Exam 4 Flashcards
How does biodiversity arise (4)?
from interactions between and w/in organisms, environments, and consequences of these interactions over long periods of time
- Geography (species range, distribution, dispersal)
- Environment (climate, ecological conditions)
- Interactions (population, species, community levele)
- Organismal traits (life history, sexual systems)
What are the selective pressures? (5)
- Environmental conditions (abiotic factors)
- Competition (for food, territory, mates)
- Predators/ Pathogens
- Facilitation: species interactions, like mutualism, commensalism
- Mates Preference
What is an example of competition?
Darwins finches and competition for food.
- During favorable years, species share food=lack of selective pressure
- During drought, small seeded plants were few= strong selective pressure favoring finches with lager beaks
How can competition lead to ecological character development? give an example
divergence based on competition for resources
ex: Native anolis unable to compete with exotic lizards which occupied lo canopy= native lizard started to forage from hi canopy= shift in allele freq for ridges on feet to climb up tree
ex: Hawkmoth which is only pollinator has lead to divergence in flower phenology so bloom at dif times so don’t fight over # of hawkmoths
What is an example of predation? give an example
Black and white beach mice
-predators (hawks) selecting on variation in coat colo
=brown mice in white background= easier to spot and be eaten= evolution of dif phenotype (WHITE, increases in freq.; vice versa)
What is aposematism?
biological means (usually phenotypic) where dangerous or poisonous animal advertises dangerous nature to predators
ex: Coral Snake is poisinous and brighly colored, patterned, Mimicry- Kingsnake not poisnous but brighly colored to mimic Coral Snake
What is mimicry, what are the 2 types?
phenomenon characterized by the superficial resemblance of two or more organisms that are not closely related taxonomically. This resemblance confers an advantage—such as protection from predation—upon one or both organisms by which the organisms deceive the animate agent of natural selection.
2 types of Mimicry (both positive freq dependence)
- Batesian: unpalatable model (poisonous), palatable model (not poisonous); harmful model and harmless mimic
- mimic share protection by mimicking unpalatable species
- not sister species/closely related - Mullerian: 2 species (often unpalatable/poisonous) share predators and mimic each other to their MUTUAL BENEFIT
positive-frequency dependent
ex: Poison Dart Frogs
- dif mimic morphs can exist in SAME species
- morphs tend to prefer similar color pattern (assortative mating, reason why can have dif phenotype in same species)
- leads to reduced gene flow and reproductive isolation
- so same species but look dif/mimics dif frogs
What is deceptive mimicry?
flower example
- 1 flower does not produce nectar (since energetically costly)
- however, flower being pollinated bc flowers next to each other (a flower that does have nectar)
- if mimicry flower is alone/not co-occurring no advantage to not producing energy (bc despite saving energy by not making nectar u are not getting pollinated)
What is sexual mimicry?
plants can produce pheromone for pollinators to attract bugs/bees
What is significant about Darwins Orchid?
Darwin found species of orchid in Madigascar (Angraecum sesquipedale) which has very long nectar spur, hypothesized that bug that pollinates must have long tongue
- years later Hawkmoth found (Xanthopan morgani)
- Evolutionary Arms Race (Red Queen Hypothesis)
- reciprocal selective pressures can drive co-evolution= orchids require cross-pollination (touch reproductive parts) so Hawkmoths can reach nectar without touching reproductive part so its BENEFICIAL for flower to have longer nectar spur= longer tongue of hawkmoth increases fitness, while short have decreased fitness
What is the evolutionary arms race/ red queen hypothesis?
interactions explain how reciprocal selective pressures can drive co-evolution
- 2 species that interact closely can cospeciate
ex: Body lice and host, figs and fig wasps (1 species of wasp pollinates 1 species of fig)–lifecycle of wasps starts and ends in the fig (tomb blossoms)
What are the key innovations of co-speciation/ co-dispersal?
traits that raise diversification rate of lineages that have it
- raise lineage-splitting (speciation) rate
- lower extinction rate
Can be tested for traits
-one occurrence of diversification is not enough to say the trait promoted diversification NEED TO have sister lineage to prove it; needs to make sure rate of evolution is the same (i.e. look for repeated patterns across sister-groups) ex: nectar spurs in flowers
What is character displacement?
