Species and Speciation Chapter PDF

Species and Speciation Group 1 Presents What Are Species? Species - Latin word for “kind” and are used by biologists. For Linnaeus and other early taxonomists, species were simply groups of organisms that could...

Species and Speciation Group 1 Presents What Are Species? Species - Latin word for “kind” and are used by biologists. For Linnaeus and other early taxonomists, species were simply groups of organisms that could be distinguished. But as knowledge of organisms grew, this criterion became inadequate. For example, two kinds of small owls in eastern North America look very different: one is gray and the other bright reddish brown Biological Species Concept (BSC) - “Species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups. Reproductive isolation - any of several biological differences between the groups greatly reduce gene exchange between them, even if they are not geographically separated. The biological species concept was developed partly to acknowledge variation, both within a single population (such as the color morphs of the eastern screech owl) and among different geographic populations, which often show evidence of interbreeding where they meet. The BSC also recognizes cases of “sibling species” (such as the gray forms of the two screech owls), which are almost identical in appearance and are often discovered by differences in ecology, behavior, chromosomes, or genetic markers. The term “sibling species” differs from sister species, which are two species descended from a single ancestral species, and are therefore one another’s closest relatives.  Modes of Speciation: Allopatric Speciation - Speciation by geographic isolation: Populations are separated by physical barriers. - Vicariance: A physical barrier divides a population, leading to isolation. - Dispersal: A subset of individuals colonizes a new area, becoming isolated from the parent population.  Modes of Speciation: Peripatric Speciation - A special case of dispersal: A small group of individuals colonizes a geographically isolated area. - Genetic drift: Random changes in allele frequencies can lead to rapid speciation. - Founder Effect: A small group of individuals establishes a new population, leading to a reduced genetic diversity. FIGURE 9.21 Variation among paradise kingfishers in New Guinea. Tanysiptera galatea is distributed throughout the New Guinea lowlands (regions 1, 2, 3) and some satellite islands (4, 5). The very localized forms T. riedelii on Biak Island (6) and T. carolinae on Numfor Island (7) are distinct species. Mayr proposed that these represent cases of founder effect speciation. (T. galatea photo courtesy of Rob Hutchinson/Birdtour Asia; T. riedelii and T. carolinae courtesy of Mehd Halaouate.)  Modes of Speciation: Parapatric Speciation - Speciation with partial isolation: Populations are partially isolated, with limited gene flow. - Ecological Isolation: Species occupy different ecological niches within the same geographic area. - Ecological Speciation: Selection for different ecological adaptations drives speciation.  Modes of Speciation: Sympatric Speciation - Speciation without geographic isolation: Populations diverge within the same geographic area. - Sexual Isolation: Differences in mating preferences or behaviors lead to reproductive isolation. - Disruptive Selection: Selection favors extreme phenotypes, leading to speciation. Modes of Speciation: FIGURE 9.22 Schematic showing three types of speciation. In allopatric speciation, populations diverge (shown as increasing difference in color) while separated by a geographic barrier (such as a mountain range). In this drawing, an allopatric population is established by colonization. When the two populations have become so different that reproductive isolation has evolved, the two can coexist without interbreeding even if each form disperses into the range inhabited by the other (shown by the double- headed arrow). In parapatric speciation, neighboring populations diverge while still exchanging genes. In sympatric speciation, two new species emerge from a single ancestor without any geographic isolation.  Phylogenetic Species Concepts - Defining species based on evolutionary history: This concept defines a species as the smallest group of organisms that share a common ancestor and are distinct from other groups. - Focus on monophyly: A species is considered a monophyletic group, meaning all members descend from a single common ancestor. Key Concept: Reproductive Isolation - The foundation of speciation: The inability of individuals from different populations to interbreed and produce viable, fertile offspring. - Gene flow: The movement of genes between populations. - Reproductive isolation: The absence of gene flow between populations. - Reproductive Isolating Barriers: Mechanisms that prevent gene flow, these barriers can act before or after fertilization.  