A labyrinth lake provides surprising benefits for an endangered seal


Date:
February 23, 2023
Source:
University of Helsinki
Summary:
The endangered Saimaa ringed seal is an Ice Age relict living in
the highly labyrinthine Lake Saimaa, Finland. The newly published
work shows that although individual seals have greatly reduced
genetic variation, the loss of variation has been complementary,
preserving the adaptive potential of the whole population.


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FULL STORY ==========================================================================
The endangered Saimaa ringed seal is an Ice Age relict living in the
highly labyrinthine Lake Saimaa, Finland. The newly published work shows
that although individual seals have greatly reduced genetic variation,
the loss of variation has been complementary, preserving the adaptive
potential of the whole population.


==========================================================================
Lake Saimaa, a highly labyrinthine lake in eastern Finland,
provides a unique opportunity for assessing the effects of population fragmentation. The lake hosts a population of ringed seals (Pusa hispida saimensis) that became landlocked as the land rebounded after the retreat
of the continental ice sheet 10,000 years ago. Today, the Saimaa ringed
seal, with some 400 individuals, is one of the world's most endangered
seals.

Researchers from the University of Helsinki together with colleagues
from the University of Eastern Finland and the University of Copenhagen compared over 100 genomes of Saimaa ringed seals preserved in a tissue
bank.

"The Saimaa ringed seals have gone through a severe population size
contraction resulting in greatly reduced genetic variation. This
raises concerns about their ability to adaptively respond to ongoing
climate change," Petri Auvinen and Jukka Jernvall from the University
of Helsinki say.

The analyses revealed that the genomes of individual seals contained
long stretches of DNA sequences that were inherited identically from
both parents.

Comparisons of these homozygous regions among seals living in far-flung
nooks of the lake revealed something unexpected. "The good news is that
the labyrinthine shape of Lake Saimaa has generated three subpopulations
that are homozygous for largely different, complementary parts of their
genome. This means that the population as a whole has retained much
of its original genetic variation," explains Ari Lo"ytynoja from the
University of Helsinki.

Modelling the population history of the Saimaa ringed seals further
suggested that the intricate shape of Lake Saimaa has been optimal
in compensating for the detrimental effects of small population
size. Detailed analyses also revealed a beneficial genetic signature
of a seal individual that was translocated decades ago from one part of
the lake to another. For the conservation of other endangered species,
the lesson learned from the labyrinthine Lake Saimaa is the importance
of careful gene flow management among poorly connected populations.

* RELATED_TOPICS
o Plants_&_Animals
# Zoology # Marine_Biology # Endangered_Animals #
Evolutionary_Biology
o Earth_&_Climate
# Ecology # Global_Warming # Ice_Ages # Biodiversity
* RELATED_TERMS
o Heritability o Common_Seal o Ice_age o Genetics o
Genetic_recombination o Evolution o Allele_frequency o Deciduous

========================================================================== Story Source: Materials provided by University_of_Helsinki. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ari Lo"ytynoja, Pasi Rastas, Mia Valtonen, Juhana Kammonen,
Liisa Holm,
Morten Tange Olsen, Lars Paulin, Jukka Jernvall, Petri Auvinen.

Fragmented habitat compensates for the adverse effects of genetic
bottleneck. Current Biology, 2023; DOI: 10.1016/j.cub.2023.01.040 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/02/230223132910.htm

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