Species abundance dynamics under neutral assumptions: a Bayesian approach to the controversy

1. Hubbell's 'Unified Neutral Theory of Biodiversity and Biogeography' (UNTB) has generated much controversy about both the realism of its assumptions and how well it describes the species abundance dynamics in real communities. 2. We fit a discrete-time version of Hubbell's neutral model to long-term macro-moth (Lepidoptera) community data from the Rothamsted Insect Survey (RIS) light-traps network in the United Kingdom. 3. We relax the assumption of constant community size and use a hierarchical Bayesian approach to show that the model does not fit the data well as it would need parameter values that are impossible. 4. This is because the ecological communities fluctuate more than expected under neutrality. 5. The model, as presented here, can be extended to include environmental stochasticity, density-dependence, or changes in population sizes that are correlated between different species

Life history and environmental variation interact to determine effective population to census size ratio

Successful recovery and sustainability of threatened and exploited species depends in part on retention and maintenance of genetic diversity. Theory indicates that genetic diversity is lost at a rate inversely proportional to the genetically effective population size (N(e)), which is roughly equal to one-half the adult census size (N) in many organisms. However, N(e) has been reported to be up to five orders of magnitude lower than N in species with life histories that result in type III survivorship (high fecundity, but heavy mortality in early life stages, e.g. bony fishes), prompting speculation that low values of N(e) may be a general feature of such organisms despite sometimes vast abundances. Here, we compared N(e) and the ratio N(e)/N across three ecologically similar fish species from the arid southwestern United States, all with type III life histories but with differing expectations of egg and larval survivorship that correlate with the degree of human-imposed habitat fragmentation. Our study indicates that type III life history may be necessary, but this alone is insufficient to account for extraordinarily low values of N(e)/N. Rather, life history interacts with environmentally imposed mortality to determine the rate and magnitude of change in genetic diversity in these desert fish species

Unraveling the genetic diversity of Belgian Milk Sheep using medium‐density SNP genotypes

The present study focuses on the Belgian Milk Sheep in Flanders (Belgium) and compares its genetic diversity and relationship with the Flemish Sheep, the Friesian Milk Sheep, the French Lacaune dairy sheep and other Northern European breeds. For this study, 94 Belgian Milk Sheep, 23 Flemish Sheep and 22 Friesian Milk Sheep were genotyped with the OvineSNP50 array. In addition, 29 unregistered animals phenotypically similar to Belgian Milk Sheep were genotyped using the 15K ISGC chip. Both Belgian and Friesian Milk Sheep as well as the East Friesian Sheep were found to be less diverse than the other seven breeds included in this study. Genomic inbreeding coefficients based on runs of homozygosity (ROH) were estimated at 14.5, 12.4 and 10.2% for Belgian Milk Sheep, Flemish Sheep and Friesian Milk Sheep respectively. Out of 29 unregistered Belgian Milk Sheep, 28 mapped in the registered Belgian Milk Sheep population. Ancestry analysis, PCA and FST calculations showed that Belgian Milk Sheep are more related to Friesian Milk Sheep than to Flemish Sheep, which was contrary to the breeders' expectations. Consequently, breeders may prefer to crossbreed Belgian Milk Sheep with Friesian sheep populations (Friesian Milk Sheep or East Friesian Sheep) in order to increase diversity. This research underlines the usefulness of SNP chip genotyping and ROH analyses for monitoring genetic diversity and studying genetic links in small livestock populations, profiting from internationally available genotypes. As assessment of genetic diversity is vital for long-term breed survival, these results will aid flockbooks to preserve genetic diversity

Tracing fish and fish products from ocean to fork using advanced molecular technologies

The ability to determine authenticity and provenance of fish and fish products throughout the international fish trade distribution chain is of paramount importance, and in many countries traceability in the fisheries sector is based on labelling rules. As shown by numerous fraud cases worldwide, however, and the relentless global problem of illegal, unreported and unregulated (IUU) fishing, independent control technologies are urgently needed to ensure appropriate implementation of traceability schemes. Here,we discuss opportunities and challenges arising from the rapid progress in research and technology pertinent to traceability. In support of an integrative approach, several technologies will be considered, though emphasis is placed on DNA technology as an approach witnessing major recent development

Rapid loss of genetic variation in an endangered possum

The endangered mountain pygmy possum is the only Australian marsupial that hibernates under snow cover. Most of its alpine habitat was burnt by a rare fire in 2003, and habitat loss and disturbance have also occurred owing to ski resort development. Here we show that there has been a rapid loss of genetic variation following habitat loss associated with resort development, but no detectable loss of alleles or decrease in heterozygosity following the fire