Prey temporarily escape from predation in the presence of a second prey species

1. Indirect interactions between populations of different prey species mediated by a shared predator population are known to affect prey dynamics. 2. Depending on the temporal and spatial scale, these indirect interactions may result in positive (apparent mutualism), neutral or negative effects (apparent competition) of the prey on each other's densities. Although there is ample evidence for the latter, evidence for apparent mutualism is scarce. 3. The effectiveness of using one species of predator for biological control of more than one pest species depends on the occurrence of such positive or negative effects. 4. We used an experimental system consisting of the two prey species Western flower thrips (Franklineilla occidentalis Pergande) and greenhouse whitefly (Trialeurodes vaporariorum Westwood) and a shared predator, the phytoseiid mite Amblyseius swirskii Athias‐Henriot. We released all three species on the same plant and studied their dynamics and distribution along rows of plants. 5. We expected that the more mobile prey species (thrips) would escape temporarily in the presence of the other prey species (whitefly) by dispersing from plants with the predator. The predator was expected to disperse slower in the presence of two prey species because of the higher availability of food. 6. Evidence was found for slower dispersal of predators and short‐term escape of thrips from predation when whiteflies were present, thus confirming the occurrence of short‐term apparent mutualism. 7. The apparent mutualism resulted in a cascade to the first trophic level: a higher proportion of fruits was damaged by thrips in the presence of whiteflies. 8. We conclude that apparent mutualism can be an important phenomenon in population dynamics, and can significantly affect biological control of pest species that share a natural enemy.     

A partial revision of Gyptis (Gyptini,Ophiodrominae, Hesionidae,Aciculata, Annelida), with descriptions of a new tribe,a new genus and five new species

Phylogenetic analyses of molecular data (COI, 16SrDNA, 18SrDNA, and 28SrDNA) show that the hesionid genus Gyptis Marion & Bobretzky in Marion, 1874, and the tribe Gyptini Pleijel, 1998, are nonmonophyletic as currently delineated. We introduce the new tribe Amphidurini and the new genus Neogyptis to accommodate these new findings. Amphidurini is sister to Gyptini and Ophiodromini and includes Amphiduros Hartman, 1959, Amphiduropsis, Pleijel, 2001, Neogyptis gen. nov. , and, possibly, Parahesione Pettibone, 1956. Morphologically, Amphidurini can be separated from Gyptini by the distally, rather than subdistally, inserted ventral cirri, and Neogyptis by the combination of this feature, the presence of a median antenna, and a distal ring with papillae on the proboscis. We redescribe and transfer the four species Gyptis crypta Pleijel, 1993, Gyptis mediterranea Pleijel, 1993, Gyptis plurisetis Hilbig, 1992, and Gyptis rosea (Malm, 1874) from Gyptis to Neogyptis gen. nov. , and describe five new species from shallow waters in Belize, Hong Kong, off Vladivostok, and deep‐sea hydrothermal vents in the Lau Basin off Fiji.     

Responses of potential hosts of Asian cuckoos to experimental parasitism

In the arms race between avian brood parasites and their hosts, several adaptations and counter‐adaptations have evolved. The most prominent host defence is rejection of parasitic eggs. We experimentally parasitized nests of 10 potential host species breeding in sympatry with four different cuckoo species in an area in Bangladesh using differently coloured model eggs to test host responses. In four species we introduced both mimetic and non‐mimetic eggs. Black Drongos Dicrurus macrocercus, hosts of the Indian Cuckoo Cuculus micropterus, rejected all model eggs. Common Mynas Acridotheres tristis and Jungle Babblers Turdoides striata accepted all eggs regardless of mimicry. These two species are parasitized by Asian Koels Eudynamys scolopaceus, Common Hawk‐cuckoo Hierococcyx varius and, in the case of Jungle Babblers, Jacobin Cuckoos Clamator jacobinus. Pied Mynas Gracupica contra, with no records of parasitism in our study area, also accepted all eggs regardless of mimicry. In the six remaining species, all of which lay spotted eggs, we introduced only non‐mimetic eggs. Black‐hooded Orioles Oriolus xanthornus rejected all model eggs, even though we have found no records of natural parasitism. Long‐tailed Shrikes Lanius schach and House Crows Corvus splendens, hosts of Asian Koels, rejected 75 and 9.1% of model eggs, respectively. Large‐billed Crows Corvus macrorhynchos, apparently not used as hosts in our study area, accepted all blue but rejected all brown model eggs. Oriental Magpie‐Robins Copsychus saularis and Red‐vented Bulbuls Pycnonotus cafer accepted all non‐mimetic model eggs. In Black Drongos, Long‐tailed Shrikes and Black‐hooded Orioles, all model eggs were ejected within 24 h of introduction. The results show considerable variation in egg rejection rates among various species, providing baseline data for further investigation of co‐evolutionary interactions between brood parasites and hosts in this region.     

