An experimental examination of the effects of habitat quality on the dispersal and local abundance of the butterfly Parnassius smintheus

Abstract 1. Nectar flower abundance was manipulated through flower removal, and sex ratio was manipulated by moving individual butterflies within a series of nine alpine meadows. The movement and abundance of the butterfly Parnassius smintheus in the meadows were monitored using mark–release–recapture methods.
2. A total of 937 butterflies, 698 males and 239 females, was captured. There were 223 observed between-meadow movements. Fifty-two per cent of males and 35% of females moved among meadows.
3. The immigration of male butterflies was related positively to nectar flowers, host plant abundance, and female butterflies. Male emigration was not affected by any of the treatments. The number of males captured was related positively to nectar flowers and host plants but not affected by sex ratio. The number of resident male butterflies was greater in meadows containing flowers and was related positively to host plant abundance, but unaffected by sex ratio.
4. Flower removal, sex ratio, and abundance of Sedum had no significant effect on the abundance, movement, or residence time for female butterflies, in part due to small sample size.
5. The fact that males immigrate to higher quality meadows suggests that male butterflies are assessing meadow quality, either by sampling meadows or potentially from a distance using olfactory cues.     

The demography of coarse wood in north temperate lakes

1. Exchange of material across habitat boundaries is a key process in riparian zones. The movement of coarse wood from lakeshore forests to the littoral zone, where it provides habitat for aquatic organisms, is not well understood. In 2003, we resampled coarse wood within the littoral zone of four lakes in Northern Wisconsin (U.S.A.), that had originally been surveyed in 1996, to quantify the spatial arrangement of littoral coarse wood and estimate input, loss and movement rates.
2. All four lakes had a clumped pattern of littoral coarse wood, and the locations of clusters were similar in both census years. Littoral coarse wood was more abundant than expected on moderate to steep slopes, on southern shorelines, and in areas with sparse residential development.
3. All four lakes had a net accumulation of coarse wood; rates of wood input ranged from 0.5 to 1.9 logs km⁻¹ year⁻¹, i.e. there was more wood in 2003 than 1996. Movement rates of tagged logs varied 14-fold among lakes, with a maximum in one lake of 42% of logs recovered in 2003 more than 20 m from their 1996 location. Median distance moved ranged from 22 to 323 m among the four lakes.
4. Areas of persistently high wood density may be keystone habitats whose presence enables the persistence of populations of certain aquatic organisms. Conservation of locations with high wood density may be important to maintain target densities of coarse wood of lakes with human development.     

Experimental investigations of diel vertical movements by lotic mayflies over substrate surfaces

SUMMARY. 1. The vertical distribution within the substrate of three lotic mayflies (Rhithrogena sp., Paraleptophlebia sp. and Baetis tricaudalus Dodds) was examined in laboratory streams to determine if diel patterns of vertical movement across substrate surfaces existed and whether light intensity, temperature, substrate composition or food availability influenced the observed movement patterns.
2. Rhithrogena sp. and B. tricaudatus exhibited significant diel movement from lower substrate surfaces during the day to upper surfaces at night, although >64% of B. tricaudalus occupied the upper surfaces throughout the 24 h period. In contrast, Parakplophlebia sp. larvae did not change their vertical distribution over the 24 h period.
3. The proportion of mayflies occupying substrate surfaces was influenced by the amount of upper and lower surface area available in the substrate and, possibly, crevice sizes associated with lower surfaces.
4. The movement of Rhiihrogena sp. from lower surfaces during the day to the upper surfaces during the night was influenced by changes in light intensity, but not by changes in food availability or water temperature.
5. The diel patterns of vertical movement exhibited by lotic mayflies in this investigation raise the possibility that at least some biotic interactions may vary over a diel cycle. These could include competitive interactions or temporal cycling of prey availability to predators.     

Scattered trees: a complementary strategy for facilitating adaptive responses to climate change in modified landscapes?

