lecture 21 Flashcards

species are groups of potentially interbreeding populations that are reproductively isolated from other such groups (work pretty well for sexually reproducing animals)

smallest possible group descending from a common ancestor and recognizable by unique, derived traits (useful for systematics; focuses on phylogenetic history)

species are metapopulations that exchange alleles frequently enough to compreise the same gene pool

group of spatially separated populations of the same species that interact at some level

no single definition of a "species" will fit all taxa

evolutionary process by which new species arise (key step in the evolution of new species is the splitting in two of an original population)

an aspect of the environment, genetics, behavior, physiology, or ecology of a species that reduces or impedes gene flow from individuals of other species (geographic or reproductive)

extrinsic properties of landscape that prevent gene flow (allopatry)

features of organisms that prevent interbreeding (barriers effective even in sympatry)

-behavioral isolation

-ecological isolation: habitat, temporal, pollinator

-mechanical isolation

-copulatory behavioral isolation

-gametic isolation

-hybrid inviability

-hybrid sterility: physiological and behavioral

-ecological inviability

-behavioral sterility

two populations are geographically isolated but will reproduce when brought together

330 but 2014 was 3.5k

timing of reproduction

two species of Montastraea corals remain reproductively isolated due to spawning times

distinct courtship rituals

closely related animals

specific courtship displays for mating

pollinator isolation (two species of partially sympatric monkey flowers are pollinated, not hybridized in nature as pollinators aren't interested in the other species)

mating between species results in damage to the female reproductive tract; different species males' copulatory courtship results in eggs not fertilized by deposited sperm

sperm or pollen from one species fails to penetrate and fertilize the egg of another species

low fitness

the hybrid embryos of sheep and goats, for example, die in the early developmental stages birth

mules

outbreeding depression can lead to coadapted gene complexes being broken apart without the forging of new coadapted gene complexes to take their place

e.g., behavioral sterility of hybrid males in acoustically communicating grasshoppers

genetic incompatibility in hybrid offspring arising from epistatic interactions at two or more loci

one population evolves the A1B0 genotype and the other evolves the A0B1 hybrids if the populations were to come into contact

QTL was used to identify Hms1 on chromosome 6 and Hms2 on chromosome 13. Hybrids with M. guttatus alleles for Hms1 produce viable pollen if they also inherit at least one M. guttatus allele at Hms2. if they get M. nasutus the pollen is sterile.

result of geographic isolation, after a geographic boundary separate them, the populations become increasingly divergent

the increase of reproductive isolation between populations through selection against hybrid offspring

-fusion of incipient populations back into one species

-reinforcement

-stable or transient hybrid zone formation

-speciation of hybrids

prezygotic reproductive isolation

natural selection favors prezygotic isolation mechanisms that prevent the formation of hybrids with reduced fitness (postzygotic isolation must evolve in allopatry)

-extinction of one of the initial populations

-the initial populations can hybridized

-the initial populations can speciate, are determined by both initial divergence and level of fitness of the hybrids

reproductive isolation evolves without geographic isolation (requires nonrandom mating based on genetic or phenotypic factors )

geographic barrier only partially separates populations (some gene flow possible), for example, grass Agrostis tenuis, individuals are tolerant to heavy metals, a heritable trait, survive well on contaminated soil, but poorly on non-contaminated soil (the reverse occurs for intolerant populations)

populations tend to breed with those in close proximity (causes variation across the range of the species)

is a connected series of neighboring populations, each of which interbreed with closely sited related populations, but for which there exist at least two "end" populations

selection for different ecological traits in different niches creates reproductive barriers (can lead to pre- ad postzygotic isolation

traits that simultaneously confer divergent local adaptation and act as reproductive barriers

speciation of the flower populations

a land bridge from north america to south america only arose 3mya. allopatric speciation resulted.

there was also a shift in flowering times

opportunity for allopatric speciation

speciation

loci associated with male pulse rate also maps to female song preference

populations on the same island often differ in male songs and female preferences for the songs

500,000 years ago

polar bears and brown bears

-APOB proteins (to handle high levels of cholesterol from diet rich in fatty acids)

-heart function (long-distance swimming)

-hair pigmentation

(interbreeding has occurred since divergence)

no longer interbreed, using molecular clocks, it takes hundreds of thousands of years for them to diverge into new biological species.

extremely rapid speciation

an individual having two or more complete sets of chromosomes derived from different species

compromise two or more taxa that are grounded under a single name because they are more-or-less indistinguishable morphologically (important for detailed biodiversity assessments)

cryptic species

texas

3% in microbial species

same species

10,000 different species of bacteria (soil has one trillion species by locey and lennon 2016)

E.coli, however, core genome is only 3188 genes, but there are 90,000+ gene across the entire E.coli genome

the mixing genes makes it difficult, if not impossible, to delineate species boundaries

common

specific adaptations

species concept for microbes, species is long-lived population of genetically related individuals that share a stable set of adaptations for hte same ecological niche, yet scientist criticize this method

shapiro et al. suggests that gene acquired from other lineages can be important for the emergence of lineages with new adaptations

physically separate populations (important for all species concepts)

intrinsic features of organisms that reduce likelihood of interbreeding

reduce gene flow

pollinator isolation and reduce interbreeding

important barriers to gene flow

populations rarely interbreed

measures of biodiversity

easily distinguishable morphologies

developed eaukaryotes