Performance of Myrmica ant colonies is correlated with the presence of social parasites

1. The performance of ant colonies depends on different factors such as nest site, colony structure or the presence of pathogens and social parasites. Myrmica ants host various types of social parasites, including the larvae of Maculinea butterflies and Microdonmyrmicae (Schönrogge) hoverfly. How these social parasites affect host colony performance is still unexplored. 2. It was examined how the presence of Maculinea teleius Bergsträsser, Maculinea alcon (Denis & Schiffermüller), and M. myrmicae larvae, representing different feeding and growth strategies inside host colonies, is associated with worker survival, the number of foragers, and colony productivity parameters such as growth and reproduction. 3. It was found that the presence of social parasites is negatively associated with total colony production and the production of ant larvae and gynes. Male production was lower only in nests infested by M. teleius, whereas the number of worker pupae was significantly higher in all types of infested colonies than in uninfested colonies. Laboratory observations indicated that nests infested by Maculinea larvae are characterised by a higher number of foragers compared to uninfested nests but we did not find differences in worker survival among nest types. 4. The observed pattern of social parasite influence on colony productivity can be explained by the feeding strategies of parasitic larvae. The most negative effect was found for M. teleius, which feeds on the largest host brood and eliminates a high number of sexual forms. The strong, adverse influence of all studied parasite species on gyne production may result in low queen production in Myrmica populations exposed to these social parasites.     

Electrophysiological characterization of pathways for K+ uptake into growing and non-growing leaf cells of barley

Potassium is a major osmolyte used by plant cells. The accumulation rates of K⁺ in cells may limit the rate of expansion. In the present study, we investigated the involvement of ion channels in K⁺ uptake using patch clamp technique. Ion currents were quantified in protoplasts of the elongation and emerged blade zone of the developing leaf 3 of barley ( Hordeum vulgare L.). A time-dependent inward-rectifying K⁺-selective current was observed almost exclusively in elongation zone protoplasts. The current showed characteristics typical of Shaker-type channels. Instantaneous inward current was highest in the epidermis of the emerged blade and selective for Na⁺ over K⁺. Selectivity disappeared, and currents decreased or remained the same, depending on tissue, in response to salt treatment. Net accumulation rates of K⁺ in cells calculated from patch clamp current–voltage curves exceeded rates calculated from membrane potential and K⁺ concentrations of cells measured in planta by factor 2.5–2.7 at physiological apoplastic K⁺ concentrations (10–100 m m ). It is concluded that under these conditions, K⁺ accumulation in growing barley leaf cells is not limited by transport properties of cells. Under saline conditions, down-regulation of voltage-independent channels may reduce the capacity for growth-related K⁺ accumulation.     

Y chromosome microsatellite markers identified from the tammar wallaby (Macropus eugenii) and their amplification in three other macropod species

Microsatellites were identified from three fully sequenced Y chromosome‐specific bacterial artificial chromosome clones from the tammar wallaby, Macropus eugenii. Ten microsatellites were genotyped in male tammar wallabies. Four loci were polymorphic with between two and six alleles per locus. Eleven different haplotypes were identified from 22 male tammar wallabies. No amplifications were obtained from female samples. Each microsatellite was also shown to amplify reliably in at least one other macropod species. These markers may therefore prove useful as some of the first male‐specific genetic markers for marsupials, with potential application to studies of male‐biased dispersal and mating systems.     

Reproductive biology of Phillyrea angustifolia L.(Oleaceae) and effect of galling-insects on its reproductive output

The breeding system of Phillyrea angustifolia is examined in several Spanish populations, both in the southeastern Iberian Peninsula and in the Balearic IslandS. Hand-pollination experiments performed on one of the mainland and on one of the island populations demonstrated that the plant is functionally androdioeciouS. Pollen from males was several times more fertile than pollen from hermaphrodite flowers or self-pollen in the island population, but not so in the Iberian Peninsula. The interpretation of such a result is that androdioecy must have an adaptive advantage in an island system, where inbreeding depression is expected to be greater. Male individuals are much less common than hermaphrodites in all populations studied, thus supporting the prediction made by the models for the maintenance of androdioecy. Sex expression in an individual plant differs between populations. The frequency of sexes was purely bimodal in one population, whereas it was not so in another. Pollen from both male and hermaphrodite flowers appears to be morphologically different, although it remains unknown at what stage of the fertilization process the difference becomes functional. Fruitset in the hermaphrodite individuals was always less than 10%.Most fruits abort at an early stage and there is also a great flower abscission. Fruitset does not appear to be influenced by any of the plant traits describing size or fecundity. A high unpredictability of flowering in an individual was also observed in all populations.P.angustifolia is attacked by a cecidomyiid fly that induces the formation of galls in the ovaries (producing ‘deforme’ fruits which have been confused until recently with parthenocarpic fruits), thus reducing the plant reproductive output. The production of such galls (most of them in the hermaphrodite individuals but a small proportion also in males) is highly variable among plants and among populations, representing from 0 to 97% of the initiated fruitS. Such variability in gall incidence does not respond to variability in plant size, fecundity, distance to flowering conspecifics or time that flowers are available for fly oviposition. A high consistency in gall production was found in both the mainland and the island populations. The greater abundance of galls in the islands compared with the mainland populations is interpreted as a result of the higher temperatures in the former which might influence the activity period of the flies.     

