Restoring islands and identifying source populations for introductions

Article impact statement: Structured decision making can be used to identify an optimal source population for conservation introductions.     

Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics

Social groups are at particular risk for parasite infection, which is heightened in eusocial insects by the low genetic diversity of individuals within a colony. To combat this, adult ants have evolved a suite of defenses to protect each other, including the production of antimicrobial secretions. However, it is the brood in a colony that are most vulnerable to parasites because their individual defenses are limited, and the nest material in which ants live is also likely to be prone to colonization by potential parasites. Here, we investigate in two ant species whether adult workers use their antimicrobial secretions not only to protect each other but also to sanitize the vulnerable brood and nest material. We find that, in both leaf-cutting ants and weaver ants, the survival of the brood was reduced and the sporulation of parasitic fungi from them increased, when the workers nursing them lacked functional antimicrobial-producing glands. This was the case for both larvae that were experimentally treated with a fungal parasite (Metarhizium) and control larvae which developed infections of an opportunistic fungal parasite (Aspergillus). Similarly, fungi were more likely to grow on the nest material of both ant species if the glands of attending workers were blocked. The results show that the defense of brood and sanitization of nest material are important functions of the antimicrobial secretions of adult ants and that ubiquitous, opportunistic fungi may be a more important driver of the evolution of these defenses than rarer, specialist parasites.     

Leader‐signaled knowledge hiding: Effects on employees' job attitudes and empowerment

The authors introduce the concept of leader‐signaled knowledge hiding (LSKH) and conduct two studies observing what happens when leaders signal employees that knowledge hiding (KH) is practiced, tolerated, and expected. Social learning theory provides the basis for predicting that LSKH encourages subordinates to hide knowledge, even though they suffer from negative job attitudes in reaction. In Study 1, data measured at two time points (N = 1,162) shows that LSKH positively predicts KH among subordinates. The KH dimensions of evasive hiding and playing dumb (but not rationalized hiding) negatively relate to job satisfaction and positively affect turnover intentions. Study 2 (N = 1,169) replicates these results with cross‐sectional data. Moreover, Study 2 demonstrates that evasive hiding and playing dumb negatively affect empowerment, whereas rationalized hiding has a positive effect. Both studies reveal that subordinates will show less KH when they work under leaders who avoid LSKH and in turn have more job satisfaction, feel more empowered, and harbor fewer turnover intentions. The results in this study provide important practical implications for knowledge management activities.     

Close-range acoustic signaling and mate choice in Hawaiian crickets (Gryllidae: Laupala)

Evolution of the mate recognition system (MRS) can play a central role in animal speciation. One dramatic consequence of changes in the MRS is the failure of individuals from divergent lineages to successfully court and mate, thereby reducing gene flow between these groups. Here, we test the role of an acoustic mating signal on mate choice in a Hawaiian cricket genus (Gryllidae: Laupala). Speciation in Laupala is proceeding at an extremely rapid rate, apparently driven by divergence in aspects of the mate recognition system, most conspicuously the pulse rate of male calling song. Previous studies demonstrate that females prefer the pulse rate of a conspecific male’s song when perceived at long range, in laboratory phonotaxis trials. In this study, we examined mate choice in two species that differ dramatically in pulse rate: Laupala paranigra and Laupala kohalensis. We tested the female’s preference in both species for pulse rates at close range, by providing females an opportunity to mate with hybrid males producing a range of intermediate pulse rates. Results of our study demonstrate that while strong behavioral barriers exist between these two species, variation in the pulse rate of male calling song did not predict female mate choice at close range. These results suggest a more complex architecture to mate recognition in Laupala than previously hypothesized.     

Molecular and morphological analyses of the cuttlefish<Emphasis Type="Italic"> Sepia apama</Emphasis> indicate a complex population structure

The giant Australian cuttlefish Sepia apama Gray, 1849 annually forms a massive and unique spawning aggregation in northern Spencer Gulf, South Australia, which has attracted commercial fishing interests in recent years. However, many basic life-history characteristics of S. apama are unknown, and anecdotal evidence suggests that there is more than one species. The present study assessed the population structure and species status of S. apama using data from allozyme electrophoresis, microsatellite loci, nucleotide sequences of the mitochondrial COXIII gene, multivariate morphometrics and colour patterns. Analyses of allozyme and microsatellite allele frequencies revealed two very divergent but geographically separated populations consisting of specimens from the east coast and southern Australia. However, the presence of a heterozygote in a putative contact zone between the east coast and southern Australia suggested that these populations were not reproductively isolated. Mitochondrial haplotypes seem to have introgressed further north into the contact zone than have nuclear alleles. Differences in colour patterns that previously had been attributed anecdotally to different geographic populations were, in fact, correlated with sexual dimorphism. These data are most consistent with S. apama being one species the populations of which were geographically isolated in the past (historical vicariance) and have come into secondary contact. Comparison of microsatellite allele frequencies among four South Australian samples indicated significant deviations from panmixia. South Australian samples were also reliably diagnosed by means of multivariate morphometrics. Significant differences in mantle length were observed among populations.Communicated by M.S. Johnson, Crawley     

