Body mass of prefledging Emperor Geese Chen canagica: large-scale effects of interspecific densities and food availability

We studied body mass of prefledging Emperor Geese Chen canagica at three locations across the Yukon–Kuskokwim Delta, Alaska, during 1990–2004 to investigate whether large-scale variation in body mass was related to interspecific competition for food. From 1990 to 2004, densities of Cackling Geese Branta hutchinsii minima more than doubled and were c . 2–5× greater than densities of Emperor Geese, which were relatively constant over time. Body mass of prefledging Emperor Geese was strongly related (negatively) to interspecific densities of geese (combined density of Cackling and Emperor Geese) and positively related to measures of food availability (grazing lawn extent and net above-ground primary productivity (NAPP)). Grazing by geese resulted in consumption of ≥ 90% of the NAPP that occurred in grazing lawns during the brood-rearing period, suggesting that density-dependent interspecific competition was from exploitation of common food resources. Efforts to increase the population size of Emperor Geese would benefit from considering competitive interactions among goose species and with forage plants.     

Widespread hybridization between the Greater Spotted Eagle Aquila clanga and the Lesser Spotted Eagle Aquila pomarina (Aves: Accipitriformes) in Europe

Hybridization is a significant threat for endangered species and could potentially even lead to their extinction. This concern applies to the globally vulnerable Greater Spotted Eagle Aquila clanga, a species that co‐occurs, and potentially interbreeds, with the more common Lesser Spotted Eagle Aquila pomarina in a vast area of Eastern Europe. We applied single nucleotide polymorphism (SNP) and microsatellite markers in order to study hybridization and introgression in 14 European spotted eagle populations. We detected hybridization and/or introgression in all studied sympatric populations. In most regions, hybridization took place prevalently between A. pomarina males and A. clanga females, with introgression to the more common A. pomarina. However, such a pattern was not as obvious in regions where A. clanga is still numerous. In the course of 16 years of genetic monitoring of a mixed population in Estonia, we observed the abandonment of A. clanga breeding territories and the replacement of A. clanga pairs by A. pomarina, whereby on several occasions hybridization was an intermediate step before the disappearance of A. clanga. Although the total number of Estonian A. clanga × A. pomarina pairs was twice as high as that of A. clanga pairs, the number of pairs recorded yearly were approximately equal, which suggests a higher turnover rate in interbreeding pairs. This study shows that interspecific introgressive hybridization occurs rather frequently in a hybrid zone at least 1700‐km wide: it poses an additional threat for the vulnerable A. clanga, and may contribute to the extinction of its populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 725–736.     

Interspecific offspring killing in owls

In Baranya County (Southern Hungary), tawny owls (Strix aluco) and barn owls (Tyto alba) sequentially use the same nest boxes in a significant number of cases. A total of 460 broods were observed between 1996 and 2003 and, in 12 cases, whole broods of dead tawny owl chicks were registered that had apparently been killed. On investigating the reproductive life characteristics, population sizes, and frequency of killing in these two species, it was concluded that: (1) with growing barn owl population, the number of sequential broods increases but changes in tawny owl population size have no effect on the frequency of sequential broods; (2) the number of killings depends on the number of sequential broods; and (3) with growing barn owl population, the number of killings also grows and this change is unaffected by the size of the tawny owl population. However, no killing occurs as long as 50–60% of the nest boxes are unoccupied. There is no killing either until the percentage of nest boxes occupied by barn owls reaches 40%, although a threshold value like this cannot be shown for the tawny owl. In the cases when a barn owl breeding follows the tawny owl's, the percentage of killing is significantly higher compared to that when barn owls do not breed in the same box. These results indicate that barn owls kill the offspring of tawny owls. By these means, they obtain a breeding place earlier than without killing the chicks of the other species, and this results in higher reproductive success. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 488–494.     