Dobzhansky-Muller incompatibilities (DMIs) Incompatible interactions between genes inherited from the two parents were postulated by Theodosius Dobzhansky in 1937 and by Hermann Muller in 1942. Example: DMIs between Drosophila simulans and D. mauritiana cause male F1 hybrids to be sterile, while females are fertile. The genetics of the hybrid male sterility have been studied with laboratory crosses that produce different combinations of chromosome segments. Two results emerge. The first is that many combinations of chromosomes from the two species reduce male fertility, showing that there are many DMIs throughout their genomes. The second is that male sterility is caused by interactions between the autosomes of simulans and the X chromosome of mauritiana. This reflects a general phenomenon called Haldane’s rule: hybrid sterility or hybrid inviability is often limited to the heterogametic sex. (The heterogametic sex is the one with two different sex chromosomes, while the homogametic sex has two sex chromosomes of the same type.)  How fast does reproductive isolation evolve? The time required for reproductive isolation to become strong, after it has started to evolve, varies greatly. The origin of a new species by polyploidy, which is especially common in plants, requires only one or two generations.  Genetic Mechanisms - Epistasis: Interactions between genes at different loci can contribute to reproductive isolation. - Inversion: A chromosomal rearrangement that can reduce gene flow between populations. - Reciprocal Translocation: An exchange of genetic material between non-homologous chromosomes. - Segregation Distortion: Genes that bias their own transmission can lead to reproductive isolation. - Genetic Conflict: Conflicts between genes can drive speciation.  Introgression The transfer of genetic material from one species to another through hybridization: Can introduce new alleles into a population. Impact on speciation: - Can promote speciation: Introgression can introduce novel alleles that contribute to reproductive isolation. - Can hinder speciation: Introgression can also counteract the effects of reproductive isolation by mixing gene pools. - Examples: The transfer of genes between human and Neanderthal populations.  Classification of Isolating Barriers I. Premating barriers: features that impede transfer of gametes to members of other species A. Ecological isolation: potential mates do not meet 1. Temporal isolation: species breed at different seasons or times of day 2. Habitat isolation: species mate and breed in different habitats 3. Immigrants between divergent populations do not survive long enough to interbreed B. Potential mates meet but do not mate 1. Sexual isolation in animals: individuals prefer mating with members of their own species 2. Pollinator isolation in plants: pollinators do not transfer pollen between species  Classification of Isolating Barriers II. Postmating prezygotic barriers: mating occurs, but zygotes are not formed A. Mechanical isolation: reproductive structures of the sexes do not fit B. Copulatory isolation: female is not stimulated by males of the other species C. Gametic isolation: failure of fertilization  Classification of Isolating Barriers III. Postzygotic barriers: hybrids are formed but have reduced fitness A. Extrinsic: hybrids have low fitness for environmental reasons 1. Ecological inviability: hybrids are poorly adapted to both of the parental habitats 2. Behavioral sterility: hybrids are less successful in obtaining mates B. Intrinsic: low hybrid fitness is independent of environmental context 1. Hybrid inviability: reduced survival is due to genetic incompatibility 2. Hybrid sterility: reduced production of viable gamates  Reinforcement The process by which prezygotic barriers become stronger due to selection against hybridization: Natural selection favors individuals that avoid mating with other species. Introgression and reinforcement: Introgression can sometimes lead to reinforcement by increasing the strength of prezygotic barriers.  Reinforcement of Reproductive Isolation Reinforcement of reproductive isolation by flower color in Phlox. (A) The geographic distributions of P. cuspidata and P. drummondii overlap in Texas. Allopatric populations of both species are light blue, but populations of P. drummondii are dark red where the species is sympatric. (B) The flower color difference in P. drummondii is based on two loci. (C) Results of common-garden field experiments, in which all four color types of P. drummondii were grown together with P. cuspidata. Both parental types (light blue and dark red) and hybrid genotypes with light red and dark blue flowers have equal fruit production (top graph), but differ in the proportion of their offspring that are hybrids with P. cuspidata (bottom graph). SPECIATION BY SEXUAL SELECTION Evolution of sexual isolation by sexual selection. The pulse rate of the mating call of male crickets (Laupala cerasina) and the pulse rate preferred by females both vary among local populations. These differences are genetically based. The confidence intervals around each point show that the preference ranges of females of the most widely different populations would not include the most divergent males.  