bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foraging ecology and patterns of diversification in dipteran parasitoids of fire ants in south Brazil
Authors: ORR MATTHEW , SEIKE SERGIO , GILBERT LAWRENCE 
Published: November 2003

1. At least sixteen species of parasitoid flies in the genus Pseudacteon (family Phoridae) attack fire ants in the Solenopsis saevissima subcomplex in South America. Little is known of behavioural or ecological differences among Pseudacteon parasitoids of fire ants, although their coexistence in multispecies communities would suggest that important differences exist. Seven Pseudacteon species in two separate communities were studied in south‐east Brazil. The way in which hosts detect and respond to the presence of parasitoids, attack rates of the parasitoids, and host location behaviour of the parasitoids were examined.2. Reductions in fire ant recruitment were more closely related to the number of ants attacked along a foraging trail than to the amount of time that a phorid was present.3. Pseudacteon solenopsidis differed from other phorid species by flying backwards while pursuing ants, by attacking at lower rates than other phorids, and by spending longer around fire ant foraging trails than other phorids before departing. Fire ant recruitment to food often rebounded in the continued presence of P. solenopsidis.4. In each of the two communities, certain Pseudacteon species appeared frequently at Solenopsis foraging trails, whereas others appeared predominantly at mound disturbances. Two distinct size classes of phorids were present in each community, and the community with the larger ant host species also had a third and larger phorid species. No phorid species from the same community had similar body sizes and similar host location behaviours, although numerous species from different communities shared both of these traits.5. Heterogeneity in host size and in the ecological circumstances under which hosts are vulnerable to attack appears to have influenced the evolution and perhaps maintenance of diverse Pseudacteon communities.
Three ways of assessing metapopulation structure in the butterfly Plebejus argus
Authors: LEWIS OWEN , THOMAS CHRIS , HILL JANE , BROOKES MARTIN , CRANE T. P. , GRANEAU YVONNE , MALLET JAMES , ROSE OWEN 
Published: November 2003

1. Three independent methods were used to investigate population structure in the butterfly Plebejus argus. First, migration and dispersal ability were measured by mark–release–recapture in seven adjacent habitat patches, and by release of butterflies in unoccupied habitat. Secondly, colonization of newly created habitat was observed over 7 years. Finally, genetic differentiation of local populations within a metapopulation was investigated. Sampled local populations included parts of the mark–release–recapture study area.2. Plebejus argus is relatively sedentary: the maximum movement detected was 395 m, and only 2% of individuals moved further than 100 m between recaptures on different days. None the less, adjacent local populations in the mark–release–recapture study area were linked by occasional migration, with ≈ 1.4% of individuals moving between patches separated by 13–200 m.3. Despite low mobility, observed colonizations occurred rapidly over distances of 1 km. Because P. argus occurs at high population densities, 1.4% migration can generate enough migrants to colonize newly suitable habitat quickly at this spatial scale.4. Mark–release–recapture data were used to predict that there would be limited genetic differentiation through drift between local populations at this spatial scale. The prediction was supported by allele frequency data for the same local populations.5. Genetic differentiation often indicates higher levels of migration than are revealed by the movements of marked individuals. This study shows that when experimental releases and extensive marking are undertaken in areas that are large relative to most movements, indirect measures of gene flow and direct measures of dispersal can concur.6. Evidence from the three different approaches was complementary, indicating that P. argus occurs as metapopulations within the study area.
Controlling resource acquisition to reveal a life history trade‐off: egg mass and clutch size in an iteroparous seed predator, Prostephanus truncatus
Authors: GUNTRIP J. , SIBLY R. M. , SMITH R. H. 
Published: November 2003

1. A trade‐off constraining egg production was investigated and the consequences of egg mass for the offspring life history in Prostephanus truncatus investigated. Fresh egg mass was found to vary between 0.065 and 0.109 mg (about 20% of fresh body mass at emergence) and was correlated both with dry egg mass (r = 0.8) and with the mass of first‐instar larvae (r = 0.8).2. There was a negative correlation between egg mass and clutch size: doubling clutch size from eight to sixteen eggs resulted in a reduction in egg mass from 0.09 to 0.07 mg. Resource allocation per clutch was not constant but increased with clutch size. After allowing for the relationship between egg mass and clutch size, heavier females were found to oviposit both heavier eggs and more eggs in a clutch.3. By placing eggs in prepared seeds that minimized variation in resource acquisition, it was discovered that development period of females, but not of males, was negatively correlated with egg mass. Egg size was not correlated with body size at emergence in either sex.4. The results are interpreted as revealing a resource‐allocation trade‐off in egg production.
Factors affecting size, longevity and fecundity in the reindeer oestrid flies Hypoderma tarandi (L.) and Cephenemyia trompe (Modeer)
Authors: NILSSEN ARNE 
Published: November 2003

