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.

©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.

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.

This darling is nearly ready for submission. Very cool results from a study led by Guðbjörg Ósk Jónsdóttir and Sarah Steele, based on pioneering work by Finnur Ingimarsson and Sigurður S. Snorrason.

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. 

One cool figure from the manuscript, showing shape variation in bones in the four sympatric morphs of Arctic charr in Lake Þingvallavatn.

Shape variation in the articular angular, part of the lower jaw, PCA of individuals and the first two axes of shape variation (after size correction).

Colour coding follows previous publications, large benthic (Green), small benthic (blue), planktivorous (red) and piscivorous charr (purple).

The morphs are genetically separable, with a twist...

Jóhannes Guðbrandsson, Kalina H. Kapralova, Sigríður R. Franzdóttir, Þóra Margrét Bergsveinsdóttir, Völundur Hafstað, Zophonías O. Jónsson, Sigurður S. Snorrason, Arnar Pálsson. 2019. Extensive genetic differentiation between recently evolved sympatric Arctic charr morphs Ecology and Evolution.  9:10964–10983. doi: 10.1002/ece3.5516.

A nice paper by Valgerður Hjaltalín and colleagues was accepted to Autophagy Reports. She worked on this during covid, with some help from us and others. Then added a nice experimental data to the manuscript during revisions. More on this as it emerges on the journal website.

A novel region within a conserved domain in ATG7 emerged in vertebrates.

Valgerdur J. Hjaltalin, Vivian Pogenberg, Kévin J. A. Ostacolo, Arnar Pálsson, Margrét Helga Ogmundsdottir

Changes in DNA methylation in specific coding or non-coding regions can influence development and potentially divergence in traits within species and groups. While the impact of epigenetic variation on developmental pathways associated with evolutionary divergence is the focus of intense investigation, few studies have looked at recently diverged systems. Phenotypic diversity between closely related populations of Arctic charr (Salvelinus alpinus), which diverged within the last 10 000 years, offers an interesting ecological model to address such effects. Using bisulfite sequencing, we studied general DNA methylation patterns during development in the four sympatric morphs of Arctic charr from Lake Thingvallavatn. The data revealed strong differences between developmental timepoints and between morphs (mainly along the benthic – limnetic axis), both at single CpG sites and in 1,000bp-regions. Genes located close to differentially methylated CpG sites were involved in nucleosome assembly, regulation of osteoclast differentiation, and cell-matrix adhesion. Differentially methylated regions were enriched in tRNA and rRNA sequences, and half of them were located close to transcription start sites. The expression of 14 genes showing methylation differences over time or between morphs was further investigated by qPCR and nine of these were found to be differentially expressed between morphs. Four genes (ARHGEF37-like, H3-like, MPP3 and MEGF9) showed a correlation between methylation and expression. Lastly, histone gene clusters displayed interesting methylation differences between timepoints and morphs, as well as intragenic methylation variation. The results presented here provide a motivation for further studies on the contribution of epigenetic traits, such as DNA methylation, to phenotypic diversity and developmental mechanisms.