| 1. |
- Barth, Julia M.I., et al.
(author)
-
Disentangling structural genomic and behavioural barriers in a sea of connectivity
- 2019
-
In: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 28:6, s. 1394-1411
-
Journal article (peer-reviewed)abstract
- © 2019 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd Genetic divergence among populations arises through natural selection or drift and is counteracted by connectivity and gene flow. In sympatric populations, isolating mechanisms are thus needed to limit the homogenizing effects of gene flow to allow for adaptation and speciation. Chromosomal inversions act as an important mechanism maintaining isolating barriers, yet their role in sympatric populations and divergence with gene flow is not entirely understood. Here, we revisit the question of whether inversions play a role in the divergence of connected populations of the marine fish Atlantic cod (Gadus morhua), by exploring a unique data set combining whole-genome sequencing data and behavioural data obtained with acoustic telemetry. Within a confined fjord environment, we find three genetically differentiated Atlantic cod types belonging to the oceanic North Sea population, the western Baltic population and a local fjord-type cod. Continuous behavioural tracking over 4year revealed temporally stable sympatry of these types within the fjord. Despite overall weak genetic differentiation consistent with high levels of gene flow, we detected significant frequency shifts of three previously identified inversions, indicating an adaptive barrier to gene flow. In addition, behavioural data indicated that North Sea cod and individuals homozygous for the LG12 inversion had lower fitness in the fjord environment. However, North Sea and fjord-type cod also occupy different depths, possibly contributing to prezygotic reproductive isolation and representing a behavioural barrier to gene flow. Our results provide the first insights into a complex interplay of genomic and behavioural isolating barriers in Atlantic cod and establish a new model system towards an understanding of the role of genomic structural variants in adaptation and diversification.
|
|
| 2. |
- Hinrichsen, Hans-Harald, et al.
(author)
-
Survival and dispersal variability of pelagic eggs and yolk-sac larvae of central and eastern baltic flounder (Platichthys flesus) : application of biophysical models
- 2017
-
In: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 74:1, s. 41-55
-
Journal article (peer-reviewed)abstract
- A hydrodynamic model coupled with a Lagrangian particle tracking technique was utilized to simulate spatially and temporally resolved long-term environmentally related (i) size of habitat suitable for reproduction, (ii) egg/yolk-sac larval survival, (iii) separation of causes of mortality, and (iv) connectivity between spawning areas of Baltic flounder with pelagiceggs. Information on reproduction habitat requirements and mortality sources were obtained from field or laboratory studies. In our modelling study we only quantified physical processes generating heterogeneity in spatial distribution of eggs and yolk-sac larvae, as e.g. predation is not accounted for. The spatial extent of eggs and larvae represented as modelled particles is primarily determined by oxygen and salinity conditions. The reproduction habitat most suitable was determined for the Gdansk Deep, followed by the Bornholm Basin. Relatively low habitat suitability was obtained for the Arkona Basin and the Gotland Basin. The model runs also showed yolk-sac larval survival to be to a large extent affected by sedimentation. Eggs initially released in the Arkona Basin and Bornholm Basin are strongly affected by sedimentation compared with those released in the Gdansk Deep and Gotland Basin. Highest relative survival of eggs occurred in the Gdansk Deep and in the Bornholm Basin. Relatively low survival rates in the Gotland Basin were attributable to oxygen-dependent mortality. Oxygen content had almost no impact on survival in the Arkona Basin. For all spawning areas mortality caused by lethally low temperatures was only evident after severe winters. Buoyancy of eggs and yolk-sac larvae in relation to topographic features appear as a barrier for the transport of eggs and yolk-sac larvae and potentially limits the connectivity of early life stages between the different spawning areas.
|
|
| 3. |
- Nissling, Anders, et al.
(author)
-
Egg buoyancy of flounder, Platichthys flesus, in the Baltic Sea-adaptation to salinity and implications for egg survival
- 2017
-
In: Fisheries Research. - : ELSEVIER SCIENCE BV. - 0165-7836 .- 1872-6763. ; 191, s. 179-189
-
Journal article (peer-reviewed)abstract
- Vertical distribution of eggs as determined by the egg buoyancy, i.e. the difference in specific gravity between the egg and the ambient water, have profound implications for the reproductive success and hence recruitment in fish. Here variability in egg specific gravity of flounder, Platichthys flesus, was studied along a salinity gradient and by comparing two reproductive strategies, spawning pelagic or demersal eggs. Egg characteristics of 209 egg batches (covering ICES subdivisions (SD) 22-29 in the brackish water Baltic Sea) was used to reveal the significance of egg diameter and egg dry weight for egg specific gravity (ESG), subpopulations, and egg survival probabilities of pelagic eggs following a major saline water inflow event. As an adaptation to salinity, ESG (at 7 degrees C) differed (p <0.001) between areas; three subpopulations of flounder with pelagic eggs: 1.0152 +/- 0.0021 (mean +/- sd)g cm(-3) in SD 22, 1.0116 +/- 0.0013 g cm(-3) in SD 24 and 25, and 1.0096 +/- 0.0007 g cm(-3) in SD 26 and 28, contrasting to flounder with demersal eggs, 1.0161 +/- 0.0008 g cm(-3). Egg diameter differed (p <0.001) between subpopulations; from 1.08 +/- 0.06 mm (SD 22) to 1.26 +/- 0.06 mm (SD 26 and 28) for pelagic eggs and 1.02 +/- 0.04 mm for demersal eggs, whereas egg dry weight was similar; 37.9 +/- 5.0 mu g (SD 22) and 37.2 +/- 3.9 mu g (SD 28) for pelagic, and 36.5 +/- 6.5 mu g for demersal eggs. Both egg diameter and egg dry weight were identified as explanatory variables, explaining 87% of the variation in ESG. ESG changed during ontogeny; a slight decrease initially but an increase prior to hatching. Egg survival probabilities judged by combining ESG and hydrographic data suggested higher egg survival in SD 25 (26 vs 100%) and SD 26 (32 vs 99%) but not in SD 28 (0 and 3%) after the inflow event, i.e. highly fluctuating habitat suitability. The results confirm the significance of ESG for egg survival and show that variability in ESG as and adaptation to salinity is determined mainly by water content manifested as differences in egg diameter; increase in diameter with decreasing salinity for pelagic eggs, and decreased diameter resulting in demersal eggs.
|
|
