On the 13C/12C isotopic signal of day and night respiration at the mesocosm level

While there is currently intense effort to examine the ¹³C signal of CO₂ evolved in the dark, less is known on the isotope composition of day‐respired CO₂. This lack of knowledge stems from technical difficulties to measure the pure respiratory isotopic signal: day respiration is mixed up with photorespiration, and there is no obvious way to separate photosynthetic fractionation (pure c_i/c_a effect) from respiratory effect (production of CO₂ with a different δ¹³C value from that of net‐fixed CO₂) at the ecosystem level. Here, we took advantage of new simple equations, and applied them to sunflower canopies grown under low and high [CO₂]. We show that whole mesocosm‐respired CO₂ is slightly ¹³C depleted in the light at the mesocosm level (by 0.2–0.8‰), while it is slightly ¹³C enriched in darkness (by 1.5–3.2‰). The turnover of the respiratory carbon pool after labelling appears similar in the light and in the dark, and accordingly, a hierarchical clustering analysis shows a close correlation between the ¹³C abundance in day‐ and night‐evolved CO₂. We conclude that the carbon source for respiration is similar in the dark and in the light, but the metabolic pathways associated with CO₂ production may change, thereby explaining the different ¹²C/¹³C respiratory fractionations in the light and in the dark.     

Winter Distribution,Movements, and Annual Survival of Radiomarked Vancouver Canada Geese in Southeast Alaska

ABSTRACT Management of Pacific Flyway Canada geese (Branta canadensis) requires information on winter distribution of different populations. Recoveries of tarsus bands from Vancouver Canada geese (B. canadensis fulva) marked in southeast Alaska, USA, ≥4 decades ago suggested that ≥83% of the population was non-migratory and that annual adult survival was high (Ŝ = 0.836). However, recovery distribution of tarsus bands was potentially biased due to geographic differences in harvest intensity in the Pacific Flyway. Also, winter distribution of Vancouver Canada geese could have shifted since the 1960s, as has occurred for some other populations of Canada geese. Because winter distribution and annual survival of this population had not recently been evaluated, we surgically implanted very high frequency radiotransmitters in 166 adult female Canada geese in southeast Alaska. We captured Vancouver Canada geese during molt at 2 sites where adults with goslings were present (breeding areas) and 2 sites where we observed nonbreeding birds only. During winter radiotracking flights in southeast Alaska, we detected 98% of 85 females marked at breeding areas and 83% of 70 females marked at nonbreeding sites, excluding 11 females that died prior to the onset of winter radiotracking. We detected no radiomarked females in coastal British Columbia, or western Washington and Oregon, USA. Most (70%) females moved ≤30 km between November and March. Our model-averaged estimate of annual survival (Ŝ = 0.844, SE = 0.050) was similar to the estimate of annual survival of geese marked from 1956 to 1960. Likely <2% of Vancouver Canada geese that nest in southeast Alaska migrate to winter areas in Oregon or Washington where they could intermix with Canada geese from other populations in the Pacific Flyway. Because annual survival of adult Vancouver Canada geese was high and showed evidence of long-term consistency, managers should examine how reproductive success and recruitment may affect the population.     

Seasonal declines in incubation periods of Brünnich's Guillemots Una lomvia:testing proximate causes

In many species of bird, eggs laid late in the laying period hatch after a shorter incubation period than do eggs laid early. These seasonal declines in incubation period are generally thought to confer evolutionary advantages, but the proximate mechanisms that underlie them are poorly understood. Seasonal declines in incubation period are usually attributed to: (1) seasonal increases in ambient air temperatures; (2) seasonal changes in the behaviour of incubating birds; and/or (3) seasonal declines in egg size. In a previous study, Common Guillemot Una aalge incubation periods declined with laying date at a low-Arctic colony. As there was no support for hypotheses 1 or 2, it was suggested that this occurred because egg size declined with laying date, but eggs were not measured in that study. We recorded similar seasonal declines in the incubation periods of the single eggs laid by Brünnich's Guillemots Una lomvia at two low-Arctic colonies in four years. Neither seasonal variation in ambient air temperatures, nor in the behaviour of incubating adults, appeared to cause the declines. As predicted for Common Guillemots, incubation period increased with egg size among Briinnich's Guillemots, in one of two years. However, incubation period declined with laying date in the absence of corresponding declines in egg size. We conclude that none of the three commonly proposed proximate mechanisms adequately explains the seasonal variation in guillemot incubation periods. Several testable, alternative mechanisms are explored.     

