Kimura vs Darwin

 Wait, is that...? It is! It's JOHN CENA!

     If you heard his theme after reading that, I want you to know how proud I am of you. Brownie points if you pictured him doing his signature "You can't see me." Mustn't forget that. Now, moving on from that: Kimura vs Darwin vs John Cena. Who will win?

    If you guessed John Cena, please reward yourself with one of your favorite indulgences. You've earned it. It would be horrifically unfair to include him in the mix, since he'd obviously destroy them. So, we'll just look at Motoo Kimura's and Charles Darwin's theories to see similarities and differences.

    The neutral theory of molecular evolution argues that most mutations in DNA are selectively neutral and remain in the genome because they are not eliminated by natural selection. His theory emphasizes random fixation of nearly-neutral or entirely-neutral mutations and assumes that genetic variation results primarily from a mixture of mutation-generating variation AND its elimination by genetic drift.

    So, the long and the short of it: the theory of  neutral evolution suggests that genetic diversity is impacted more by genetic drift and mutations, NOT selection. The theory got its name because the allele and genotype differences at a gene are selectively neutral with respect to one another.

    The theory of natural selection is basically the opposite and NOT considered to be either random, nor neutral. Natural selection tends to zero in on what would be considered advantageous phenotypes and mutations therein in order to benefit that species over a period of time. There'd be no point in evolution if it doesn't benefit the organism/species in some way, right? This theory also has a focus of importance on fitness of select alleles and is part of the driving force for those changes that an organism/species will experience. 

    TL;DR: Both theories acknowledge that mutation is a driving force in evolution. They differ in how they address how the changes impact a species and how they come about. While natural selection focuses on (generally) advantageous phenotypes, neutral evolution doesn't care about phenotypes and is more random. 

    All the sass aside, neutral evolution has been beneficial for molecular biology. I think that Kimura's theory and Darwin's theory work well together for some things.

(Now, obligatory memes.)

Sources: Princeton Guide to Evolution

Inbreeding

 *Banjos playing in the distance*

 

    Inbreeding can have some desirable benefits. Inbreeding within small groups has the potential to fix desirable genotypes within that group. It can also help maintain a level of genetic "purity" in that bloodline that can pass on advantageous phenotypes or evolutionary traits. In an example of a hermaphrodite organism, it can fertilize itself (there's a joke here, but I'm not gonna say it) and has the advantage of passing on two copies of its genes into each of its offspring. Another impact it could have is mutations, which could be beneficial to the species. It's these kind of benefits that can lead to assortative mating among species. The big difference is that inbreeding will affect all loci, while assortative mating affects only those that play a role in similar phenotype characteristics.

    Downsides to inbreeding are many. Inbreeding impacts the allele combinations that are on the same locus of diploid individuals, and more inbred organisms are more likely to have two copies of the same allele at a locus vs if they were randomly mating. This creates a problem of them being more likely to be homozygous with an increased expression of the effects of the recessive alleles. Since many of those alleles are deleterious, the organisms' fitness level will be reduced. Inbred organisms can also develop mutations that aren't beneficial to them, creating health problems and impacting their fitness.

    It's also been found that inbreeding in smaller, isolated populations can actually increase their risk of becoming extinct, something they found out with the Glanville fritillary butterfly (oof). Another problem is the lack of genetic variation. Evolutionary advantages that they could receive through outbreeding are lost to them, whether it's by choice or force (i.e., isolated/cut off from other potential mates). There's also the problem of inbreeding depression, which gives a lower survival rate or fertility of progeny of inbred matings. This problem occurs when there's a high frequency of homozygosity in a population that comes from inbreeding and drastically cuts down on heterozygous organisms. 

    These reasons are what can lead to the disassortative matings. Disassortative matings can increase/improve heterozygosity, genetic variation, achieve evolutionary advantages, and have better overall fitness as a species.

    I could honestly probably list even more problems associated with inbreeding (and maybe some other benefits), but I'm not trying to bore you to death. 

(Memes ahoy, m'fellows)

(What a throwback, phew)

    Sources: The Princeton Guide to Evolution, 2013.
    https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/assortative-mating 

Slithery, Sneaky Snakes

 Snakes in the Plains

    

        Starting from Ontario and going through the islands and mainlands therein, there's obviously very little change in the phenotype between Ontario and the Peninsular mainland, as there was likely little to no need for it. The snakes in those locations maintained their stripes as it was ideal for the camouflage of these locations. Kelleys Island, Bass complex islands, and the Middle and Pelee island all show greater variation.

     These distributions of variation in phenotype are likely due to the migrations of snakes from different islands going around to one another, as well as a need to maintain their phenotypic appearance in order to protect themselves. Since the animals are always moving about, whether for the food, curiosity, breeding, weather, or something else, there will likely always be variation and - equally likely - there won't be a phenotype that gets wiped out by selection or adaptation, since they probably won't stick around long enough for it to impact all of them.

    Consequences of migration for populations can be few or many depending on the organism and location. In general, I think resources, potential mates, predator/prey balance/imbalance, evolutionary disadvantage/loss, and space could all be consequences of migration. 

(As always: M E M E S)