The Uptake of 63Ni by the Diatom Phaeodactylum tricornutum

Kinetic studies of the uptake of ⁶³Ni by cultures of the diatom Phaeodactylum tricornutum Bohlin revealed that the uptake capacity of the cells depended strongly on their metabolic state. Phosphate-starved cells gave saturation-type uptake curves and had low nickel-binding capacity. This was increased markedly by the addition of phosphate to the cultures. When nickel ions were added before or together with the phosphate, the increase in nickel-binding capacity of phosphate-starved cells failed to appear more or less completely. Uptake of phosphate and formation of polyphosphate by the cells were not affected by the addition of nickel to the growth medium. The phosphate dependent synthesis of the principle involved in nickel binding was induced 15–20 h after the addition of phosphate to starved cells. Whether phosphate was directly or indirectly involved in this process could not be established.     

Phylogeny and reproduction in Syllidae (Polychaeta)

The phylogeny of 12 representatives of the four syllid subfamilies is analysed using 44 morphological characters and 96 character states. The analysis is designed to answer two questions: are the four subfamilies monophyletic, and how are the different reproductive strategies related? Syllids show two modes of reproduction, epigamy and schizogamy. Epigamy is mainly constrained to two of the four subfamilies, Eusyllinae and Exogoninae but occurs also in some members of Autolytinae. Schizogamy can be of two types–scissiparity and gemmiparity–and both types are found in Syllinae and Autolytinae. Several modes of brood protection also occur in the family; in some epigamous species the eggs and even juveniles are attached to the main animal, whereas in brooding schizogamous species the stolons care for the young. Brood protection appears in Exogoninae, a few species of Eusyllinae, and some Autolytinae. The resulting tree indicates that members exhibiting brood protection are constrained to one clade, and that it is uncertain whether epigamy or schizogamy is the plesiomorphic reproductive mode. Three of the four subfamilies, Autolytinae, Exogoninae and Syllinae, are supported in the analysis whereas Eusyllinae is found to be polyphyletic.     

Two methods for the prediction of Mycocentrospora acerina infection on stored carrots

Carrot plants were collected from 26 fields located in different districts in Norway during 1985, 1986 and 1987. Leaves were sampled in the first two years, and roots were sampled in all years. Incidence of Mycocentrospora acerina on the leaves at harvest was correlated (r = 0.82) to the incidence of M. acerina on the roots after storage at 0–1°C for six months (long term storage). Incidence of M. acerina on roots sampled about six weeks before harvest (date c) and placed at 10°C for six weeks (test storage) was correlated (r = 0.84) to incidence of the pathogen after long term storage on roots sampled at harvest (date d). Test storage and long term storage data from parallel samples taken at date d was more strongly correlated (r = 0.90).     