an evolutionary change that occurs when two similar species inhabit the same environment. Under such conditions, natural selection favors a divergence in the characters–morphology, ecology, behavior, or physiology–of the organisms; occurs when closely related species are more divergent in sympatry than allopatry
-can involve reproductive traits leading to reproductive isolation, and ecological traits, leading to ecological isolation- both are required for long-term coexistence of new species
What is a sympatric species?
speciation without geographic separation. If there is strong disruptive selection + assortative mating ( among 2 extremes, extreme 1 mates with extreme 1, 2 with 2) speciation can occur without allopatry; sympatric species overlap completely in range
- depends on disruptive selection
- sympatric speciation involves disruptive selection and assortative mating
What is an allopatric species?
geographic separation usual driver; allopatric species do not overlap
*allopatric speciation involves geographic isolation
What is speciation? (Baum)
clades that are different enough to be recognized as distinct species, speciation requires lineage splitting + subsequent evolutionary divergence
-NOT a step-wise pattern rather its a gradual gradation/branching ntwork
0speeciation is byproduct of evol in genetically isolated lineages
What is adaptive radiation?
rise of diversity of ecological roles and attendant adaptions within a lineage; radiation into many different ecological niches, ex: land mammals, water mammals
- adaptive radiation does NOT always lead to speciation
- Lack argued phenotypic divergence driven by selection to avoid competition w/ closely related taxa
- noticeable on newly isolated islands, lakes, mountaintops (absence of most species)
- can occur rapidly or NOT
- can produce large # of species or NOT
- given strong selection for both divergence and convergence among colonists, may be difficult to identify ancestors or close relatives of lineages undergoing radiation
ex: Darwins finchees
What is evolutionary convergence?
members of other lineages with similar ecological roles that are driven by selection to maximize fitness from harvesting a given resource
How do we infer relationships between species now, i.e. what is the best-unbiased method?
DNA sequences and genetic markers (like non-coding regions) provide an unbiased basis for inferring relationships vs tracing the evolution of ecological roles and associated adaptations and distributions
What is an example of divergent selection caused by competition which lead to adaptive radiation?
ex #1: Fish stickleback, benthic forms advantage close to shore while Limnetic to open water/bottom
-forms have developed at least 4x independently
ex #2:Pseudomas fluoroscens, appearance of 3 dif forms (SM, WS, FS) in unstirred flasks, unstirred flask allowed this bc contents not uniform
Why does evolution occur on islands?
long-distance dispersal and origin of lineages, adaptive radiation, rise of arborescence in plants, loss of defense against vertebrate herbivores, gigantism in island animals, evolution of flightlessness in birds and insects
Where did marsupials originate from?
originated in South America, dispersed to Australia nearly 70 MA
What is the adaptive significance of sexual reproduction?
asexuality exists but sexual reproduction is the norm
- asexual increases reproductive capacity for organism/population but lacks new genetic material
- i.e. mutations that do occur will be isolated to that and only that lineage (Mullers Ratchet)
- on other hand sexual reproduction promotes novelety through recombination and generation of possible new potential phenotypes
What is sexual dimorphism?
when 2 sexes have varying degrees of phenotypic difference, exaggerated secondary sexual traits are common (usually male more decorated than female)
Why is there a differential cost of reproduction?
commonly in the 2 sexes, 1 sex contributes more, large non-motile gamete (egg) while other makes smaller, usually motile gamete (sperm)
*usually males gamete production has lower cost then when compared to females
Why is there a differential pay-off from mating?
every additional mate helps a male MORE than it helps a female, bc less costly for males to make sperm usually so beneficial for multiple mates
Why do males usually have a higher variance of reproductive success?
some males have many offspring, most have none, which places premium on mating success
Which sex will experience stronger sexual selection?
Depends, but it is usually males bc depends on if can find a mate versus females who are restricted by birthing period, why we see a variance in male reproductive success
Why are monogamous species different from species that practice polyandry or polygamy?
