Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Arnar Pálsson, 22/09/2023

Submission of Guðbjörgs manuscript to PLoS One, second version of M.S. available on bioRxiv.

Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Guðbjörg Ósk Jónsdóttir, Laura-Marie von Elm, Finnur Ingimarsson, Samuel Tersigni, Sigurdur Sveinn Snorrason, Arnar Palsson, Sarah Elizabeth Steele

doi: https://doi.org/10.1101/2023.02.17.528955

The diversity of functional feeding anatomy is particularly impressive in fishes and correlates with various interspecific ecological specializations. Intraspecific polymorphism can manifest in divergent feeding morphology and ecology, often along a benthic pelagic axis. Arctic charr (Salvelinus alpinus) is a freshwater salmonid known for morphological variation and sympatric polymorphism and in Lake Þingvallavatn, Iceland, four morphs of charr coexist that differ in preferred prey, behaviour, habitat use, and external feeding morphology. We studied variation in six upper and lower jaw bones in adults of these four morphs using geometric morphometrics and univariate statistics. We tested for allometric differences in bone size and shape among morphs, morph effects on bone size and shape, and divergence along the benthic-pelagic axis. We also examined the degree of integration between bone pairs. We found differences in bone size between pelagic and benthic morphs for two bones (dentary and premaxilla). There was clear bone shape divergence along a benthic pelagic axis in four bones (dentary, articular angular, premaxilla and maxilla), as well as allometric shape differences between morphs in the dentary. Notably for the dentary, morph explained more shape variation than bone size. Comparatively, benthic morphs possess a compact and taller dentary, with shorter dentary palate, consistent with visible (but less prominent) differences in external morphology. As these morphs emerged in the last 10,000 years, these results indicate rapid functional evolution of specific feeding structures in arctic charr. This sets the stage for studies of the genetics and development of rapid and parallel craniofacial evolution.

categories Publications

Arnar Pálsson, 07/09/2023

Genetic structure and relatedness of brown trout (Salmo trutta) populations in the drainage basin of the Ölfusá river, South-Western Iceland

​1, 1, 2, 2, 1, 1
A total of 2,597 polymorphic loci from 317 individuals out of 555 originally analysed were retained after the stringent filtering steps outlined in Materials and Methods. These markers were used to address questions about the patterns of genetic differentiation between locations. We estimated population genetic parameters for each sampling site.

Plot of two principal components separates three clusters of landlocked brown trout, the Scottish reference group, and the anadromous populations. The percentage of the variance explained by these components is shown in parentheses. See ms for three letter code.

categories Publications

Genetic structure and relatedness of brown trout (Salmo trutta) populations in the drainage basin of the Ölfusá river, South-Western Iceland

Arnar Pálsson, 08/08/2023

Accepted in PeerJ. Good job by Marcos G. Lagunas.

Background. Lake Þingvallavatn in Iceland, a part of the river Ölfusá drainage basin, was presumably populated by brown trout soon after it formed at the end of the last Ice Age. The genetic relatedness of the brown trout in Þingvallavatn to other populations in the Ölfusá drainage basin is unknown. After the building of a dam at the outlet of the lake in 1959 brown trout catches declined, though numbers have now increased. The aim of this study was to assess effects of geographic isolation and potential downstream gene flow on the genetic structure and diversity in brown trout sampled in several locations in the western side of the watershed of River Ölfusá. We hypothesized that brown trout in Lake Þingvallavatn constituted several local spawning populations connected by occasional gene flow before the damming of the lake. We also estimated the effective population size (NE) of some of these populations and tested for signs of a recent population bottleneck in Lake Þingvallavatn.

Methods. We sampled brown trout inhabiting four lakes and 12 rivers within and near the watershed of River Ölfusá by means of electro- and net- fishing. After stringent data filtering, 2,597 polymorphic loci obtained from ddRADseq data from 317 individuals were ascertained as putative neutral markers.

