Occurrence of Platyarthrus schoblii (Isopoda, Oniscidea) and its ant hosts in Hungary

The myrmecophilous Platyarthrus schoblii Budde-Lund, 1885 is widely distributed and native in the Mediterranean region. In Hungary it was first found at Budapest, in 2001, in a colony of Lasius neglectus van Loon, Boomsma and Andrásfalvy, 1990 (Hymenoptera: Formicidae). This invasive and polygynous ant species is dispersing in an antropochorous way throughout Europe. There are 16 known colonies of L. neglectus in Hungary. Fourteen of them have been surveyed for the isopod, which was detected in eight cases (57%). In addition to L. neglectus, the isopod has been recently found with other native ant species [Lasius niger (Linnaeus, 1758), Lasius emarginatus (Olivier, 1791) and Tetramorium caespitum (Linnaeus, 1758)] in the country. We have also found the joint occurrence of P. hoffmannseggii Brandt, 1833 and P. schoblii. The co-occurrence and joint expansion of the ranges of L. neglectus and P. schoblii indicates their co-habitation and antropochorous dispersal while the appearance with L. emarginatus, L. niger and T. caespitum supports our hypothesis about possible adoption by different ant species.     

Seasonal dynamics and age structure of drifting cyprinid fishes: an interspecific comparison

Abstract –  We investigated interspecific differences in the downstream drift of seven species of young-of-the-year cyprinids over a 2-year period in two central European rivers, using a comparison of drifting fish with fish collected from nurseries at the same time and the same site as the drift samples. Species varied in the utilisation of the drift; Rutilus rutilus , Gobio spp., Abramis brama and Carassius auratus gibelio drifted abundantly, while Leuciscus cephalus and Alburnus alburnus were abundant in nurseries, but drifted at low densities. Abramis bjoerkna was equally represented among drifting and resident fish. Generally, fish drifted at two major developmental intervals; L3 stage and the stage at transition between larval and juvenile periods (L6/Juv), with interspecific differences in the ontogenetic timing of drifting. The propensity to drifting of certain developmental stages was also reflected in body size comparisons between drifting and resident fish. The stage-dependent drifting may be attributed to major changes in fish morphology, behaviour and swimming ability.     

Pollen-mediated gene flow in an autogamous crop: Foxtail millet (Setavia italica)

Gene How is a key concern associated with the eonlamination of seed multiplication iields and the use of transgenic crops. The release of herbicide-resistant germplasnis and the use of male-sterile varieties make foxtail millet (Sviaria ilalicii) an appropriate material to inves-tigate this concern. Pollen dispersal from pollen donor sources and gene tlow in fertile and male-slerile varieties of fortail millet were investigated in experiments in China and France. Although foxtail millel is mainly autogamous (less than 2% oiitcrossing), pollen from a 5m diameter plot could fertilize a tertile variety up to 24 ni away, and a male-sterile variety up to 40m. Negative exponential and WeibuU fnnctions were used to tit the relationships between percentage and number i.A iubrids per cm of ear with distance from the pollen source. Wind velocity and direction resulted in variations of gene How intensity, but did nol change liie slope ofthe regression equations. Pollen competition for available target ovules was observed up to 2 m away from a 1 m diameter pollen source. The percentage of pollen grains that fertilized ovules outside the pollen donor source was 1.4% of the total pollen grain produetion. For every iflO pollen grains released under lieid conditions 1.5 seeds were produced. The probability funetion of pollen dispersal for one donor plant was calculated. It allowed predictions of gene How accord-ing to lield shapes, estimations of isolation distances to preserve /ariety purity against pollen contamination, and the fornuiiation of efficient male/female ratios Ibr hybrid seed production.     

The domestication and improvement of cowpeas (Vigna unguiculata (L.) Walp.)

Summary Physiological and morphological characteristics of the two wild and three domesticated subspecies of cowpeas are compared. The wild accessions are alike in having small, hard seeds borne in dehiscent pods, but differ in other characteristics. We suggest that the wild subsp. dekindtiana, from the seasonally-arid tropics, is more likely to have been the progenitor of modern cowpeas than the other wild subspecies (subsp. mensensis), but that subsp. dekindtiana was first cultivated in the humid tropics where its pods are slow to dehisce. Domestication has been associated with changes in the structure of pod valves and seed coats which reduce pod dehiscence and seed hardness. Pods and seeds have increased in size, mainly by increases in the rate of dry weight accumulation, and their increase has been only partly paralleled by increase in the area of subtending leaves. There has been no increase in the maximum photosynthetic rate of leaves, but the duration of their photosynthetic activity has increased. Domesticates are less sensitive than are wild plants to some environmental controls, such as in the response of germination to temperature, but in their flowering responses to daylength both wild and cultivated forms retain sensitivity under conditions where this is of adaptive value.     