1. Laboratory reared reindeer oestrid flies Hypoderma tarandi and Cephenemyia trompe (Diptera: Oestridae) were weighed to determine progressive weight loss and death weights at treatments with various temperature and humidity conditions.2. Four individual measurements of size were taken: larval weight, wet weight of newly eclosed flies, wing length, and weight of flies after dehydration and fat extraction. In H. tarandi, males were bigger than females (except for wing length), whereas the reverse was true for C. trompe.3. Size variation was not significantly related to conditions (temperature, humidity, duration) during the pupal stage, but individual reindeer produced flies (both species) of different mean sizes. These size differences were not correlated with larval burden (= number of larvae per individual host), but are hypothesized to be connected to unknown host quality factors.4. Longevity of flies kept in vials and subjected to various temperature and humidity conditions revealed that C. trompe lived significantly longer than H. tarandi (range: 4–44 and 1.2–27 days, respectively) at 5–33 °C. Male H. tarandi survived longer than females; female C. trompe survived longer than males. Longevity was not significantly correlated to any of the size measures.5. Most flies had a large portion of their fat reserves left at death.6. In H. tarandi, mean number of eggs was 609 ± SD 73 (range 354–772, n = 119). Egg number was slightly dependent on larval size, but not on wet weight of newly eclosed flies or wing length. In C. trompe, mean number of eggs was 960 ± SD 208 (range 493–1349, n = 31).7. The possible adaptive value of large size in oestrids is questioned. Benefits of flexibility in size in oestrids are hypothesized.
The relative efficiencies of Latin square and randomized complete block designs for insect trapping experiments: an investigation using field data on tsetse flies
Authors: ODULAJA A. , ABU‐ZINID I. M. 
Published: November 2003

1. The Latin square design (LSD) is usually preferred over the randomized complete block design (RCBD) in insect trapping experiments because of its ability to cater for variations due to both sites and days in addition to treatments.2. The efficiency of LSD relative to RCBD is quantified for tsetse trapping experiments using a data set comprising 2200 trap‐days. LSD was found to be more efficient than RCBD when blocks ≅ days, but less efficient when blocks ≅ sites, especially when experiments involve only three or four treatments.3. The importance of sites relative to days as sources of variation in tsetse trapping experiments is quantified. Effects due to site differences were shown to be more important than day to day variability.4. By relating LSD relative efficiency to the relative importance of sites, it was found that LSD efficiency depended on the relative magnitude of effects of sites and days.
Preferences for nectar sugars in the peacock butterfly, Inachis io
Authors: RUSTERHOLZ HANS‐PETER , ERHARDT ANDREAS 
Published: November 2003

1. Peacock butterflies, Inachis io, were tested experimentally for their preferences for nectar sugars.2. In tests with different plain sugar solutions (25%, weight to total weight) the butterflies strongly preferred sucrose and fructose over glucose. They also preferred sucrose over fructose.3. In tests with mixed sugar solutions the butterflies clearly preferred both sucrose‐dominant (sucrose : hexoses = 5 : 1) and balanced sugar solutions (sucrose : glucose : fructose = 1 : 1 : 1) over hexose‐dominant sugar solutions (sucrose : hexoses = 1 : 5).4. Females consumed significantly more of the balanced sugar solution than did males.5. These results are discussed with respect to previous experiments on nectar preferences of butterflies, nectar sugar composition of butterfly‐pollinated flowers, and flower preferences, physiological and reproductive aspects of butterflies.
Relationship of queen number and queen relatedness in multiple‐queen colonies of the fire ant Solenopsis invicta
Authors: GOODISMAN MICHAEL , ROSS KENNETH 
Published: November 2003

1. The relationship between the number of queens per nest and their relatedness was examined in the polygyne (multiple queens per nest) social form of the fire ant Solenopsis invicta.2. No significant relationship between these two variables was found. Moreover, the overall average relatedness among nestmate queens was not significantly different from zero.3. These findings indicate that polygyne nests of S. invicta do not represent closed societies. Furthermore, they are consistent with continual acceptance of non‐nestmate queens throughout a colony’s lifetime. This strategy differs from the expectation of kin selection theory that only related queens should be accepted as new reproductives within polygyne colonies.4. The postulated acceptance of non‐nestmate queens is associated with a decrease in the number of parasites, predators and diseases and a concomitant increase in the density of nests in introduced populations, suggesting that the permissive environment experienced by introduced fire ants may have decreased the relative importance of kinship as a stabilizing factor in the evolution of polygyny.
The pay‐off from superparasitism in the egg parasitoid Trissolcus basalis, in relation to patch defence
Authors: FIELD SCOTT , KELLER MICHAEL , CALBERT GREG 
Published: November 2003