Results. Overall, the genetic relatedness of brown trout in the Ölfusá watershed reflected the connectivity and topography of the waterways. Ancestry proportion analyses and a phylogenetic tree revealed seven distinct clusters, some of which corresponded to small populations with reduced genetic diversity. There was no evidence of downstream gene flow from Lake Þingvallavatn, although gene flow was observed from much smaller mountain populations. Most locations showed low NE values (i.e., ~14.6 on average) while the putative anadromous trout from River Sog and the spawning population from River Öxará, that flows into Lake Þingvallavatn, showed notably higher NE values (i.e., 71.2 and 56.5, respectively). No signals of recent population bottlenecks were detected in the brown trout of Lake Þingvallavatn.

Discussion. This is the first time that the genetic structure and diversity of brown trout in the Ölfusá watershed have been assessed. Our results point towards the presence of a metapopulation in the watershed of Lake Þingvallavatn (and its tributaries), which has been influenced by restoration efforts and is now dominated by a genetic component originated in River Öxará. Many of the locations studied represent different populations. Those that are isolated in headwater streams and lakes are genetically distinct presenting low genetic diversity, yet they can be important in increasing the genetic variation in downstream populations. These populations should be considered for conservation and direct management.

categories Publications

Lúsmý, maurar og fleiri dýr

Arnar Pálsson, 30/06/2023

Nýsköpunarsjóður námsmanna gerir fjórum líffræðinemar og BS líffræðingar kleift að verkefnum um skordýr á Íslandi við Líffræðistofu Háskóla Íslands nú í sumar.

Við höfum áður fjallað um maurarannsóknir en auk þess er kastljósinu nú beint að lúsmýi og ávaxtaflugum. Það eru nýlegir landnemar hérlendis. Lúsmýið er alræmt fyrir bit og almenn leiðindi, en ávaxtaflugur eru dýrkaðar og dáðar vegna fegurðar sinnar og fengileiks. Sumir eru reyndar smeykir við ávaxtaflugur, en þær bíta ekki fólk, bera ekki sjúkdóma og verða bara til ama ef þær verpa í bananann sem við gleymdum undir ískáp.

Í lúsmý verkefninu er ætlunin að kanna hvenær sumarsins þær koma fram, hvort um sé að ræða einn eða tvo toppa klaksins, hvaða búsvæðum flugurnar klekjast helst úr og hver dreifing þeirra á landsvísu er. Beitt verður aðferðum skordýrafræði og stofnerfðafræði. Hér að neðan eru myndir af klakgildrum og vettvangi rannsókna í Kjósinni.

categories General biology, Uncategorized

Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Arnar Pálsson, 28/06/2023

This manuscript was rejected by Evolutionary Biology, on grounds of "The reviewers felt there was a need to demonstrate functional aspects of morphology moreso than the current version, while both felt that some novelty was lacking." One reviewer said the results were all predictable and wanted us to study species level diversity and the other reflects lack of understanding of geometric morphometrics. We are reformatting for another journal, more to follow.

Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Jónsdóttir, G.Ó., von Elm, L-M, Ingimarsson, F., Tersigni, S., Snorrason, S.S, Pálsson, A. and Steele, S.E.

https://www.biorxiv.org/content/10.1101/2023.02.17.528955v1

Abstract

The diversity of functional anatomy related to feeding is particularly impressive in fishes and correlates with various ecological specializations across species. Polymorphism within species can manifest in divergent feeding morphology and ecology, often along a benthic–pelagic axis. Arctic charr (Salvelinus alpinus) is a freshwater salmonid known for morphological variation and sympatric polymorphism. In Lake Þingvallavatn, Iceland, four morphs of arctic charr coexist that differ in preferred prey, behaviour, habitat use, and external feeding morphology. We studied variation in upper and lower jaw bones (six bones total) related to feeding, in adults of the four morphs using geometric morphometrics and univariate statistics. We tested for allometric differences in bone size and shape among morphs, morph effects on bone size and shape, and if benthic and pelagic ecologies associate with bone size and shape. We also examined the degree of integration between bone pairs. We found differences in bone size between pelagic and benthic morphs for two bones (dentary and premaxilla). There was clear bone shape divergence along a benthic–pelagic axis in four bones (dentary, articular-angular, premaxilla and maxilla), as well as allometric differences between morphs in the dentary. Most dramatic was the dentary, where morph explained more shape variation than bone size. Comparatively, benthic morphs possess a compact and taller dentary, with shorter dentary palate, consistent with visible (but less prominent) differences in external morphology. As these morphs emerged in the last 10,000 years, these results indicate rapid functional evolution of specific feeding structures in arctic charr. This sets the stage for studies of the genetics and development of rapid and parallel craniofacial evolution.