SPECIATION BY POLYPLOIDY Several species of When a diploid species’ entire genome is goatsbeards (Tragopogon) are doubled, the result is a tetraploid that has four tetraploids that have formed by copies of every chromosome. hybridization (allotetraploids). The diploid species T. dubius and T. pratensis hybridized and produced the tetraploid species T. miscellus. Next to the pictures of the flowers are drawings of their chromosomes. The tetraploid has twice as many chromosomes as the two diploid species. T. dubius has also hybridized with the diploid T. porrifolius to produce the tetraploid T. mirus. Speciation is more likely to occur on larger islands and in species with restricted gene flow. The minimal island size allowing speciation is small in taxa with low rates of gene flow, such as snails. Islands must be much larger for speciation to occur in taxa with high rates of gene flow, such as bats. Gene flow is measured here as 1/FST between populations ranging from 10 to 100 km apart. FST is a measure of genetic differentiation that decreases with greater gene flow  Conclusion Speciation is essential for biodiversity, as it drives the emergence of new species, contributing to the richness of ecosystems and the variety of life on Earth. It enables populations to adapt to different environments and ecological niches, fostering unique traits that enhance ecosystem stability and resilience. Understanding speciation is crucial for evolutionary research, conservation efforts, and addressing human impacts on biodiversity, such as habitat destruction and climate change. Overall, speciation plays a fundamental role in maintaining the dynamic balance of life on our planet. Thank You  ALL ABOUT SEX Agapay, Astudillo, Calinaya BIOL 109 - CDK2 What is sex? Sex refers to the biological and physiological characteristics that define plants and animals as male or female, typically determined by chromosomes and reproductive systems. It also encompasses sexual activity, which involves physical intimacy between individuals for reproduction or pleasure.  A male and female adult Cygnus olor What are males and females? In eukaryotes, females produce large, immobile eggs while males produce small, mobile sperm, a distinction known as anisogamy. Some species are hermaphroditic to enhance reproductive assurance when mates are scarce, while others have separate sexes determined by genetics or environmental factors. Many species exhibit sexually dimorphic traits, allowing for differentiation between males and females. Here a brilliantly colored male Panthera tigris Euglossa igniventris collects scent from a Coryanthes orchid flower in Panama. (Courtesy of David Roubik.)  Sexual Selection It is a selection caused by competition for mates among individuals of the same sex. Sexual selection can cause the evolution of traits that decrease survival if the reproductive advantage they produce compensates for that cost. In short, a trait can evolve by sexual selection if it increases a male’s overall fitness, even if it decreases survival. Sexual Selection Primary Sexual Trait A male is attacked by a fringe-lipped bat (Trachops cirrhosus) An individual without gonads will leave that has located the túngara frog (Physalaemus pustulosus) by no genes to the next generation. his calls. Gonads and genitalia are called primary sexual traits. Secondary Sexual Trait Secondary sexual traits are characteristics that differentiate the sexes and do not directly contribute to reproduction. These traits often evolve rapidly due to sexual selection and are important for species identification. Page 05 Page 05 Page 06  R.A. Fisher’s runaway mechanism explains how a male trait, like a long tail, and a female preference for that trait can co-evolve through a feedback loop. Females with a preference for long tails mate with long-tailed males, passing on both the trait and the preference to offspring. Over generations, this leads to increasingly exaggerated traits, with natural and sexual selection amplifying the effect. Fisher’s runaway Direct selection Indirect selection This selection acts directly on genes related to mating This selection acts on genes linked to preferences preferences, meaning these genes improve survival or rather than on the preferences themselves, often due reproductive success. For example, a female may prefer to correlation with other beneficial traits. For instance, a mates who provide food or protection, directly female’s preference might evolve simply because it’s enhancing her survival. linked to genes that improve survival in other ways. Page 08 Sexual selection in flowering plants Page 10 Sexual Selection in Flowering Plants How does sexual selection occurs in plants? If: Males = No weapons Females = no nervous system OPERATIONAL SEX RATIO -determines which sex experience sexual selection - Often male-based in plants 1. Males (pollen donors) > Females (pollen receptors) 2. Pollen grain arrives on a flower Page 10 MALE-MALE COMPETITION Sexual Selection in Flowering Plants Individuals with more attractive floral displays attract more pollinators. INCREASED FITNESS Influence of grazing intensity on patterns and structuring processes in plant-pollinator networks in a subtropical grassland - Scientific Figure on ResearchGate.  