scholarly journals Divergent Fine-Scale Recombination Landscapes between a Freshwater and Marine Population of Threespine Stickleback Fish

2019 ◽  
Vol 11 (6) ◽  
pp. 1552-1572 ◽  
Author(s):  
Alice F Shanfelter ◽  
Sophie L Archambeault ◽  
Michael A White
2018 ◽  
Author(s):  
Alice F. Shanfelter ◽  
Sophie L. Archambeault ◽  
Michael A. White

AbstractMeiotic recombination is a highly conserved process that has profound effects on genome evolution. Recombination rates can vary drastically at a fine-scale across genomes and often localize to small recombination “hotspots” with highly elevated rates surrounded by regions with little recombination. Hotspot targeting to specific genomic locations is variable across species. In some mammals, hotspots have divergent landscapes between closely related species which is directed by the binding of the rapidly evolving protein, PRDM9. In many species outside of mammals, hotspots are generally conserved and tend to localize to regions with open chromatin such as transcription start sites. It remains unclear if the location of recombination hotspots diverge in taxa outside of mammals. Threespine stickleback fish (Gasterosteus aculeatus) are an excellent model to examine the evolution of recombination over short evolutionary timescales. Using an LD-based approach, we found recombination rates varied at a fine-scale across the genome, with many regions organized into narrow hotspots. Hotspots had divergent landscapes between stickleback populations, where only ~15% were shared, though part of this divergence could be due to demographic history. Additionally, we did not detect a strong association of PRDM9 with recombination hotspots in threespine stickleback fish. Our results suggest fine-scale recombination rates may be diverging between closely related populations of threespine stickleback fish and argue for additional molecular characterization to verify the extent of the divergence.


Zoomorphology ◽  
2020 ◽  
Author(s):  
Harald Ahnelt ◽  
David Ramler ◽  
Maria Ø. Madsen ◽  
Lasse F. Jensen ◽  
Sonja Windhager

AbstractThe mechanosensory lateral line of fishes is a flow sensing system and supports a number of behaviors, e.g. prey detection, schooling or position holding in water currents. Differences in the neuromast pattern of this sensory system reflect adaptation to divergent ecological constraints. The threespine stickleback, Gasterosteus aculeatus, is known for its ecological plasticity resulting in three major ecotypes, a marine type, a migrating anadromous type and a resident freshwater type. We provide the first comparative study of the pattern of the head lateral line system of North Sea populations representing these three ecotypes including a brackish spawning population. We found no distinct difference in the pattern of the head lateral line system between the three ecotypes but significant differences in neuromast numbers. The anadromous and the brackish populations had distinctly less neuromasts than their freshwater and marine conspecifics. This difference in neuromast number between marine and anadromous threespine stickleback points to differences in swimming behavior. We also found sexual dimorphism in neuromast number with males having more neuromasts than females in the anadromous, brackish and the freshwater populations. But no such dimorphism occurred in the marine population. Our results suggest that the head lateral line of the three ecotypes is under divergent hydrodynamic constraints. Additionally, sexual dimorphism points to divergent niche partitioning of males and females in the anadromous and freshwater but not in the marine populations. Our findings imply careful sampling as an important prerequisite to discern especially between anadromous and marine threespine sticklebacks.


2019 ◽  
Vol 11 (9) ◽  
pp. 2605-2618 ◽  
Author(s):  
Nadezhda V Terekhanova ◽  
Anna E Barmintseva ◽  
Alexey S Kondrashov ◽  
Georgii A Bazykin ◽  
Nikolai S Mugue

Abstract Adaptation of threespine stickleback to freshwater involves parallel recruitment of freshwater alleles in clusters of closely linked sites, or divergence islands (DIs). However, it remains unclear to what extent the DIs and the alleles that constitute them coincide between populations that underwent adaptation to freshwater independently. We examine threespine sticklebacks from ten freshwater lakes that emerged 500–1500 years ago in the White Sea basin, with the emphasis on repeatability of genomic patterns of adaptation among the lake populations and the role of local recombination rate in the distribution and structure of DIs. The 65 detected DIs are clustered in the genome, forming 12 aggregations, and this clustering cannot be explained by the variation of the recombination rate. Only 21 of the DIs are present in all the freshwater populations, likely being indispensable for successful colonization of freshwater environment by the ancestral marine population. Within most DIs, the same set of single nucleotide polymorphisms (SNPs) distinguish marine and freshwater haplotypes in all the lake populations; however, in some DIs, freshwater alleles differ between populations, suggesting that they could have been established by recruitment of different haplotypes in different populations.


