability in time and space. In this study, we investigated the uptake, accumulation, and persistence of human associated Enterococcus in the mussel Mytilus edulis .
Methods and Results:  The human associated molecular markers esp in Enterococcus faecium , and M66 in Enterococcus faecalis were targetted by PCR in seawater and mussel samples from coastal sites affected by sewage contamination. Both native mussels and mussels transplanted from pristine to polluted sites were included. The results showed that the esp and M66 markers were often not detectable in seawater whereas mussels were enriched in the markers. Human associated E. faecalis accumulated rapidly in M. edulis , and reached maximum levels after 4–6 h with concentration 30–300 times greater than in the surrounding seawater. Enterococcus faecalis retained in M. edulis showed a survival comparable to planktonic E. faecalis in seawater with half lives of 30 and 22 h, respectively. Human associated markers remained detectable for 120 h in M. edulis after faecal contamination.
Conclusions:  The study demonstrated that native and transplanted M. edulis can accumulate and retain human associated molecular markers relevant for MST.
Significance and Impact of the Study:  Mussels should be considered as additional targets in MST studies in coastal waters.     

Higher productivity at the cost of increased host-specificity when Maculinea butterfly larvae exploit ant colonies through trophallaxis rather than by predation

Abstract .1. Field studies were made of the benefits and costs of two feeding strategies in the genus Maculinea, whose final-instar larvae parasitise Myrmica ant colonies. Maculinea arion is an obligate predator of ant brood, whereas M. rebeli and M. alcon mimic ant larvae and are fed (like cuckoos) directly by the workers.
2. Samples of > 1500 Myrmica nests confirmed laboratory-based predictions that, by feeding at a lower trophic level, many (4.7-fold) more individuals of M. rebeli and M. alcon are supported per ant colony than M. arion.
3. Because of their efficient feeding, cuckoo species often occupied sites where their phytophagous early larval populations coincided to only a small extent (> 10%) with host Myrmica colonies, whereas all sites supporting M. arion had 50–100% of the phytophagous stages within foraging range of the host Myrmica species.
4. Greater host-specificity was identified as another consequence of cuckoo-feeding. The ecological cost of this is discussed .
5. The feeding of other Maculinea species had not been fully described: the data suggest that M. nausithous is a predator of ant brood and confirm that M. teleius is predacious .     

The role of habitat composition in determining breeding site occupancy in a declining Ring Ouzel Turdus torquatus population

Ring Ouzel Turdus torquatus breeding site occupancy in the Moorfoot Hills, southeast Scotland, was determined during the periods 1952–85 and 1998–2000, and sites were classed as either occupied or deserted during the latter period. Site occupancy during 1998–2000 was related to habitat data derived from a supervised classification of a Landsat 7 satellite image. Breeding sites were more likely to have remained occupied if they were at higher altitudes and had more heather cover within radii of both 200 and 450 m, although these effects became non-significant when spatial autocorrelation was accounted for. Using only topographical variables, potential breeding sites were predicted and the habitat surrounding them was compared with actual breeding sites. Actual breeding sites were more likely to have heather or grass–heather mosaic within 100 m than potential breeding sites, but there were no further habitat differences between actual and potential breeding sites within radii of 200 or 450 m. These results indicate that breeding sites at higher altitudes and with a higher cover of heather were less likely to have been deserted, and that lack of heather may prevent otherwise suitable breeding sites from becoming occupied by Ring Ouzels. More detailed field studies are needed to understand the mechanisms underlying these associations.     

Amplitude of ecological potential: chub Leuciscus cephalus (L.) spawning in an artificial lowland canal

Chub Leuciscus cephalus (L.) is a rheophilic cyprinid which prefers lotic habitat conditions, shallow water (0.1–0.3 m) and gravel banks with moderate to high water flow (0.15–0.75m s^–1) for spawning. In contrast to these spawning requirements, a self-sustaining chub population was detected in a German lowland canal, the Oder–Havel Kanal. This canal is monotonously embanked with rip rap and almost completely lacks water flow and habitats that are suitable for riverine species. In 1999 chub spawned in the absence of water flow, in depths up to 1.28 m on allochthonous gravel with a mean diameter of 39 ± 16 mm (SD). These findings indicate a substantially higher environmental plasticity and tolerance of chub than previously reported.     

Seasonal changes in the habitat use and movements of adult European grayling in a large subarctic river

In late summer (13 August–13 September 1998), at water temperatures of 12·0–15·7° C, grayling ( n =14) stayed mainly in the riffle-section where they were captured in a large regulated river in northern Finland, moving little between consecutive days. In autumn (2–30 October 1998), at 1·7–6·7° C, the fish ( n =16) migrated to potential overwintering sites 0–14 km up- or downstream by mid October, moving mainly short distances thereafter. The daily movement rates, and the total ranges covered by the fish in late summer and autumn were 54±32 m (mean± s.d ) and 1053±1636 m, and 190±168 m and 3135±1850 m, respectively. In autumn the fish used deeper habitats (most suitable range 150–400 cm) with lower current velocities (20–80 cm s⁻¹) and finer bottom substrata (mainly sand) than in late summer (depth 100–325 cm, velocity 30–110 cm s⁻¹, and cobble-boulder substrata).