Mitochondrial DNA distributions indicate colony propagation by single matri-lineages in the social spider Stegodyphus dumicola (Eresidae)

Colony-dwelling social spiders of the genus Stegodyphus are characterized by high colony turnover, within-colony mating, inbreeding and skewed sex ratios. These phenomena may purge genetic variation from the entire species gene pool. Social Stegodyphus have previously been discussed as ecologically unstable and evolutionary dead ends. We investigated the distribution and age (sequence divergence) of mitochondrial DNA variation for inferences of colony propagation, colony discreteness and maintenance of genetic variation in the social spider S. dumicola . In contrast to our expectations, we found abundant mtDNA variation, consisting of 15 haplotypes belonging to four haplotype lineages. Lineage divergence ranged between 2.75 and 6% for the gene ND1. Nearly all colonies (86%) were monomorphic and even neighbour colonies showed fixed differences. Simulations show that genetic drift in multifounder colonies cannot alone explain monomorphism within colonies. Haplotypes in polymorphic colonies and from neighbouring colonies were always genealogically similar. Monomorphism and the genealogical pattern among colonies suggest 'clonal' colony propagation involving single matrilineages. The divergence of haplotype lineages and distribution of haplotypes imply that colony turnover is not high enough to purge genetic variation in the species gene pool, and that S. dumicola as a species is old enough to question the instability (in ecological time) of a social spider.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 76 , 591–600.     

Evidence that the recessive bymovirus resistance locus rym4 in barley corresponds to the eukaryotic translation initiation factor 4E gene

Recent studies have shown that resistance in several dicotyledonous plants to viruses in the genus Potyvirus is controlled by recessive alleles of the plant translation initiation factor eIF4E or eIF ( iso ) 4E genes. Here we provide evidence that the barley rym 4 gene locus, controlling immunity to viruses in the genus Bymovirus , corresponds to eIF4E . A molecular marker based on the sequence of eIF4E was developed and used to demonstrate that eIF4E and rym 4 map to the same genetic interval on chromosome 3HL in barley . Another genetic marker was developed that detects a polymorphism in the coding sequence of eIF4E and consistently distinguishes between rym 4 and susceptible barley cultivars of diverse parentage. The eIF4E gene product from barley genotypes carrying rym 4 and allelic rym 5 and rym 6 genes, originating from separate exotic germplasm, and a novel resistant allele that we identified through a reverse genetics approach all contained unique amino acid substitutions compared with the wild-type protein. Three-dimensional models of the barley eIF4E protein revealed that the polymorphic residues identified are all located at or near the mRNA cap-binding pocket, similarly to recent findings from studies on recessive potyvirus resistance in dicotyledonous plants. These new data complement our earlier observations that specific mutations in bymovirus VPg are responsible for overcoming rym 4/5-controlled resistance. Because the potyviral VPg is known to interact with eIF4E in dicotyledonous plants, it appears that monocotyledonous and dicotyledonous plants have evolved a similar strategy to combat VPg-encoding viruses in the family Potyviridae .     

Population genetics of Galápagos land iguana (genus Conolophus) remnant populations

The Galápagos land iguanas (genus Conolophus) have faced significant anthropogenic disturbances since the 17th century, leading to severe reduction of some populations and the extinction of others. Conservation activities, including the repatriation of captive‐bred animals to depleted areas, have been ongoing since the late 1970s, but genetic information has not been extensively incorporated. Here we use nine species‐specific microsatellite loci of 703 land iguanas from the six islands where the species occur today to characterize the genetic diversity within, and the levels of genetic differentiation among, current populations as well as test previous hypotheses about accidental translocations associated with early conservation efforts. Our analyses indicate that (i) five populations of iguanas represent distinct conservation units (one of them being the recently discovered rosada form) and could warrant species status, (ii) some individuals from North Seymour previously assumed to be from the natural Baltra population appear related to both Isabela and Santa Cruz populations, and (iii) the five different management units exhibit considerably different levels of intrapopulation genetic diversity, with the Plaza Sur and Santa Fe populations particularly low. Although the initial captive breeding programmes, coupled with intensive efforts to eradicate introduced species, saved several land iguana populations from extinction, our molecular results provide objective data for improving continuing in situ species survival plans and population management for this spectacular and emblematic reptile.     

Isolation and characterization of microsatellite DNA loci from the golden cuttlefish,Sepia esculenta Hoyle (Cephalopoda)

The first microsatellite markers were isolated from the golden cuttlefish, Sepia esculenta Hoyle. Eleven primer sets were designed to amplify the marker sequences via polymerase chain reaction. The 45–50 individuals from one wild population in the coastal waters of Ehime Prefecture, Japan were used to screen polymorphism in the 11 microsatellite loci. All the microsatellite loci were polymorphic, with the range of alleles from seven to 27 per locus. The observed and expected heterozygosities ranged from 0.380 to 0.980 and from 0.654 to 0.940, respectively. These marker loci except for one locus showing significant deviation from Hardy–Weinberg equilibrium will be useful for the assessment of genetic variation and population structure of this species.