River Ecology and Management


Biology – Karlstad University

3

APR 2023

Literature Course on Evolution

Posted by Louis Addo | Literature course

This post covers chapters 6 & 7 from Futuyma & Kirkpatrick’s book on Evolution (2018). The author of this post is Jeff Marker.

Phenotypic Evolution

One major key to understanding how evolution works is based on the genetical theory related to inheritance, selection, and fitness. Through phenotypic evolution, we will now examine the quantitative traits produced by those genetic mechanisms, how the environment affects such traits, and how those traits drive evolution. Simply put, a quantitative trait is a species phenotype that is measurable in a continuous way. Quantitative traits are controlled and affected by a combination of many different genes and the environment. For example, blood pressure in humans is a product of environmental factors such as available diet in combination with genes that control a complex system of fluids, hormones, and salts in the body. Quantitative traits vary between species, but, like most phenotypes, they tend to follow a normal distribution over the entire population.

Natural selection acts on quantitative traits though the mechanism of fitness function where a specific trait of a species acts on its ability to survive or reproduce. There are three different types of selection associated with quantitative traits and fitness function: directional, stabilizing, and disruptive. First, directional selection favors either an increase or a decrease in a trait’s mean in the population, favoring individuals at one extreme of the phenotypic distribution. For example, the females of the spider Nephila clavipes (Figure 1) are selected for large body sizes as they are able to construct larger webs that capture more prey and can produce more offspring. Second, stabilizing selection is seen in species that have trait values near the population mean with intermediate phenotypes. Species of the orb-weaving spider, Argiope aurantia, capture more prey with intermediate sizes of web decoration versus other individuals with very large or very small decoration. Finally, disruptive selection is a case where both extremes of a trait are advantageous and the intermediate individuals tend to be less common. Females of the spider Gasteracantha cancriformis, prefer males with either very high levels of spines on the abdomens or low levels of spines on the abdomen and often reject those with intermediate levels of spines leading to a bimodal distribution of the number of spines on male abdomens within this species population.

Figure 1: Arigiope aurantia (Vicki DeLoach), Nephila clavipes (Dave Huth), Gastracantha cancriformis male (Sam Fraser)

Each of these types of selection is a piece of the driving force of evolution. Previously we have learned that as natural selection acts on a trait and that trait is successfully passed on to subsequent generations, then evolution of the species in question results. But the importance of quantitative traits lies in our ability to measure them and use them to make meaningful measurements about the rate of evolution. Through directional selection we can measure trait means at the start of a generation and the means of the individuals that survive and reproduce. This helps us understand the heritability, or the strength of inheritance, within a population of a species and ultimately we can calculate the rate of evolution based on that. Heritability is one piece of the overall phenotypic variance in a population. The other two sources of that variance is determined by environmental variance, such as climate or available nutrition sources, and gene dominance and epistasis. Gene dominance is where one allele expresses its phenotype over another and in epistasis a gene modifies the expression of another gene.. Natural selection acts on the existing, or standing, genetic variation within a population favoring certain traits or combinations of traits that increase an organism’s fitness. In contrast, populations with low levels of standing genetic variation may be less able to respond to changing environmental conditions, making them more vulnerable to extinction. Selection pressure, environment, and gene function all work simultaneously to determine a specie’s phenotypic traits

Humans have been using artificial selection for thousands of years to breed and improve a variety of plants and animals to aid in agricultural, industrial, and cultural advancement of our species. As a result of artificial selection, we have revealed a handful of general conclusions about phenotypic and trait based selection:

  1. When a trait is selected, it will evolve
  2. Traits can evolve beyond the variation that was present in the original population
  3. Small populations evolve slower than large populations
  4. Trait selection can cause other traits to be negatively affected

There exists a constant and strong trade-off regarding trait selection and evolution. This idea can often be boiled down to the phrase “there are no free rides in nature.” Traits are correlated. A common example is that with spiders. Large spiders tend to build larger webs while smaller spiders build smaller webs. These correlations between two (out of many) traits contribute to the overall fitness of the spiders and affect their ability to catch prey, mate, and provide specific functions within their environments. Some evolutionary trade-offs can help increase species fitness while other trade-offs balance each other out or may actually create a negative genetic correlation. For example, females in the larger species of spiders have higher fecundity and produce more eggs than small species. One trade-off is that these larger species have longer development times that often result in higher mortality rates.