Recommended isolation distances for the field multiplication of diploid tuber-bearing Solanum species

The sexual propagation of genebank accessions by hand pollination in the greenhouse is a very expensive and time-consuming routine task. The self-incompatibility of most diploid potato species allows their multiplication in isolated field plots, which is coupled with the advantage of the presence of natural pollinators and maintaining a high level of heterozygosity. The aim of this study was to determine the isolation distance required for minimizing pollen flow between neighbouring multiplication plots. The Solanum phureja clone IVP48 was used as the pollen donor since it possesses a dominant seed marker (‘embryo spot’). The centrally located pollen donor was surrounded by S. phureja recipient plots at distances of 10,20,40, and 80 m, respectively. The average pollen contamination ranged from 0.2% in the plots 80 m from the pollen donor to 5.1% in those 10 m away. In this study, procedures are suggested which will help to reduce cross-pollination between accessions.     

Life on the edge - High levels of genetic diversity in a cliff population of Bertya ingramii are attributed to B. rosmarinifolia (Euphorbiaceae)

Wind-facilitated migration of new genotypes into small, geographically disjunct populations should buffer them against local extinction. Bertya ingramii, a monoecious, wind-pollinated shrub, is restricted to three populations in a 4 km² area in eastern Australia. Populations are separated by deeply dissected gorges where it is unlikely that seeds are exchanged but where wind movement may facilitate pollen dispersal. Using 156 highly polymorphic ISSR markers, we found moderate genetic variation within and among populations of B. ingramii and less genetic diversity in a nearby and small population of the widespread Bertya rosmarinifolia. The smallest population of B. ingramii (<30 plants) had the highest genetic variation (65% polymorphic markers, Shannon Information Index = 0.30). AMOVA and a Bayesian analysis showed that molecular variance was equally distributed within and among populations suggesting that gene flow is as limited within as in among populations. Genetic distances between populations were only weakly explained by their relative geographic distances (mantel test, R² = 0.21, P = 0.001) but the distribution of private bands, the departure from Hardy-Weinberg equilibrium, and a UPGMA tree showed that the smallest population of B. ingramii was generally more similar to an upstream population of B. rosmarinifolia. Thirty-eight percent of bands in this small population of B. ingramii were exclusively shared with B. rosmarinifolia. This covert hybridisation may have been an ancient event but may be responsible for contemporary declines in germination and establishment in B. ingramii. The conservation implications are amplified by the endangered status of B. ingramii.     

Wind dispersal of oribatid mites as a mode of migration

Oribatid mites are important colonizers of young soils, but little is known about their immigration pathways. In this study, one often-stated hypothesis was tested quantitatively: that wind is an important dispersal pathway. The aim was (1) to detect wind dispersal in oribatid mites (using sticky traps at different heights above ground level) and to determine factors influencing wind dispersal, (2) to investigate whether oribatids can survive wind dispersal and immigrate by wind into young soils (using mini-pitfall traps in test plots with oribatid-free substrate, active immigration being prohibited) and (3) to find out whether those oribatids are able to colonize young soils (using soil cores from the test plots). The results demonstrate (1) that mainly arboreal oribatid species were dispersed by wind - even at 160 m height - and can therefore be spread over large distances. Nevertheless, about 10% of the wind-dispersed oribatid mites belonged to species able to live in the soil and may therefore be potential colonizers of young soils. The number of specimen and species transported by wind was the highest close to the soil surface and the number of dispersed individuals was mainly influenced by seasonality and humidity. The results also suggest that the probability of a soil oribatid being dispersed by wind depends on its original microhabitat (tree habitats > soil surface > deeper soil layers) and its body weight. It was also shown that soil-dwelling oribatid mites survived wind dispersal and immigrated by wind into the test plots and that colonization of the test plots took at least 2 months longer than immigration. However, colonization success was low during the first 2 years of investigation and only Trichoribates incisellus was found several times in the nutrient-poor substrate. Therefore, wind dispersal is an important migration pathway, especially for arboreal oribatids. We suggest that immigration into young soils most likely occurs by repeated short-distance dispersal. Only some species are able to survive the hostile conditions of wind dispersal as well as of pioneer soils, but those that do are potentially the founders of new populations.