The direct and indirect effects of predation by Hen Harriers Circus cyaneus on trends in breeding birds on a Scottish grouse moor

Two phases of an experimental reduction in management at Langholm Moor in southwest Scotland provided an insight into factors that determined trends in the abundance of moorland birds. In 1992 the historical control of breeding Hen Harriers Circus cyaneus stopped and in 2000 grouse moor management was discontinued. Golden Plover Pluvialis apricaria , Lapwing Vanellus vanellus , Curlew Numenius arquata and Red Grouse Lagopus lagopus scoticus declined, whilst Carrion Crow Corvus corone and Snipe Gallinago gallinago increased. Hen Harriers increased from two to 20 breeding females, then declined back to two. Lapwing abundance was positively associated with that of Hen Harriers, and moorland passerines (Skylark Alauda arvensis , Meadow Pipit Anthus pratensis and Stonechat Saxicola torquata ) were negatively associated. Golden Plover, Lapwing, Curlew, Red Grouse, Skylark and Hen Harrier were more abundant when the moor was managed for grouse, whilst Carrion Crow, a common predator of clutches of ground-nesting birds, increased during the second half when management ceased. Increased Crow numbers, together with an increase in Red Foxes Vulpes vulpes , probably contributed to the observed bird declines.     

Phylogenetic relationships between parthenogens and their sexual relatives: the possible routes to parthenogenesis in animals

In theory, parthenogenetic lineages have low evolutionary potential because they inexorably accumulate deleterious mutations and do not generate much genotypic diversity. As a result, most parthenogenetic taxa occupy the terminal nodes of phylogenetic trees. The rate and mode of development of parthenogenesis are important factors to consider when assessing its costs and benefits since they determine both the level of genetic diversity and the ecological adaptability of the resulting lineages. The origin of parthenogenesis is polyphyletic in many taxa, suggesting that genetic systems maintaining sexuality are often labile. In addition, the loss of sex may be achieved in several ways, leading to parthenogenetic lineages with distinct genetic profiles. This could then influence not only the fate of such lineages in the long term, but also the outcome of competition with their sexual counterparts in the short term. In this paper, we review the possible evolutionary routes to parthenogenesis based on a survey of the phylogenetic relationships between sexual and parthenogenetic lineages in a broad range of animals. We also examine the different mechanisms by which parthenogenetic lineages could arise, and discuss the influence of these mechanisms on both the genetic properties and the ecological life styles of the resulting lineages.  © 2003 The Linnean Society of London. Biological Journal of the Linnean Society , 2003, 79 , 151–163.     

Influence of adult breeding experience on growth and provisioning of Wandering Albatross Diomedea exulans chicks at South Georgia

For most seabirds, reproductive performance improves with age; in albatrosses this is thought not to be so (experience being acquired before starting breeding) but only one study (of chick growth in a single season at one site) has specifically addressed this. We compared the provisioning performance and growth rates of chicks of Wandering Albatrosses Diomedea exulans breeding for the first (IN), second and third (LE) and fourth or more times (EE) on Bird Island, South Georgia in the austral winters of 1996 and 1997. Eggs from EE adults were significantly heavier than the other two categories and these chicks had a greater mass and longer wings up to 160 days of age and longer culmen and tarsus up to 115 days old. However chicks from all categories fledged at the same average mass, size and age. No significant differences between categories in feeding frequency or meal size were detected but experienced adults made shorter long foraging trips and spent more time at the nest than less experienced birds. Adults that remained at the nest gave chicks smaller meals than those that left immediately after feeding the chick. Although provision of smaller but more frequent meals by experienced adults promotes more rapid chick growth, the resulting differences do not persist into the late chick-rearing period. Our results were very similar to those from Iles Crozet in the Indian Ocean, supporting the hypothesis that when Wandering Albatrosses start to breed they are fully competent foragers but that it takes a while, during early chick-rearing, for birds breeding for the first time to adapt to the additional demands of provisioning a chick.     

Isolation and characterization of microsatellite loci in Senecio

Interspecific hybridization has resulted in the recent origin of several hybrid Senecio taxa at diploid, tetraploid and hexaploid levels. As part of research aimed at constructing and comparing genomic maps of each of these taxa and their parents, we have isolated microsatellite loci from genomic DNA libraries of S. vulgaris and S. squalidus. Primers of 35 loci amplified microsatellites resolved in agarose gels from one or more of S. vulgaris, S. squalidus, S. aethnensis and S. chrysanthemifolius. Approximately 71% of primers amplified a product in all four species. A survey of microsatellite variation in S. chrysanthemifolius over a subset of 14 loci resolved 2–11 alleles per locus in polyacrylamide gels with expected heterozygosity (H_E) ranging from 0.26 to 0.87.     