In monogamous species, there is a decrease in sexual pressure so there is a decrease in sexual dimprhism= less variance
What are the consequences of differential sexual selection?
members of sex subject to weak sexual selection=selection to be choosy/selection for attractiveness (intersexual selection)
Members of the sex subject to strong sexual selection= selection to be competitive (intrasexual selection)
How do males compete (male-male competition)?
male-male competition occurs when individual males can monopolize females, either directly or through resources, or just can impress the female
- Combat: weapons like antlers, horns, teeth, tusk help fight off other males and reproduce more, may fight over female or resource
- Sperm Competition: sexual selection arises after mating when males compete for fertilization of a females egg
ex: Deer mice competition @ sperm level - infanticide: improves males reproductive success but is detrimental to reproductive success of females
- Alternative Strategies, like “Sneaky” Males: in many species males will adopt alternative strategies to mate, fish there are jacks which are smaller than larger males and look similar to females so males won’t notice them so they can sneak into spawning areas and fertilize eggs
* Can be more than 2 strategies, for example a marine isopod has 3 males (alpha-large and defend harem of females, beta males mimic females and sneak into harems, gamma males mimic juuveniles and “divebomb” harems to deposit sperm)
what is intersexual selection?
event, like fighting, determine reeproductive success involving interaction among SAME sex
what is intrasexual selection
key event that determines reproductive success involves interaction of the 2 sexes (male and female), can be morphological (phenotype/appearance) or behavior
ex: Morpholigical: Bird of paradise have vibrant colors and huge tail, while it is energetically costly and may decrease overall fitness, males enjoy increased reproductive fitness and genes (of extravagance) are passed onto offspring
Behavior: Bower Bird build intricate house and providee offerings to potential females mates
What is runaway sexual selection (Fisherian selection)
when females preference drives evolution of triat that becomes disadvantage to mates (like a train/tail of a peacock)
What is sexual selection?
differential reproductive success due to variation among individuals in success of getting mates
What is parental investment?
energy and time expended constructing and caring for offspring, which investment measured by fitness (so more investment=increases reproductive success of offspring but decreases reproductive success for future
What are the 5 important points of sexual selection?
- Sex creates new genetic variation and likely adaptive capacity
- There is a differential costs of reproduction
- Sex with greater variance in mating success will likely experience stronger sexual selection
- Sexual selection can drive the evolution of traits that reduce fitness- ex: runaway sexual selection, male-male competition, even if lower suvivorship
- selection for alternative mating strategies (example:sneakers)
What is female choice?
ubiquitous but MOST obvious in species where males form leks (groups)
ex: wild turkey lek, males have dangling snood
How does female choice drive male evolution?
female preference can swamp suvivorship selection (ex: longer tail makes it harder for males to fly)
How does suvivorship and mating success balance out?
female preference must be heritable, female preference variation predicts assortative mating which generates the genetic correlation between female preference and male display
assortative mating= continual preference for similar morpholoy
Is female preferences evolvable?
YES!!! runaway selection can kick in, female avg preference is for longer than avg males
ex: female favors males, sons have linger tails and daughters prefer longer tails (depending on form of genetic correlation)
How can selection in females favor acquisition of resources from males?
spermatophores (sperm-containing packages produced by male reproductive glands)
ex: male fly gives gift, if gift small females eat it and move on so not full sperm transfer, if good size then mating more likely successful
- female genes also gain advantage if they can predict how much male will help with child-rearing
What can have similar effects to sexual selection?
variance in parental care
What are the 3 mating systems
- Monogamy
- sexual monogamy-1 sexual partner for life
- social monogamy- ex: bird pair mates for life socially, but female promiscuous - Polygyny: males attempt to mate with multiple females
- Polyandry: females mate with multiple males
What are some sexual conflicts between males and females?