Sex Ratios Environmental sex determination Haplodiploid sex determination It occurs when the sex of an organism is influenced by A system where fertilized eggs develop into females external environmental factors, such as temperature and unfertilized eggs develop into males, allowing during egg development. This allows species to adapt females to control the sex ratio by choosing whether to their sex ratios based on conditions, such as where fertilize the eggs. This method is used by species like females choose to lay their eggs. ants, bees, and wasps, enabling adjustment of male and female numbers based on reproductive needs. Page 08 Sex Ratios - The relative number of males and females HUMANS & PLANTS Seychelles warbler - Sex is determined by chromosomes Offspring production (daughters) SEX RATIO = 50% 87% 23% UNEQUAL SEX RATIO Sex Ratios Environmental sex determination (ESD) Haplodiploid sex determination When a female lays an egg, she can fertilize it - Sex is determined not by chromosomes with sperm that she but by the physical and social environment. has stored from an earlier mating. Male = Unfertilized (Haploid) Male = 31 °C Hymenoptera red-eared slider turtle (Trachemys scripta elegans) Page 09  Why sex? The simplest but most profound question about sex is why it exists at all. Page 09  Why sex? About 1 percent of plant species and 0.1 percent of animal species reproduce by making genetic clones of themselves, a reproductive mode called parthenogenesis. Evolutionary advantage: Two fold cost of males Single unfertilized egg starts a new population Avoidance of STDs Page 09 Recombination gives sexual reproduction several advantages that compensate for its disadvantages and thereby explain why it is so common. The Red Queen Hypothesis refers to a coevolutionary concept where species must continually evolve new adaptations in response to evolutionary changes in other organisms to avoid extinction. Selective interference favors sex and recombination Many of the advantages of sex revolve around the fact that sex reduces selective interference because it separates alleles from their genomic backgrounds and allows selection to act more efficiently. Page 09 Forms of selective interferences: CLONAL INTERFERENCE - happens when two or more beneficial mutations spread through a population at the same time. RUBY – IN – THE RUBBISH EFFECT - the loss of beneficial mutations as the result of their linkage to deleterious mutations Page 09 Forms of selective interferences: MULLER’S RATCHET - the irreversible accumulation of deleterious mutations in an asexual population - each time the most fit genotypes fail to reproduce, the population’s mean fitness is ratcheted downward. It can never recover, and in principle this process can lead to the extinction of an asexual species. Page 09  Selfing & Outcrossing Self-fertilization -selfing provides reproductive assurance—a single individual can reproduce without a partner. Ways to prevent pollen from fertilizing the ovules of the same individual: SELF INCOMPATIBILITY POLLEN & OVULES MATURE AT DIFFERENT TIMES ANTHERS & STIGMAS ARE SEPARATED Page 07 Major downside of self fertilization: INBREEDING DEPRESSION - the loss in fitness shown by offspring whose parents are close relatives compared with offspring whose parents are unrelated. Page 07 THANK You!  Bacadon, Dumalagan, Hororhoro, Hidalgo HOW TO BE FIT Unit III, Chapter 11 Introduction Some other species live much longer. Some organisms might well be immortal: they show no signs of senescence, the intrinsic changes that lower survival and reproduction with age. There exists enormous variation among organisms not only in maximum life span, but also in the process of senescence that foreshadows ultimate demise. life span variation Bristlecone pines Pinus longaeva Surviving in the punishing environment of desert Corals mountaintops in California, are among the known may not age, and persist for individual organisms. thousands of years. Draba verna Rotifers , a member of the mustard family, is an annual plant that Some rotifers live for only germinates in early spring, a few weeks. sets seed within a few months, and dies.  different levels of fecundity Although life durations can change throughout time, natural selection has shaped them and they are strongly correlated with fitness. Different species have different levels of fecundity; some have huge offspring, while others only produce once before dying. Some animals reach adulthood before their young are born, and others reach reproductive age more slowly. For instance, periodic cicadas spend years feeding underground before emerging, reproducing, and dying in less than a month. Life History Traits as Components of Fitness Mutations that increase fecundity or survival increase individual fitness, but understanding how low fecundity or short life spans can evolve by natural selection is challenging. Some biologists suggest species produce eggs to compensate for high mortality or die of old age to make room for a vigorous new generation, but future species persistence or extinction is irrelevant to natural selection among individuals. So how can individual selection result in low reproductive rates or short life spans?  Lifespan and Fecundity Life history traits, including reproduction ages, fecundity, and average survival, impact population growth and genotype fitness. Survival age is often shorter than potential life span due to extrinsic mortality factors. Maximum life spans are closer to potential life spans than average realized life spans.  