Losing anti‐predatory behaviour: A cost of translocation

Translocation of endangered species to habitats where exotic predators have been removed is now a common conservation practice around the world. Many of these translocated populations have thrived, and they are often used as sources for the harvesting of individuals for translocations to sites where exotic predators still exist, albeit at reduced densities. This study investigates how isolation from exotic predators affects the ability of individuals to recognize such predators using the North Island robin (Petroica longipes) as a model. The study was carried out in three robin populations in the North Island, New Zealand: a translocated population on Tiritiri Matangi Island, where exotic mammalian predators are absent; a population reintroduced from Tiritiri Matangi Island to Wenderholm Regional Park, a mainland site where these mammals are controlled to low densities; and a mainland population at Benneydale where exotic predatory mammals are common. The response intensity of robins to a model stoat was high at Benneydale and low at Tiritiri Matangi and Wenderholm. This result indicates that isolation from mammalian predators on Tiritiri Matangi has suppressed the ability of North Island robins to recognize these predators. It is possible that the low predatory mammal densities at Wenderholm have reduced robin contact with stoats, therefore reduced the opportunity for robins to learn to recognize stoats. Thus, translocation of individuals from populations without predators to places where key predators still exist could be unsuccessful if translocated individuals fail to perform appropriate anti‐predator behaviours.     

A multidisciplinary approach to discriminating different taxa in the species complex Pachycondyla villosa (Formicidae)

A multidisciplinary approach provides new evidence that strongly supports the differentiation of three taxa previously confounded in a single species, Pachycondyla villosa . All specimens studied were collected in the same location at Ilhéus, Bahia, Brazil. Bivariate plots of petiole heights vs. petiole lengths and isozyme patterns clearly differentiate the three taxa. Chain lengths and chemical structures of cuticular hydrocarbons are characteristic of each taxon. This congruent evidence shows that there are three different valid species. Ecological hypotheses are discussed to explain the benefits of these species remaining sympatric. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 249–259.     

Age-specific effect of heterozygosity on survival in alpine marmots, Marmota marmota

The fitness consequences of heterozygosity and the mechanisms underpinning them are still highly controversial. Using capture–mark–recapture models, we investigated the effects of individual heterozygosity, measured at 16 microsatellite markers, on age-dependent survival and access to dominance in a socially monogamous mammalian species, the alpine marmot. We found a positive correlation between standardized multilocus heterozygosity and juvenile survival. However, there was no correlation between standardized multilocus heterozygosity and either survival of older individuals or access to dominance. The disappearance of a significant heterozygosity fitness correlation when individuals older than juveniles are considered is consistent with the prediction that differences in survival among individuals are maximal early in life. The lack of a correlation between heterozygosity and access to dominance may be a consequence of few homozygous individuals attaining the age at which they might reach dominance. Two hypotheses have been proposed to explain heterozygosity-fitness correlations: genome-wide effects reflected by all markers or local effects of specific markers linked to genes that determine fitness. In accordance with genome-wide effects of heterozygosity, we found significant correlations between heterozygosities calculated across single locus or across two sets of eight loci. Thus, the genome-wide heterozygosity effect seems to explain the observed heterozygosity-fitness correlation in the alpine marmot.     

Bi-directional soil/atmosphere N2O exchange over two mown grassland systems with contrasting management practices

Nitrous oxide (N₂O) fluxes from soil under mown grassland were monitored using static chambers over three growing seasons in intensively and extensively managed systems in Central Switzerland. Emissions were largest following the application of mineral (NH₄NO₃) fertilizer, but there were also substantial emissions following cattle slurry application, after grass cuts and during the thawing of frozen soil. Continuous flux sampling, using automatic chambers, showed marked diurnal patterns in N₂O fluxes during emission peaks, with highest values in the afternoon. Net uptake fluxes of N₂O and subambient N₂O concentrations in soil open pore space were frequently measured on both fields. Flux integration over 2.5 years yields a cumulated emission of +4.7 kgN₂O‐N ha^?1 for the intensively managed field, equivalent to an average emission factor of 1.1%, and a small net sink activity of ?0.4 kg N₂O‐N ha^?1 for the unfertilized system. The data suggest the existence of a consumption mechanism for N₂O in dry, areated soil conditions, which cannot be explained by conventional anaerobic denitrification. The effect of fertilization on greenhouse gas budgets of grassland at the ecosystem level is discussed.     

The diet of Emperor Penguins Aptenodytes forsteri in Adelie Land, Antarctica

This first quantitative study of the diet of Emperor penguins is based on 29 stomach contents collected with a water off-loading method in Adelie Land. The Emperor is largely ichthyophagous (65% by number and 95% by weight) and feeds extensively on small nototheniids (97% of the fish are 40–125 mm in overall length). These results and data on meal size and feeding frequency of the chick suggest that Emperors are off-shore foraging birds offering little competition for food with other sea-birds or mammals.     

Effects of coexistence on habitat use and trophic ecology of interacting native and invasive amphipods

1. Invasive species in aquatic systems are major drivers of changes in biodiversity. Amphipods are key species in freshwaters, with invasive amphipods either replacing or coexisting with native species and often damaging local biodiversity. However, the consequences of interactions among native and invasive amphipods for their habitat use and feeding ecology and ecosystem function are not yet well understood. 2. We examined a number of streams in Brittany and Northern Ireland, with native and invasive amphipods, to evaluate the consequences of species interactions for both habitat use and diet. Our field studies centred on testing two proposed models: a cohabitation model without competition between two native species (Gammarus pulex vs Echinogammarus berilloni), and a competition model between an invasive and a native species (Gammarus pulex vs Gammarus duebeni celticus). For these three species, alone and in combination, we assessed their habitat use and feeding patterns, the latter through gut contents and stable C and N isotope analyses of their tissues. 3. When existing as single‐species populations, all three species used stream habitats broadly similarly, although G. pulex was more strongly associated with leaf litter and vegetation compared to pebble substrata than the other species. When G. pulex coexisted with either E. berilloni or G. d. celticus, the latter two changed to using all habitats equally, whereas the former retained its habitat preferences. 4. Similarly, all three species when alone had similar gut contents, with inorganic material predominating, followed by leaf and woody material and more rarely algae and invertebrates. When G. pulex coexisted with E. berilloni, the diet of the latter did not change; however, the frequency of inorganic matter, leaves and wood declined in the gut contents of G. pulex. When G. pulex coexisted with G. d. celticus, the pattern of gut contents did not change in either species. 5. When existing as single‐species populations, G. pulex had a broader range of isotopic signatures, both for δ¹³C and for δ¹⁵N, than the two other species, indicating a more variable diet among individuals. When G. pulex coexisted with either E. berilloni or G. d. celticus, the latter two had similar ranges of δ¹³C and δ¹⁵N, whereas for G. pulex the range was much less for δ¹³C and δ¹⁵N, suggesting a less diverse diet. 6. Our results infer two different modes of coexistence between native and non‐native amphipods. We have shown that the native species, which coexist stably, appear to show interference competition, leading to spatial habitat segregation, whereas competition for food and possible intraguild predation by G. pulex on G. d. celticus would explain why the distribution and density of the latter is affected by G. pulex. However, since all the species have a similar diet and feeding habit, we expect no great overall effect on ecosystem processes as a consequence of species interactions and displacements.