Zoo Animals

Well good news is that I picked up some juvenile virgin males at the zoo. Now I am waiting for some juveniles to molt. Basically, I have 8 virgin females and I have 16 males. Soon, I should be able to run one trial run. I will mate two sterile males to one female. Then I will vary the number of intromissions allowed which will be a 1 to 5 first to second male ratio. Then I will do the same two manipulations for the other groups (the 1st sterile, 2nd fertile & 1st fertile, 2nd sterile & 1st fertile, 2nd fertile). Then I should have some data hopefully. The idea is to be able to manipulate number of sperm so that we can control priority pattern. Usually, in this species, the first male has the advantage because he plugs up the female. However, we are not allowing the male to form a plug. Therefore, if there is sperm mixing going on in the female's spermatheca (storage sac), then we should be able to influence the priority pattern. We also sat down and dissected a female the other day and the storage sac is perfectly round, which would seem to facilitate sperm mixing. The other hypothesis is that priority pattern is determined by placement of sperm (location in the spermatheca). I am excited and hope that this first run goes well.

Baby Spiders

Well lost another male to a voracious female the other day!! Oh, well. Anyways, I have finally figured out how to rear my spiderlings successfully! I have isolated them in screw cap vials. I feed them about once a week with a knat-like insect. These babies are about the size of your pencil point and they spin the much larger insect up in their web. It is pretty phenomenal! I should be doing some more collecting at the zoo with Dr. Christenson on Friday. Hopefully, I will be able to ask him some questions about the experimental design. More to come about the project after Mardi Gras...

JV Ch.3 in class

I really liked the way we worked on Chapter 3 in lab yesterday. It was extremely helpful to be able to target one problem and do it well. Then we could even move onto others if we finished. I thought that everyone presenting a problem was very helpful because everyone brought a different way of doing things. I feel like I learned so much more about UsingR in this week's session versus in the past. Keep it up Mike!!

Floating Islands

I am taking a Primate Behavior and Ecology course this semester, which has so far been really interesting. I am learning about the differences between apes and monkeys and all that jazz. New World monkeys or platyrrhines diverged from Old World monkeys about 35 mya, but South America split off of Africa much earlier around 100 mya. The earliest fossils were established 26 mya in the New World probably because fossils do not form as well in wet, tropical climates. The real question is: How did the platyrrhines get to South America? The best supported hypothesis is by rafting across on islands of floating vegetation.

A study by Alaine Houle was conducted to examine the effects of wind velocity and direction as well as current velocity and direction on the number of days that it would take take to cross a water barrier during the Paleogene. Very simple summary statistics were used like in G&E Chapter 3 like mean, variance, and standard deviation. Conclusions were that around 40 mya, it would have taken about 11 days to cross the Atlantic Ocean at a most conservative measurement. The shortest measurement was 7 days. In this light, this theory does not seem all that implausible because the survival limit of monkeys has been estimated to be 11-15 days. Rafting earlier would also have decreased the amount of time. It is likely that monkeys could survive this trip and find enough food on the island to sustain them for two weeks. Now, what sort of population size would be needed, I have no idea. But imagine that Houle did this study with just summary statistics!! By the way, the link is http://www.jstor.org/view/13669516/di005208/00p0189i/0.

Warming

I have been taking this ecosystem ecology class this semester, and we have been talking a lot about global warming. Apparently, the concentration of carbon dioxide in the atmosphere has risen 30% since the Industrial Revolution. It is around 380 ppm. Just for reference, the glacial maximum concentration of carbon dioxide is 180 ppm, while that of an interglacial period is 280 ppm. Scientists have gotten these measurements by directly measuring the carbon dioxide concentration from the Vostok ice core. Then they have manipulated this data to somehow look at the flux of temperature over millions of years ago. How they do this, I am not really sure. It seems like an unbiased statistician would have to take into account the natural cycles instead of just human impact. The temperature rise should not be solely based on the rise in carbon dioxide concentration because in the past great changes in climate have taken place before humans. Anyway, just a thought. I was just trying to think of ways to be less biased about global warming because a lot of people seem to think that ecologists have an agenda.

She Ate What?!

I want to go into a little more detail for my study so that I can relay an interesting occurrence that took place yesterday. A priority pattern study investigates the multiple mates of a female and their respective reproductive successes. Most insects have a second male advantage meaning that the second male with whom a female mates fathers more of the offspring than the first male. In spiders, however, there is usually a first male advantage. I am going to directly (I hope) test the priority pattern for Nesticodes rufipes. The design for the experiment includes controlling the number of intromissions (insertions) the male makes when mating, which linearly correlates with the amount of sperm that he releases. I will have two types of males: 1) Normal fertile ones and 2) Sterile ones. The sterilization process is an interesting one in itself. Basically we irradiate the male, which leaves his sperm intact, but scrambles the DNA of the sperm leading to infertility. I will have four groups. The first control group will involve mating a virgin female with two fertile males. Then the control for the irradiation process will involve mating a female with two sterile males. The last two groups involve alternating the mating order of one sterile and one fertile male. Then the amount of offspring produced in the experimental groups will help to elucidate the priority pattern. I might try varying some of the number of percentage of intromissions of the two males (ie: 50/50, 25/75 & 75/25) just to see the results.

I currently have been in the process of trying to foster a breeding colony for my spiders so that I can produce a large enough sample size for controls and manipulations. Nesticodes rufipes is a species that is generally found indoors of laboratories, prey rooms of zoos, and perhaps barns. E.O. Wilson had these babies in his lab when he was doing his ant research. Anywho, these spiders mate for a total of 3 hours!! Talk about stamina! What takes so long? Well, the sperm producing organs are found in the lower abdomen of the male, but his organ of copulation are palps on his antennae. He has to build a sperm web and then dab his palps in it (called induction) so that he can then inseminate the female. It is a curious process because during intromission, he inserts one palp and basically turns the female in a semicircle. Then he switches palps and turns her the other way. Imagine a much bigger female just calmly putting up with this turbulence! Anyways, I put in a male with my most aggressive female yesterday and came back three hours later. She had mated with him, and then decided she was hungry and spun him up in her web. This is not the most common behavior but it does happen on rare occasions. I guess I am glad to be breeding some hearty stocks, but males are hard to come by and I would rather my females not consume their mates. Thought you all would find this amusing!

Hamilton and Altruism

In my evolutionary psychology seminar, I just got the chance to read one of W.D. Hamilton's papers. This is the first time that I have actually read him directly. Of course, he is a staple in evolution and ecology courses with his theory of inclusive fitness as a means to explain "altruistic" behavior. I have always found his exploration of natural selection at the level of the gene and its effect on social behavior quite fascinating. The great thing about reading him was his very straightforward writing style. Imagine such complex ideas with mathematical models and all being lucid! The man is a good writer. Anywho, I know that a lot of mathematical manipulations have been done to test his theory of altruism with current ecological data and that it holds up pretty well. Anyone have an idea of what these statistics look like? How exactly would you assign a numerical value to the cost to the altruist or the benefit to the recipient? These, unlike a coefficient of relatedness, very hard to quantify. It would be really interesting to examine an ecological study that tests Hamilton's theories. Anybody know of a good one?