House Finch Carpodacus mexicanus roosting behaviour during the non-breeding season and possible effects of mycoplasmal conjunctivitis

We studied House Finch Carpodacus mexicanus roosting behaviour during the non-breeding season using radiotracking and direct observations in Ithaca, NY, USA. In contrast to what has been reported in the literature and in contrast to what should be expected from Newton's European studies of cardueline finches, House Finches roost in small groups (mean 3.5; maximum 11) and do not display at roost sites. Seventy-seven per cent of the birds re-used the same tree on successive observations. In winter, birds re-used the same roost tree more often than in the autumn, and birds with mycoplasmal conjunctivitis tended to move more between roost trees than did birds without conjunctivitis. A small number of radiotagged birds that roosted in the same tree were observed together in the daytime more often than by chance, suggesting the existence of social bonds between birds (some same sex) during the non-breeding season. In the autumn the birds often roosted in leafed deciduous trees and closer to their daytime feeding locations than they did in winter. In winter all birds roosted in evergreen trees. It is possible that the reliable and predictable food sources at feeding sites offered by the public might have changed House Finch roosting behaviour.     

Adjustment of growth, starch turnover, protein content and central metabolism to a decrease of the carbon supply when Arabidopsis is grown in very short photoperiods

Arabidopsis was grown in a 12, 8, 4 or 3 h photoperiod to investigate how metabolism and growth adjust to a decreased carbon supply. There was a progressive increase in the rate of starch synthesis, decrease in the rate of starch degradation, decrease of malate and fumarate, decrease of the protein content and decrease of the relative growth rate. Carbohydrate and amino acids levels at the end of the night did not change. Activities of enzymes involved in photosynthesis, starch and sucrose synthesis and inorganic nitrogen assimilation remained high, whereas five of eight enzymes from glycolysis and organic acid metabolism showed a significant decrease of activity on a protein basis. Glutamate dehydrogenase activity increased. In a 2 h photoperiod, the total protein content and most enzyme activities decreased strongly, starch synthesis was inhibited, and sugars and amino acids levels rose at the end of the night and growth was completely inhibited. The rate of starch degradation correlated with the protein content and the relative growth rate across all the photoperiod treatments. It is discussed how a close coordination of starch turnover, the protein content and growth allows Arabidopsis to avoid carbon starvation, even in very short photoperiods.     

Long-term survival despite low genetic diversity in the critically endangered Madagascar fish-eagle

The critically endangered Madagascar fish-eagle ( Haliaeetus vociferoides ) is considered to be one of the rarest birds of prey globally and at significant risk of extinction. In the most recent census, only 222 adult individuals were recorded with an estimated total breeding population of no more than 100–120 pairs. Here, levels of Madagascar fish-eagle population genetic diversity based on 47 microsatellite loci were compared with its sister species, the African fish-eagle ( Haliaeetus vocifer ), and 16 of these loci were also characterized in the white-tailed eagle ( Haliaeetus albicilla ) and the bald eagle ( Haliaeetus leucocephalus ). Overall, extremely low genetic diversity was observed in the Madagascar fish-eagle compared to other surveyed Haliaeetus species. Determining whether this low diversity is the result of a recent bottleneck or a more historic event has important implications for their conservation. Using a Bayesian coalescent-based method, we show that Madagascar fish-eagles have maintained a small effective population size for hundreds to thousands of years and that its low level of neutral genetic diversity is not the result of a recent bottleneck. Therefore, efforts made to prevent Madagascar fish-eagle extinction should place high priority on maintenance of habitat requirements and reducing direct and indirect human persecution. Given the current rate of deforestation in Madagascar, we further recommend that the population be expanded to occupy a larger geographical distribution. This will help the population persist when exposed to stochastic factors (e.g. climate and disease) that may threaten a species consisting of only 200 adult individuals while inhabiting a rapidly changing landscape.     

Confirmation of Ancient Polyploidy in Dahlia (Asteraceae) Species using Genomic In Situ Hybridization

The successful production of interspecific hybrids between membersof the dysploid chromosome series inDahlia offers a unique opportunityto investigate chromosome evolution. Analysis of meiotic metaphaseI in these hybrids using genomic in situ hybridization (GISH)has shown that pairing occurs both between and within parentalgenomes. These results have provided clear evidence for theallotetraploid origin of Dahlia species with 2n=32 and suggeststhat species with 2n=34 and 2n=36 have also arisen via allopolyploidy.A bivalent promoting mechanism proposed for species with 2n=32also appears to be present in Dahlia species with 2n=34 and2n=36 .Copyright 1999 Annals of Botany Company Dahlia , GISH, dysploidy, chromosome pairing, karyotype analysis, polyploidy.     