Some species change their phenotypic expression as a result of their environmental conditions. This is called phenotypic plasticity. Plasticity can be either irreversible or reversible and may affect morphology, physiology, or behavior. Some web-weaving spiders will change the location, size, and shape of their webs in response to weather conditions, prey availability, or to better protect themselves from predators. These types of responses are not because of genetic changes, but rather a direct result of the surrounding environment.

Due to significant advances in DNA technology, we can now determine exactly what portions of a genome affect quantitative traits. Some quantitative traits are affected by a single locus with alleles that have large and significant effects while other quantitative traits are coded for with multiple genes. Understanding exactly which genes, alleles and nucleotides affect traits is imperative to better understand the mechanisms of evolution. Further, finding the quantitative trait loci can assist researchers in finding new therapies for infections that have generated resistance to current drugs.

Genetic drift

Chance is always a factor in evolution. We often like to idealize genomics, natural selection, and evolution as being this uncaring machine that just works. Traits are selected, species reproduce, populations evolve, or populations do not evolve. We learned in previous chapters about trait selection and reproduction and how this drives species evolution. However, what if this was all just a coin flip? What if the color of your hair, the size of a snail’s shell, or the number of leaves on a sunflower plant were all just due to random chance? Randomness and chance are both important pieces of the concept of genetic drift. Genetic drift is a random process causing changes in the frequency of traits within a population. Yes, both natural selection and genetic drift drive species evolution by varying the gene frequency within a population over some defined time. However, it is imperative to point out that genetic drift fluctuates due to chance events whereas natural selection is a process of species adaptation driven by environmental changes. Something that would be difficult to find here in Northern Europe but is nonetheless an accurate example of genetic drift in action is the unfortunate trait of lactose intolerance in humans. Genetic drift was likely an important factor in the initial spread of lactose tolerance. A single individual with the gene for lactose tolerance may, due to chance events, have had many descendants and thus increased that gene frequency over time within certain populations of humans. Although after initial rounds of genetic drift of lactose tolerance in humans, it is likely that positive selection played a role in its proliferation in Northern Europe.

Genetic drift can be particularly important in small populations, where chance events can have a larger impact. As a result, genetic drift can reduce genetic variation within a population, and can even lead to the loss of certain alleles. Other alleles can get fixated, meaning that they become the only allele for one locus present in the population.

There are five central features of genetic drift:

1. Genetic drift is impartial. Allele frequency in a population is just as likely to go up as it is to go down. Remember, genetic drift is due to chance, so alleles that move via genetic drift do so at random. Natural selection on the other hand can favor one allele over another as they are often chosen as a way to increase fitness.

2. Smaller populations are more susceptible to genetic drift. This causes larger fluctuations in allele frequency in smaller populations vs larger ones as the allele shift in larger populations tends to average out based on the larger number of species.

3. Genetic drift causes an overall loss in genetic variation in species populations. Once an allele is fixed within the genetics of a population, it is then the only one that will be passed on to subsequent generations.

4. Genetic drift changes the genomes of identical populations leading to more genetic variation on a larger scale.

5. Alleles can become fixed in a population without any assistance from natural selection.

Genealogy mapping is used to determine the positions of genes on a chromosome and their inheritance patterns. This mapping is used to understand the relationship between genetic variation and the physical traits that they are associated with. We know that different genes have different genealogies. Genes on a chromosome can be viewed similarly to human beings in a country: they have different common ancestors. Those common ancestors may have originated from many different places at many different times. For example, mitochondrial DNA (mtDNA) in humans can be traced back about 125,000 years ago to one of our common ancestors. In fact, mtDNA in all eukaryotic species can be mapped and traced back to a single common ancestor that lived about 2 billion years ago.

Genetic drift is always at work. However, the strength of that genetic drift is dependent on the effective population size (N­e). N­e is the number of individuals in a that would lose genetic variation at the same rate as the real population. N­e is influenced not only by the number of individuals but also the number that are sexually mature, the strength of random mating between individuals, and the sex ratio. In general, larger populations are less susceptible to drift than smaller populations, but only an infinitely large population would never experience genetic drift. Two types of genetic drift that work strongly on small populations are the bottleneck effect and the founder effect. The bottleneck effect occurs when a population undergoes a dramatic reduction in size, which can lead to a loss of genetic variation due to the random elimination of alleles. The founder effect occurs when a new population is established by a small group of individuals, which can lead to the loss of genetic variation from the original population. For example, the lake whitefish (Coregonus clupeaformis) in the Great Lake region of the North America have suffered major declines in genetic diversity due to intense fishing pressure over the last 100 years. As such, these small populations have been found to have very low genetic diversity likely as a result of being founded by a very small number of individuals (Graham et al., 2022; Stott et al., 2013). These events can be quite damaging to populations as low genetic diversity can lead to species’ being unable to adapt to changing environments.