categories Publications

Adaptive cellular evolution or cellular system drift in hares

Arnar Pálsson, 20/05/2023

Adaptive cellular evolution or cellular system drift in hares

Arnar Palsson and Sarah Elizabeth Steele.

Perspective, in Molecular Ecology.

Adaptations occur at many levels, from e.g. DNA sequence of regulatory elements and cellular homeostatic systems, to organismal physiology and behaviour (Mayr, 1997). Established adaptations are maintained by purifying and stabilizing selection. Students of animal diversity tend to focus on higher order traits, anatomy, physiology, organismal function and interactions. The core cellular and metabolic systems of metazoans evolved early in their history, and are assumed to be rather similar between groups. The housekeeping functions and core metabolic functions of cells are generally considered relatively static, especially among closely related species. The extent to which evolution shapes core cellular metabolism and physiology in animals is largely unexplored. Ecological opportunities or strong positive selection can alter basal metabolic rate, activity levels and life-history traits (e.g. lifespan, age of maturity, offspring number) and potentially lead to divergence in core cellular and metabolic trait systems (Norin & Metcalfe, 2019; Speakman, 2005). Furthermore, systems under stabilizing selection can also change. Developmental systems of related species may produce the same phenotype or structure, but experience drift that can alter connections and even lead to turnover of cogs in the system (True & Haag, 2001). Are the cellular functions of animals highly constrained, subject to cellular system drift or affected by positive selection? This was tackled by a new study by Kateryna Gaertner and colleagues in a From the Cover manuscript in this issue of Molecular Ecology (Gaertner et al., 2022), using fibroblasts from the closely related but ecologically distinct brown and mountain hares.

categories Publications

90 ára afmæli Guðmundar Eggertssonar erfðafræðings

Arnar Pálsson, 11/05/2023

©Kristinn Ingvarsson

Opnunarávarp dagskrár í tilefni 90 ára afmælis Guðmundar Eggertssonar erfðafræðings.

Litla Torg, HÍ, 26. apríl 2023.

Kæru gestir, vinir og Guðmundur. Í dag fögnum við með Guðmundi Eggertssyni erfðafræðingi. Hann átti 90 ára afmæli á mánudaginn, 24. Apríl. Það er sérstakur heiður að fá að opna þennan fund. Lærlingar Guðmundar munu í dag fjalla um feril hans og störf, rannsóknir og áhrif.

Í gær voru 70 ár síðan þrjár greinar birtust um eiginleika og byggingu DNA, eftir Wilkins, Stokes og Wilson, Franklin og Gosling og Watson og Crick. Spurning hvort þetta sé tilviljun eða nauðsyn?

DNA sameinar allar lífverur á jörðinni, ásamt lögmálum lífefna, fruma, vistkerfa og þróunar. Titill fyrstu bókar Guðmundar var "líf af lífi". Viðfangsefni erfðafræði er hvernig gen kemur af geni. Og í dag sjáum hvernig af Guðmundi koma margir Guðmundar. Ekki bókstaflega litlir Guðmundar, heldur lærlingar innblásnir af fræðunum sem hann kenndi okkur og áhuga á sameindalíffræði sem hann smitaði okkur af.

Guðmundur hefur birt fjölda greina um bakteríuerfðafræði, hvernig erfðatáknmálið er túlkað af frumum og virkni. Einnig erfðafræði hitakærra baktería, sem lagði grunn að rannsóknum í líftækni og örveruvistfræði hverasvæða. Það verður fjallað minna um þessi flóknu og forvitnilegu kerfi í dag, og meira um söguna, störf, persónu og fyrirmyndina.

