The status of the swallowtail butterfly in Britain

• 1 Since the early 1950s, when the British swallowtail butterfly (Papilio machaon britannicus) became extinct at Wicken Fen, this subspecies has been confined to marshes around the Norfolk Broads. Here too, however, its abundance appears to be declining.
• 2 The ecology of the butterfly has been studied in Norfolk and at Wicken (by small-scale introductions) and the main factors determining its abundance are described.
• 3 A morphometric study of museum specimens has shown that populations of the butterfly in Norfolk and at Wicken differed in a number of size and shape characters. These differences were most marked between 1890 and 1920, but subsequently were almost lost.
• 4 Studies of the status and performance of the butterfly's food plant, Peucedanum palustre have shown that it is smaller, produces less seed, and is shorter-lived at Wicken than in Norfolk.
• 5 In the light of these findings, the possibility of successfully re-establishing the butterfly at Wicken, and the possible causes of the decline of the species in Norfolk are discussed.

     

Variations in groundwater chemistry and hydrology at Wicken Fen,Cambridgeshire, UK

This paper presents the results of a project in which the seasonal changes in the chemistry of groundwater in dipwells at Wicken Fen National Nature Reserve were investigated for the first time. Thirteen dipwells arranged in two roughly perpendicular transects across Wicken Fen were sampled for groundwater on a monthly basis between April 2010 and April 2011. Surface water from a drainage ditch (Gardiner’s Drain) and groundwater from a further location (dipwell 17) were also sampled at the same interval. The water samples were analysed for pH, electrical conductivity (EC), major solutes (Ca, Na, Mg, S), nutrients (N, P, K) and trace elements (Al, Fe, Mn) in the laboratory. Measurements of pH and electrical conductivity were also taken from the soil at the fourteen dipwell locations. The results of these analyses are compared to borehole data, groundwater levels and precipitation data to form a new conceptual model of the spatial and temporal variations in groundwater chemistry at Wicken Fen, which have important implications for future hydrological and vegetation management regimes.     

Recent changes in body weight and wing length among some British passerine birds

We tested the prediction that global warming has caused recent decreases in body weight (Bergmann's rule) and increases in wing length (Allen's rule) in 14 species of passerine birds at two localities in England: Wicken Fen (1968–2003) and Treswell Wood (1973–2003).
Predicted long-term linear decreases in residual body weight occurred in four species: dunnocks (Wicken Fen), and great tits, blue tits and bullfinches (Treswell Wood). Non-linear decreases also occurred in reed warblers and blackcaps at Wicken Fen, which also had a surprising linear increase in residual body weight in blackbirds.
Residual wing lengths increased linearly, as predicted, in six of seven species at Wicken Fen. Whereas there were non-linear long-term increases in wrens, dunnocks and blackbirds in Treswell Wood. Unexpected linear decreases also occurred in residual wing lengths in willow warblers (Wicken Fen), and blue tits, great tits and chaffinches (Treswell Wood).
The most parsimonious explanation for such long-term changes in body weight is global warming, as predicted by Bergmann's rule. Greater site and species-specific effects on wing length (e.g. non-linear changes plus shorter wings in the woodland habitat) suggest a less straightforward conclusion concerning Allen's rule, probably because wing length involved variation in both bone and feather growth.
Changes in residual body weights and wing lengths often differed between species and were sometimes non-linear, perhaps reflecting short-term modifications in selection pressures. Human-induced influences are discussed, such as avian predator population densities and land-use change. Short-term variation in temperature had little effect, but rainfall did explain the unusual increase in blackbird body weight, possibly as a result of improving food (earthworm) availability.     