environment provides energy and nutrients for self- maintenance An organism's environment provides energy and nutrients for self-maintenance, growth, and reproduction. These resources are allocated among functions, with fitness benefits and costs correlated. Reproductive effort, or the fraction allocated to reproduction, is referred to as the cost of reproduction, highlighting the trade-offs between functions  COST OF PRODUCTION The concept of a cost of reproduction is crucial in life history evolution theory. Genotypes with more resources for reproduction may have decreased survival or growth, resulting in a negative genetic correlation between reproduction and survival. However, variation in resource acquisition can also lead to a positive correlation A. allales at locus A affect the amount of energy or other between reproduction and survival. resurces that individuals acquire from the environment B. genotypes that differ in their ability to acquire resources (for example, bacause of variation at locus A) are represented by blue circles. Genotypes that differ in how resources are allocated between survival and reproduction (for example because of variation at locus B) are shown by red circles. The overall genetic correlation between survival and reproduction depend on the relative magnitude of variation in resource acquisition versus resource allocation  Genetic Correlation Genetic correlations in a wild Drosophila melanogaster population revealed strong trade-offs between egg lay and longevity and fecundity later in life. Longer-lived genotypes showed higher fecundity. In a study of brown anoles, ovaries were surgically removed from wild females, resulting in higher growth and survival compared to sham- operated females with intact ovaries.  FITNESS IN AGE- STRUCTURED POPULATIONS Fitness Iteroparousn Semelparous organism’s ability to survive and - reproduce multiple times reproduce only once reproduce, thereby passing on its over their lifespan before dying genes to the next generation  Lifetime reproductive success (R) For instance, an asexual lizard that starts reproducing at age 2 and lives no longer than 3 years illustrates this concept well. A life table can help calculate R, listing the probability that a newborn will reach a certain age (survivorship, lx) and the average fecundity (offspring production) at each age (mx). Lifetime reproductive success ( R ) – total reproductive output across an individual’s entire lifespan REPRODUCTIVE TIMING Absolute fitness, or the rate at which an organism’s genes spread within a population, depends not only on R but also on REPRODUCTIVE TIMING. In cases where two organisms have the same R, those that reproduce earlier will spread their genes more quickly Example: consider two lizards, each with an R of 2. One matures after 2 years, reproduces, and dies, while the other matures after just 1 year and reproduces. The second lizard’s lineage will spread more quickly, demonstrating that in growing populations, natural selection favors earlier reproduction. SENESCENCE AND NATURAL SELECTION Senescence the gradual decline in biological function with age, illustrates how natural selection shapes life histories Natural selection strongly favors traits that enhance survival and fecundity at earlier ages  Antagonistic Pleiotropy some genes may have opposing effects on early versus late life Alleles that increase reproductive effort early in life often reduce biological functions later  Population Growth In simple ecological models, a population’s per capita growth rate (r) decreases proportionally as population size increases. The maximum possible growth rate (rm) is generally achieved when the population density is very low. As density increases, competition and limited resources slow growth, eventually stabilizing population size at a point called the carrying capacity (K), where birth and death rates are balanced.  K- selection When populations approach carrying capacity, natural selection favors alleles that enhance competitive ability r-selection some species often experience rapid, exponential growth, where higher per capita growth rates (r) lead to greater fitness. These species are termed r-selected and typically exhibit traits such as high fecundity, especially at young ages, and early reproduction, which shortens generation time and increases growth rates Ecological succession Ecological succession illustrates the dynamics between r-selected and K-selected species. For example, newly exposed soil, such as that on landslides or abandoned farmland, is often first colonized by r-selected species like fast-growing weeds, which reproduce quickly to take advantage of available resources. Over time, these early colonizers are replaced by K-selected species, like slow-growing trees, which reproduce later but sustain a longer reproductive life span.  DIVERSE LIFE HISTORY Strategies organisms use for growth, reproduction, and survival. Species adapt reproductive strategies based on ecological pressures and survival rate  Semelparity seen in species like annual plants, Antechinus( marsupialmice) Maximize reproductive output in a single event. Iteroparity seen in perennial plants, most trees, and many animals like humans and albatrosses. Spread reproductive effort across multiple seasons. Specialists and generalists Specialists are highly adapted to specific Generalists can adapt to a wide range of environmental conditions and resources. environmental conditions and resources. They have narrow niches and are often They have broad niches and are more less resilient to environmental changes. resilient to environmental changes.  