Carbon dynamics in an ultra-oligotrophic epishelf lake (Beaver Lake, Antarctica) in summer

1. Microbial plankton dynamics in an ultra‐oligotrophic epishelf lake (Beaver Lake, Antarctica) were investigated over an austral summer (December 2002 to January 2003). The aim was to characterise carbon cycling in an environmentally extreme lake. 2. The lake had an unusual temperature profile with peak temperatures of 1.3–1.9 °C between 20 and 25 m. Photosynthetically active radiation penetrated to the lake bottom (110 m) on occasions. The ice cover underwent marked thinning and melting during the study period. 3. Chlorophyll a concentrations were consistently low, usually below 1 μg L^?1, with highest concentrations close to the lake bottom, where the photosynthetic elements showed strong autofluorescence. Mean photosynthetic nanoflagellates ranged between 34.9 × 10⁴ L^?1 ± 33.5 (23rd December) and 130.9 × 10⁴ L^?1 ± 112.3 (4th December). Highest photosynthetic activity was usually recorded below 25 m. Rates of carbon fixation varied between 0.089 μg C L^?1 h^?1 ± 0.002 and 0.579 μg C L^?1 h^?1 ± 0.156. Primary production was limited by low temperature and orthophosphate availability. 4. Mean bacterial concentration throughout the water column ranged between 9.3 × 10⁷ L^?1 ± 1.2 (23rd December) and 14.0 × 10⁷ L^?1 ± 1.8 (28th January). Bacterial production was low, less than 10% of primary production and ranged between 2.1 ng C L^?1 h^?1 ± 0.8 and 12 ng C L^?1 h^?1 ± 0.9. Highest rates coincided with times of highest primary production. On occasion dissolved organic carbon (DOC) concentrations dropped to 20 μg L^?1, probably below accurate limits of detection, suggesting that carbon substratum and phosphorus may have limited bacterial growth. 5. Heterotrophic nanoflagellates varied significantly over the summer from a mean of 26.6 × 10⁴ L^?1 ± 14.2 (23rd December) to 133.8 × 10⁴ L^?1 ± 33.5 (14th December). They imposed a significant grazing impact on the bacterioplankton, removing in excess of 100% of bacterial production in December. 6. The total organic carbon pool [DOC and particulate organic carbon (POC)] was below 600 μg L^?1. The ratio of DOC : POC ranged between 0.44 : 1 and 2.8 : 1 in the upper 40 m of the water column, and 1.8 : 1 and 3.7 : 1 in the lower waters. The microbial plankton contributed 1–29% of POC, thus detrital POC made up the largest fraction of the POC pool. 7. Beaver Lake is an extreme lacustrine ecosystem where heterotrophic processes occasionally appear to be carbon limited. Significant summer ice‐melt, not seen in a previous opportunistic sampling, may be having an impact on the carbon cycle.     

New polymorphic microsatellite loci in two fish species: bluefin killifish (Lucania goodei) and yellow bullhead (Ameiurus natalis)

We identified four new polymorphic microsatellite loci in bluefin killifish (Lucania goodei) and five loci in yellow bullheads (Ameiurus natalis). We screened 400 killifish from 20 populations and 180 bullheads from nine populations, finding a high degree of polymorphism (nine to 54 alleles per locus; average expected heterozygosity 0.678–0.976). We found no evidence for linkage disequilibrium. Three of the loci found in bluefin killifish show heterozygote deficiency; the other loci do not deviate from Hardy–Weinberg expectations.     

Density‐dependent prophylaxis in primary anti‐parasite barriers in the velvetbean caterpillar

1. Organisms rely on a set of primary barriers to prevent invasion by parasites, and secondary defences to fight parasites that breach the primary barriers. However, maintaining these defences to be active and effective is costly. Thus, hosts increase investment in anti‐parasite defences under situations of high risk of infection and reduce defences when the risk is reduced (the ‘Density‐Dependent Prophylaxis’ hypothesis). 2. In the present study, it was tested whether the midgut primary defences of the velvetbean caterpillar Anticarsia gemmatalis Hübner present density‐dependent plasticity, and also whether these defences could be induced by a viral pathogenic challenge. The aim was to examine whether morphometry and the structure of the midgut and peritrophic matrix (PM) change in accordance with colour transition in caterpillars, and whether such changes may provide the caterpillars a more protective barrier against invasion by Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV). 3. It was found that PM and the midgut epithelium of the velvetbean caterpillar change plastically according to phenotype, itself a response to changes in population density. Caterpillars reared at high densities (black phenotype) had a considerably thicker midgut epithelia and peritrophic matrices than those reared individually (green phenotype), and there was also more chitin in the PM of the former. 4. This was interpreted as the first demonstration of increased investment in primary, barrier, defences against parasites, in response to increased conspecific density and an increased risk of infection. The possibility that this arises as a positive result of pleiotropy is discussed further, wherein the biochemical pathways responsible for the up‐regulation of the immune system are also involved in midgut properties.     