Rapid decline of host defences in response to reduced cuckoo parasitism: behavioural flexibility of reed warblers in a changing world

On Wicken Fen and nearby watercourses eastern England, parasitism by cuckoos, Cuculus canorus, declined from 26% and 16% of reed warbler (Acrocephalus scirpaceus) nests in 1985 and 1986, respectively, to 2 to 6% of nests in 1995 to 1997, owing to a decline in cuckoos. Experiments with model eggs showed that over this 12-year period there was a marked decline in host rejection of non-mimetic eggs, from rejection at 75% of reed warbler nests in 1985 to 1986 to 25%, nests in 1997. Calculations suggest that this decline in host defences is too rapid to reflect only genetic change, and is more likely to be the outcome of adaptive phenotypic flexibility. Two other results show flexibility in host responses. First, there was a seasonal decline in rejection, which accompanied the seasonal decline in parasitism. Second, although rejection did not vary with proximity to a naturally parasitized nest within the 3.4km² of Wicken Fen and its surrounds, there was no rejection at a small unparasitized population 11km away. Flexible host defences will be advantageous when there are costs of rejection as well as short-term temporal changes and small-scale geographical variation in parasitism rate. Other recent studies reporting changes in host defences may also reflect phenotypic flexibility rather than evolutionary change.     

Hydrological assessment for wetland conservation at Wicken Fen

Wicken Fen in East Anglia, UK is a unique habitat and a wetland of international importance. A comparison of water table measurements made between 1928 and 1931 with contemporary observations indicates that summer minimum water table elevations are between 0.20 m and 0.45 m lower than in the past. The disparity cannot be attributed to differences in rainfall. There are a number of reasons why the Fen may be 'drying', but it was not possible to identify a single dominant cause. A simple water balance model that simulates groundwater levels in different areas of the Fen has been developed. This indicates that although locally important, in most years flows of water from ditches into the Fen comprise less than 10% of total summer inputs and in wet summers there is a net outflow from the Fen into the ditches. Based on an assessment of the water requirements of desired vegetation communities, a more active water management strategy than is presently implemented is proposed. This paper highlights how a better quantitative understanding of ecosystem functioning and the impact of human interventions are a pre-requisite for the development and implementation of sustainable wetland conservation strategies.     

Rapid turnover of traps in Utricularia vulgaris L.

Summary Utricularia vulgaris growing at Wicken Fen, England, showed rapid turnover of the trapping apparatus. New groups of leaves, each bearing many traps, were produced at a rate of 1.4–2.8 groups per day from April to September, 1987. Old leaves decayed at a comparable rate, so that individual leaves survived for less than 50 days. In July, trapping efficiency of individual bladders was greatest between 1 and 6 days of age and then declined rapidly. Very few traps more than 19 days old could capture prey and most were lost from the leaves within 32 days. The lifespan of traps was closely related to their size and position on the leaves. Because of the rapidity of changes in trap condition with age, trap age is a vital consideration in any studies of the functional ecology of U. vulgaris     

Benefits and costs of ecological restoration: Rapid assessment of changing ecosystem service values at a U.K. wetland

Restoration of degraded land is recognized by the international community as an important way of enhancing both biodiversity and ecosystem services, but more information is needed about its costs and benefits. In Cambridgeshire, U.K., a long-term initiative to convert drained, intensively farmed arable land to a wetland habitat mosaic is driven by a desire both to prevent biodiversity loss from the nationally important Wicken Fen National Nature Reserve (Wicken Fen NNR) and to increase the provision of ecosystem services. We evaluated the changes in ecosystem service delivery resulting from this land conversion, using a new Toolkit for Ecosystem Service Site-based Assessment (TESSA) to estimate biophysical and monetary values of ecosystem services provided by the restored wetland mosaic compared with the former arable land. Overall results suggest that restoration is associated with a net gain to society as a whole of $199 ha⁻¹y⁻¹, for a one-off investment in restoration of $2320 ha⁻¹. Restoration has led to an estimated loss of arable production of $2040 ha⁻¹y⁻¹, but estimated gains of $671 ha⁻¹y⁻¹ in nature-based recreation, $120 ha⁻¹y⁻¹ from grazing, $48 ha⁻¹y⁻¹ from flood protection, and a reduction in greenhouse gas (GHG) emissions worth an estimated $72 ha⁻¹y⁻¹. Management costs have also declined by an estimated $1325 ha⁻¹y⁻¹. Despite uncertainties associated with all measured values and the conservative assumptions used, we conclude that there was a substantial gain to society as a whole from this land-use conversion. The beneficiaries also changed from local arable farmers under arable production to graziers, countryside users from towns and villages, and the global community, under restoration. We emphasize that the values reported here are not necessarily transferable to other sites.     