Coregonus clupeaformis (National Oceanic and Atmospheric Association, USA)

Genetic drift and natural selection work together to move advantageous mutations through a population. Sometimes they work together to increase the mutation frequency, but occasionally, especially in smaller populations, genetic drift can cause an advantageous mutation to decrease or even be completely removed from a population. Drift can also be responsible for harmful mutations to spread and eventually become fixed. Again, this can be common in small populations that are bottle-necked sometime during their history or in populations with significant inbreeding. Inbreeding load is the weakening of fitness in a small population where harmful genetic mutations become fixed in the genome. Here, inbreeding load is different from inbreeding depression where closely related parents produce offspring with reduced fitness. Florida panthers (Puma concolor coryi) in the southern reaches of Florida have declined into the hundreds and as a result, significant inbreeding load has caused this species to have many health and physical problems including heart defects and lower reproductive success. Unfortunately, genetic drift also causes highly beneficial mutations to become completely lost in a population. This essentially acts as an “evolutionary speed limit” on how quickly species adapt to environmental changes.

Gene adaptation and local adaptation are related mechanisms in evolution referring to different ways in which populations adapt to changing environmental conditions. Gene adaptation refers to the evolution of specific genetic variants. This typically happens through natural selection where beneficial and harmful alleles increase and decrease in frequency, respectively.  Local adaptation refers to the evolution of populations that are adapted to their local environment. Local adaptation can involve both genetic and non-genetic factors such as changes in morphology and behavior.

References

Graham, C. F., Boreham, D. R., Manzon, R. G., Wilson, J. Y., & Somers, C. M. (2022). Population structure of lake whitefish (Coregonus clupeaformis) from the Mississippian lineage in North America. FACETS, 7(1), 853-874.

Stott, W., Ebener, M. P., Mohr, L., Hartman, T., Johnson, J., & Roseman, E. F. (2013). Spatial and temporal genetic diversity of lake whitefish (Coregonus clupeaformis (Mitchill)) from Lake Huron and Lake Erie. Adv Limnol, 64, 205-222.

31

MAR 2023

Seminar: Citizen Science and Learning Biology – examples and insights from two Austrian projects

Posted by Louis Addo | Okategoriserad
Martin Scheuch

Two very different biology Citizen Science projects lead to insights into students´ and teachers´ learning. But learning must not be restricted to learning at school, a social learning theory widens the scope, where learning can take place. Join us as Martin Scheuch from University College for Agrarian and Environmental Pedagogy, Austria gives a seminar entitled Citizen Science and Learning Biology – examples and insights from two Austrian projects. Time & Date: 13:15 CET, 31.03.2023. Venue: 5F322 or over zoom through https://kau-se.zoom.us/my/magnuslovenwallerius.

16

MAR 2023

Seminar: Management of invasive species in riparian forests

Posted by Louis Addo | Seminar

On 21 March, Katharina Lapin will be giving a seminar with the title Management of invasive species in riparian forests to our department. Her work centers on the recognition and handling of invasive species in forested areas, but even their effects on forest ecological functions.

Katharina Lapin

As researcher at and head of the Forest Biodiversity & Nature Conservation department of the  Austrian Research Centre for Forests (BFW), Katharina works on the interface of research and management of natural resources. This results in both scientific papers and handbooks that can be immediately applied in the management of Austrian forests. Read about the Centre for Forestry on https://www.bfw.gv.at/ (in German) and join us on Tuesday 21 March at 13:15 CET via <https://kau-se.zoom.us/my/magnuslovenwallerius>.

14

MAR 2023

Literature Course on Evolution

Posted by Louis Addo | Literature course

This post covers chapters 4 & 5 from Futuyma & Kirkpatrick’s book on Evolution (2018). The author of this post is Sam Shry.

We are all special: mutation and variation

It is quite obvious to see variation among individuals, but how does this variation come about? Chapter 4 takes us on a journey through the evolutionary processes of mutations, variations, and how they are linked to inheritance.