Factors influencing specialization and generalization: Environmental Trade-offs Genetic Drift Variability Organisms often face In stable environments, Random genetic drift can trade-offs between specialization may be lead to the loss of traits specialization and favored, while in variable that are not currently generalization. For environments, under selection, example, a specialist may generalization may be potentially reducing a be highly efficient at one more advantageous. species' niche breadth. task but less efficient at others.  Advantages of Specialization Efficiency Predator Avoidance Reduced Competition Specialists can become Specialization can By focusing on a highly efficient at allow organisms to specific niche, exploiting specific access resources that specialists can reduce resources or habitats. are inaccessible to competition with other generalists, reducing species. predation risk.  Cost of Specialization Resource Limitation If their specific resource becomes scarce, specialists may struggle to survive. Vulnerability to Environmental Change Specialists are more susceptible to environmental fluctuations that affect their specific niche. Trade-offs in Specialization Morphological Trade-offs Specialized structures, such as the hooked bill of a flowerpiercer, can enhance performance in one task but limit ability in others. Physiological Trade-offs Adaptations to specific environments, like salt tolerance in a copepod, can compromise performance in other conditions. Behavioral Trade-offs Specialized behaviors, such as host plant preference in insects, can reduce flexibility in response to changing conditions. Specialization Without Trade-offs While many cases of specialization involve trade-offs, it's possible for a population to evolve specialization without sacrificing performance in other environments. Key mechanisms for specialization without trade-offs: Unequal Selection Pressures If a particular habitat or resource is Mutational Decay more abundant, selection for adaptations to that environment will Genetic Drift The accumulation of deleterious be stronger. In small populations, random mutations in genes that are not genetic drift can lead to the actively selected can lead to a decline Over time, this can lead to the loss of traits that are not in performance in less used evolution of specialized traits currently under selection. environments. without compromising performance in less frequently used environments. Experiments on Niche Evolution Variable Environments Populations exposed to variable environments tend to evolve broader niches, encompassing both generalist and specialized genotypes. Constant Environments In contrast, populations in constant environments often become more specialized. This can lead to negative correlations in fitness and mutational decay, as traits that are not actively selected can be lost. Key findings from experimental studies Loss of Unused Traits Traits that are not essential for survival in a given environment can be lost over time. This can occur through both natural selection and genetic drift. Pleiotropic Effects Genetic changes that improve one trait can sometimes have negative effects on other traits. This can limit the ability of organisms to evolve in certain directions. UNIT III: CHAPTER 12 COOPERATION AND CONFLICT GROUP 4: CASTILLO, JOHN CLEFFORD DIAMA, LIAN JOY GAVIA, GIRLIE GENON, SHANE RHEY TABLE OF CONTENT 01 Introduction of Cooperation and Conflict 04 Family Conflicts Cooperation among Unrelated Individuals 02 05 Levels of Selection and Reciprocity Shared Genes and the Evolution of Major Evolutionary Transitions and 03 06 Summary Altruism COOPERATION AND CONFLICT Are found at all levels of biological organization Genes compete against genes Offspring fight with their parents Cooperation is also ubiquitous: the functioning of your body depends on harmonious interactions among its cells. COOPERATION CONFLICT VISION GROUP SELECTION was thought to involve the increased survival of populations of altruistic individuals, and a high extinction rate of populations of selfish individuals. COOPERATION AMONG UNRELATED INDIVIDUALS those who aren’t related often occurs when there is mutual benefit or when it increases each individual’s chances of survival, success, or well- being. THE COSTS AND BENEFITS OF INTERACTING Mutualistic Selfich Altruistic Spiteful COOPERATIVE when one individuals behavior benefits another as an mutualism and altruism. SOCIAL INTERACTIONS AND COOPERATION fundamental aspects of human and animal behavior that enable individuals to work together for mutual benefit RECIPROCITY is the social principle of responding to a positive action with another positive action, fostering mutual benefit and cooperation. GAME THEORY developed and applied to evolutionary biology by John Maynard Smith a mathematical approach for understanding strategies in situations of conflict or cooperation between individuals. EVOLUTIONARY STABLE STRATEGIES OR ESS a strategy in game theory that, when adopted by a population, cannot easily overtaken by an alternativestrategy. famous example of one of the scenarios is the “prisoner’s dilemma” SHARED GENES AND THE EVOLUTION OF ALTRUISM Direct Fitness Indirect Fitness Inclusive Fitness CALCULATING RELATEDNESS Key Concept: Relatedness, denoted by r, measures the genetic overlap between individuals. Diploid Species Example: Haplodiploid Species Example (e.g., bees): Parents contribute 50% of their alleles to their Workers (females) are more related to their sisters (r = 0.75) offspring (r = 0.5). than to their own offspring. Full siblings share on average 50% of alleles KIN SELECTION