1.  Facilitating adaptive responses of organisms in modified landscape will be essential to overcome the negative effects of climate change and its interaction with land use change. Without such action, many organisms will be prevented from achieving the predicted range shifts they need to survive.
2.  Scattered trees are a prominent feature of many modified landscapes, and could play an important role in facilitating climate change adaptation. They are keystone structures because of the disproportionally large ecological values and ecosystem services that they provide relative to the area they occupy in these landscapes. The provision of habitat and connectivity will be particularly relevant.
3.  Scattered trees are declining in modified landscapes due to elevated tree mortality and poor recruitment often associated with intensive land use. The continuing global decline of scattered trees will undermine the capacity of many organisms to adapt to climate change.
4.   Synthesis and applications. The sustainable management of scattered trees in modified landscapes could complement other strategies for facilitating climate change adaptation. They create continuous, though sparse, vegetation cover that permits multi-directional movements of biota across landscapes and ecological networks. They have the capacity to span ecosystems and climatic gradients that cannot be captured in formal reserves alone. The management of scattered trees should be an integral part of conservation objectives and agricultural activities in modified landscapes. Public investment, through mechanisms such as agri-environmental schemes, in rotational grazing, temporary set-asides, tree-planting and regulations that reduce clearing and early mortality among standing trees will improve the capacity of biota to adapt to climate change.     

Flight activity of adult stoneflies in relation to weather

Abstract. 1. Dispersal of adult aquatic insects between streams may have important consequences for local and regional population dynamics, but little is known about how dispersal is affected by weather conditions.
2. The influence of meteorological variables on flight activity of adult stoneflies (Plecoptera: Leuctridae, Nemouridae, and Chloroperlidae) was investigated using Malaise traps adjacent to three upland streams in the Plynlimon area of mid Wales, U.K.
3. Numbers of adult stoneflies captured weekly in the traps were related positively to air temperature and related negatively to wind speed. Meteorological conditions during daylight showed stronger relationships with flight activity than did conditions at night.
4. There was inter-site variation in the strength of weather effects on stonefly flight. Wind speed was significant at only one site, which had higher average wind speed than the other sites.
5. Annual variation in weather conditions during adult flight periods may result in varying extent of dispersal between sites, influencing community dynamics over a wide area.     

Tidal movements of shallow water fishes in Kuwait Bay

The intertidal migrations of shallow water fishes in Kuwait Bay were studied during two 24 h periods using an otter trawl. Most species wereconcentrated at a location corresponding to Low Low Water mark. At the other tidal levels some fishes migrated with the tide to High High Water mark through a horizontal distance of up to 2 km. Any effect of day and night on the catch was masked by the effect of tidal condition.
Leiognarhus decorus (de Vis) was typically concentrated at Low Water but a proportion of the population followed the rising tide toward the shore. There was a die1 effect whichmay have been due to fish moving to shallower water at night compared with the day. Length-frequency distribution changed slightly with tidal state so that larger fish were not captured at High Water during the day. Of the fishes captured at high tide, the largest individuals of L. decorus were captured at a depth of 2.0 m deep. Solea elongata Day did not migrate with tidal fluctuations and was captured in large numbers only at Low Water. Arius tenuispinis Day was captured in shoals at or around Low Water.     

Field studies of foraging behaviour of an intertidal beetle

Abstract. 1. Adult staphylinid beetles Thinopinus pictus LeC. are noct turnal predators of sand beach amphipods, Orchestoidea califomiana (Brandt). I made continuous observations of Thinopinus near the drift patches on which amphipods feed.
2. Thinopinus alternated between active and ambush foraging modes.
3. Thinopinus had greater attack rates and captured smaller amphipods while in active foraging mode.
4. Thinopinus attacked 0.147 amphipods/min, and captured 9.1% of the amphipods attacked. The attack rate on amphipods increased with the proportion of time spent by Thinopinus in active mode.
5. Thinopinus remained longer near types of drift patches which were more attractive to amphipods.     

