Plants that eat... plants?

There's a good chance that you've heard of Rafflesia spp. plants. They're often cited as having the largest flowers in the world, which is true depending on the perspective you're taking. They're also known for smelling like a dead possum you'd pull out from under you deck after wondering what that smell was for 3 days, yummy! Oh, and if you were a nerdier kid you'd probably recognize that the Pokémon Vileplume was inspired by their enormous petals:

Rafflesia arnoldii on its host vine,  Tetrastigma sp.

Vileplume from Pokémon

Now, even if you knew about Rafflesia, you probably didn't know that it's actually a holoparasite, i.e., it exclusively receives its nutrients from a host. In other words, this is a plant that forgot how to be a real plant: it cannot photosynthesize. They exist, rather, more like fungal mycelium nestled amongst the fibers of host Tetrastigma vines (which are in the same family as grapes) in thin strands of cells that are quite lackluster. That is, until they decide to bloom. 

    Jeanmaire Molina, an evolutionary plant biologist, was the one to find out that these plants in the Rafflesiaceae family have completely ditched any functional chloroplast genes. A team at Harvard uncovered in a closely related species, Sapria himalayana, that these plants have shed all photosynthetic capacities in order to be more efficient parasites, outsourcing the labor of metabolic processes to their hosts. Hauntingly, 1.2% of Sapria's genome comes from hosts of Christmas past and present (which is bigger than it sounds given these are complex eukaryotes here). Their genome has been described as a "huge graveyard of DNA" by Liming Cai, a systematic biologist postdoc. Also, like 60% of these things' genome is repeating retrotransposons, but no one really knows what that's about yet. All in all, they have evolved exclusively to get really good at schmoozing their hosts out of their hard-made food and then making one hell of a scene when they're ready to get some.

To summarize, some of the largest flowers in the world are made by plant vampires. Sleep well! :)

Thanks for reading!

P.S. if you're interested in more parasitic plants, One-Flower Indian Pipe (Monotropa uniflora) are native (albeit, rare) to the Eastern part of Kansas :)

Resources:

Article by Quanta Magazine: https://www.quantamagazine.org/dna-of-giant-corpse-flower-parasite-surprises-biologists-20210421/

The perks of being a variant

    Most generally, I honestly feel as though genetic variation is a happy chance of nature. In a sense, mutation is kind of always an accident that is arguably taken advantage of by cell-regulation proteins, so to me that makes most of evolution a bit of an accident (that then makes the most of itself.) On the opposite side of the coin, though, variation also naturally serves as a buffer against selective forces: plants with variable genetics are protected from blights, same goes for animals and parasites, coat/skin color variation aids for camouflage in novel territory, etc. Variation serves to give populations, not necessarily individuals, more opportunity for survival.

    Pragmatically speaking, variation isn't cut out of the equation due to the chance of evolutionary mechanisms. Mutations don't just stop happening when a species is adapted to its environment. Gene flow brings in genetics from disparate infraspecific populations that provide variation that hasn't resulted from a population's own gene pool. Selection being blind to unexpressed recessive alleles in homozygotes allows for the potential for homozygous recessives of Mendelian traits to always have a chance for increasing in frequency if for some reason that phenotype becomes beneficial. Normal distribution of quantitative traits allows for similar genotypes to have a wider range of possibility in their expression within a population, subtle differences that can potentially lend great advantages to their fitness. Even something as basic as random assortment of genes during sexual reproduction allows for variation to be maintained. Even if on an empirical level, variation is governed by collections of chance events, it's almost as if they purposefully work together to make sure that no specific threat can wipe out populations singlehandedly, to ensure life's ability to continue past catastrophes.

The One-Island Model and the Importance of Size

     The most important facet of the one-island model of migration, the way I understand it, is the homogenizing effect of migration on whatever selection is happening on the island(s). In any relationship between a mainland and an island, there is going to be a size difference in the population; and in this case, size does indeed matter. This difference leads to any movement between the island and the mainland as having a negligible impact, in terms of allele frequencies, on the mainland, while the island's frequencies can be radically impacted by migration. As seen in the example with the water snakes, populations can be selected upon differently by variable environments even within a relatively close spatial distribution and thus have different phenotypes. However, this variation is negatively impacted by the movement of genetic material from the mainland(s) to any of the islands. 

    As seen in the above model from the textbook, m represents migration rates between the populations of snakes (from the mainland to the islands, specifically).  With an increase in the rate of m, seen on the right, there is an increase in the speed at which the allelic frequencies between the populations is homogenized. Moreover, with the assumption that this migration is chronic and not just happening in small, impactful bursts, then there is an implication that a constant migration is going to homogenize the populations over time no matter what. I honestly don't know if I can say that this is an accurate assumption, because we see in places like Madagascar and New Zealand that there has been quite rampant speciation from the mainlands (Africa and Australia, respectively.) However, maybe this is frequently true for less extreme spatial differences between the mainland and the island(s), and that's why there is a maintenance of a single species between differently selected upon populations in more confined locales (like this water snake example). So, it appears that this adverse effect of migration on selection's work could in turn be affected by the amount of space between the populations and, thus, how easy it is for migration to occur.