Áhrif hans á íslensk vísindi og sérstaklega líffræði eru ákaflega jákvæð, víðtæk og margslungin. Ég má til með að deila einni sögu. Grensásvegur 12 var kumbaldi sem lak í rigningu. Guðmundur mætti á slíkum dögum til að tæma og staðsetja fötur sem tóku við lekanum. Einnig fór hann upp á þak til að kítta.

Þrennt vil ég minnast á að síðustu.

Í fyrsta lagi vill ég minnast Sigríðar Helgu Þorbjarnardóttur sem féll frá alltof ung. Hún var sérfræðingur Líffræðistofnunar og vann mjög náið með Guðmundi, var meistaraleiðbeinandi minn og margra annara nemenda. Hún var sérlega klár og vönduð. Ég naut þeirrar forréttinda að hafa bæði Siggu og Guðmund sem leiðbeinendur.

Í öðru lagi vil ég minnast gæsku Guðmundar. Hann er alltaf jákvæður og hvetjandi. Munið þið eftir styggðaryrði eða ofsakasti hans? Nei, því slíkt gerðist ekki. Jafnvel þegar hann og aðrir voru að spyrna við gerræðislegum hugmyndum um gagnagrunn á heilbrigðissviði.

Í þriðja lagi er það frábært skopskyn. Guðmundur hefur mikið gaman að góðu gríni. Hann laumaði litlum bröndurum inn í umfjöllun um tRNA og önnur apparöt frumunar,  og lagði oft glæru með bröndurum úr New Yorker eða sambærilegu á skjávarpan áður en fyrirlestrar hófust, nemendum til ánægju.

Að síðustu, hjartanlega til hamingju með afmælið Guðmundur. Ágæta samkunda, ég lýsi þetta málþing og bjórfund settann.

 

Þakkir fá aðrir í skipulagsnefnd, Sigríður Rut Franzdóttur, Snædís Björnsdóttur, Eiríkur Steingrímsson og Zophonías O. Jónssoni. Einnig þökkum við Verkfræði og náttúruvísindasviði og Líf- og umhverfisvísindadeild fyrir fjárhagslegan stuðning.

Söngfjélagið syngur kl 17:00.

categories Talks and events

The moral status of stem cell-derived embryo models

Arnar Pálsson, 10/05/2023

The moral status of stem cell-derived embryo models

Event Health and welfare A socially sustainable Nordic region
15/09/2023
09:30 - 13:00
The University of Iceland (the university aula), Sæmundargata 2, 102 Reykjavik, Iceland

Sign up

Photo of embryonic stem cells (red and blue colours)
From Nordforsk page

"This event will be organised as a mini symposium at the University of Iceland (venue: the university aula). The Nordic Committee on Bioethics has invited some of the most prominent researchers from the Nordics and beyond, with expertise in stem cells- and embryonic research, ethics and law. They will share their research and their reflections in the form of presentations and conversations.

The symposium is in collaboration with the Graduate programme in molecular life sciences, BioMedical Center (BMC) at the University of Iceland and is open to the public (registration is required). No registration fee.

The symposium will also be live-streamed. Please note that the time zone is GMT/Iceland.

Background

Currently, the 14-day rule in science policy and regulation, limits research on human embryos (outside the uterus) to the first 14 days of gestation. This is referred to as the 14-day rule. This means, that week 3-4 of human embryonic development is something of a “black box” because scientists cannot see what is taking place in the uterus during the early stages of gestation beyond the first two weeks. In recent years, progress has been made in early embryo research beyond the first two weeks, via “human embryo models,” developed from stem stells, and the study of mouse embryos. Making further use of these discoveries would, however, require researchers to go beyond the 14-day rule when culturing human embryos and embryo models. This raises various ethical issues, not the least concerning the ethical and legal status of such “embryo models” and it re-actualises the debate on a potential extension of the 14-day rule.

Various ethical dilemmas emerge, which forces us to think about moral principles such as the duty to prevent suffering and the duty to respect the value of human life. Where is the balance concerning the benefits these embryo models provide vs. ethical concerns? What is the legal and ethical status of human-embryo-like structures now and in the future – should it be the same for embryo models as for human embryos? What are the financial interests and how should they be regulated? Why should we want to go beyond the 14-day rule? What are the particular questions that arise from a Nordic point of view with regards to the moral status of a human embryo model and culturing human embryos beyond the 14 days?