We start off small with DNA (or RNA for some organisms), genetic material made up of base pairs that are the building blocks of all forms of life. DNA is carried by chromosomes, with one inherited from each parent in humans. Interestingly enough, the complexity of an individual has no correlation with the size of their genome (e.g. salamanders are more complex gnomically than humans). These chromosomes contain genes, which are the areas of a chromosome that perform a function. The chapter covers in-depth the processes in which a gene’s DNA is used to make proteins, via transcription, splicing, and translation, but that’s all a little dense for a blog. What is interesting to me is how only 2% of our genetic makeup is actually used for making proteins while the rest is just there as non-coding “stuff”. Even in our DNA we are hoarders…We find, however, that protein synthesis is the driver that creates variation in our appearance (phenotype) and genetic makeup (genotype) via inheritance. Inheritance is really just a locus or gene that is passed down to the next generation, but this locus varies in its DNA sequence, giving rise to alleles, a term given to locus variation in a population. The mixing of genes in sexually reproducing organisms causes variation in allele frequencies for a population. This mixing is done through segregation and recombination, where segregation selects one or two gene copies from a locus of each parent and recombination combines gene copies from each parent. Segregation is interesting in how the frequencies of genotypes and alleles change over time. We have developed a mathematical model (Hardy-Weinberg equilibrium) in order to understand how evolutionary forces affect populations. Similarly, with recombination, we have developed a model (linkage equilibrium) in order to study the effects of recombination rates in loci. Of course, the models do not represent reality, but give us a starting point that we can use to examine how evolution is occurring in a population and what factors are having the largest effects on which loci. We also have a large proportion of species reproducing asexually, using horizontal gene transfer to move DNA between individuals, which is particularly important to bacteria’s ability to evolve antibiotic resistance.

Even with all this inheritable mixing, most variation occurs from mutations. Mutations are errors, messed up DNA replication that is the ultimate source of genetic variation. See! It’s good to mess up sometimes! They can be small, dented my car screw-ups like point mutations, which only occur at a single DNA base, or they can be hot mess situations like whole genome duplications tetraploidy, where offspring can’t reproduce with their parental population, resulting in a whole new species with a single mutation. Each type of mutation can occur at a different rate and can cause different degrees of effect. Usually, there is a linear trend in genome size and mutation rate, which can affect almost every aspect of an organism. Mutations can affect both an individual’s traits as well as their fitness. Natural selection tries to drive mutation rates down, but ironically it is mutations that drive adaption and allow us to survive. We’ve been hyping up mutations, but most of them are bad, with natural selection “picking out” what mutations are favorable in an individual’s environment, or in other words, what works in an environment doesn’t die or at least has a chance to “get-it on” before dying. There are also a vast number of fields that delve into the inheritable, but non-genetic, cultural changes that can alter the physical behavior and learning of the offspring, but we steer clear of that in this book.

Just natural selection bro

In chapter 5 we can explain the genetic theory of natural selection as fundamental and simple, though Darwin may disagree as he wrecked himself trying to understand this “simple” concept till he died. It wasn’t till after his death that Mendelian genetics was fused with Darwinian selection theory. Of all organisms, the peppered moth is our shining example of documented evolution via natural selection, ironically adapting to survive our coal burning in the industrial revolution. After documenting this discovery we went straight to work figuring out how we could exploit this beautiful, natural process by developing the technique of industrial artificial selection; selecting the best traits of what we consume to make it taste, tastier.

What is key to evolution by natural selection is that the trait (phenotype) has to be good enough to allow individuals to make lots of offspring (absolute fitness) and that the trait is inherited by the offspring, which in turn causes the evolution of the species. Fitness is a combination of the probability of survival to maturity and the expected number of offspring the individual will have. If we think of a male bodybuilder, he may seem “fit” physically, but from an evolution standpoint his fitness is only measured in his survival to maturity and the number of offspring he produces, which could be a problem due to all the steroids…

If an allele has higher fitness after a mutation, this will cause a positive selection of that mutation in the population. One example of this is the adaption to drinking cow’s milk (lactase persistence) in Northern European populations. We can calculate a measurable selection strength score for these beneficial alleles (selection coefficient), which can then be compared with the genetic variation in the population to predict the rate of adaptation. The rate of adaptation can vary based on the organisms’ generation time (bacteria vs. humans) and the allele dominance (dominant, non-dominant, recessive). There can also be crappy mutations (deleterious) that decrease fitness and unfortunately due to their lousy recessive qualities and low frequency, selection can’t remove them easily. Just like gambling, mutations are subject to chance and can be removed from a population even if they are beneficial, such as via genetic drift.