often coevolution betweeen male and female
sexual conflicts include:
1. forced mating: usually causes great harm, water fowl forced mating has led to selective pressure for female defense, where reproductive organ spins opposite way of malee penis, pockets to hold male sperm and eject vs keep
2. spiky/shovel genitals: scrape out competing sperm ex:shiny phallus
3. Penis fencing, love darts: only hermaphroditic organisms like snails and flatworms, benefits the “giver” harms reciever (get stabbed)
4. sexual cannabalism: females eat males once mated
5. semen toxitcity: females sick after mating, benefits male cuz female will only mate with male, not attractive to other males (only toxic when MALES compete)
6. traumatic insemination: tears through abdomen/ female is greatly harmed
How can sex of offspring be determined?
sex determination can be environmental or genetic
- genetic: sex-determining chromosomes or genes (genetic sex determination, GSD)
- –2 types of GSD:
1. male heterogamety: XY=males, XX=females (mammals;flies)
2. female heterogametry: ZW= female, ZZ=male (birds; butterflies)
-environmental: temp-dependent sex determonation (TSD) or some plants start as hermaphrodites and change sex
What is chromosomal conflict?
- a gene on a Y that makes males fitter at the expense of females is favored (or W genes favoring females)
- leads to an arms-race with X-linked genes spend a lot of time in females (or Z in males
Dr. Pavitra research suggest that W-lined genes that caused females to pick males that carry sexually-antagonistic genes (good for females, bad for males) would increase in frequency if they result in very unfit males= decline in male survivorship
Why are sexual systems so dynamic?
- many changes among polygamy, monogamy, polyandry
- sexual-signaling traits (exaggerated secondary characteristics) diverge rapidly
What is virulence?
capacity for bacteria to cause disease and disease damage
What is a pangenome?
population, all genes present in entire population
core genes: in all individuals of population
accesory genes: only some individuals in the population have it
Where do pathogens come from?
most diseases attributable to small # of bacterial species
Lecture 27: Evolutionary Medicine Summary
specific adaptation in Aas gene (adhesion gene) allowed staph to become virulent in humans and transmitted via humans, animals, indoor/outdoor environments, food;
lateral gene transfer in M. abscesses dominant circulating clones, opportunities for LGT include soil + complex environment however deep tissue of mammal is pathogenic niche so harder for bacteria to gene transfer
What is group selection?
traits that improve the success of a multi-individual group may be favored even if there are disadvantages so a gene that enhances group fitness can increase in frequency EVEN IF it lowers individual fitness
What is altruism?
genetic tendency for organisms to help another (increasing their fitness) at their own fitness expense (individual fitness decease); for example, some altruists may give up the ability to reproduce themselves to rear other individuals’ offspring (support survival and repoduction)
*if one single group altruist freq will go down in next gen but if multiple sub groups (2 or more) then freq of altruists will go UP== means alturists can have lower fitness than non-alturists in EACH group but still have higher OVERALL fitness (when u add them up!!) this is an example of Simmons Paradox
What is the relationship between altruism and group selection?
groups compete, groups with more altruists do disproportionately better than groups with few
What is cooperation?
when organisms help one another ex: worker ants are sterile and help mother+sister reproduce
What is kin selection and why is it advantageuous?
natural selection leading to spread of alleles that increase indirect component of fitness
if beneficiary of an altruist act is close kin, then gene causing behavior can gain a net advantage (bc kin are more likely to also carry that gene)
What is Hamilton’s rule?
under which altruism will increase in freq:
Br-C>0=Br>C
B=benefit to recipient
C=cost to actor
r=relatedness, 1/2 if full sibling, 1/4 if half sibling
- inequality indicates altruism MORE LIKELY to spread when benefits to recipients are great and cost to actor is low and participants are closely related
- personally costly behavior can evolve and increase in freq if benefit to kin is high enough
- altruist traits tend to be directed towards kin, adopting kin enhances inclusive fitness
What is direct fitness? What is indirect fitness?