AND INDIRECT FITNESS Implications of Kin Selection Hamilton’s Rule: Altruism evolves when rB > C. Altruistic behavior is more common r: Relatedness among closely related individuals. B: Benefit to the recipient C: Cost to the altruist Haplodiploid species like bees have Altruism is more likely to spread when unique social structures due to relatedness is high, or when the benefits are higher relatedness among sisters. substantial. Kin selection explains behaviors like In species with kin groups, cooperative behaviors cooperative breeding, care for can help relatives survive and reproduce. siblings, and complex social hierarchies. ALTRUISTIC MATING DISPLAYS IN TURKEYS Wild Turkeys (Meleagris gallopavo) Subordinate males help dominant brothers in mating displays, boosting the dominant’s reproductive success. Hamilton’s Rule (rB > C): The relatedness (r) between brothers allows the benefit (B) for the dominant male to outweigh the cost (C) to the subordinate. Example: The fitness benefit for the dominant is 6.1 offspring, whereas the subordinate’s cost is 0.9 offspring. COOPERATION IN BACTERIA AND THE GREEN BEARD EFFECT Pseudomonas aeruginosa bacteria Cooperative bacteria excrete siderophores to help neighbors absorb iron. Experiment findings: High relatedness + weak competition = more cooperation. Low relatedness or strong competition = cheaters benefit. Green Beard Effect: Genes like csa enable bacteria to recognize and prefer similar genotypes, enhancing cooperation. SPITE AND CONFLICT IN BACTERIA Spiteful behavior: Actions that harm both the actor and the recipient, promoting the actor’s genetic lineage. Example: Bacteriocin-producing bacteria release toxins that kill competing strains, aiding the survival of related bacteria. Conflict in bacteria illustrates evolutionary strategies where harming competitors can indirectly benefit related individuals. CONFLICT WITHIN FAMILIES: MATING CONFLICTS Intra-family conflict can arise even among closely related individuals. Mating conflict: Males and females may have opposing reproductive interests. Example: Mallard ducks and bedbugs, where males’ aggressive mating tactics increase their own reproductive success. Sexually Antagonistic Selection: Traits that benefit one sex can harm the other, balancing cooperation for reproduction with conflict to maximize individual fitness. Evolutionarily Stable Strategies (ESS) Shows optimal parental effort by each parent. Male Effort vs. Female Effort: Each parent's effort affects the other's. ESS is reached when parental investment is stable for both. Both parents invest optimally to maximize offspring survival. EXAMPLES OF PARENTAL CARE IN DIFFERENT SPECIES Cooperative Care: Both parents actively care for offspring. Result: Increases offspring survival and reproductive success. Birds- Great Crested Grebes Male-Only Care: Male guard eggs to attract mates. Trade-off: Higher energy investment from males, potential for additional mating. Fish- Three-Spined Stickleback MARKET SIZE PARENTAL INVESTMENT CONFLICTS OUR CLIENTS COME FROM EVERYWHERE Trade-Offs in Parental Care: Species Variation: Parental care varies between males and females depending on costs and benefits. ESS Outcome: One parent may invest less if the other is highly invested. Species Example: Scorpions & Poison Dart Frogs: Some species show single-parent care as an ESS due to minimal benefit in shared effort. With a global perspective, our marketing agency has proudly served multinational clients, delivering tailored strategies that transcend borders and cultures, ensuring consistent brand success on a worldwide scale.  MARKET SIZE MURDER IN THE FAMILY OUR CLIENTS COME FROM EVERYWHERE Infanticide: Behavior: Some individuals kill offspring of other parents in social species. Reason: Reduces competition, increases reproductive success for the infanticidal individual Example: Lions, Baboons: Males may kill offspring of rivals to pass on their own genes. With a global perspective, our marketing agency has proudly served multinational clients, delivering tailored strategies that transcend borders and cultures, ensuring consistent brand success on a worldwide scale. MURDER IN THE FAMILY 1.) Infanticide 2.) Siblicide - siblings in a brood actively fight for resources, and larger individuals may kill smaller siblings. ex. Brown booby PARENT - OFFSPRING CONFLICT - conflict of interest between parents and their offspring over the allocation of resources. ex. between mother and the embryo EUSOCIAL ANIMALS Eusocial animals - species in which some individuals do not reproduce much or at all themselves, and instead rear the offspring of others, usually their parents. ex. Ants, bees, and wasps  LEVELS OF DNA SELECT Levels of Selection Transposable Elements (Transposons) - type of selfish DNA that is closet to home — they make up A. Selfish DNA almost half our genome. - refers to genetic sequences that can replicate and spread within a genome, often at the expense of the organism’s - short sequence of DNA that are able to insert additional overall fitness. copies of themselves in the genome. B. Selfish Mitochondria - mitochondria that have mutations that give them a replication or transmission advantage, often at the expense of the organism’s overall fitness. Cytoplasmic male sterility (CMS) -Sterility in plants caused by mutations in mitochondrial genes - inherited through the