There is also a mix of situations where natural selection has side effects, some of which are good and others not so good. Some of these genetic side effects are genetic correlations, allele hitchhiking, and trade-offs between alleles, all of which are a by-product of selection that can have serious effects on the population. For example, the Scottish soay sheep have an evolutionary trade-off in their population where a polymorphism at a single locus causes homozygous individuals to grow vestigial horns. These sad-looking horns make it harder with the ladies (decreasing mating success) but increase survival (no macho fights).

Just as natural selection can lead to new forms of variation, it can also preserve variation available in a population via balancing selection. This can occur when hard-core heterozygote alleles have higher fitness than the homozygotes (overdominance) and lead to polymorphic equilibrium, where both alleles are maintained in the population. Balancing selection can also occur with frequency–dependent selection, where the frequency of the alleles determines their fitness. Specialization can also balance polymorphism, either via niche specialization or space specialization. Just as yin and yang, genetic variation can also be destroyed by natural selection via under-dominance and positive-frequency-dependent selection. Almost nothing can escape time though, with alleles spreading to fixation in the population, with the deep, thought-provoking idea that “the outcome of evolution is determined by where the population begins” (page 125).

Where a population begins is important, because natural selection is continuously adapting species to the environment in which they live, making this coupling between species to the environment. Fitness can increase or decrease based on the organism’s mutations, but the same ebbs and flows in fitness can be the result of environmental changes too.

To measure the fitness of a population over time, mean fitness can be calculated and compared between populations. This theorem of natural selection mathematically demonstrates that populations evolve via natural selection in order to increase their average survival and reproduction through time. The measurable adaptive landscape is the balance between fitness selection, environmental gains, mutations, etc., and though the fundamental theorem doesn’t exactly apply to real-world situations sometimes (typical math), it acts as a guide to understanding approximately what the hell is going on in the population from an evolutionary point of view. Some instances where the math is way off is when selection is frequency dependent, which can lead to mean fitness decline of the population. The same can be said for competition within a population, where some individuals develop nasty traits that become dominant in the population, but then turn out to bring down the fitness of the group.

Most of the time though, these mutations, usually bad, are killed off (deleterious). Selection does an adequate job of “purifying” our DNA from these crap mutations, but the problem is they can reappear at almost the same rate, causing the numbers to balance out. What’s interesting is it doesn’t matter how crap the mutation is (strong or weak deleterious mutations), the population’s mean fitness still decreases by the same amount. It’s important to understand how this load of crap (mutation load) is spread throughout the genome in order to understand its effect on the mean population fitness. These deleterious mutations cause a lot of problems in humans a.k.a. death, but modern medicine has decreased and postponed these deaths, and individuals have lived long enough to reproduce, making a controversial discussion as to the future impact this will have on humans, but maybe concentrating on climate change and keeping us from catching on fire is a more pressing issue


7

MAR 2023

Seminar: Effects of historical land-use and landscape structure on arthropod and plant communities in grassland

Posted by Louis Addo | Seminar
Jan Thiele

Jan Thiele from Thünen Institute for Biodiversity, Braunschweig-Germany will be giving a seminar today 7th March 2023 at 13.15 CET live over zoom. The title of this seminar is Effects of historical land-use and landscape structure on arthropod and plant communities in grasslands. To attend visit https://kau-se.zoom.us/my/magnuslovenwallerius

1

MAR 2023

Literature Course on Evolution

Posted by Louis Addo | Literature course

This is a literature course on the book Evolution by Douglas J. Futuyma & Mark Kirkpatrick (Fourth Edition) during the first half of 2023. This write-up covers chapters 1 to 3 and is authored by Louis Addo (a Ph.D. student at KAU)

The historical background of Evolution Biology

Evolution in biology refers to the shift in the heritable traits of biological populations over successive generations. Charles Robert Darwin (English naturalist and biologist, Figure 1. left) and Alfred Russel Wallace (an English naturalist, explorer, geographer, anthropologist, biologist and illustrator, Figure 1. right) separately developed the theory of evolution by natural selection in the middle of the 19th century, and it was extensively outlined in Darwin’s book On the Origin of Species. The hypotheses of evolution postulated that all living things share a common ancestor, and that natural selection acting on genetic variations is responsible for the changes in their populations over time. The theory of evolution became a scientific fact supported by other scientists in paleontology, genetics, and biochemistry. Prior to the postulation of the theory of evolution, the dominant worldview was that each species was uniquely created by God and had set characteristics. However, this worldview was challenged by the Enlightenment movement leading to the emergence of science. The foundation for evolutionary thought was laid by astronomers and geologists who postulated theories about the creation of stars, planets, and the earth including the changes the earth has gone through as well as its many extinct species. Unique to Darwin’s theory were its five components explaining concepts “descent with modification” and “natural selection”.