Radiotelemetry reveals differences in individual movement patterns between outbreak and non-outbreak Mormon cricket populations

Abstract.  1. Outbreaks of insect pest populations are common and can have devastating effects on natural communities and on agriculture. Little is known about the causes of these outbreaks or the causes of en masse migrations during outbreaks.
2. Flightless Mormon crickets ( Anabrus simplex ) were the focus of this study. They are a katydid species that forms large, dense, mobile groups (migratory bands) during outbreak periods, eating vegetation in their path.
3. Radiotelemetric methods were used to measure differences in movement rate and directionality in outbreak and non-outbreak populations, testing the hypothesis that these populations differ in their travel rate and consistency of direction.
4. Daily individual movement in outbreak populations differs substantially from non-outbreak populations that are at much lower density. In addition to large differences in distances travelled (1.6 km as compared with 1 m) and rates of travel, there is evidence for collective movement among individual Mormon crickets travelling in migratory bands.
5. These data suggest that the direction of group movement may be influenced by local environmental conditions such as wind direction and movement of nearby band members. This work forms the basis for ongoing work testing hypotheses about mass migrations in outbreak populations.     

Seasonal variation in vertical and horizontal movement of the freshwater bivalve Elliptio complanata (Mollusca: Unionidae)

1. Vertical and horizontal movement were studied in the freshwater bivalve Elliptio complanata at a sandy site in an oligotrophic lake over 3 years. Mussel movement did not vary significantly between day and night. On average, between 2 and 8% of 527 mussels moved each month during the ice-free season and the distance travelled by moving mussels averaged 0.6 cm day^–1.
2. Mussels were endobenthic during the winter, emerged from the sandy substrate in mid-May, peaked in sediment surface abundance in July, and descended into the sediments for the winter in September–October. Vertical displacement of mussels was closely correlated with water temperature although daylength may play a role. Mussels apparently move very little beneath the sediment during the winter.
3. The number of mussels moving horizontally at any given time was linearly correlated with daylength, but the distance travelled during a sampling period was related to daylength in a non-linear fashion. Greatest horizontal displacement of epibenthic mussels was found during spring and early summer, coincident with spawning in E. complanata     

Seasonal variation in vertical and horizontal movement of the freshwater bivalve Elliptio complanata (Mollusca: Unionidae)

1. Vertical and horizontal movement were studied in the freshwater bivalve Elliptio complanata at a sandy site in an oligotrophic lake over 3 years. Mussel movement did not vary significantly between day and night. On average, between 2 and 8% of 527 mussels moved each month during the ice-free season and the distance travelled by moving mussels averaged 0.6 cm day^–1.
2. Mussels were endobenthic during the winter, emerged from the sandy substrate in mid-May, peaked in sediment surface abundance in July, and descended into the sediments for the winter in September–October. Vertical displacement of mussels was closely correlated with water temperature although daylength may play a role. Mussels apparently move very little beneath the sediment during the winter.
3. The number of mussels moving horizontally at any given time was linearly correlated with daylength, but the distance travelled during a sampling period was related to daylength in a non-linear fashion. Greatest horizontal displacement of epibenthic mussels was found during spring and early summer, coincident with spawning in E. complanata     

Interactions of the ant Crematogaster scutellaris with the fig/fig wasp mutualism

Abstract. 1. A classical example of specialised pollination mutualisms is the relationship between fig trees and their pollinating wasps, in which each partner depends completely on the other for its reproduction; however the fig/fig wasp association is also the target of a great diversity of other species, ranging from specialised parasites to opportunistic foragers, among them ants.
2. The ant community and the sources of ant attraction observed on the Mediterranean fig tree Ficus carica were characterised.
3. A guild of ants attracted by homopterans tended on the plant was distinguished from a second guild composed of two co-dominant ant species ( Crematogaster scutellaris and Pheidole pallidula ) that prey mostly on pollinating wasps, abundant during certain parts of the fig cycle.
4. Foraging workers of C. scutellaris search for prey on the fig inflorescence (syconium), capturing pollinating wasps mostly at the peak of wasp emergence and at a rate estimated to reach 600 prey per day for an entire tree.
5. Detailed study of the predatory sequences displayed under experimental conditions showed that ant workers captured 100% of the pollinating wasps offered, while they captured only 5.5% of the parasitoid wasp specific to the pollinator. The respective impacts of the interaction on ants and on the figs are discussed, as well as several behavioural traits of predation by the dominant ant on pollinators.     