Effects of herbicides on two submersed aquatic macrophytes, Potamogeton pectinatus L. and Myriophyllum sibiricum Komarov, in a prairie wetland

Clopyralid, picloram, 2,4-D and a mixture of 2,4-D plus picloram, (Tordon 202C) were added to the water of 1 m square enclosures in a prairie wetland in Saskatchewan, Canada to produce concentrations of 0.01 and 0.1 mg active ingredient litre(-1). Effects on the submersed macrophytes, Potamogeton pectinatus and Myriophyllum sibiricum, were monitored by taking repeated measurements of plant weight, flower and tuber production and inspecting for injuries at 30 and 60 days after application. Clopyralid did not inhibit weight gain (growth) in either species, but stimulated growth and flowering by M. sibiricum at 0.01 mg litre(-1) and tuber production by P. pectinatus at both rates. The low rate of 2,4-D stimulated flowering by M. sibiricum and tuber production by P. pectinatus, whereas the high rate inhibited growth of M. sibiricum and injured both species. Picloram did not affect growth of either species, but injured M. sibiricum at both concentrations and inhibited flowering at 0.1 mg litre(-1). Tordon 202C at 0.1 mg litre(-1) caused reduced growth and flowering in M. sibiricum and injured both species; 0.01 mg litre(-1) also injured M. sibiricum. Mortality resulted only from Tordon 202C and 2,4-D. Field data are lacking to assess the extent to which submerged macrophytes in prairie ponds are exposed to harmful concentrations of herbicide from aerial spraying, drift from ground application, runoff or wind erosion of soil.     

An integrated approach using bioaccumulation and biomarker measurements in female shore crab, Carcinus maenas

The shore crab Carcinus maenas, was used as a biomonitoring organism to measure the potential impact that the mining spill in the Guadalquivir Estuary (SW, Spain), in 1998 may have exerted on local biota. Female intermoult C. maenas were exposed to dissolved cadmium, copper and zinc at concentrations found in local waters following the spill (3 microgl-1 Cd, 15 microgl-1 Cu, 700 microgl-1 Zn). Groups of shore crabs were exposed for 21 days to these metals, both singularly and in combination. Residues of metals were measured in gill, midgut gland and muscle tissues, together with metallothioneins in the midgut gland, at the end of the exposure period. Haemolymph samples were taken every seven days, and vitellogenin/vitellin analysed to determine the flux of these compounds. Biomarker results suggested that they would be good indicators of the effects of heavy metal environmental contamination, particularly in the case of Cd and Zn. Variation in results was obtained between responses measured in crabs exposed to single metals and those exposed to combinations of metals.     

Loss of particulate contaminants from plant canopies under wet and dry conditions

There is a requirement for data describing the loss with time of particulate contamination from plant canopies. Measurements were made of the loss rates of monodispersed silica spheres (three sizes, with Mass Median Aerodynamic Diameters (MMADs) 1.9, 5.3 and 8.4 microm) from wheat (Triticum aestivum) and broad bean (Vicia faba) canopies. The spheres were labelled with tracers detectable by Instrumental Neutron Activation Analysis (INAA). Canopies were contaminated under realistic turbulence conditions in a wind tunnel, then removed to sheltered and exposed field sites or to a glasshouse containing a rain simulator. Samples were taken periodically, and the level of contamination per plant determined by INAA. Statistical analysis of the resulting data suggested an offset exponential loss model, with a residue of deposit that is not lost over time. Loss half-lives in the order of 1-2 days were obtained for an exposed wheat crop and 3-4 days for a partially sheltered wheat crop, with permanent residues of initial deposit for the exposed crop of 4-8%, and for the partially sheltered crop of 22-52%. A broad bean crop under glasshouse conditions showed loss half-lives of 0.5-1.5 days with residues of 22-26% initial contamination. A double exponential loss model also fitted the data well in some cases, and it is possible that a slow loss of the residual deposit occurs, being masked by noise in the current data set.