Speakers

  • Magdalena Zernicka-Goetz, professor of Development and Stem Cells at the University of Cambridge, UK and California Institute of Technology, USA
  • Fredrik Lanner, Assistant Professor at Department for Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
  • Johanna-Ahola Launonen, Post-Doctoral Researcher at Aalto University, Helsinki, Finland
  • Garðar Árnason, Professor of Philosophy at the University of Akureyri, Iceland"

categories Talks and events

Variation in personality shaped by evolutionary history, genotype, and developmental plasticity in response to feeding modalities in the Arctic charr

Arnar Pálsson, 04/05/2023

Variation in personality shaped by evolutionary history, genotype, and developmental plasticity in response to feeding modalities in the Arctic charr

AUTHORS

Marion Dellinger, Sarah E. Steele, Evert Sprockel, Joris Philip, Arnar Pálsson, David Benhaïm

Submitted manuscript, sorry not on BioRxiv.

ABSTRACT

Animal personality has been shown to be influenced by both genetic and environmental factors and shaped by natural selection. Currently, little is known about mechanisms influencing personality traits development. This study examines the extent to which personality development is genetically influenced and/or environmentally responsive (plastic). We also investigated the role of evolutionary history, assessing whether personality traits could be canalized along a genetic divergence gradient. We tested the plastic potential of boldness in juveniles of five Icelandic Arctic charr morphs (Salvelinus alpinus) displaying various degrees of genetic divergence from the ancestral charr, split between treatments mimicking benthic vs. pelagic feeding modalities. We show that differences in mean boldness are mostly affected by genetics. While the benthic treatment led to bolder individuals, the environmental effect was rather weak, suggesting that boldness lies under strong genetic influence with reduced plastic potential. Nevertheless, the repeatability of boldness response to treatment varied among morphs, suggesting the early environment may drive personality emergence within populations. Finally, we found hints of differences by morphs in boldness canalization through reduced variance and higher consistency in boldness within morphs. These findings provide new insights on how behavioural development may impact adaptive diversification.

categories Publications

Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Arnar Pálsson, 24/02/2023

Diversity in the internal functional feeding elements of sympatric morphs of Arctic charr (Salvelinus alpinus)

Jónsdóttir, G.Ó., von Elm, L-M, Ingimarsson, F., Tersigni, S., Snorrason, S.S, Pálsson, A. and Steele, S.E.

Submitted to Evolutionary Biology. https://www.biorxiv.org/content/10.1101/2023.02.17.528955v1

Abstract

The diversity of functional anatomy related to feeding is particularly impressive in fishes and correlates with various ecological specializations across species. Polymorphism within species can manifest in divergent feeding morphology and ecology, often along a benthic–pelagic axis. Arctic charr (Salvelinus alpinus) is a freshwater salmonid known for morphological variation and sympatric polymorphism. In Lake Þingvallavatn, Iceland, four morphs of arctic charr coexist that differ in preferred prey, behaviour, habitat use, and external feeding morphology. We studied variation in upper and lower jaw bones (six bones total) related to feeding, in adults of the four morphs using geometric morphometrics and univariate statistics. We tested for allometric differences in bone size and shape among morphs, morph effects on bone size and shape, and if benthic and pelagic ecologies associate with bone size and shape. We also examined the degree of integration between bone pairs. We found differences in bone size between pelagic and benthic morphs for two bones (dentary and premaxilla). There was clear bone shape divergence along a benthic–pelagic axis in four bones (dentary, articular-angular, premaxilla and maxilla), as well as allometric differences between morphs in the dentary. Most dramatic was the dentary, where morph explained more shape variation than bone size. Comparatively, benthic morphs possess a compact and taller dentary, with shorter dentary palate, consistent with visible (but less prominent) differences in external morphology. As these morphs emerged in the last 10,000 years, these results indicate rapid functional evolution of specific feeding structures in arctic charr. This sets the stage for studies of the genetics and development of rapid and parallel craniofacial evolution.

 

categories Publications