Daphnia community analysis in shallow Kenyan lakes and ponds using dormant eggs in surface sediments

1. Water fleas of the genus Daphnia are considered rare in tropical regions, and information on species distribution and community ecology is scarce and anecdotal. This study presents the results of a survey of Daphnia species distribution and community composition in 40 standing waterbodies in southern Kenya. The study sites cover a wide range of tropical standing aquatic habitats, from small ephemeral pools to large permanent lakes between approximately 700 and 2800 m a.s.l. Our analysis combines data on Daphnia distribution and abundance from zooplankton samples and dormant eggs in surface sediments. 2. Nearly 70% (27 of 40) of the sampled waterbodies were inhabited by Daphnia. Although their abundance in the active community was often very low, this high incidence shows that Daphnia can be equally widespread in tropical regions as in temperate regions. 3. Analysis of local species assemblages from dormant eggs in surface sediments was more productive than snapshot sampling of zooplankton communities. Surface‐sediment samples yielded eight Daphnia species in total, and allowed the detection of Daphnia in 25 waterbodies; zooplankton samples revealed the presence of only four Daphnia species in 16 waterbodies. 4. Daphnia barbata, D. laevis, and D. pulex were the most frequently recorded and most abundant Daphnia species. Canonical correspondence analysis of species–environment relationships indicates that variation in the Daphnia community composition of Kenyan waters was best explained by fish presence, temperature, macrophyte cover and altitude. Daphnia barbata and D. pulex tended to co‐occur with each other and with fish. Both species tended to occur in relatively large (>10 ha) and deeper (>2 m) alkaline waters (pH 8.5). Daphnia laevis mainly occurred in cool and clear, macrophyte‐dominated lakes at high altitudes.     

Molecular analysis of Gigaspora (Glomales, Gigasporaceae)

This work presents a cooperative effort to integrate new molecular (isozyme and SSU analyses) characters into the morphological taxonomy of the genus Gigaspora (Glomales). Previous analyses of published Gigaspora SSU sequences indicated the presence of a few polymorphic nucleotides in the region delimited by primers NS71-SSU 1492'. In our study, the SSU of 24 isolates of arbuscular mycorrhizal (AM) fungi from the Gigasporaceae were amplified and the NS71-SSU 1492' region was directly sequenced. The corresponding sequences of four more isolates of AM fungi from Gigasporaceae, already published, were also included in our analyses. Three Gigaspora groups were identified on the basis of a 6 nucleotide-long 'molecular signature': Gigaspora rosea group ( G. rosea + G. albida ), Gigaspora margarita group ( G. margarita + G. decipiens ) and Gigaspora gigantea , which constituted a group by itself. The isozyme profiles (malate dehydrogenase, MDH) of 12 of these 28 isolates, and seven other isolates not sequenced, were compared. The results obtained further supported the grouping of isolates provided by the SSU analysis. Both SSU and MDH analysis indicated that two out of the 35 isolates had been misidentified, which was confirmed when their morphology was reassessed. The use of the Gigaspora intrageneric molecular signature as a quick, unambiguous and objective method to recognize Gigaspora isolates under any (field or laboratory) experimental conditions is suggested.     

Wind-borne short-range egg dispersal in anostracans (Crustacea: Branchiopoda)

Evidence is provided for the first time that at least part of the egg bank of the southern African fairy shrimp Branchipodopsis wolfi is dispersed over short distances by wind. A total of 423 sticky surfaces were mounted around and between individual basins at three rock pool sites, to trap any dispersing eggs during a 3 day period. Eight viable eggs were found in different egg traps (1.9% of the total), seven of which were located at one site with shallow basins. Given the proximity of vast egg banks to the egg traps, the low observed dispersal rate cautions against overestimating the importance of wind dispersal for population genetic processes. By generating egg banks to hedge against drought catastrophes, and producing egg types with different potential dispersibility, B. wolfi is a strong bet-hedger which has established a means of escaping temporal and spatial stress. These life history functions enable populations to persist in small desert rock-pools, which are the most extreme of temporary habitats.     

Five polymorphic microsatellite markers for the study of Cardiocondyla elegans (Hymenoptera: Myrmicinae)

We describe primer sequences for five microsatellite markers in Cardiocondyla elegans, an ant species with ergatoid males. Polymorphism of these loci was investigated using 236 individuals from 22 colonies from four locations. The microsatellites are dinucleotide repeats with four to 16 alleles, and the observed heterozygosity ranges from 0.244 to 0.720. We characterized these markers for the study of the population as well as the social structure of colonies.     

