Genetics and Speciation

Genetic Bottleneck in Illinois Prairie Chickens

  • Agriculture expansion in the 1950s eliminated habitat, impacting the genetics of the Illinois Prairie Chicken population.
  • The population experienced a bottleneck, decreasing significantly in size.
  • Genetic variation decreased measurably: alleles per locus went from 5-6 to 4 in the Illinois population.
  • This loss of genetic variation resulted in less egg hatching.
  • To combat this, conservationists introduced prairie chickens from other, more genetically diverse populations, into Illinois.
  • They continue to introduce individuals because the genetic diversity is not stable without intervention.

The Founder Effect

  • The founder effect is less common than genetic bottlenecks.
  • It occurs when a few breeding individuals (typically two for the purpose of the class demonstration) establish a new population in a new location.
  • All offspring in the new population are related to these founding individuals.
  • Inbreeding occurs within a few generations.
  • Inbreeding is a natural phenomenon in many populations.

Isle Royale Wolves: A Case Study

  • Isle Royale is an island in Lake Superior, closer to Canada than the U.S.
  • In 1949, a pair of wolves crossed an ice bridge from Canada to Isle Royale.
  • The island had no existing wolf population but had abundant moose, beaver, and arctic hares.
  • The two wolves thrived and the wolf population grew, leading to inbreeding over multiple generations (average wolf lifespan is about 10 years).
  • By 1980, a tremendous amount of genetic similarity existed within the wolf population.
  • Wolves are homeothermic predators; a wolf pack can take down a moose about every three days. Moose weigh 800-1000 pounds, and wolves can consume 10-25 pounds of meat at a time

Research Methods on Isle Royale

  • Researchers used radio collars to track wolf movements and behavior.
  • DNA sequencing of scat (feces) provided genetic profiles for each wolf on the island.
  • GPS trackers on radio-collared wolves provided real-time data on their movements.
  • This research is considered one of the best studies of predator-prey relationships due to the island's isolation and national park status.
  • Research has been ongoing since the 1950s, providing a long-term view of these ecological relationships.

Canine Parvovirus Impact

  • In the 1980s, canine parvovirus swept through North America.
  • Researchers tried to prevent the virus from reaching the Isle Royale wolf population by banning dogs from the island.
  • Despite these efforts, the virus was introduced by a dog on a sailboat.
  • The wolf population decreased significantly, from 50 to 14, within a couple of years.
  • The remaining 14 wolves bred, but litter sizes were smaller than before.
  • The population never rebounded to its previous size.

Phenotypic Results of Inbreeding

  • The genetic similarity among the remaining wolves was very high.
  • A phenotypic result of this inbreeding was the presence of an extra vertebra in some wolves.
  • This malformation is thought to be due to genetic mutation caused by inbreeding.
  • Researchers are investigating whether this malformation affects fitness.
  • Muscles attach to the processes of the extra vertebrae, so there may be mechanical effects, but the effects may not be significant.

Local Extinction and Lack of Genetic Diversity

  • Genetic similarity led to fewer offspring.
  • By the late 2000s, the wolf population was down to two individuals.
  • These two wolves, despite breeding season activity, did not mate successfully.
  • The assumption is that they were too closely related, leading the female to reject the male.
  • This raised concerns about local extinction.
  • Genetic diversity is crucial for a population's strength and flexibility in dealing with changes.

Increasing Genetic Diversity: Gene Flow

  • One way to increase genetic diversity is through gene flow.
  • Mutations are a very slow source of genetic diversity (about one in every 10,000 to 100,000 cell divisions).
  • Gene flow involves the introduction of new breeding individuals from a different population.
  • The offspring of these individuals will have a combination of genetic variations.

Isle Royale: Male Wolf #93

  • In 1997, a single male wolf crossed the ice bridge to Isle Royale.
  • Within ten years, all wolves on the island had his genes.
  • While gene flow initially increased genetic diversity, the population eventually returned to a state of genetic similarity.

Wolf Reintroduction Program 2019

  • By 2018, with only two wolves remaining, researchers feared local extinction.
  • They initiated a reintroduction program in 2019 to prevent ecosystem collapse (too many moose browsing the ecosystem).
  • Wolves were sourced from Minnesota, Ontario (Canada), and the Upper Peninsula (Michigan) to ensure genetic diversity.
  • One wolf initially reintroduced from Minnesota actually walked off the island and back to the mainland.
  • As of last year, the wolf population had grown to over 30 individuals.

Moose Population and Ecosystem Effects

  • With the wolf reintroduction the moose population stabilized.
  • Moose eat about 40 pounds of browse a day.
  • As the moose population exploded it led to ecosystem shifts because of their dietary habits.
  • As wolves were reintroduced, there was a decrease not only in the moose population but also in the beaver population.
  • The graphs showed the relationship between wolves, beavers, and moose.
  • This is important because If wolves can keep the moose population down, there will be more balsam fir.
  • Balsam fir, a keystone species, is a favorite food of moose.
  • When moose overconsume balsam fir, the ecosystem shifts and changes.
  • Wolves can keep the moose population down, leading to more balsam fir and a more diverse and stable ecosystem.

