Welcome to Gametophyte Junction. Here, I will be making (hopefully) frequent updates on my progress through grad school. Most who know me, visiting this site, already have a very vague idea of what I'm doing: evolutionary biology of mosses. This site is intended to give a more in-depth view of what the crap I'm spending my mid-twenties doing. It's also a place for me to practice boiling down my research to layman terms, and hopefully also a place for me to come back to in a few years to observe how wide-eyed I was as a first-year grad student. So, feel free to say hi in the comments, and please: ask questions! If you're interested, then I'm doing a good job making it sound interesting, and that would make me happy. Anyway, I thought I'd start with a short overview of what I'm working on and the kinds of questions I'm interested in. I'll probably go into further detail on lots of these things in future posts, so stay tuned!
The genus of moss I'm going to be working on is called Funaria, which looks like this:
It's a very common, small, weedy type moss that grows in all kinds of disturbed habitats: recently burned forests, roadsides, sidewalk cracks, etc. It is a monoicious moss, which means it has produces both male and female parts, eventually releasing egg and sperm from the same plant. I'll try to avoid jargon as much as possible, and so I'll refer to this condition as being "bisexual." It will probably get me blocked by filters, but that's okay, it keeps the riffraff out. It's also very closely related to the species Physcomitrella patens, which recently became the first moss to have its entire genome sequenced. That's going to make a lot of what I'll be doing a lot easier.
To explain what it is I'll be doing with this moss, you'll have to take a trip with me back to basic bio:
Most organisms are diploid; they have two copies of every chromosome for most of their life cycle- this is true of all animals and most all plants. The organism you see (whether it's a dog or a tree) is diploid. All organisms, when they sexually reproduce, reduce their chromosome number to "haploid" to make sperm and egg, which then fuse to produce a new diploid individual. In plants, the haploid stage lasts a bit longer, with multicellular haploid structures forming from which the sperm and egg are derived. This is called an "alternation of generations," and in mosses, it is to the extreme. In the Funaria picture, the green tufts at ground level are the haploid stage- a bisexual "gametophyte" that produces both sperm and egg
(gametes). These fuse just like in any organism and produce a diploid individual- in the picture, that's the green glob on the end of a long white stem. Inside the green glob, meiosis occurs, producing haploid spores that are released to grow into new gametophytes.
Ok, so a couple of interesting things going on here, one of which is the issue of inbreeding. One of the fundamental rules of evolutionary biology is that inbreeding is bad... very bad. Recently,
the entire diploid genome of DNA-helix discoverer James Watson was sequenced, and he was found to have 12 lethal mutations... but he only had one copy of those mutations, and because they were recessive (like blue eyes), he is able to survive. But he most likely shares many of
these 12 mutations with his sister, and if they were to inbreed, the child would not survive, because the chances are very high that the child would have two copies of a lethal mutation. In evolutionary terms, this decreased "fitness" due to inbreeding is known as "inbreeding depression," and is the measure of decreased fitness that is caused by related individuals mating.
So, back to the moss. Remember I said that Funaria is bisexual, and produces both egg and sperm on the same plant- these egg and sperm will be (genetically) completely identical to one another, and if they fuse to produce a diploid, it will immediately have two identical copies of every gene, including any recessive mutations. This could be very bad news for the diploid offspring, if the mutations are lethal or even simply disadvantageous. So, one of the basic questions I want to ask is what relationship is there between relatedness and fitness in a moss. I'll be growing moss from different populations together to see if there is an effect- do related individuals produce unfit offspring, and do unrelated individuals produce more fit offspring? I'll be measuring relatedness by using a DNA-fingerprinting technique known as microsatellites- short regions of DNA repeat the same thing over and over, and it varies from individual to individual how many copies there are. By comparing the patterns of the numbers of copies in the offspring, I can estimate how related its parents were.
The other major part of my research involves the components of mating success. Many studies have been done looking at this topic in other organisms, under the umbrella of sexual selection. Briefly, this kind of selection typically involves animal species which evolve specialized characters that are most related to finding mates. For example, deer bull antlers are characteristics by which does select their mate- the bigger the antler, the higher probability of mating. Similarly, cardinals which are bright red have a better chance at mating. There are a few hypotheses regarding why such traits evolve, but I'm more interested in which traits are important, rather than why. When we see a patch of moss like pictured above, what traits of a particular individual give it a higher chance of mating? I will also be testing hypotheses with my mosses using a combination of field research and experimental studies, such as having two male mosses compete over a single female, and measuring the offspring to determine who got the girl.