Postfire carbon balance in boreal bogs of Alberta, Canada

Boreal peatland ecosystems occupy about 3.5 million km² of the earth's land surface and store between 250 and 455 Pg of carbon (C) as peat. While northern hemisphere boreal peatlands have functioned as net sinks for atmospheric C since the most recent deglaciation, natural and anthropogenic disturbances, and most importantly wildfire, may compromise peatland C sinks. To examine the effects of fire on local and regional C sink strength, we focused on a 12 000 km² region near Wabasca, AB, Canada, where ombrotrophic Sphagnum‐dominated bogs cover 2280 km² that burn with a fire return interval of 123±26 years. We characterized annual C accumulation along a chronosequence of 10 bog sites, spanning 1–102 years‐since‐fire (in 2002). Immediately after fire, bogs represent a net C source of 8.9±8.4 mol m⁻² yr⁻¹. At about 13 years after fire, bogs switch from net C sources to net C sinks, mainly because of recovery of the moss and shrub layers. Subsequently, black spruce biomass accumulation contributes to the net C sink, with fine root biomass accumulation peaking at 34 years after fire and aboveground biomass and coarse root accumulation peaking at 74 years after fire. The overall C sink strength peaks at 18.4 mol C m⁻² yr⁻¹ at 75 years after fire. As the tree biomass accumulation rate declines, the net C sink decreases to about 10 mol C m⁻² yr⁻¹ at 100 years‐since‐fire. We estimate that across the Wabasca study region, bogs currently represent a C sink of 14.7±5.1 Gmol yr⁻¹. A decrease in the fire return interval to 61 years with no change in air temperature would convert the region's bogs to a net C source. An increase in nonwinter air temperature of 2 °C would decrease the regional C sink to 6.8±2.3 Gmol yr⁻¹. Under scenarios of predicted climate change, the current C sink status of Alberta bogs is likely to diminish to the point where these peatlands become net sources of atmospheric CO₂‐C.     

Genetically and geographically isolated lineages of a tropical bat (Chiroptera: Molossidae) show demographic stability over the late Pleistocene

The newly described molossid bat, Chaerephon atsinanana Goodman et al., 2010, endemic to eastern Madagascar, shows notably high levels of phylogeographic and genetic structure compared with allopatric Chaerephon leucogaster Grandidier, 1869 from western Madagascar. Such highly significant structuring of haplotypes among altitudinally and latitudinally stratified population groups is contrary to the expected panmixia in strong flying bats. The null model of concordance in historical demographic patterns across these two Chaerephon species was not supported. Mismatch and Bayesian skyline analyses indicated ancient stable C. atsinanana populations of constant size during the last two major Pleistocene glacial periods, making retreat into and expansion from glacial refugia an unlikely explanation for such high levels of structure, in accordance with expectations for tropical bats. Analyses were consistent with post‐refugial population expansion in the less diverse and structured C. leucogaster during the end of the last Pleistocene glacial period. We hypothesise that the pronounced genetic structuring in C. atsinanana may result from female philopatry. Furthermore, differing demographic histories of the two species may have been shaped by differing climate or habitat preferences, consistent with evidence from MaxEnt ecological niche modelling, which shows differences in variables influencing the current predicted distributions. Fossil Quaternary pollen deposits further indicate greater stability in past climatic patterns in eastern versus western Madagascar. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 18–40.     

Development of polymorphic microsatellite markers for the zebra finch (Taeniopygia guttata)

To study the population genetics as well as the mating system of captive zebra finch (Taeniopygia guttata) populations, we developed primers for 12 microsatellite loci and screened them in 529 individuals from two successive generations of a single captive population. All markers were polymorphic with five to 14 alleles per locus. We checked all markers for Mendelian inheritance in 307 offspring whose parents were known for sure. Four markers showed evidence for the presence of null alleles. Once allowing for null alleles, we found no mismatches between offspring and parents, suggesting a very low rate of mutation. Average observed and expected heterozygosities across the eight loci showing no evidence for null‐alleles was 0.819 and 0.812, respectively.     

Testing evolutionary hypotheses for phenotypic divergence using landscape genetics

Understanding the evolutionary causes of phenotypic variation among populations has long been a central theme in evolutionary biology. Several factors can influence phenotypic divergence, including geographic isolation, genetic drift, divergent natural or sexual selection, and phenotypic plasticity. But the relative importance of these factors in generating phenotypic divergence in nature is still a tantalizing and unresolved problem in evolutionary biology. The origin and maintenance of phenotypic divergence is also at the root of many ongoing debates in evolutionary biology, such as the extent to which gene flow constrains adaptive divergence ( Garant et al. 2007 ) and the relative importance of genetic drift, natural selection, and sexual selection in initiating reproductive isolation and speciation ( Coyne & Orr 2004 ). In this issue, Wang & Summers (2010) test the causes of one of the most fantastic examples of phenotypic divergence in nature: colour pattern divergence among populations of the strawberry poison frog (Dendrobates pumilio) in Panama and Costa Rica ( Fig. 1 ). This study provides a beautiful example of the use of the emerging field of landscape genetics to differentiate among hypotheses for phenotypic divergence. Using landscape genetic analyses, Wang & Summers were able to reject the hypotheses that colour pattern divergence is due to isolation‐by‐distance (IBD) or landscape resistance. Instead, the hypothesis left standing is that colour divergence is due to divergent selection, in turn driving reproductive isolation among populations with different colour morphs. More generally, this study provides a wonderful example of how the emerging field of landscape genetics, which has primarily been applied to questions in conservation and ecology, now plays an essential role in evolutionary research.

Figure 1 Open in figure viewer PowerPoint Divergent colour morphs observed among populations of the strawberry poison frog, Dendrobates pumilio. Frogs are from San Cristobal (upper left), Cerro Brujo (upper right), Bastimentos (lower right), and Agua (lower left).