Locomotion in Elliptio complanata (Mollusca: Unionidae): a reproductive function?

1. Temporal variation in the spatial aggregation of the freshwater bivalve Elliptio complanata was studied at a sandy site in an oligotrophic lake over three years.
2. Epibenthic populations varied in aggregation over the season bringing animals closer together during spawning. The complex link between movements of mussels and aggregation dynamics suggested a functional reproductive role for horizontal locomotion of unionid mussels in lentic systems.
3. The rate of locomotion did not differ systematically among males, females or hermaphrodites, and was independent of gravidity, whether compared during spawning, after spawning or throughout the ice‐free season.
4. In spite of the high reproductive output of mussels and the energetic cost of locomotion, no relationship was found between the rate of movement of spawning gravid mussels and reproductive output.     

Mechanisms of predator accumulation in a mixed crop system

Abstract. 1. In a previous study, Orius tristicolor (White), a generalist predator of soft-bodied insects and mites, invaded patches with a mixed plant assemblage at a faster rate than it did single-species stands. This study was designed to determine experimentally the underlying mechanisms of predator movement patterns that cause more intense colonization of crop mixtures.
2. Plots were established in a randomized complete block design. Treatments reflected different components of mixed crop patches: species richness, plant density, colour contrast, structural complexity, and volatile plant compounds.
3. O. tristicolor colonists were more abundant on squash intercropped with corn and cowpea than in squash monocultures even though early season prey densities were similar. Initial accumulation of the generalist predator was also higher in densely planted monocultures and in monocultures with artificially enhanced structural complexity than in normally-spaced squash monocultures.
4. Therefore, mechanisms underlying rates of predator colonization in a stand initially depended upon aspects of plant architecture and density and were independent of prey density and plant diversity. O. tristicolor densities at the end of the colonization period, however, were greater on squash ( Cucurbita pepo L.) in polyculture than in any other treatment.
5. These results suggest that attributes of the vegetation can influence the colonization rates of interacting organisms on different trophic levels and thus can alter predator-prey interactions and the development of community structure.     

The Fungal and Bacterial Flora of Stored White Cabbage

1. The predominant organisms isolated from the outer wrapper leaves of freshly harvested white cabbages were: bacteria, yeasts, Alternaria spp., Aureobasidium pullulans, Botrytis cinerea, Cladosporium spp. and Penicillium spp.
2. Few qualitative or quantitative changes were seen in the leaf surface flora during storage at 2°C for up to 33 weeks.
3. Numbers of bacteria, particularly fluorescent and pectolytic pseudomonads, were considerably higher on cabbages drenched with fungicide or water than on corresponding undrenched cabbages.     

Patterns of abundance, distribution, and alary polymorphism among the salt marsh Delphacidae (Homoptera: Fulgoroidea) of Northwest Florida