The importance of landscape and habitat properties in explaining instantaneous and long‐term distributions of large branchiopods in subtropical temporary pans

1. The notion that the spatial configuration of habitat patches has to be taken into account to understand the structure and dynamics of ecological communities is the starting point of metacommunity ecology. One way to assess metacommunity structure is to investigate the relative importance of environmental heterogeneity and spatial structure in explaining community patterns over different spatial and temporal scales. 2. We studied metacommunity structure of large branchiopod assemblages characteristic of subtropical temporary pans in SE Zimbabwe using two community data sets: a community snapshot and a long‐term data set covering 4 years. We assessed the relative importance of environmental heterogeneity and dispersal (inferred from patch occupancy patterns) as drivers of community structure. Furthermore, we contrasted metacommunity patterns in pans that occasionally connect to the river (floodplain pans) and pans that lack such connections altogether (endorheic pans) using redundancy models. 3. Echoes of species sorting and dispersal limitation emerge from our data set, suggesting that both local and regional processes contribute to explaining branchiopod assemblages in this system. Relative importance of local and regional factors depended on the type of data set considered. Overall, habitat characteristics that vary in time, such as conductivity, hydroperiod and vegetation cover, best explained the instantaneous species composition observed during a snapshot sampling while long‐term species composition appeared to be linked to more constant intrinsic habitat properties such as river connectivity and spatial location.     

Modelling stress in the feeding apparatus of seahorses and pipefishes (Teleostei: Syngnathidae)

Seahorses and pipefishes are extremely fast suction feeders, and the fast strikes probably result in large and rapid pressure drops in the buccal cavity. These rapid drops in pressure imply heavy mechanical loading on the cranium; hence, the feeding apparatus is thought to experience high levels of stress. We used finite element analysis (FEA) to investigate where stress accumulates under strong suction pressure, and whether there is a difference in craniofacial stress distribution between long‐ and short‐snouted species. The expectation was that high stress levels would occur at the articulations and in the cartilaginous regions of the cranium, and that, given the same pressure, the skulls of long‐snouted species would exhibit lower stress levels than the skulls of short‐snouted species, as an evolutionary increase in snout length might have made these species structurally better adapted to deal with high suction pressures. The results partially support the first hypothesis: except for Dunckerocampus dactyliophorus, all models show peak stress concentrations at the articulations and cartilaginous regions. However, no simple relationship between snout length and the magnitudes of stress predicted by the FEA was found. In an attempt to explain this lack of a relationship, the methodology was evaluated by assessing the effect of hyoid position and model construction on the stress distribution. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 680–691.     

Growth,development, and life‐history strategies in an unpredictable environment: case study of a rare hoverfly Blera fallax (Diptera,Syrphidae)

1. Development in organisms can vary in response to fluctuating environments. In holometabolous insects, variation in adult phenotypic traits is strongly influenced by growth conditions experienced by larvae. The main aim of this study was to assess how much environmental insight can be gained from analysis of the phenotypic changes in an insect's life history parameters in response to realistic food limitations. 2. This investigation was motivated by a need for more information about the developmental requirements of the endangered pine hoverfly Blera fallax (Linnaeus) (Diptera, Syrphidae) in Scotland. Blera fallax depends on a scarce and often ephemeral habitat, rot holes of Scots pine Pinus sylvestris L. stumps. We studied how rearing conditions affected growth in captive larvae, and compared these responses with a wild population. 3. The growth curve observed in the field was similar to that in resource‐limited, lab conditions, suggesting that resources are limiting in nature. The effects of resource availability on development time and body size depended on sex. Adult females were larger but had more variable size at maturity compared with males. In contrast, males typically were not smaller in resource‐limited conditions, but rather continued to develop for another year. Between 2% and 20% of larvae extended development over 2 years regardless of growth conditions, perhaps indicating a semivoltine strategy to circumvent extinction during years with a low breeding success. 4. These results identify life history traits that may be important for other saproxylic Diptera in rot holes, and organisms that experience food restrictions during growth.     

Natural 15N abundance of vegetation and soil in the Kapalga savanna,Australia

Abstract The natural abundance of the stable isotope ¹⁵N was measured in different vegetation components and in the soil of a northern Australian savanna. Most of the vegetation was found to be ¹⁵N-depleted compared to atmospheric N₂. Herbaceous legumes, perennial grasses, tree legumes, non-legume trees and annual grasses exhibited mean δ¹⁵N of ? 1.7, ? 0.8, ? 0.7, 0.0 and + 0.3‰, respectively. These results are in good agreement with previous studies. Legumes exhibit slightly negative values, indicating that they are likely to be nitrogen-fixing plants. Non-legume plants have a δ¹⁵N close to zero, which could equally result from non-symbiotic fixation, soil organic matter mineralization, or fresh root litter mineralization. In contrast, soil organic matter was ¹⁵N-enriched. Values of δ¹⁵N increased with depth and were + 2.5, + 5.2 and +6.1‰ in the 0–10, 10–20 and 20–40cm layers, respectively. Soil organic matter δ¹⁵N shows a typical profile of mature soils.     

Double Stranded RNA from Rat Liver induces Interferon in Rat Cells

Double stranded RNA from rat liver induces interferon in rat ergbryo fibroblasts. This shows that the production of interferon is not only a reaction to “foreign” RNA but can also be obtained with RNA of the same species.