Worldwide mitochondrial DNA diversity and phylogeography of pilot whales (Globicephala spp.)

Pilot whales (Globicephala spp.) provide an interesting example of recently diverged oceanic species with a complex evolutionary history. The two species have wide but largely non‐overlapping ranges. Globicephala melas (long‐finned pilot whale; LFPW) has an antitropical distribution and is found in the cold‐temperate waters of the North Atlantic and Southern Hemisphere, whereas Globicephala macrorhynchus (short‐finned pilot whale; SFPW) has a circumglobal distribution and is found mainly in the tropics and subtropics. To investigate pilot whale evolution and biogeography, we analysed worldwide population structure using mitochondrial DNA (mtDNA) control region sequences (up to 620 bp) from a variety of sources (LFPW = 643; SFPW = 150), including strandings in New Zealand and Tasmania, and whale‐meat products purchased on the markets of Japan and Korea. Phylogenetic reconstructions failed to support a reciprocal monophyly of the two species, despite six diagnostic substitutions, possibly because of incomplete lineage sorting or inadequate phylogenetic information. Both species had low haplotype and nucleotide diversity compared to other abundant widespread cetaceans (LFPW, π = 0.35%; SFPW, π = 0.87%) but showed strong mtDNA differentiation between oceanic basins. Strong levels of structuring were also found at the regional level. In LFPW, phylogeographic patterns were suggestive either of a recent demographic expansion or selective sweep acting on the mtDNA. For SFPW, the waters around Japan appear to represent a centre of diversity, with two genetically‐distinct forms, as well as a third population of unknown origin. The presence of multiple unique haplotypes among SFPW from South Japan, together with previously documented morphological and ecological differences, suggests that the southern form represents a distinct subspecies and/or evolutionary significant unit. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 729–744.     

Use of remote sensing to measure change in the extent of habitat for the critically endangered Jerdon's Courser Rhinoptilus bitorquatus in India

Jerdon's Courser Rhinoptilus bitorquatus is one of the most endangered and least understood birds in the world. It is endemic to scrub habitats in southeast India which have been lost and degraded because of human land use. We used satellite images from 1991 and 2000 and two methods for classifying land cover to quantify loss of Jerdon's Courser habitat. The scrub habitats on which this species depends decreased in area by 11–15% during this short period (9.6 years), predominantly as a result of scrub clearance and conversion to agriculture. The remaining scrub patches were smaller and further from human settlements in 2000 than in 1991, implying that much of the scrub loss had occurred close to human population centres. We discuss the implications of our results for the conservation of Jerdon's Courser and the use of remote sensing methods in conservation.     

Molecular analysis of the efficiency of sloughed skin sampling in whale population genetics

Sloughed whale skin contains enough DNA for genetic analysis, and offers a nonintrusive method for collecting tissue. Here, we examine the efficiency of sloughed skin sampling using 1460 samples collected from free-ranging humpback whales. Samples were sexed and screened for up to 10 microsatellite markers. The vast majority of samples appear genetically compatible with field observations. About 1% of groups revealed more genotypes than whales, but we argue that this is more likely to be due to unobserved whales than to contamination. Sloughed skin sampling is particularly effective when applied to active groups and offers a viable alternative to biopsy darting in regions where darting is either not permitted or otherwise undesirable.