Figure 1 Famous fathers of evolution: Charles Robert Darwin (left) and Alfred Russel Wallace (right) (Futuyma & Kirkpatrick pp 11-13)

The five distinct components of Darwin’s theory of evolution are natural selection which means that species characteristics change over time to meet changes in their environment, evolution which proposes that organisms change over time, gradualism which means that the differences between even fundamentally different organisms have evolved through intermediate forms rather than by large leaps, common descent which suggests that species diverged from shared progenitors and that species might be seen as one enormous family tree that represents ancestry, and finally population change which means that evolution occurs by changes in the proportions (frequencies) of different variant kinds of individuals within a population.

Most scientists acknowledged the historical truth of evolution through descent with modification from common ancestors by the 1870s, but natural selection, which drives evolution, was not widely accepted until around 60 years after The Origin of Species was published. Many ideas, including neo-Lamarckian, orthogenetic, and mutationist theories, were put out during this period.

In general, the idea of evolution is a scientific truth that explains how ancestors give rise to various descendants and how species change over time. Biologists generally agree with the theory, and while work is still being done in some areas, the fundamental ideas of evolutionary theory are well-supported.

The “Tree of Life” and phylogenetics

The concept of the Tree of Life was first proposed in Charles Darwin’s book On the Origin of Species and proposes that all species, alive and extinct, descended from a single ancestral form of life that existed billions of years ago. The history of the events by which species or other taxa have arisen from common ancestors is called phylogeny, which is often represented by a phylogenetic tree that shows the genealogical relationships among the taxa. Anagenesis, which is the evolutionary modification of a lineage’s (species’) physical characteristics, and cladogenesis, which is the division of a lineage into two or more descendant lineages, are the two main processes that contribute to the development of higher taxa. After cladogenesis, anagenesis causes each descendant lineage to diverge even farther from the others. The branching order and the length of the branch in the phylogenetic tree can show which species are more closely and less distantly related to one another.

Phylogenetic studies reveal the evolutionary relationships between organisms and gene sequences, often showing the pattern of separate and divergent lineages. However, sometimes branches of a phylogenetic tree rejoin, forming a network rather than just a branching tree. Hybrid speciation is one example of this, which is especially common in plants, where some species evolve from hybrid crosses between two different ancestors. Another example is horizontal gene transfer (HGT) where genes are passed among organisms, enabling them to adapt to changing circumstances.

Phylogenetic analysis is an effective method for determining how different traits in organisms have evolved through time. This approach shows that species have evolved from similar creatures since it is based on homologous traits that have descended from them. The majority of an organism’s traits are changed from traits that already existed in its ancestors and do not develop independently. Although they often have comparable genetic and developmental bases, homologous physical characteristics between species can vary more than the finished products. For instance, in the 1970s, scientists analyzed the protein amino acid sequences of pairs of animals that split from their common progenitors at various points in time. They created a molecular clock by plotting the matching DNA sequence discrepancies against predicted divergence periods and finding that the rise in differences increased linearly with time (Futuyma & Kirkpatrick 41). Assuming the genes in these lineages had developed at the same pace as those in the animals with fossil records, this permitted calculation of the period of divergence even for lineages lacking a fossil record. Yet, there is no one molecular clock and rates of sequence evolution vary among different types of organisms.

The analysis of the evolution of different organismal traits with phylogenetic analysis offers overwhelming proof of evolution. It is feasible to evaluate homologous traits that are descended from common ancestors since characteristics of organisms nearly invariably evolve from pre-existing aspects of their predecessors. However, a character may be shared by several species but not necessarily in the same character state. It can be challenging to determine if two species’ traits are homologous, but embryological research and anatomical correspondence of position and structure, are the two most often used methods for making this determination are often successful methods.

