| 1. |
- Hooper, Rebecca, et al.
(författare)
-
Host-derived population genomics data provides insights into bacterial and diatom composition of the killer whale skin
- 2019
-
Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 28:2, s. 484-502
-
Tidskriftsartikel (refereegranskat)abstract
- Recent exploration into the interactions and relationship between hosts and their microbiota has revealed a connection between many aspects of the host's biology, health and associated micro-organisms. Whereas amplicon sequencing has traditionally been used to characterize the microbiome, the increasing number of published population genomics data sets offers an underexploited opportunity to study microbial profiles from the host shotgun sequencing data. Here, we use sequence data originally generated from killer whale Orcinus orca skin biopsies for population genomics, to characterize the skin microbiome and investigate how host social and geographical factors influence the microbial community composition. Having identified 845 microbial taxa from 2.4 million reads that did not map to the killer whale reference genome, we found that both ecotypic and geographical factors influence community composition of killer whale skin microbiomes. Furthermore, we uncovered key taxa that drive the microbiome community composition and showed that they are embedded in unique networks, one of which is tentatively linked to diatom presence and poor skin condition. Community composition differed between Antarctic killer whales with and without diatom coverage, suggesting that the previously reported episodic migrations of Antarctic killer whales to warmer waters associated with skin turnover may control the effects of potentially pathogenic bacteria such as Tenacibaculum dicentrarchi. Our work demonstrates the feasibility of microbiome studies from host shotgun sequencing data and highlights the importance of metagenomics in understanding the relationship between host and microbial ecology.
|
|
| 2. |
- van der Valk, Tom
(författare)
-
Genomics of population decline
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With human populations forecasted to grow in the next decades, many mammals face increasing anthropogenic threats. The consequential population declines are a precursor to extinctions, as small populations are not only more sensitive to stochastic events, but reduction in population size is generally also followed by a decrease in genetic diversity, which in turn reduces adaptive potential and fitness of the population. By using molecular methods I aimed to estimate the magnitude of the genomic consequences as a result of rapid population declines with a focus on the endangered eastern gorillas. First, I genotyped Grauer’s gorilla (Gorilla beringei graueri) faecal samples, which revealed lower genetic diversity and high differentiation in the peripheral compared to the central populations, indicating a strong effect of genetic drift and limited gene flow among the small, isolated forest fragments (Chapter 1). Next, by using a target capture approach I obtained complete mitochondrial genomes from degraded Grauer’s and mountain (Gorilla beringei beringei) gorilla faecal and museum samples (Chapter 2) which showed a loss of mitochondrial diversity within the last century in Grauer’s gorillas, mainly driven by the extinction of peripheral populations (Chapter 3). Genome-wide sequence data from historical samples suggests that this loss has also affected the nuclear genome, as modern Grauer’s gorillas carry on average more genetic variants with putatively negative fitness consequences than historically. No significant temporal changes were observed in the closely related mountain gorillas, which might be due to their contrasting demographic history (Chapter 4). I then switched study species to the endangered Dryas monkey and find that, despite its possible small population size, the current Dryas monkey population is genetically diverse with low levels of inbreeding and as such likely viable in the long-term if appropriate conservation measures are taken (Chapter 5). Finally, I aimed to estimate the strength of genetic purging across a range of mammalian species. This revealed that although genetic purging might be common among endangered species, it mainly acts on long evolutionary time scales with limited strength during the rapid population declines as experienced by many species today (Chapter 6).
|
|
| 3. |
- van der Valk, Tom, et al.
(författare)
-
Historical Genomes Reveal the Genomic Consequences of Recent Population Decline in Eastern Gorillas
- 2019
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 29:1, s. 165-170.e6
-
Tidskriftsartikel (refereegranskat)abstract
- Many endangered species have experienced severe population declines within the last centuries [1, 2]. However, despite concerns about negative fitness effects resulting from increased genetic drift and inbreeding, there is a lack of empirical data on genomic changes in conjunction with such declines [3-7]. Here, we use whole genomes recovered from century-old historical museum specimens to quantify the genomic consequences of small population size in the critically endangered Grauer's and endangered mountain gorillas. We find a reduction of genetic diversity and increase in inbreeding and genetic load in the Grauer's gorilla, which experienced severe population declines in recent decades. In contrast, the small but relatively stable mountain gorilla population has experienced little genomic change during the last century. These results suggest that species histories as well as the rate of demographic change may influence how population declines affect genome diversity.
|
|
