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)