Abstract. 1. The species of Delphacidae captured in nearly 16000 sweeps of salt marsh vegetation in Northwest Florida, U.S.A., are examined. Individuals belonging to fourteen species were captured during the 15-month study, a somewhat larger number than is found in most locations.
2. Abundances ranged from one to 1064 individuals per species. The abundances, habitat preferences, and patterns in wing-polymorphism among the species collected were similar to those reported previously from other locations, but important differences were found which reflect the vegetational composition typical of our study area.
3. Wing-morph ratio differences between delphacid populations may reflect strategies for dealing with differences in stability and distribution of their respective habitats. The ratio of macropter/brachypter individuals in various populations of delphacids investigated correlates with the probability that a dispersing individual will find a more suitable habitat patch. The phenomenon is illustrated with a comparison of wing-morph ratios in populations of Prokelisia marginata (Van Duzee) from locations which differ in the extent, distribution, and stability of their stands of Spartina alterniflora Loisl. (smooth cordgrass), the common host of P.marginata .
4. Macroptery is favoured in Atlantic Coast marshes, where habitat patches are differentially suitable, but extensive and predictable. The probability of finding a better patch by dispersing is therefore high.
5. Brachyptery predominates at Cedar Key, Florida, where habitat patches are extensive, stable, and equally suitable during most of the year; and at St Marks, Florida, where resource patches are small, infrequent, isolated, and regularly disturbed. Under these conditions, the probability of finding a better patch by dispersal is low.
6. The conditions at St Marks may have promoted a local host expansion by P.marginata at this location.     

Effects of eutrophication on seasonal patterns of mesozooplankton in a tropical reservoir: a 4‐year study in Pampulha Lake, Brazil

1. Pampulha Lake has undergone rapid eutrophication. Annual maxima of total phosphorus and conductivity increased steadily from 1993 to 1996. Nitrogen quickly decreased after macrophyte removal in 1994, but increased again in the following years
2. The zooplankton was dominated by Daphnia gessneri , D. laevis , Diaphanosoma birgei and Thermocyclops decipiens . The biomass of major zooplankton organisms, including Daphnia and rotifers, increased during the period covered in this study.
3. Autocorrelation coefficients have confirmed the existence of recurrent seasonal patterns for both chemical and biological variables.
4. Daphnia , calanoid copepods and rotifers showed clear and recurrent seasonal patterns. Cyclopoid copepods and Diaphanosoma had temporal patterns more affected by long‐term trophic changes. Other organisms such as Moina, Ceriodaphnia and Bosmina exhibited high temporal variability with no recurrent patterns.
5. There was a strong and positive correlation between total phosphorus and Daphnia biomass. Seasonal patterns of this cladoceran were also inversely associated with sestonic C:P ratios. Thus, Daphnia may be limited primarily by phosphorus and not by total food availability as expressed by particulate carbon.
6. This study suggests that increasing eutrophication has changed the structure as well as seasonal patterns of the zooplankton community in Pampulha Reservoir.     

Movement patterns of the bush cricket Platycleis albopunctata in different types of habitat: matrix is not always matrix

Abstract.  1. Inter-patch movement is usually assumed to be homogeneous across a landscape. As the intervening area between suitable patches is usually richly textured, it cannot be assumed to be uniform in real landscapes.
2. In an experimental mark-and-resight study, the movement behaviour of the bush cricket Platycleis albopunctata in four habitat types as well as at the border between two of these habitat types was observed.
3. Analysis of recapture data indicated differences in mortality risk (or emigration rates) between habitat types.
4. When released at the border between suitable habitat and a crop field, P. albopunctata did not show a consistent preference for the suitable habitat. This suggests that the crop field is at least temporarily attractive for P. albopunctata .
5. Movement in suitable habitat was not always different from movement in the matrix, and movement between different types of matrix also differed.
6. The results indicate that the movement behaviour of P. albopunctata is influenced not only by suitability for breeding but also by structural resistance and other factors (e.g. food availability or habitat-specific mortality risk).     

