Costs of parasitism are predicted to be higher with greater parasite intensities and higher inter-parasite competition (diversity). We tested whether greater helminth intensities and diversity were associated with poorer body composition (whole-body fat, protein, mineral and true body mass) in lesser snow geese, Chen caerulescens caerulescens. As part of a larger study on nutritional ecology, 828 wintering or migrating geese were shot between January and May 1983 in 27 different date-locations (samples) during their northward migration through mid-continental North America. A large proportion of overall variation in body composition and parasite communities was among samples, so we analyzed data within each of the 27 samples, controlling for structural body size (the first principal component of 10 body size measurements), sex and the age of geese. There was no compelling evidence that cestodes, trematodes or helminth diversity were associated with variation in body composition but nematodes had several negative associations with fat reserves. However, negative associations between fat reserves and nematodes occurred most often in geese collected between March and May when nematode prevalences and intensities were relatively low. This suggests several possibilities: that the most common nematodes (Heterakis dispar and Trichostrongylus tenuis) were more virulent at this time, that infected individuals had been chronically infected and suffered cumulative nutrient deficits that lasted until late in the spring migration, or that geese became more vulnerable to the effects of parasites at this time of year, possibly because they redirected resources away from immunity toward fat storage in preparation for reproduction.
In this study, we characterized for the first time the gut microbiota of Greylag geese (Anser anser) using high-throughput 16S rRNA gene sequencing technology. The results showed that the phyla Firmicutes (78.55%), Fusobacteria (9.38%), Proteobacteria (7.55%), Bacteroidetes (1.82%), Cyanobacteria (1.44%), and Actinobacteria (0.61%) dominated the gut microbial communities in the Greylag geese. Then, the variations of gut microbial community structures and functions among the three geese species, Greylag geese, Bar-headed geese (Anser indicus), and Swan geese (Anser cygnoides), were explored. The greatest gut microbial diversity was found in Bar-headed geese group, while other two groups had the least. The dominant bacterial phyla across all samples were Firmicutes and Proteobacteria, but several characteristic bacterial phyla and genera associated with each group were also detected. At all taxonomic levels, the microbial community structure of Swan geese was different from those of Greylag geese and Bar-headed geese, whereas the latter two groups were less different. Functional KEGG categories and pathways associated with carbohydrate metabolism, energy metabolism, and amino acid metabolism were differentially expressed among different geese species. Taken together, this study could provide valuable information to the vast, and yet little explored, research field of wild birds gut microbiome.
When and where to move is a fundamental decision to migratory birds, and the fitness-related costs and benefits of migratory choices make them subject to strong selective forces. Site use and migration routes are outcomes of opportunities in the surrounding landscape, and the optimal migration strategy may be conservative or explorative depending on the variability of the environment occupied by the species. This study applies 25 years of resighting data to examine development in winter migration strategy of pink-footed geese divided among Denmark, the Netherlands and Belgium, and analyse potential drivers of strategy change as well as individuals' likelihood to break with migratory tradition. Contrary to the general notion that geese are highly traditional in their winter site use, our results reveal that winter migration strategy is highly dynamic in this species, with an average annual probability of changing strategy of 54%. Strategy was not related to hunting pressure or winter temperature, but could be partly explained by a tracking of food resources in a landscape of rapid land use changes. The probability of individuals changing strategy from year to year varied considerably between birds, and was partly related to sex and age, with young males being the most likely to change. The annual probability of changing wintering strategy increased substantially from ≈ 40% to ≈ 60% during the study period, indicating an increasingly explorative behaviour. Our findings demonstrate that individual winter strategies are very flexible and able to change over time, suggesting that phenotypic plasticity and cultural transmission are important drivers of strategy choice in this species. Growing benefits from exploratory behaviours, including the ability to track rapid land use changes, may ultimately result in increased resilience to global change. This article is protected by copyright. All rights reserved.
The impacts of hybridization on the process of speciation are manifold, leading to distinct patterns across the genome. Genetic differentiation accumulates in certain genomic regions, while divergence is hampered in other regions by homogenizing gene flow, resulting in a heterogeneous genomic landscape. A consequence of this heterogeneity is that genomes are mosaics of different gene histories that can be compared to unravel complex speciation and hybridization events. However, incomplete lineage sorting (often the outcome of rapid speciation) can result in similar patterns. New statistical techniques, such as the D-statistic and hybridization networks, can be applied to disentangle the contributions of hybridization and incomplete lineage sorting. We unravel patterns of hybridization and incomplete lineage sorting during and after the diversification of the True Geese (family Anatidae, tribe Anserini, genera Anser and Branta) using an exon-based hybridization network approach and taking advantage of discordant gene tree histories by re-sequencing all taxa of this clade. In addition, we determine the timing of introgression and reconstruct historical effective population sizes for all goose species to infer which demographic or biogeographic factors might explain the observed patterns of introgression.
The physiological and biomechanical requirements of flight at high altitude have been the subject of much interest. Here, we uncover a steep relation between heart rate and wingbeat frequency (raised to the exponent 3.5) and estimated metabolic power and wingbeat frequency (exponent 7) of migratory bar-headed geese. Flight costs increase more rapidly than anticipated as air density declines, which overturns prevailing expectations that this species should maintain high-altitude flight when traversing the Himalayas. Instead, a “roller coaster” strategy, of tracking the underlying terrain and discarding large altitude gains only to recoup them later in the flight with occasional benefits from orographic lift, is shown to be energetically advantageous for flights over the Himalayas.