Elimination of a specialised facultative symbiont does not affect the reproductive mode of its aphid host

Abstract.  1. Microorganisms that manipulate the reproduction of their hosts through diverse mechanisms including the induction of parthenogenesis are widespread among arthropods.
2. The pea aphid, Acyrthosiphon pisum , shows a variation in its reproductive mode, with lineages reproducing by cyclical parthenogenesis (obligate alternation of parthenogenetic and sexual generations each year) and others by obligate parthenogenesis (continuous asexual reproduction all year round). In addition, the pea aphid harbours, along with Buchnera the primary aphid endosymbiont, several facultative symbionts whose prevalence differs among host populations.
3. The possible influence of a Rickettsia facultative symbiont on the reproductive mode of its host was tested on two pea aphid clones by comparing the response of infected and uninfected individuals with the same genetic background to conditions that typically induce the production of sexual morphs.
4. No significant effect of the Rickettsia infection was found on the type of reproductive morphs produced (sexual vs. asexual) or on their quantities for the two clones.
5. However, the Rickettsia had a detrimental effect on the fitness of its aphid host, in apparent contradiction to the high prevalence of this symbiont in some host populations. It is suggested that this negative impact may disappear under specific environmental conditions, transforming a parasitic association into a mutualistic one.     

Palaeoenvironmental implications of the ichnology and geochemistry of the Westbury Formation (Rhaetian), Westbury‐on‐Severn,south‐west England

Abstract: The Westbury Formation (Rhaetian) beds of Westbury Garden Cliff, Westbury‐on‐Severn, west of Gloucester, Britain, show an unusual combination of features. Both deep water and emergent characteristics are present within the sediments and the trace fossils. The ichnoassemblage consists of abundant Selenichnites, Planolites beverlyensis and Lockeia with rarer Oniscoidichnus, Chondrites, Rhizocorallium irregulare, Taenidium serpentium, an unusual form of Walcottia and Merostomichnites‐like traces. These trace fossils display an interesting relationship with the sediments: low‐energy Cruziana ichnofacies is found within high‐energy sandstones. The sandstones are interbedded with laminated mudstones, apparently deposited in deep water, but some aspects of the ichnoassemblage, preservation and sedimentation indicate shallower water. One new trace fossil, Radichnus allingtona igen. et isp. nov., closely resembles the traces of modern fiddler crabs and imply emergence, by analogy. This ichnofauna is similar to early stage disaster colonisation in recent experiments in Long Island Sound (south of Connecticut, USA) and with storm‐influenced deposits within the Cardium Formation (Seebe, Alberta, Canada). This indicates a lagoonal environment with influxes of sand and oxygen. Total organic carbon levels were found to fluctuate greatly between stratigraphic layers but remained relatively high. This implies low oxygen conditions. The abundance of sulphur (in pyrite) also supports an interpretation of anoxic conditions, and low sedimentation rates within the shale layers. A restricted shallow basin or lagoonal environment is proposed for the palaeoenvironment, with fluctuating oxygen influencing diversity.     

The challenges of conservation for declining migrants: are reserve‐based initiatives during the breeding season appropriate for the Pied Flycatcher Ficedula hypoleuca?

Creating conservation policies for declining migrant species in response to global change presents a considerable challenge. Migrant species are affected by factors at breeding grounds, overwintering areas and during migration. Accordingly, reserve-based management during the breeding season is not always a suitable conservation strategy. Recent Pied Flycatcher population decline typifies the pattern for many migrants. The UK population has declined by 43% in the past decade, but explanations, and possible solutions, remain elusive. We use 15 years of data (1990–2004) from a declining British population to establish possible reasons for decline, considering: (1) breeding performance (including the influences of competition and predation); (2) weather patterns caused by the winter phase (December–March) of the North Atlantic Oscillation (NAO), which modify conditions experienced at wintering grounds and on migration; and (3) possible impacts of climate change on spring temperatures. We conclude that decreasing breeding performance is contributing to decline, but that non-breeding factors are more important. Winter NAO index is a strong predictor of breeding population, probably because it influences food abundance in Africa and at migratory stopover points. Importantly, however, year itself enhances the predictive model, indicating that influences on population remain unaccounted for by current research. Management strategies based on increasing breeding productivity cannot fully address population decline because non-breeding factors appear important. However, as breeding performance is declining, breeding-based strategies remain useful conservation tools. To this end, our research indicates that optimal placement of nestboxes as regards orientation and habitat management to increase larval food supplies could increase productivity significantly.