Unexpected early extinction of the European pond turtle (Emys orbicularis) in Sweden and climatic impact on its Holocene range

Using ancient DNA sequences of subfossil European pond turtles ( Emys orbicularis ) from Britain, Central and North Europe and accelerator mass spectrometry radiocarbon dating for turtle remains from most Swedish sites, we provide evidence for a Holocene range expansion of the pond turtle from the southeastern Balkans into Britain, Central Europe and Scandinavia, according to the 'grasshopper pattern' of Hewitt. Northeastern Europe and adjacent Asia were colonized from another refuge located further east. With increasing annual mean temperatures, pond turtles reached southern Sweden approximately 9800 years ago. Until approximately 5500 years ago, rising temperatures facilitated a further range expansion up to Östergötland, Sweden (approximately 58°30'N). However, around 5500 years ago pond turtle records suddenly terminate in Sweden, some 1500 years before the Holocene thermal maximum ended in Scandinavia and distinctly earlier than previously thought. This extinction coincides with a temporary cooling oscillation during the Holocene thermal maximum and is likely related to lower summer temperatures deteriorating reproductive success. Although climatic conditions improved later again, recolonization of Sweden from southern source populations was prevented by the Holocene submergence of the previous land connection via the Danish Straits that occurred approximately 8500 years ago.     

Niche segregation of coexisting Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) constrains food web coupling in subarctic lakes

1. Generalist fish species are recognised as important couplers of benthic and pelagic food‐web compartments in lakes. However, interspecific niche segregation and individual specialisation may limit the potential for generalistic feeding behaviour. 2. We studied summer habitat use, stomach contents and stable isotopic compositions of the generalist feeder Arctic charr coexisting with its common resource competitor brown trout in five subarctic lakes in northern Norway to reveal population‐level and individual‐level niche plasticity. 3. Charr and trout showed partial niche segregation in all five lakes. Charr used all habitat types and a wide variety of invertebrate prey including zooplankton, whereas trout fed mainly on insects in the littoral zone. Hence, charr showed a higher potential to promote habitat and food‐web coupling compared to littoral‐dwelling trout. 4. The level of niche segregation between charr and trout and between pelagic‐caught and littoral‐caught charr depended on the prevailing patterns of interspecific and intraspecific resource competition. The two fish species had partially overlapping trophic niches in one lake where charr numerically dominated the fish community, whereas the most segregated niches occurred in lakes where trout were more abundant. 5. In general, pelagic‐caught charr had substantially narrower dietary and isotopic niches and relied less on littoral carbon sources compared to littoral‐caught conspecifics that included generalist as well as specialised benthivorous and planktivorous individuals. Despite the partially specialised planktivorous niche and thus reduced potential of pelagic‐dwelling charr to promote benthic–pelagic coupling, the isotopic compositions of both charr subpopulations suggested a significant reliance on both littoral and pelagic carbon sources in all five study lakes. 6. Our study demonstrates that both interspecific niche segregation between and individual trophic specialisation within generalist fish species can constrain food‐web coupling and alter energy mobilisation to top consumers in subarctic lakes. Nevertheless, pelagic and littoral habitats and food‐web compartments may still be highly integrated due to the potentially plastic foraging behaviour of top consumers.     

A demographic comparison of two Nordic populations of Greylag Geese Anser anser

Greylag Geese Anser anser have been neck-banded on an annual basis in Scania, southern Sweden since 1984 and in Norway since 1986 as part of a Nordic Greylag project. This has yielded a large database of resightings, which we used here to estimate and compare survival rates between the two populations by means of mark–recapture models. Estimated adult survival was sex-dependent in the Scanian population, probably a result of differential neck band retention rates in this population. Mean juvenile survival was about 12% higher in the Scanian population (0.603 vs. 0.485). Adult survival in the Norwegian population was 0.728 (males 0.733; females 0.725), and in males and females from the Scanian population was 0.711 (0.752 after accounting for higher neck band loss in males) and 0.771, respectively. Over the course of the study, juvenile survival in the Scanian population increased substantially, and adult survival was constant, whereas both these parameters declined in the Norwegian population. This study demonstrates that the two Nordic populations are demographically distinct and gives further support to the notion that they should be treated as separate management units. The decline of 10% in adult survival in the Norwegian population, the cause of which still remains uncertain, is likely to have had a major impact on the growth of this population.     

A new species of Chrysophthalmum Schultz Bip. (Asteraceae-Inuleae) from TVirkey

The new species Chrysophthalmum gueneri Aytac & Anderb. sp. nov. from southwestern Turkey is described and illustrated. A key to the three species is presented; the systematic position and distribution of the genus are discussed.