The concepts of Natural Selection and Adaptation

Changes in the environmental adaptation requirements of organisms trigger biological changes in their behavior and physical features to ensure their existence in the altered environment. Thus, altered environments can cause natural selection on the genetic variation in many characteristics of a species or population. For instance, soapberry beetles adapted to new food sources by changing the length of their beaks, and several insect and plant species have developed a resistance to heavy metals and chemical pesticides. Fish overfishing has also affected behavior and accelerated the onset of sexual maturity. The process by which individuals with advantageous traits have a better chance of surviving and reproducing than those without, resulting in the preservation of preferred variations and the rejection of harmful ones, is referred to as natural selection. Darwin first introduced this idea in “On the Origin of Species.” When various biological entities consistently vary in fitness, natural selection takes place. It is important to understand that evolution, which may also be brought about by other mechanisms like genetic drift, is not the same as natural selection. The environmental conditions that force natural selection on a species are determined by its traits. Certain species can create ecological niches for themselves by eliminating elements of their environment so that these no longer force natural selection. Natural selection can take place at several scales, including genes, cell types, individual organisms, populations, and species.

Selfish genes, which multiply in the genome whether they are advantageous to the organism or not, are an illustration of gene-level selection. Gene-level selection can conflict with individual selection and cause harm to organisms. Selection among individuals occurs at a higher level than selection among genes. Characteristics develop through individual selection; altruism can lower individual fitness but may develop through social selection; cooperation develops through kin selection. By varying the percentage of species throughout time, species selection modifies the diversity of biological traits. It has an impact on organism disparity but not adaptations. For instance, more asexual populations experience extinction than sexual groups.

Adaptation in biology refers to both the process by which organisms evolve over generations to improve survival and reproduction, and to a characteristic that evolved by natural selection. A trait must be developed and give greater fitness than the ancestral condition in order to qualify as an adaptation. A feature that unintentionally fulfills a new purpose is known as a preadaptation. For instance, parrots can eat fruits and seeds with the help of their strong, pointed beaks but, in case a new resource is presented, they can also use it to feed on that resource. Exaptation is the process of adapting a characteristic for use unrelated to the one for which it was originally selected. In birds that initially evolved feathers to keep warm, an example of an adaptation would be the use of feathers for mating displays or flying. Pre-adaptation is another name for an exaptation. Exaptations and preadaptations are common in the early stages of the evolution of new adaptations. To determine if a certain characteristic is an actual adaptation, scientists examine the available data. Species traits are not always adaptations or random characteristics but can be flawed and limited, such as in the case of mammals that are unable to evolve beneficial modifications in the number of vertebrae. The vast diversity of life is the result of natural selection, as varied habitats and other factors may force selection on different traits within a species.

The next blog will cover chapters 4 and 5 and will be authored by Samuel Shry.

References

Futuyma, D. J., & Kirkpatrick, M. (2017). Evolutionary. Evolution (Fourth ed.). pp. 3-76. Sunderland, Massachusetts: Sinauer Associates, Inc.

28

FEB 2023

Två nya projekt till biologin

Posted by Louis Addo | Okategoriserad

Forskargruppen Naturresurs rinnande vatten (NRRV) har fått två ny forskningsprojekt beviljade. Lutz Eckstein är projektledare i ett projekt om effekter av korttidsreglering i vattendrag under vintern på ekologisk status av strandzonen som finansieras genom Kompetenscentret Svenskt vattenkraftcentrum (SVC) med 3,8 Mkr. Projektet är ett samarbete mellan Karlstads universitet (Eva Bergman, Larry Greenberg, Johan Watz) och Umeå universitet (Roland Jansson, Birgitta Malm-Renöfält) och kommer att undersöka vattendrag i både norra och södra Sverige. John Piccolo är projektledare i det andra projektet som kommer att fokusera på att upprätthålla vattenkraftsproduktion och värdefulla fiskpopulationer genom att utveckla Individual-Based Models (IBM) för att bedöma hur fiskpopulationer kan återställas samtidigt som flödesförhållanden för vattenkraftproduktion upprätthålls. Projektet finansieras genom Energimyndighetens program hållbar svensk vattenkraft (HåVa) med 2,9 Mkr och är ett samarbete mellan Karlstads universitet (Mahboobeh Hajiesmaeili och Johan Watz), Vattenfall AB (David Aldvén och Patrik Andreasson) och Fortum AB (Marco Blixt och Markku Lahti) och kommer att undersöka två viktiga vattenkraftsproducerande vattendrag i Sverige: Gullspångsävlen och Luleälven.