Direct fitness: results from reproduction an individual achieves on own, w/out help from related individuals
Indirect fitness: results from additional reproduction by relatives that made possible by individual actions (Br-C)
inclusive fitness is the SUM of both direct and indirect fitness
What is the greenbeard effect?
hypothetical alleles that cause individuals to recognize other carriers and act altruistically towards them , RARE bc requires 1 allele to generate 3 distinct phenotypees” the phenotype (beard), ability to recognize, and discriminating altruism
ex: slime mold, are free-living organisms but under starvation they will come together to cooperate, this results in fruiting body (used as bridge) then slimes can go across but bridge left behind (altruist)
How do organisms recognize kin?
context of interactions determines likelihood of interacting with kin, selection COULD favor a gene that promotes altruism only torwards individuals u growth with
What is Simons paradox?
trend that appears in several independent groups of data reverses/disapears when groups combined=== i.e. alturists in group vs multiple groups!
When is group selection effective?
many groups compete, group fitness if sensitive to degree of cooperation w/in groups, groups vary in proportion of cooperators and cheats, cooperation has genetic basis
- group selection helped IF groups composed of kin, which increase variance among groups in proportion of cooperators (some groups have lots of cooperators, some will have lots of cheats)
What is the difference between kin and group selection?
kin selection implies intention and focuses on individuals carrying genes while
group selection looks @ fitness of effects on genes on dif levels of organization, i.e. helps explain new levels of organization like multicellular organisms, bee colonies, etc.
What is eusociality?
a type of altruism, give up ability to reproduce for others
ex:bee colonies
What is pre-zygotic isolation?
can be caused by character displacement, assortative mating, pollinators, chromosome #
Give an example of pre-mating isolation/pre-zygotic isolation?
timing: individuals do not mate due to time of reproduction, selection promotes isolation of species
pollinators: on landscape flowers attract dif pollinators
behavior: bird calls, dancing, morphs attracted to each other
What is post-mating/ post- zygotic isolation
- gamete incompatibility: usually via independent substitution, genetic drift, selection; no fusion of gamete
- Zygotic inviability: fusion of gamete forming zygote but cannot develop into individual
- ploidy difs can prevent production of viable hybrids, allows for allopolyploid hybrids
* evolution of reproductive incompatibility requires mutation @ 2 or more loci
What is Bateson-Dobzhansky-Muller Incompatibility?
called speciation genes, often genes involved with immunity or sexual conflict
What is vicariance? What is dispersal?
vicariance: when natural situation arises to physically divide organisms (ex: river)
dispersal: founder event, subset of population moves to NEW location and establish itself there (usually more uncommon)
ex: Hawaii islands filled with exotic wildlife through multiple lineage dispersals, why hi endemism:species found no where else on earth
* sometimes we see repeated patterns of dispersal, ex snapping shrimp disperse from across panama canal so shrimp across panama are more related than shrimp living in the same location
What is the sequence that allopatric speciation occurs?
- Differential sorting of pre-existing allelic variation (like assortative mating after geographic isolation)
- Dif mutations and selection regimes accumulate
therefore, given allopatry evolution divergence is expected
What is reinforcement?
is a process by which natural selection increases reproductive isolation
can occur when: When two populations which have been kept apart, come back into contact, the reproductive isolation between them might be complete or incomplete. (post-mating but not pre-mating isolation)
If it is complete, speciation has occurred.
If it is incomplete, hybrids would be produced.
- selection favors alleles that promote assortative mating (avoids wasted mating opportunities)
What are the 2 imperatives for taxonomy?
- grouping: deciding which groups are taxa
- ranking: deciding which taxa are species, genera, etc.
* ranks established by convention so NOT objective
What is phylogenetic species concept?
species unit of taxonomy, part of hierachical of named groups, products of evolution
- phylogenetic concept is now the basis for designating species as it provides objective grouping criterion and does not provide an objective ranking criterion
What is biological species concept?
populations or sets of linked populations, players in evolution
What is a ring species?
is a circular arrangement of populations with one boundary characterized by reproductive isolation, but intergradation among populations elsewhere.
“species complex” illustrates that distinct forms in sympatry could be parts of 1 continuous cline
What are hybrid zones?
Hybrid zones are locations where hybrids between species, subspecies, or races are found. Typically, hybrid zones are described as clines, spatial gradients in traits or alleles across a geographic transect where two taxa meet.
What is a cryptic species?
one of two or more morphologically indistinguishable biological groups that are incapable of interbreeding , co-occur in sympatry but have very similar morphology