The independent and interactive effects of fine sediment and flow on benthic invertebrate communities characteristic of small upland streams

SUMMARY 1. Floods are an important mechanism of disturbance operating in streams that can markedly influence the abundance and diversity of benthic fauna. In upland streams many studies cite the scouring effects of fine transported sediments as a potential source of disturbance to the biota during spates, but few studies have sought to test this hypothesis critically.
2. Here we used a series of eight artificial streams to test whether high suspended-sediment concentrations influenced the short-term response of benthic invertebrate fauna to increases in flow. In an experiment designed to simulate a small spate, flow and sediment loads were each manipulated to examine their independent and interactive effects. Benthic invertebrates were sampled before and after the manipulation, and drift samples were taken at regular intervals during the experiment. The experiment was repeated twice, once at the end of winter (June, 1998), and once in summer (February, 1999).
3. Flow increases caused large increases in the number and diversity of drifting animals, and significant declines in the numbers and diversity of organisms found in benthic samples, but these declines were apparently not affected by the addition of fine sediment. The addition of sediment alone had little effect on the fauna. These results were consistent across both experiments.
4. The results suggest that flow increases alone can disturb benthic fauna, and that neither substrate movement nor suspended sediment increases are necessary for floods and spates to disturb the benthic assemblage. However, as argued elsewhere, the effects of flow increases are likely to be contingent upon the presence or absence of local flow refugia, which can allow animals to escape the shear forces that would otherwise remove them from the surface or interstitial areas of the streambed.     

Pheromone response and sexual behviour of Cephalcia lariciphila Wachtl (Hymenoptera: Pamphiliidae)

Abstract. 1. Trapping experiments and observations of sexual behaviour were made on Cephalcia lariciphila in infested larch forests in Hereford and Worcester and Mid-Glamorgan in early May 1977.
2. The results indicated that virgin females and dichloromethane extract of crushed virgin females were highly attractive to males.
3. On 17 May males responded to females throughout the warmest part of the day. First response occurred before 09.00 hours, the last after 17.00 hours and peak activity was from 11.00 to 14.00 hours.
4. Mated females became unattractive to males within 10 min after mating. When mated females or males were paired with virgin females there was no evidence of an anti-attractive pheromone or pheromone mask.
5. A few males dispersed out of larch into adjacent spruce forests and were captured in virgin female-baited traps up to 135 m distant from infested larch. Virgin female-baited traps at 0–0.5 m from the ground captured over seven times the number of males as traps at 1, 2 or 4 m, supporting visual observations that the preferred flight level for males is very near the ground.
6. Horizontal board traps with an acetate surface coated with 'Stikem Special' were superior to Pherocon IC, vertical board and gypsy moth traps in that order.
7. The observations and results suggest that the best applied uses of C. lariciphila pheromone would be in survey and detection, and male disruption techniques.     

A seasonal sequence of diel distribution patterns for the planktonic dinoflagellate Ceratium hirundinella in a eutrophic lake

SUMMARY. 1. Diel depth distribution patterns of Ceratium hirundinella were studied during eleven sampling periods, covering the seasonal growth cycle. They were shown to result from short-term periodic or non-periodic external factors, endogenous responses of the alga, and interactions between these.
2. Diel variations in wind stress resulted in the net transport of algae into or out of the sampling position due to lateral water movements. A progressive surface accumulation of Ceratium , leading to a 3-fold increase in cell numbers at the sampling site over a 24 h period, was due to wind-induced upwelling of deeper cells. Near-surface accumulation of Ceratium on a completely overcast afternoon, similar to that associated with migrations, was attributable to advection.
3. Under sufficiently calm conditions, depth-differentiation of Ceratium was regulated by its vertical swimming movements with a diel periodicity. Migration patterns observed in earlier work were confirmed and extended. The alga migrated towards the surface during the daytime and downward during the night; this rhythm had an endogenous component.
4. At high surface illumination, the alga retreated from the surface and formed discrete sub-surface maxima; at low irradiance Ceratium showed positive phototaxis and concentrated near the surface. Under either condition of irradiance Ceratium actively aggregated at depths associated with irradiance levels of about 125–155 μEinsteins m ⁻² s ⁻¹. Downward movement was restricted by anoxic conditions and possibly by thermal/ density gradients. However, given sufficient light penetration, dissolved oxygen and nutrient availability, the thermal density gradient does not apparently eliminate downward movement by Ceratium.