1. In species such as quasi‐gregarious egg parasitoids, which exploit defendable patches, the fitness pay‐off from superparasitism is an important factor in considering the evolution of patch defence and optimal patch defence strategies.2. When oviposition in a previously parasitized host has a non‐zero fitness pay‐off, competing parasitoids are not only able to diminish the future value of a patch to other females by depleting unparasitized hosts, but also devalue the previous investment of other females in the patch by superparasitizing.3. In Trissolcus basalis, an egg parasitoid of pentatomid bugs, the fitness pay‐off from superparasitism is higher than 0.5 when the time interval between ovipositions is less than 3 h, suggesting that defending a previous investment will be an important component of patch defence behaviour.4. The data suggest a mechanism for the high early pay‐off, which involves the superparasitizing female adjusting the sex ratio of its offspring in favour of males. Males develop more quickly than females and thus may have a competitive advantage.
Dissolved organic matter and its parent organic matter in grass upland soil horizons studied by analytical pyrolysis techniques
Authors: Huang Y. , Eglinton G. , Van Der Hage E. R. E. , Boon J. J. , Bol R. , Ineson P. 
Published: November 2003

SummaryWe have sought to understand the molecular mechanisms by which dissolved organic matter (DOM) forms and soil organic matter (SOM) degrades in upland peaty gley soil under grass. Pyrolysis mass spectrometry (Py‐MS) and pyrolysis gas chromatography mass spectrometry (Py‐GC/MS) were applied to characterize the DOM collected from lysimeters and its parent SOM. The macromolecular organic matter in the litter and fermentation (Lf) horizon of the soil consists primarily of little decomposed lignocellulose from grass, whereas the humus (Oh) horizon is characterized by an accumulation of selectively decomposed lignocellulose material, microbial metabolites and bound fatty acids. The mineral horizon produced a relative enrichment of furan structures derived from microbial reworking of plant polysaccharides but virtually no lignin signals. A series of exceptional long chain C43to C53fatty acids with odd over even predominance, probably derived from mycobacteria, were also identified in the Oh horizon. Side‐chain oxidation and shortening, increase of carboxyl functionality and selective removal of syringyl (S) > guaiacyl (G) > p‐hydroxyphenyl (P) lignin units were the main reactions when lignin degraded. Compared with SOM, the DOM shows a large accumulation of more oxidized lignin and aromatic structures, especially those containing carboxylic and dicarboxylic acid functionalities and with shorter side‐chain length. The polysaccharide‐type compounds in the DOM were more modified (greater abundance of furan structures in pyrolysis products), and had significantly lower molecular weight and more diverse polymeric structures than did those in soils. Increased temperature and rainfall appeared to result in greater relative abundance of lignin degradation products and aromatic compounds in DOM.
Prey selectivity and diel feeding chronology of juvenile chinook (Oncorhynchus tshawytscha) and coho (O. kisutch) salmon in the Columbia River plume
Authors: Schabetsberger R. , Morgan C. A. , Brodeur R. D. , Potts C. L. , Peterson W. T. , Emmett R. L. 
Published: November 2003

AbstractWe studied salmon feeding selectivity and diel feeding chronology in the Columbia River plume. Juvenile chinook and coho salmon were caught by trawling at 2–3 h intervals throughout a diel period on three consecutive days (21–23 June 2000) at stations located 14.8 and 37 km offshore from the mouth of the Columbia River. A total of 170 chinook salmon were caught at the inshore and 79 chinook and 98 coho salmon were caught at the offshore station. After each trawl, potential prey were sampled at different depths with 2–3 different types of nets (1‐m diameter ring net, bongo net, neuston net). Despite the variability in zooplankton abundance, feeding selectivity was surprisingly constant. Both salmon species fed selectively on larger and pigmented prey such as hyperiid amphipods, larval and juvenile fish, various crab megalopae, and euphausiids. Hyperiid amphipods were abundant in the salmon diets and we hypothesize that aggregations of gelatinous zooplankton may facilitate the capture of commensal hyperiid amphipods. Small copepods and calyptopis and furcilia stages of euphausiids dominated the prey field by numbers, but were virtually absent from salmon diet. Juvenile chinook salmon, with increasing body size, consumed a larger proportion of fish. Stomach fullness peaked during morning hours and reached a minimum at night, suggesting a predominantly diurnal feeding pattern. In general, both chinook and coho salmon appear to be selective, diurnal predators, preying mostly on large and heavily pigmented prey items, in a manner consistent with visually oriented, size‐selective predation.
Tracking environmental processes in the coastal zone for understanding and predicting Oregon coho (Oncorhynchus kisutch) marine survival
Authors: Logerwell E.A. , Mantua N. , Lawson P.W. , Francis R.C. , Agostini V.N. 
Published: November 2003