28

FEB 2023

Two new projects for biology

Posted by Louis Addo | Okategoriserad

The River Ecology and Management research group (RivEM) has been granted two new research projects. Lutz Eckstein is the project manager in a project, which is financed through the Competence Center Swedish Hydropower Center (SVC) with 3.8 million SEK, on the effects of short-term regulation of rivers during winter on the ecological status of the riparian zone. The project is a collaboration between Karlstad University (Eva Bergman, Larry Greenberg, Johan Watz) and Umeå University (Roland Jansson, Birgitta Malm-Renöfält) and will investigate rivers in both northern and southern Sweden. John Piccolo is the project manager in the second project that will focus on sustaining hydropower production and high-value fish populations by developing Individual-Based Models (IBM) to assess how fish populations can be restored while maintaining streamflows for hydropower production, which is financed through the hållbar svensk vattenkraft (HåVa) program of Energimyndigheten with 2.9 million SEK. The project is a collaboration between Karlstad University (Mahboobeh Hajiesmaeili and Johan Watz), Vattenfall AB (David Aldvén and Patrik Andreasson) and Fortum AB (Marco Blixt and Markku Lahti) and will investigate two key hydropower producing rivers in Sweden: Gullspångsävlen and Luleälven.

28

FEB 2023

Seminar: The value of road verges and power-line corridors for landscape-scale diversity and connectivity

Posted by Louis Addo | Seminar
Juliana Daniela-Ferreira

Juliana Daniela-Ferreira (a postdoc researcher from SLU Uppsala) will be giving a talk about the value of road verges and power-line corridors for landscape-scale diversity and connectivity. This will be streamed live on zoom at 13:15 CET on Tuesday 28th February 2023.

Juliana is interested in the relative effects that different land use practices (e.g. agricultural land, productive forests, semi-natural grasslands) have on biodiversity and on how these effects change at different spatial scales. Also, Juliana has an interest in developing strategies for biodiversity conservation that account not only for local disturbances but also for human-induced changes in the landscapes.

The zoom link to attend this seminar is (https://kause.zoom.us/my/magnuslovenwallerius).

16

JAN 2023

New paper out on the biology of the invasive forb Garden lupine

Posted by Louis Addo | Invasive species, Papers

Lutz Eckstein is the lead author of a paper summarizing the current knowledge on the biology of the invasive legume Lupinus polyphyllus Lindley. The paper has recently been published in the journal Perspectives in Plant Ecology, Evolution and Systematics in the series “Biological Flora of Central Europe” (https://doi.org/10.1016/j.ppees.2022.125715). This work is a cooperation with Erik Welk (Martin-Luther-University Halle-Wittenberg and German Centre for Integrative Biodiversity Research (iDiv) Halle, Germany), Yves Klinger and Wiebke Hansen (both Justus Liebig University Giessen, Germany), Tommy Lennartsson and Jörgen Wissman (both Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden), Kristin Ludewig (University of Hamburg, Germany), and Satu Ramula (University of Turku, Finland).

The paper gives a thorough review of the species’ taxonomy, presents distribution maps for North America, Europa and the world (Fig. 1), illustrates the life cycle of L. polyphyllus, and it contains a comprehensive discussion of potential management options. During the research for this review, the authors encountered some doubtful information about L. polyphyllus that uncritically reiterates in several fact sheets, reports and webpages. One such erroneous piece of information refers to the apparently very high longevity of seeds, which was taken from a modelling study on seed longevity under optimal dry and cold storage conditions. Similarly, there is some uncertainty and large variation concerning the actual lifespan of the species. Another piece of doubtful information is the deep rooting depth of L. polyphyllus, which may rather characterize a maximum than a representative average value. Finally, the species is sometimes considered a “rhizomatous perennial” although it lacks true rhizomes. These points highlight some critical knowledge gaps, which partly relate to aspects of the species’ life cycle and morphology that may be either time-consuming or labor-intensive to study.


Fig 1. Distribution of Lupinus polyphyllus s.l. (A) In North America, the native segregates in the west partly overlap in their distribution and are delimited by outlines according to the color scheme in the legend. Non-native, synanthropic occurrences are indicated by black dots. Distribution data based on digitally available herbarium specimen locations and county records (for data sources see Table 1 in the paper). (B) In Europe, numbers give the first records for the species in different countries/regions (cf. Table 6 in the paper). (C) Numbers refer to the textual descriptions (for details, see the paper) of the non-native naturalized distribution across the globe

The authors conclude that there is currently no evidence-based strategy for a cost-efficient management of L. polyphyllus. The development of such control measures is necessary because L. polyphyllus is among the most problematic non-native plant species in Europe with respect to environmental and socio-economic impacts. The species has significant negative effects on community structure, composition, species richness and diversity, especially in nutrient-poor habitats such as alpic mountain hay meadows, alpic mat-grass swards but also nutrient-poor road verges or riparian terraces.