The catchment and climate regulation of pCO2 in boreal lakes

The regulation of surface water pCO₂ was studied in a set of 33 unproductive boreal lakes of different humic content, situated along a latitudinal gradient (57°N to 64°N) in Sweden. The lakes were sampled four times during one year, and analyzed on a wide variety of water chemistry parameters. With only one exception, all lakes were supersaturated with CO₂ with respect to the atmosphere at all sampling occasions. pCO₂ was closely related to the DOC concentration in lakes, which in turn was mainly regulated by catchment characteristics. This pattern was similar along the latitudinal gradient and at different seasons of the year, indicating that it is valid for a variety of climatic conditions within the boreal forest zone. We suggest that landscape characteristics determine the accumulation and subsequent supply of allochthonous organic matter from boreal catchments to lakes, which in turn results in boreal lakes becoming net sources of atmospheric CO₂.     

Diet of the King Penguin Aptenodytes patagonicus during three summers at South Georgia

King Penguins Aptenodytes patagonicus which were rearing chicks were studied during three summers from November 1991 to March 1994 at South Georgia. Stomach samples ( n =115) collected by flushing had a mean mass of 1308 g. Fish mass was allocated to each species based on the relationship between fish mass and otolith length. Three mesopelagic lanternfishes (Myctophidae), Krefftichthys anderssoni, Electrona carlsbergi and Protomyctophum choriodon , dominated the diet both by numbers and mass. They were small fish with mean mass of 3–7 g. Overall, K. anderssoni dominated the diet in terms of numbers and mass. Although Barracudina Notolepis coatsi occurred in <3% of the diet by numbers, it was large (106 g) and was second most important in terms of mass. Squid represented <3% of the diet by mass. Although the chick-rearing success was poor in the 1993–1994 summer, meal size was not reduced but foraging trips were longer. In the 1993–1994 summer, a larger proportion of the otoliths were not identifiable because they were more completely digested. Fewer otoliths were identified as being those of K. anderssoni , but we argue that about 90% of the unidentified otoliths were K. anderssoni. There was also more squid and N. coatsi in the diet during the poor summer. A consistent trend was that P. choriodon was rare or absent in early summer but more important later in the year, and at the end of 1992–1993, it was the dominant prey. We conclude that myctophid fish, especially K. anderssoni , are the main summer prey of King Penguins rearing chicks at South Georgia, as found in other recent studies in the Southern Ocean.     

Nutrient budgets and the regulation of nutrient concentrations in a small sub-arctic lake in northern Sweden

SUMMARY. A 5-year study was made of the hydrology and water chemistry in the watershed of Lake Stugsjön, a small lake in the sub-arctic region of northern Sweden. Of the total yearly runoff, 80% occurs during the spring thaw in May and June and largely regulates the nutrient loading. The ice-free period of the lake is June—October. Atmospheric deposition of nitrogen and phosphorus was among the lowest recorded anywhere, in spite of which it accounts for approximately half of the total summer nutrient loading. Dry fall-out made up the major part of the total atmospheric deposition of nitrogen and phosphorus during the summer.
Conductivity measurements showed that the major constituents were not influenced by processes within the lake.
The nitrogen concentration in the lake during the summer was probably regulated by benthic algae which assimilated inorganic nitrogen from the sediments and released organic nitrogen to the lake water.
Phosphorus loading and water temperature in combination showed a clear relationship with the mean concentration of chlorophyll-α during the ice-free period.     

Biomass and structure of planktonic communities along an air temperature gradient in subarctic Sweden

1. Air temperature will probably have pronounced effects on the composition of plankton communities in northern lake ecosystems, either via indirect effects on the export of essential elements from catchments or through direct effects of water temperature and the ice‐free period on the behaviour of planktonic organisms. 2. We assessed the role of temperature by comparing planktonic communities in 15 lakes along a 6 °C air temperature gradient in subarctic Sweden. 3. We found that the biomass of phytoplankton, bacterioplankton and the total planktonic biomass were positively related to air temperature, probably as a result of climatic controls on the export of nitrogen from the catchment (which affects phytoplankton biomass) and dissolved organic carbon (affecting bacterioplankton biomass). 4. The structure of the zooplankton community, and top down effects on phytoplankton, were apparently not related to temperature but mainly to trophic interactions ultimately dependent on the presence of fish in the lakes. 5. Our results suggest that air temperature regimes and long‐term warming can have strong effects on the planktonic biomass in high latitude lakes. Effects of temperature on the structure of the planktonic community might be less evident unless warming permits the invasion of fish into previous fishless lakes.     