cytoplasm, not the nucleus. - can be counteracted by a nuclear gene called R+ WHY? BECAUSE The Mitochondria are maternally inherited. Natural selection therefore favors any GREETING FROM US mutation in mitochondria that increases the number of ovules that females produce. - The effect on male reproduction does not matter in the slightest to the mitochondria, since they are not transmitted through pollen. THUS HOW? The spread of the CMS+ allele leads to an excess of females in the population. - the CMS+ allele knocks out male But selection on nuclear genes favors a very different outcome, selection on nuclear genes favors a 1:1 ratio of males to females. That in turn favors the reproductive function, resources are spread of any mutation in a nuclear gene that cancels the action of the CMS+ diverted from making pollen to making allele. more ovules. GROUP SELECTION evolution by group selection results from changes in allele frequencies, just as when selection acts on individuals. - In most situations, competition between individuals for survival and reproduction leads to the evolution of traits that increase each individual’s fitness. However: Under the right conditions selection groups of individuals can lead to the evolution of traits that are not favored by selection acting on differences between individuals within each group. whats the difference ? Group selection results from a difference between the rates of survival or reproduction of groups, rather than of individuals. - Group selection and kin selection can be interchangeable EXPERIMENT FLOUR BEETLE (TRIBOLIUM CASTANEUM) EXPERIMENT. Shows that: Shows that group selection can cause large evolutionary changes, and noticed three particular trends. 01 there were nine times more beetles per group in the treatment that selected for high population size than in the treatment that selected for low size. 02 second pattern that was noticed is that 03 In the treatment that selected for high population size declined in all three population size, cannibalism rates were lower. treatments. (which can be thought of as the evolution of an - due to cannibalism. altruistic behavior. PATHOGENS Virulence in pathogens, As Selection on pathogens favors traits that increase the number of hosts that they Infect.  They can multiply rapidly within the host, they are more virulent. - The viral genotypes within a host that replicate fastest are favored by individual selection. On the other hand, some pathogens reproduce much more slowly. This prolongs the life of the host, which increases the number of other hosts that they infect in the long term.  COOPERATION AND MAJOR EVOLUTIONARY TRANSITIONS fitness of most parasites and pathogens depends on horizontal transmission - infecting other hosts that are not the offspring of their current host Parasites and pathogens transmitted this way are sometimes selected to become highly virulent if that increases the probability they will infect a new host. Endosymbionts are mutualists that live within the cells of their hosts. Some, like mitochondria, are passed by vertical transmission. Filler content: not relevant to the report, but hey, unsolicited hamster pic VERTICAL AND HORIZONTAL TRANSMISSION WHAT WE COULD DO DIFFERENCES BETWEEN PARASITES AND PATHOGENS TO ENDOSYMBIOTES ARE THAT: SUMMARY - Altruism benefits other individuals and reduces the fitness of the actor while Endosymbiont and its host fate are chained cooperative behavior need not reduce the actor’s fitness Cooperation can evolve together. The endosymbiont’s fitness depends because it is directly beneficial to the actor although the benefit may be delayed. entirely on the fitness of its host - Altruism can evolve by kin selection In the extreme case, the symbiont may become an essential part of the host, forming a new - Conflict and kin selection together affect the evolution of many interactions among collective entity. family members. - most extreme examples of cooperation and altruism are in eusocial species in which KEY EVENTS: some individuals reproduce little or not at all and instead help relatives rear their offspring. - First the symbiotic union of a bacterial endosymbiont and a host cell, probably an archaean, about 1.5 billion years ago. The bacterium evolved into the mitochondrion. - Kin and group selection explains three of the major transitions in the evolution of life on Earth: - Second was the incorporation of blue-green bacteria (cyanobacteria) into a one-celled eukaryote. That enabled the -Eukaryotes evolved by the union of two organisms in which the fitness of eukaryote to photosynthesize, bevoming the ancestors pf green Each depends on the other. algae and plants. -The union of a eukaryote with cyanobacteria produced photosynthetic - third major transition occurred with the origin of multicellular Eukaryotes: algae and plants organisms. Instead of a group of loosely related cells that operate individually, cells of a multicellular organism cooperate in ways -Multicellular organisms could evolve only because their cells are nearly reminiscent of the ants in a colony. Genetically identical and so cooperate due to kin selection - differentiate into tissues specialized for different tasks that Contribute to the fitness of the group (host individual) THANK YOU FOR YOUR NICE ATTENTION Reference: Douglas J. Futuyma, & Mark Kirkpatrick (2017). EVOLUTION, 4th Edition