The unusually high quality of census data for large waterbirds in Europe facilitates the study of how population change varies across a broad geographical range and relates to global change. The wintering population of the greylag goose Anser anser in the Atlantic flyway spanning between Sweden and Spain has increased from 120 000 to 610 000 individuals over the past three decades, and expanded its wintering range northwards. Although population sizes recorded in January have increased in all seven countries in the wintering range, we found a pronounced northwards latitudinal effect in which the rate of increase is higher at greater latitudes, causing a constant shift in the centre of gravity for the spatial distribution of wintering geese. Local winter temperatures have a strong influence on goose numbers but in a manner that is also dependent on latitude, with the partial effect of temperature (while controlling for the increasing population trend between years) being negative at the south end and positive at the north end of the flyway. Contrary to assumptions in the literature, the expansion of crops exploited by greylag geese has made little contribution to the increases in population size. Only in one case (expansion of winter cereals in Denmark) did we find evidence of an effect of changing land use. The expanding and shifting greylag population is likely to have increasing impacts on habitats in northern Europe during the course of this century.
During the adaptive evolution of a particular trait, some selectively fixed mutations may be directly causative and others may be purely compensatory. The relative contribution of these two classes of mutation to adaptive phenotypic evolution depends on the form and prevalence of mutational pleiotropy. To investigate the nature of adaptive substitutions and their pleiotropic effects, we used a protein engineering approach to characterize the molecular basis of hemoglobin (Hb) adaptation in the high-flying bar-headed goose (Anser indicus), a hypoxia-tolerant species renowned for its trans-Himalayan migratory flights. To test the effects of observed substitutions on evolutionarily relevant genetic backgrounds, we synthesized all possible genotypic intermediates in the line of descent connecting the wildtype bar-headed goose genotype with the most recent common ancestor of bar-headed goose and its lowland relatives. Site-directed mutagenesis experiments revealed one major-effect mutation that significantly increased Hb-O2 affinity on all possible genetic backgrounds. Two other mutations exhibited smaller average effect sizes and less additivity across backgrounds. One of the latter mutations produced a concomitant increase in the autoxidation rate, a deleterious side-effect that was fully compensated by a second-site mutation at a spatially proximal residue. The experiments revealed three key insights: (i) subtle, localized structural changes can produce large functional effects; (ii) relative effect sizes of function-altering mutations may depend on the sequential order in which they occur; and (iii) compensation of deleterious pleiotropic effects may play an important role in the adaptive evolution of protein function.
Sound decisions on control actions for established invasive alien species (IAS) require information on ecological as well as socio-economic impact of the species and of its management. Cost-benefit analysis provides part of this information, yet has received relatively little attention in the scientific literature on IAS.
Bar-headed goose (Anser indicus), a species endemic to Asia, has become one of the most popular species in recent years for rare bird breeding industries in several provinces of China. There has been no information on the gut metagenome configuration in both wild and artificially reared Bar-headed geese, even though the importance of gut microbiome in vertebrate nutrient and energy metabolism, immune homeostasis and reproduction is widely acknowledged. In this study, metagenomic methods have been used to describe the microbial community structure and composition of functional genes associated with both wild and artificially reared Bar-headed goose. Taxonomic analyses revealed that Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes were the four most abundant phyla in the gut of Bar-headed geese. Bacteroidetes were significantly abundant in the artificially reared group compared to wild group. Through functional profiling, we found that artificially reared Bar-headed geese had higher bacterial gene content related to carbohydrate transport and metabolism, energy metabolism and coenzyme transport, and metabolism. A comprehensive gene catalog of Bar-headed geese metagenome was built, and the metabolism of carbohydrate, amino acid, nucleotide, and energy were found to be the four most abundant categories. These results create a baseline for future Bar-headed goose microbiology research, and make an original contribution to the artificial rearing of this bird.
Microorganisms in vertebrate guts have been recognized as important symbionts influencing host life. However, it remains unclear about the gut microbiota in long-distance migratory Anseriformes herbivores, which could be functionally important for these wetland-dependent animals. We collected faeces of the greater white-fronted goose (GWFG), bean goose (BG) and swan goose (SG) from Shengjin Lake (SJL) and Poyang Lake (PYL) in the Yangtze River Floodplain, China. High-throughput sequencing of 16S rRNA V4 region was employed to depict the composition and structure of geese gut microbiota during wintering period. The dominant bacterial phyla across all samples were Firmicutes, Proteobacteria and Actinobacteria, but significant variations were detected among different goose species and sampling sites, in terms of α diversity, community structures and microbial interactions. We found a significant correlation between diet and the microbial community structure in GWFG-SJL samples. These results demonstrated that host species and diet are potential drivers of goose gut microbiota assemblies. Despite these variations, functions of geese gut microbiota were similar, with great abundances of potential genes involved in nutrient metabolism. This preliminary study would be valuable for future, exhaustive investigations of geese gut microbiota and their interactions with host.