Rapid root closure after fire limits fine root responses to elevated atmospheric CO2 in a scrub oak ecosystem in central Florida, USA

Elevated atmospheric carbon dioxide (CO₂) often stimulates the growth of fine roots, yet there are few reports of responses of intact root systems to long‐term CO₂ exposure. We investigated the effects of elevated CO₂ on fine root growth using open top chambers in a scrub oak ecosystem at Kennedy Space Center, Florida for more than 7 years. CO₂ enrichment began immediately after a controlled burn, which simulated the natural disturbance that occurs in this system every 10–15 years. We hypothesized that (1) root abundance would increase in both treatments as the system recovered from fire; (2) elevated CO₂ would stimulate root growth; and (3) elevated CO₂ would alter root distribution. Minirhizotron tubes were used to measure fine root length density (mm cm^?2) every three months. During the first 2 years after fire recovery, fine root abundance increased in all treatments and elevated CO₂ significantly enhanced root abundance, causing a maximum stimulation of 181% after 20 months. The CO₂ stimulation was initially more pronounced in the top 10 cm and 38–49 cm below the soil surface. However, these responses completely disappeared during the third year of experimental treatment: elevated CO₂ had no effect on root abundance or on the depth distribution of fine roots during years 3–7. The results suggest that, within a few years following fire, fine roots in this scrub oak ecosystem reach closure, defined here as a dynamic equilibrium between production and mortality. These results further suggest that elevated CO₂ hastens root closure but does not affect maximum root abundance. Limitation of fine root growth by belowground resources – particularly nutrients in this nutrient‐poor soil – may explain the transient response to elevated CO₂.     

NEXT GENERATION HEALTHY SOUP: AN EXPLORATION USING CONJOINT ANALYSIS

This paper presents results on consumer attitudes towards healthy soup, using conjoint analysis, executed on the Internet. The results show moderate interest in new ideas for the total panel, but reveal three concept-response segments. The first segment responds to nutrition and functional ingredients. The second segment responds to packaging and convenience. The third segment responds to taste and ingredients. Statistical analysis confirms the idea that they represent different 'mind-sets'. The segmentation based on psychographic variables is a useful tool to identify the features of the next generation "healthy soups" and to design custom products on the basis of consumer requirements.     

On the Identity of the Amoeboflagllates Didascalus throntoni and Adelphamoeba galeacystis

ABSTRACT. Didascalus thorntoni , Singh 1952 has been classified alternately as a separate genus or as a species of Naegleria. In the 18th edition of the American Type Culture Collection catalogue it is classified as Naegleria thorntoni. To resolve the question of its identity we have used riboprinting and sequencing of the small subunit ribosomal DNA. The results indicate that D. thorntoni does not belong to the genus Naegleria. The sequence of the small subunit ribosomal DNA differs only in 20 nucleotides (1%) from that of the Paratetramitus jugosus. The difference is much smaller than between some species of Naegleria. Therefore, it is not clear whether D. thorntoni should be considered as a species of Paratetramitus or as a separate genus. The strain used in different laboratories as the type strain of Adelophamoeba gleacystis has been identified as a Naegleria strain. We believe that the type strain of A. galeacystis was mislabeled prior to submission to the American Type Culture Collection and to the Culture Collection of Algae and Protozoa. A recent isolate, which on the basis of morphology was identified as a strain of A. Galeacystis , has the identical small subunit ribosomal DNA sequence as D. throntoni. Our results prove Page was right when he stated that Adelphamoeba might be a synonym of Didascalus.     

X-ray investigation of gas bubble formation, and water loss in tsetse fly pupae

ABSTRACT. Using a microfocal X-ray apparatus, a gas bubble was detected within the puparium of Glossina morsitans. The bubble appeared between 6 and 15 h after pupariation and was associated with one of the longitudinal tracheal trunks of the third instar larva. The bubble grew and achieved maximum size approximately 96 h after pupariation. It then disappeared at the time of eversion of the pupal appendages. There was a close correlation between bubble size and the weight of water lost since the time of pupariation. At the time of eversion of the pupal appendages the gas bubble apparently passed out through the longitudinal tracheal trunk and posterior spiracle to occupy the space between larval (puparial) and pupal cuticle. It is suggested that the bubble plays a vital role in the separation of these cuticular layers and that to this end water loss from the puparium is essential.