AbstractTo better understand and predict Oregon coho (Oncorhynchus kisutch) marine survival, we developed a conceptual model of processes occurring during four sequential periods: (1) winter climate prior to smolt migration from freshwater to ocean, (2) spring transition from winter downwelling to spring/summer upwelling, (3) the spring upwelling season and (4) winter ocean conditions near the end of the maturing coho's first year at sea. We then parameterized a General Additive Model (GAM) with Oregon Production Index (OPI) coho smolt‐to‐adult survival estimates from 1970 to 2001 and environmental data representing processes occurring during each period (presmolt winter SST, spring transition date, spring sea level, and post‐smolt winter SST). The model explained a high and significant proportion of the variation in coho survival (R2 = 0.75). The model forecast of 2002 adult survival rate ranged from 4 to 8%. Our forecast was higher than predictions based on the return of precocious males (‘jacks’), and it won't be known until fall 2002 which forecast is most accurate. An advantage to our environmentally based predictive model is the potential for linkages with predictive climate models, which might allow for forecasts more than 1 year in advance. Relationships between the environmental variables in the GAM and others (such as the North Pacific Index and water column stratification) provided insight into the processes driving production in the Pacific Northwest coastal ocean. Thus, coho may be a bellwether for the coastal environment and models such as ours may apply to populations of other species in this habitat.
The use of Percent Model Affinity to assess the effects of agriculture on benthic invertebrate communities in headwater streams of southern Ontario, Canada
Authors: BARTON DAVID 
Published: November 2003

1. Benthic invertebrates were surveyed in 213 headwater streams in southern Ontario to test the utility of Percent Model Affinity (PMA) for assessing the relative impact of agriculture on invertebrate communities. Qualitative samples were collected from reference (= forested, sixty‐nine samples) and agricultural (195 samples) streams between May 1990 and August 1993. The percentage composition of samples from reference streams was averaged by season and type of substratum, and the most homogeneous groupings were used as expected communities for the calculation of PMA.2. The lower confidence limit about the mean PMA for each expected community was calculated as for a one‐tailed t‐test comparing a single observation with the mean of a sample. Samples from agricultural streams whose PMA scores were outside these confidence limits were judged to indicate significant impact.3. The sensitivity of PMA to differences in land use increased with taxonomic resolution: 40% of agricultural sites were significantly different from reference communities at the ordinal level, 79.5% were significantly different at the lowest practical taxonomic level. Most of the increase in discrimination between reference and agricultural sites was due to Chironomidae. Identification to species, rather than genus, yielded only a small increase in discrimination between reference and agricultural sites, largely because of taxonomic difficulties and because most members of several diverse genera were very similar in their distributions.4. All of the samples from streams which drained orchards and vinyards (n = 7) were significantly different from the expected communities, as were 89% of those from streams draining corn (n = 94). A larger percentage of streams draining hay (78%, n = 26) were impacted than were streams bordered by pasture (66%, n = 51), but the average magnitude of impact was greater in pasture streams. Only six of eleven samples from streams draining tobacco indicated significant impact.5. The effect of land use adjacent to the sampling site was greatest early in the growing season. Comparison of natural channels and ditches draining agricultural land suggests that channelization and subsurface tile drainage eliminate most of the benefits of riparian buffer strips and magnify the effects of farming practices on the benthic fauna.
Seasonal and spatial variation in zooplankton community structure and their relation to possible controlling variables in Lake Okeechobee
Authors: BEAVER JOHN , HAVENS KARL 
Published: November 2003

1. Lake Okeechobee is a large (1732 km2), shallow (mean depth 2.7 m), eutrophic, subtropical lake located in southern Florida. Approximately 25% of the lake surface area is occupied by an extensive littoral zone. From August 1988 to June 1992, ≈ 2000 zooplankton samples were collected throughout the lake.2. During the study period, a severe drought lowered lake levels more than 1 m. At low and normal lake stage, the average lake‐wide abundance of rotifers (c. 2000 l–1) was greater than during high water periods (c. 1600 l–1). The average abundance of adult crustaceans (cladocerans and copepods) (c. 30 l–1) varied little regardless of lake stage.3. Although only minor differences were apparent when lake‐wide means in rotifers and adult crustaceans for each lake stage were compared, pronounced differences were evident in the distribution of zooplankton communities within Lake Okeechobee. During high and normal lake stage, both rotifer and adult crustacean populations were more uniformly distributed throughout the lake. At low lake stage, the densest zooplankton populations were concentrated in the transition area between the central lake and the littoral fringe. The abundance of all zooplankton groups was inversely correlated with lake stage, but the relationship was much stronger for rotifers than crustaceans. Both rotifer and crustacean zooplankton population densities were positively related to increased phytoplankton biomass (as measured by chlorophyll a) but the relationship was much stronger for rotifers than crustaceans.