Dispersal of adult Trichoptera at a Danish forest brook

• 1 The dispersal of adult Trichoptera at the small Danish forest brook, Stamperenden, was studied from 10 May to 6 October 1990 using Malaise traps placed across the brook, parallel to the brook at distances of 2, 20 and 40m, and perpendicular to it at a distance of 1–3m.
• 2 Of the total of 4175 specimens caught, lotic species breeding in Stamperenden accounted for 95.6%. The dominant species were Agapetus fuscipes, Lype reducta, Plectrocnemia conspersa, Potamophylax nigricornis and Silo pallipes.
• 3 The sex ratios in the catches of most species were uneven. Agapetus fuscipes males were in excess, probably because males fly more frequently than females.
• 4 The dominant species flew predominantly above the surface of the brook. Whereas both sexes of A. fuscipes, L. reducta and S. pallipes were rarely found even as little as 20–40m from the brook, the dispersal range of P. conspersa was much wider.
• 5 The implications of low dispersal for the biological recovery of damaged but subsequently restored streams and stream catchments are discussed. It is concluded that complete biological recovery may be a process requiring decades unless the original aquatic fauna is re-established artificially.

     

REED WARBLER HOSTS FINE‐TUNE THEIR DEFENSES TO TRACK THREE DECADES OF CUCKOO DECLINE

Interactions between avian hosts and brood parasites can provide a model for how animals adapt to a changing world. Reed warbler (Acrocephalus scirpaceus) hosts employ costly defenses to combat parasitism by common cuckoos (Cuculus canorus). During the past three decades cuckoos have declined markedly across England, reducing parasitism at our study site (Wicken Fen) from 24% of reed warbler nests in 1985 to 1% in 2012. Here we show with experiments that host mobbing and egg rejection defenses have tracked this decline in local parasitism risk: the proportion of reed warbler pairs mobbing adult cuckoos (assessed by responses to cuckoo mounts and models) has declined from 90% to 38%, and the proportion rejecting nonmimetic cuckoo eggs (assessed by responses to model eggs) has declined from 61% to 11%. This is despite no change in response to other nest enemies or mimetic model eggs. Individual variation in both defenses is predicted by parasitism risk during the host's egg‐laying period. Furthermore, the response of our study population to temporal variation in parasitism risk can also explain spatial variation in egg rejection behavior in other populations across Europe. We suggest that spatial and temporal variation in parasitism risk has led to the evolution of plasticity in reed warbler defenses.     

The Influence of Time on the Soil Seed Bank and Vegetation across a Landscape‐Scale Wetland Restoration Project

Wicken Fen National Nature Reserve (NNR) in Cambridgeshire, U.K. is a wetland of international importance isolated in a landscape dominated by arable farming. The prospect of species extinctions within the NNR led to the creation of the Wicken Fen Vision, an ambitious project that will eventually expand the reserve boundary by the purchase and restoration of c.50 km² of arable land. We sampled three fields from each of three distinct age‐categories of restoration land (5, 15, and 60 years post‐arable), and three fields within the adjacent, undrained NNR, to determine (1) differences in seed bank composition across age‐categories, (2) relationships between restoration age, the seed bank and standing vegetation, and (3) changes in species traits across age‐categories. Historic arable management contributed to an apparent “vertical mixing” effect in the seed bank of the youngest two age‐categories, with associated and significant differences in species functional traits across the study area. Almost all plants associated with NNR vegetation were absent from restoration area seed banks and standing vegetation. Seed bank species common to all ages‐categories exhibited a bias toward moderate to high Ellenberg F (moisture) values, persistent seed banks, and lateral vegetative spread. Relatively short (c. 6 years) periods of drainage and plowing impact heavily upon seed bank diversity and soils, resulting in a lack of predrainage vegetation, even after decades of subsequent restoration adjacent to intact, species‐rich habitat. However, the seed banks of highly degraded fields can contribute toward the creation of novel wetland vegetation assemblages over time and under suitable environmental conditions.     