Well, I think that's a good start. Stay tuned for more hot moss on moss action! I mean, serious science.
The genus of moss I'm going to be working on is called Funaria, which looks like this:
It's a very common, small, weedy type moss that grows in all kinds of disturbed habitats: recently burned forests, roadsides, sidewalk cracks, etc. It is a monoicious moss, which means it has produces both male and female parts, eventually releasing egg and sperm from the same plant. I'll try to avoid jargon as much as possible, and so I'll refer to this condition as being "bisexual." It will probably get me blocked by filters, but that's okay, it keeps the riffraff out. It's also very closely related to the species Physcomitrella patens, which recently became the first moss to have its entire genome sequenced. That's going to make a lot of what I'll be doing a lot easier.
To explain what it is I'll be doing with this moss, you'll have to take a trip with me back to basic bio:
Most organisms are diploid; they have two copies of every chromosome for most of their life cycle- this is true of all animals and most all plants. The organism you see (whether it's a dog or a tree) is diploid. All organisms, when they sexually reproduce, reduce their chromosome number to "haploid" to make sperm and egg, which then fuse to produce a new diploid individual. In plants, the haploid stage lasts a bit longer, with multicellular haploid structures forming from which the sperm and egg are derived. This is called an "alternation of generations," and in mosses, it is to the extreme. In the Funaria picture, the green tufts at ground level are the haploid stage- a bisexual "gametophyte" that produces both sperm and egg
(gametes). These fuse just like in any organism and produce a diploid individual- in the picture, that's the green glob on the end of a long white stem. Inside the green glob, meiosis occurs, producing haploid spores that are released to grow into new gametophytes.
Ok, so a couple of interesting things going on here, one of which is the issue of inbreeding. One of the fundamental rules of evolutionary biology is that inbreeding is bad... very bad. Recently,
the entire diploid genome of DNA-helix discoverer James Watson was sequenced, and he was found to have 12 lethal mutations... but he only had one copy of those mutations, and because they were recessive (like blue eyes), he is able to survive. But he most likely shares many of
these 12 mutations with his sister, and if they were to inbreed, the child would not survive, because the chances are very high that the child would have two copies of a lethal mutation. In evolutionary terms, this decreased "fitness" due to inbreeding is known as "inbreeding depression," and is the measure of decreased fitness that is caused by related individuals mating.
So, back to the moss. Remember I said that Funaria is bisexual, and produces both egg and sperm on the same plant- these egg and sperm will be (genetically) completely identical to one another, and if they fuse to produce a diploid, it will immediately have two identical copies of every gene, including any recessive mutations. This could be very bad news for the diploid offspring, if the mutations are lethal or even simply disadvantageous. So, one of the basic questions I want to ask is what relationship is there between relatedness and fitness in a moss. I'll be growing moss from different populations together to see if there is an effect- do related individuals produce unfit offspring, and do unrelated individuals produce more fit offspring? I'll be measuring relatedness by using a DNA-fingerprinting technique known as microsatellites- short regions of DNA repeat the same thing over and over, and it varies from individual to individual how many copies there are. By comparing the patterns of the numbers of copies in the offspring, I can estimate how related its parents were.
The other major part of my research involves the components of mating success. Many studies have been done looking at this topic in other organisms, under the umbrella of sexual selection. Briefly, this kind of selection typically involves animal species which evolve specialized characters that are most related to finding mates. For example, deer bull antlers are characteristics by which does select their mate- the bigger the antler, the higher probability of mating. Similarly, cardinals which are bright red have a better chance at mating. There are a few hypotheses regarding why such traits evolve, but I'm more interested in which traits are important, rather than why. When we see a patch of moss like pictured above, what traits of a particular individual give it a higher chance of mating? I will also be testing hypotheses with my mosses using a combination of field research and experimental studies, such as having two male mosses compete over a single female, and measuring the offspring to determine who got the girl.
Well, I think that's a good start. Stay tuned for more hot moss on moss action! I mean, serious science.
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