Evolutionary Biology

*When it comes to evolutionary bilology the hierarchy is atoms, molecules, cell, tissue, organ, organism, population, community, ecosystem, and biosphere. This is how evolutionary biology operates.

Mechanisms of Evolution

  • Evolution involves both internal and external factors.
  • Natural selection requires longer periods, many individuals, and multiple generations to observe molecular changes or gene flow.
  • Stark external events lead to internal changes.

Speciation Misconception

  • Individuals do not evolve; populations do.
  • Populations evolve, as evolution is a large scale with patterns that affect the larger context, which is an event that causes interal changes.

Prezygotic Isolation

  • Prezygotic isolation mechanisms prevent sperm and egg from combining.
  • Examples of prezygotic isolation:
    • Habitat isolation: Species may live in different habitats and not interact.
    • Temporal isolation: Species may breed at different times.
    • Behavioral isolation: Species may have different mating rituals or signals.
    • Mechanical isolation: Physical differences may prevent mating.
    • Gametic isolation: Molecular differences may prevent fertilization.

Specific Examples:

 * Habitat Isolation:
     *Flycatchers, where the acadian flycatcher likes to breed in the habitat that's shown in blue, and our older flycatcher houses habitat is in the red. Though they can migrate very hard distances, one of the things that we find interesting is that when they are operating habitat, they really have a side of the mountain of preference. Human activity and fragmentation leading to turtles being isolate two populations.
     * The beltline highway, isolating two turtle populaitons. This is because a a turtle that’s about this big around, it can’t cross six lanes of traffic and survive, which is especially during rush hour, they put these great big troubles on a belt line highway specifically so it turns people to a little habitat.
 * Temporal Isolation: 
     *Where american toads start making noises and want to breed in just a few weeks, or our followers toad is going to be August into September. So that timing, when they are making their gadgets when they want a green switch.
 *Behavioral Isolation:
     *Fireflies, where they will start to come out in a few weeks and what keeps them separated is the different species of fireflies which are separated is in my times of male will flash. 
 *Mechanical Isolation:
     * Snails: where all of our snails show us mechanical isolation where if you're not familiar with snails, the directionality of their shell means that they can only mate with snails that have the same directionality to their shell.
 *Gamete Isolation: All the action is happening at the molecular level.
     *Oceans where sea urchins release all their sperm and eggs to the ocean making the ocean a vat of biology so how do they prevent hybrids occurring? The way how they prevent it is that molecular the sea urchin egg will suppress the sperm from entering unless they are of the same species.
     *Air and pollen where if think of the air similar to the ocean, and we've got all of the pollen, we've got all those plants from all kinds of different species of plants, how are the plants controlling how are they controlling the fertilization?

Postzygotic Isolation

  • Postzygotic mechanisms occur after sperm and egg combine.
  • Examples of postzygotic isolation:
    *Zygote mortality: The zygote cannot persist.
    *Hybrid sterility: Hybrids cannot reproduce.
    *Reduced hybrid fitness: Hybrid offspring cannot reach maturity.
    *This is like dire wolves where it's Basically a wolf with all of the characteristics of a dire wolf, but none of the actual genetics of it, which is a patchwork wolf.

Examples of Postzygotic Isolation

 * Zygote mortality:is one of the problems that scientists have when they're trying to bring organisms back from extinction of the prenean ibex situation. Even though the DNA was in really good shape, even though we had a closely related bone species that you put the pyrenean ibex zygote into, that vertical bones did not form.
 *Hybrid sterility: Mules (horse + donkey) are sterile where you have to keep remaking meals from dogs, of course, with them or the cross between lions and tigers = ligers.

*Key thing to keep in mind is that populations that are isolated will often experience with that genetic differences can drive genome frequency changes, leading to the anticiaption these populations will become spererate spieces eventually.
*Even the domesticated dog and gray wolf show the domesticated dog is not genetically separate enough which also means, unfortunately, frequently, because people don't understand the wolf community is there.

Allopatric Speciation

  • In allopatric speciation, a geographic barrier separates populations.
  • This is the more common type of speciation.
  • Different abiotic and biotic factors drive genetic change and speciation.

Examples of Allopatric Speciation

 * Allopatric Speciation: Salamanders where as a salamander born from from the Rock Valley College, in order for it to get to the state line, there needs to be several generations. Multiple multiple generations in order for salamanders to finally get to Southern California.
 * The Grand Canyon, where there are different species of squirrels on either side and the brown squirrels phonotypically look very similar to one of them.
 *Snapping shrimp. where, looking down in that Patagonal region connecting South America to Central America, you see some phenotypic differences between the second species on their side

Sympatric Speciation

  • Individuals living in the same geographic location undergo genetic changes that lead to speciation.
  • This is less common than allopatric speciation.
  • Isolation occurs inside some of those individuals that causes speciation work
    • Fish where after sympatic speciation, the internal changes that belong to all looking until I can look. Okay.