Reproduction in two submersed macrophytes declines progressively at low pH

• 1 Greenhouse experiments tested the effect of pH 5 v pH 7.5 on reproductive success for the freshwater macrophytes Najas flexilis, an annual, and Vallisneria americana, which perennates as a tuber.
• 2 Seed production by the small Najas plants grown at pH 5 averaged 0.25 seeds/plant, in contrast to 95.5 seeds/plant at pH 7.5. At low pH, Vallisneria grown from seeds produced no flowers and too few tubers to replace themselves, so that sexual reproduction failed nearly completely for both species.
• 3 Vallisneria grown from tubers produced 97% less total tuber mass at pH 5 (0.4 v 14.9 g), the compounded result of producing, on average, 89% fewer and 82% smaller tubers. The smaller tubers developed at pH 5 were less likely to overwinter in the field, and those surviving tubers subsequently grew into smaller plants.
• 4 These findings generated the hypothesis of a closing spiral: growth at low pH (and relatively low CO₂ concentrations) results in small plants that produce a smaller number of progressively smaller tubers each autumn, which in turn develop into progressively smaller plants each summer. This hypothesis was supported by field transplant experiments in two acidic Adirondack Mountain (NY) lakes.

     

Invertebrate predation of leaf-miners at low densities

Abstract.

• 1 Predation on a species of leaf-mining insect, Eriocraniella sp., by two species of ants, Crematogaster ashmeadii Mayr and Pseudomyrmex brunnea F. Smith, is documented.
• 2 Exclusion experiments show that ants and other terrestrial invertebrates can greatly contribute to mortality of leaf-miners and significantly decrease survivorship of the larval stages even when densities are low.
• 3 Comparison of two leaf-mining species, Eriocraniella sp. and Cameraria sp. nov. Davis, indicates that factors of mortality depend on the maturity of the leaf being mined.

     

Oviposition and feeding on red pine by jack pine budworm at a previously unrecorded scale

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Mutation of the rice TCM12 gene encoding 2,3‐bisphosphoglycerate‐independent phosphoglycerate mutase affects chlorophyll synthesis,photosynthesis and chloroplast development at seedling stage at low temperatures

• Glycolysis is a central metabolic pathway that provides energy and products of primary metabolites. 2,3‐Biphosphoglycerate‐independent phosphoglycerate mutase (iPGAM) is a key enzyme that catalyses the reversible interconversion of 3‐phosphoglycerate (3‐PGA) to 2‐phosphoglycerate (2‐PGA) in glycolysis. Low temperature is a common abiotic stress in rice production. However, the mechanism for rice iPGAM genes is not fully understood at low temperature.
• In this study, the rice mutant tcm12, with chlorosis, malformed chloroplasts and impaired photosynthesis, was grown at a low temperature (<20 °C) to the three‐leaf stage, while the normal phenotype at 32 °C was used. Chlorophyll fluorescence analysis and transmission electron microscopy were used to examine features of the tcm12 mutant. The inheritance behaviour and function of TCM12 were then analysed thorough map‐based cloning, transgenic complementation and subcellular localisation.
• The thermo‐sensitive chlorosis phenotype was caused by a single nucleotide mutation (T→C) on the fifth exon of TCM12 (LOC_Os12g35040) encoding iPGAM, localised to both nucleus and membranes. In addition, TCM12 was constitutively expressed, and its disruption resulted in down‐regulation of some genes associated with chlorophyll biosynthesis and photosynthesis at low temperatures (20 °C).
• This is the first report of the involvement of rice iPGAM gene in chlorophyll synthesis, photosynthesis and chloroplast development, providing new insights into the mechanisms underlying early growth of rice at low temperatures.

     

Another look at prey detection by coccinellids

Abstract.

• 1 Adult and fourth instar larvae of Coccinella septempunctata (L.) were tested to see whether or not they could detect prey prior to physical contact.
• 2 Adult predators found aphid prey and a silver foil dummy significantly faster than an X-mark on the floor of the arena covering the same area.
• 3 Fourth instar larvae found crushed prey more quickly than the X-mark but were not able to detect whole frozen prey.
• 4 The distances at which the predators could detect prey were calculated. This distance was found to be about 1.0 cm for the adults and 0.7 cm for the fourth instar larvae.