Morphological, vocal and genetic divergence in the Cettia acanthizoides complex (Aves: Cettiidae)

We used morphological, vocal and molecular (one mitochondrial and two nuclear loci) data to re-evaluate the taxonomic status of the taxa acanthizoides , concolor , and brunnescens in the Cettia acanthizoides (J. Verreaux, 1871) complex. We conclude that all three are valid taxa, and that acanthizoides of China and concolor of Taiwan are best treated as conspecific, whereas brunnescens of the Himalayas is better considered as a separate species. The degree of morphological, vocal, and genetic differentiation is variably congruent among all taxa; the recently separated acanthizoides and concolor differ slightly in plumage and structure but are indistinguishable in vocalizations, whereas the earlier diverged brunnescens and acanthizoides/concolor differ only slightly more in morphology but to a much greater degree in vocalizations. We stress the essential nature of taxonomic revisions as a prerequisite for the biodiversity estimates required for conservation planning.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 437–452.     

Giving offspring a head start in life: field and experimental evidence for selection on maternal basking behaviour in lizards

The timing of birth is often correlated with offspring fitness in animals, but experimental studies that disentangle direct effects of parturition date and indirect effects mediated via variation in female traits are rare. In viviparous ectotherms, parturition date is largely driven by female thermal conditions, particularly maternal basking strategies. Our field and laboratory studies of a viviparous lizard (Niveoscincus ocellatus) show that earlier‐born offspring are more likely to survive through their first winter and are larger following that winter, than are later‐born conspecifics. Thus, the association between parturition date and offspring fitness is causal, rather than reflecting an underlying correlation between parturition date and maternal attributes. Survival selection on offspring confers a significant advantage for increased maternal basking in this species, mediated through fitness advantages of earlier parturition. We discuss the roles of environmentally imposed constraints and parent–offspring conflict in the evolution of maternal effects on parturition date.     

Description of a new species of Phylloscopus warbler from Vietnam and Laos

A new species of Phylloscopus warbler, which we name Phylloscopus calciatilis Limestone Leaf Warbler, is described from central and northern Vietnam and central and northern Laos; it probably also breeds in southernmost China. In morphology, the new species is very similar to Sulphur-breasted Warbler Phylloscopus ricketti , but it is smaller with a proportionately larger bill and rounder wing. Its song and calls are diagnostic. Based on mitochondrial and nuclear DNA, the new species is most closely related to P. ricketti and Yellow-vented Warbler Phylloscopus cantator , and it is inferred to be sister to the latter. The mitochondrial divergences between these three species are at the low end of the variation found in other species of Phylloscopus and Seicercus warblers, but greater than in other taxa generally treated as subspecies. Possible introgressive hybridization between the new species and P. ricketti is discussed, but more data are needed to establish whether it does occur and, if it does, to what extent. The new species appears to have a restricted breeding range in limestone karst environments, where it is locally common and therefore not under any immediate threat. In view of the recognition of the new species, all previous records of P. ricketti sensu lato need to be re-evaluated.     

Another arborescent umbellifer: a new species of Steganotaenia from north-east tropical Africa

THULIN, M., 1991. Another arborescent umbellifer: a new species of Steganotaenia from north-east tropica] Africa. The new species Steganotaenia commiphoroides is described from central and southern Somalia, and south-eastern Ethiopia. It differs from the likewise arborescent S. araliacea , widespread in tropical Africa, in, for example, its 3-foliolate or occasionally simple leaves, leaf teeth with shorter aristae, shorter petioles and pedicels, and fruits with a pair of distinctly winged dorsal ridges.