Genetic consequences of breaking migratory traditions in barnacle geese Branta leucopsis.

Cultural transmission of migratory traditions enables species to deal with their environment based on experiences from earlier generations. Also, it allows a more adequate and rapid response to rapidly changing environments. When individuals break with their migratory traditions, new population structures can emerge that may affect gene flow. Recently, the migratory traditions of the Barnacle Goose Branta leucopsis changed, and new populations differing in migratory distance emerged. Here, we investigate the population genetic structure of the Barnacle Goose to evaluate the consequences of altered migratory traditions. We used a set of 358 single nucleotide polymorphism (SNP) markers to genotype 418 individuals from breeding populations in Greenland, Spitsbergen, Russia, Sweden and the Netherlands, the latter two being newly emerged populations. We used discriminant analysis of principal components, FST , linkage disequilibrium and a comparison of geneflow models using migrate-n to show that there is significant population structure, but that relatively many pairs of SNPs are in linkage disequilibrium, suggesting recent admixture between these populations. Despite the assumed traditions of migration within populations, we also show that genetic exchange occurs between all populations. The newly established nonmigratory population in the Netherlands is characterized by high emigration into other populations, which suggests more exploratory behaviour, possibly as a result of shortened parental care. These results suggest that migratory traditions in populations are subject to change in geese and that such changes have population genetic consequences. We argue that the emergence of nonmigration probably resulted from developmental plasticity.

Bryophyte DNA sequences from faeces of an arctic herbivore, barnacle goose (Branta leucopsis).

We tested DNA extraction methods and PCR conditions for the amplification of bryophyte DNA from barnacle goose (Branta leucopsis) faeces collected from Spitsbergen (Svalbard). Both the Qiagen stool kit and a silica-based extraction method received sufficient DNA from fresh and older droppings, as indicated by successful amplification of the plastid psbA-trnH spacer. Standard Taq polymerase outperformed two hot start polymerases. Sequencing of cloned PCR products revealed at least ten moss and two angiosperm sequences. This first example of identifying bryophyte DNA from faeces will allow analysing moss diets of arctic herbivores with a DNA barcoding approach.

Goose-mediated nutrient enrichment and planktonic grazer control in Arctic freshwater ponds.

A dramatic increase in the breeding population of geese has occurred over the past few decades at Svalbard. This may strongly impact the fragile ecosystems of the Arctic tundra because many of the ultra-oligotrophic freshwater systems experience enrichment from goose feces. We surveyed 21 shallow tundra ponds along a gradient of nutrient enrichment based on exposure to geese. Concentrations of total phosphorus (P) and dissolved inorganic nitrogen (DIN) in the tundra ponds ranged from 2-76 to 2-23 microg l(-1) respectively, yet there was no significant increase in phytoplankton biomass (measured as chlorophyll a; range: 0.6-7.3 microg l(-1)) along the nutrient gradient. This lack of response may be the result of the trophic structure of these ecosystems, which consists of only a two-trophic level food chain with high biomasses of the efficient zooplankton grazer Daphnia in the absence of fish and scarcity of invertebrate predators. Our results indicate that this may cause a highly efficient grazing control of phytoplankton in all ponds, supported by the fact that large fractions of the nutrient pools were bound in zooplankton biomass. The median percentage of Daphnia-N and Daphnia-P content to particulate (sestonic) N and P was 338 and 3009%, respectively, which is extremely high compared to temperate lakes. Our data suggest that Daphnia in shallow arctic ponds is heavily subsidized by major inputs of energy from other food sources (bacteria, benthic biofilm), which may be crucial to the persistence of strong top-down control of pelagic algae by Daphnia.