Behaviour ◽  
2000 ◽  
Vol 137 (7-8) ◽  
pp. 933-945 ◽  
Author(s):  
Jennifer Jenkins ◽  
William Rowland

AbstractMale threespine stickleback, Gasterosteus aculeatus, from a marine population on Long Island, New York were presented simultaneously with two dummies, one simulating a normally distended ('thinner') gravid female and the other a highly distended ('fatter') one. Males initially courted the dummies much as they do real females, but showed stimulus-specific and response-specific habituation to the dummies. Males initially courted the fatter dummy slightly more than the thinner one but showed clear signs of habituation toward the thinner dummy after about 4 min while courtship to the fatter one continued throughout the 1 hr presentation period. Thus, within 12 min males were directing a much greater proportion of courtship to the fatter dummy, and this difference increased over time. Males also attacked both dummies and, in contrast to their courtship response, divided biting equally between the two dummies. Moreover, bite rates to the thinner and the fatter dummy doubled within the first 12 min and then fluctuated around that level for the remainder of the trial. The stimulusspecific and response-specific nature of habituation may be adaptive for male mating success because it leads the male to focus courtship on the preferred female and to direct attack against the fish presenting a greater threat to the nest but a lower potential reproductive payoff.


Author(s):  
Russell L. Steere

Complementary replicas have revealed the fact that the two common faces observed in electron micrographs of freeze-fracture and freeze-etch specimens are complementary to each other and are thus the new faces of a split membrane rather than the original inner and outer surfaces (1, 2 and personal observations). The big question raised by published electron micrographs is why do we not see depressions in the complementary face opposite membrane-associated particles? Reports have appeared indicating that some depressions do appear but complementarity on such a fine scale has yet to be shown.Dog cardiac muscle was perfused with glutaraldehyde, washed in distilled water, then transferred to 30% glycerol (material furnished by Dr. Joaquim Sommer, Duke Univ., and VA Hospital, Durham, N.C.). Small strips were freeze-fractured in a Denton Vacuum DFE-2 Freeze-Etch Unit with complementary replica tooling. Replicas were cleaned in chromic acid cleaning solution, then washed in 4 changes of distilled water and mounted on opposite sides of the center wire of a Formvar-coated grid.


2020 ◽  
Vol 655 ◽  
pp. 185-198
Author(s):  
J Weil ◽  
WDP Duguid ◽  
F Juanes

Variation in the energy content of prey can drive the diet choice, growth and ultimate survival of consumers. In Pacific salmon species, obtaining sufficient energy for rapid growth during early marine residence is hypothesized to reduce the risk of size-selective mortality. In order to determine the energetic benefit of feeding choices for individuals, accurate estimates of energy density (ED) across prey groups are required. Frequently, a single species is assumed to be representative of a larger taxonomic group or related species. Further, single-point estimates are often assumed to be representative of a group across seasons, despite temporal variability. To test the validity of these practices, we sampled zooplankton prey of juvenile Chinook salmon to investigate fine-scale taxonomic and temporal differences in ED. Using a recently developed model to estimate the ED of organisms using percent ash-free dry weight, we compared energy content of several groups that are typically grouped together in growth studies. Decapod megalopae were more energy rich than zoeae and showed family-level variability in ED. Amphipods showed significant species-level variability in ED. Temporal differences were observed, but patterns were not consistent among groups. Bioenergetic model simulations showed that growth rate of juvenile Chinook salmon was almost identical when prey ED values were calculated on a fine scale or on a taxon-averaged coarse scale. However, single-species representative calculations of prey ED yielded highly variable output in growth depending on the representative species used. These results suggest that the latter approach may yield significantly biased results.


2019 ◽  
Vol 609 ◽  
pp. 151-161 ◽  
Author(s):  
CO Bennice ◽  
AP Rayburn ◽  
WR Brooks ◽  
RT Hanlon

2017 ◽  
Vol 569 ◽  
pp. 187-203 ◽  
Author(s):  
AM McInnes ◽  
PG Ryan ◽  
M Lacerda ◽  
J Deshayes ◽  
WS Goschen ◽  
...  

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