     

The effect of host developmental stage at parasitism on sex‐related size differentiation in a larval endoparasitoid

• 1 For their larval development, parasitoids depend on the quality and quantity of resources provided by a single host. Therefore, a close relationship is predicted between the size of the host at parasitism and the size of the emerging adult wasp. This relationship is less clear for koinobiont than for idiobiont parasitoids.
• 2 As size differentiation in host species exhibiting sexual size dimorphism (SSD) is likely to occur already during larval development, in koinobiont larval endoparasitoids the size of the emerging adult may also be constrained based on the sex of the host caterpillar.
• 3 Sex‐specific growth trajectories were compared in unparasitised Plutella xylostella caterpillars and in second and fourth instar hosts that were parasitised by the solitary larval koinobiont endoparasitoid Diadegma semiclausum. Both species exhibit SSD, where females are significantly larger than males.
• 4 Healthy female P. xylostella caterpillars developed significantly faster than their male conspecifics. Host regulation induced by D. semiclausum parasitism depended on the instar attacked. Parasitism in second‐instar caterpillars reduced growth compared to healthy unparasitised caterpillars, whereas parasitism in fourth‐instar caterpillars arrested development. The reduction in growth was most pronounced in hosts producing male D. semiclausum.
• 5 Parasitism itself had the largest impact on host growth. SSD in the parasitoid is mainly the result of differences in growth rate of the parasitoid–host complex producing male and female wasps and differences in exploitation of the host resources. Female wasps converted host biomass more efficiently into adult biomass than males.

     

Population ecology of the endangered aquatic carnivorous macrophyte Aldrovanda vesiculosa at a naturalised site in North America

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Predicting probability of occurrence and factors affecting distribution and abundance of three Ozark endemic crayfish species at multiple spatial scales

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Interference of allelopathic rice with paddy weeds at the root level

• Despite increasing knowledge of the involvement of allelopathy in negative interactions among plants, relatively little is known about its action at the root level. This study aims to enhance understanding of interactions of roots between a crop and associated weeds via allelopathy.
• Based on a series of experiments with window rhizoboxes and root segregation methods, we examined root placement patterns and root interactions between allelopathic rice and major paddy weeds Cyperus difformis, Echinochloa crus‐galli, Eclipta prostrata, Leptochloa chinensis and Oryza sativa (weedy rice).
• Allelopathic rice inhibited growth of paddy weed roots more than shoots regardless of species. Furthermore, allelopathic rice significantly reduced total root length, total root area, maximum root width and maximum root depth of paddy weeds, while the weeds adjusted horizontal and vertical placement of their roots in response to the presence of allelopathic rice. With the exception of O. sativa (weedy rice), root growth of weeds avoided expanding towards allelopathic rice. Compared with root contact, root segregation significantly increased inhibition of E. crus‐galli, E. prostrata and L. chinensis through an increase in rice allelochemicals. In particular, their root exudates induced production of rice allelochemicals. However, similar results were not observed in C. difformis and O. sativa (weedy rice) with either root segregation or root exudate application.
• The results demonstrate that allelopathic rice interferes with paddy weeds by altering root placement patterns and root interactions. This is the first case of a root behavioural strategy in crop–weed allelopathic interaction.

     

Response of the egg parasitoids of the pine processionary moth to host density and forest cover at the southern edge of the range

1. Thaumetopoea pityocampa is the most important pine defoliator in the Mediterranean basin. Despite being attacked by a number of natural enemies, populations occur frequently at high density in several areas.
2. Egg parasitism was studied in 27 pine and cedar forests in Algeria, in relation to the host density (tents per tree) and the proportion of forest cover in the landscape.
3. Egg parasitism varied from 2% to 25%, accounted by two parasitoid species, the specialist Baryscapus servadeii and the generalist Ooencyrtus pityocampae.
4. Tent density was negatively correlated with parasitism by B. servadeii but not with that of O. pityocampae. Conversely, parasitism by O. pityocampae increased with the proportion of forest and agricultural cover, but not in the case of B. servadeii.
5. Maximum summer temperature showed no correlation with parasitism rates. Still, temperature frequently exceeded 40 °C during the period of adult parasitoid activity.
6. The low performance of the egg parasitoids at the southern edge of the host range could be explained by the reduced fecundity of the host, climate effects, and phenological mismatching between the parasitoids and the egg development. These and other factors potentially involved the need to be further explored with a long-term study of population dynamics.