Many more talks today, here's some notes on the ones that stood out:
Jennifer Kovacs told us about a cool ability of the endosymbionts of aphids and how they defend against ladybugs. When a female ladybug eats the infected aphids, she suffers no immediate consequences, but her offspring show a reduced ability to successfully pupate. Those that do pupate are on average larger than normal which may be due to a “filter” effect where the smaller, weaker ones were weeded out by the bacteria. As aphids reproduce clonally, the relatedness between two aphids on the same leaf is 1. This means there is strong selection to stop the adult ladybug’s offspring from consuming other aphid clones. The only hole in the story so far is that no one has been able to show that the aphid’s bacteria survives the adult ladybug’s stomach and gets into her ovaries. Somehow it must get into her eggs, but they haven’t been able to show that yet. Still a really cool story of host defense.
Taichi’s talk was fun too. He’s looking at Bergman’s Rule (body size increases with latitude) and how it correlates with the gut microbiome. He’s showed that especially in the east coast there is a strong correlation between composition of microbes and latitude that also correlates with average body size in house mice. There is less of a pattern on the west coast, but that is likely because the colonization was much more recent and there has been subsequent gene flow from Mus spretus that may be confounding the pattern.
Jamie Zuniga-Vega talked about superfetation in live-bearing fish. Superfetation is where one female carries many broods at different developmental timepoints concurrently. There are three main hypotheses for superfetation which are: (1) it lowers the peak cost of reproduction - at any given time, female must invest less per unit time. (2) It results from morphological constraint - many offspring take up a lot of space forcing the female to not be hydrodynamic anymore, if the offspring are at different stages, they take up less space. And (3) it compensates for high adult mortality. If there is a high probablility of adult mortality, high fecundity may be able to comensate. Thus superfetation may increase rate of offspring production rate. They found that hypothesis 2 is best model for two species where fast water causes higher rates of superfetation, but the third species doesn't have anything that shows preference of one hypothesis over another.
Keenan Morrison then talked about anamniotic eggs and how they may predispose species for the evolution of matrotrophy. Amniotic eggs are impermeable and cannot absorb nutrients, but anamniotic eggs can assimilate resources across the “shell.” As these eggs already can accept nutrients from the environment, it is easy to make the next step to accepting nutrients from the mother’s uterus.
David Reznick followed the previous two talks and discussed how placental or matrotrophic fish should have greater male-female conflict. Furthermore he argued that placentas should correlate with long gonopodium (penises), small body size, lack of courtship, and sneaker mating strategies, non-placentals on the other hand should show strong sexual dimorphism, elaborate mating rituals etc. I was unclear on his logic as to why this is true (can’t placentals have pre-mating sexual selection as well as post-mating conflict?) and am looking forward to reading a paper he will hopefully publish ont eh topic (I felt better about my confusion as Doug was also unsure of his logic here). Surprisingly, he has found that there is an elevated speciation rate in non-placentas compared to placental fish. This is opposite of what I would have expected given the opportunity for maternal-offspring conflict in placental species. The species that do not have placentas instead show elaborate mating rituals and are characterized by strong premating sexual selection. This may then go hand-in-hand with the observation that birds, where strong premating sexual selection/sexual dimorphism is common, speciate twice as fast as mammals, where developmental conflict is more pervasive. Reznick also found that there is no support for “adaptive hypotheses” of the origin of placentas, but I’ll need to see his paper to remember/understand why he thinks so. Hopefully the paper with come out soon.
I was lost with Turelli’s talk. He went fast and had a ton of words on his slides. It sounded impressive, but I couldn’t follow anything he was saying.
Rob Unckless’ talk was a great conclusion for the day. He talked about the drive system in Drosophila affinis. He and I had spent many hours talking about this system back in the Jaenike lab and creating recursion equations to model it. the equations we made then were comparatively quite simple - one driver, one suppressor. What he talked about today was how this system may maintain polymorphism of the Y chromosome given many drivers and many suppressors. Apparently he had to make a perl script to generate the recursion equations as they got so complicated. I am going to invite him out for a talk in the spring if I can manage it.
The last talk of the evening was Jack Sullivan’s SSB presidential address. It was really fun and he showed great pictures of bacula and was quite entertaining. Much of his talk was work done by J~ either as his masters student or recently in collaboration. He ended with the statement that you should always treat your students well so that you can exploit them years into the future.
I got to hang out with Rob and Yaniv, Erica, Mike Shapiro, Yasir, Daniel Matute and a bunch of others in the evening which was a blast. All in all it was a superb conference.
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