Following up on our inaugural reading list post, here are our reads of the week for April 16–22, 2016:
Emily: Paixãoa and Barton (2016) seek to sort out how selection is being shifted by gene interactions. Epistasis’s role in evolution has been long questioned, and its overall effects were thought to be negligible over the course of selection in the long run. Using calculations to examine the overall effects of epistasis in haploid and diploid populations, they found that when drift is stronger than selection, the interactions between many loci has little effect, whereas when selection is stronger than drift, the response between different alleles has a stronger pull on the phenotype. Overall, this is all dependent on the initial amount of variance in the population. While this paper makes a lot of simple predictions for the conditions, I found it to be challenging and thought-provoking, making me really think about basic principles of genetics.
Carolyn: This week I revisited Donald L. J. Quicke’s Parasitic Wasps, combing through the text for all mentions of Megaspilidae. Most of the information I found was related to Dendrocerus carpenteri, which I learned has larval behaviors that defend against predation. When attacked, the larvae thrash wildly; fourth instar larvae actually have protective spines to enhance this defensive behavior.
I also found a paper by Basibuyuk and Quicke (1999) that looked at the grooming behaviors of wasps across all Hymenoptera, and looked at how grooming behavior could be used to predict phylogenetic relationships. There are some common behaviors among Hymenoptera that Megaspilidae do not demonstrate, such as scraping the surface of the fore wings with the mid legs or scraping both antennae with both fore legs. The authors mapped the presence and absence of grooming behaviors on a proposed phylogeny of Hymenoptera and found that specific grooming behaviors were shared among different groups.
Kyle: I chose to read Perl and Niven (2016) this week because I’m interested in allometry, which is the study of the relationship between body size and shape. Ceraphronoidea can vary greatly in body size, even within a single species, which means that the relative size and shape of body structures and organs can be so different between individuals that one might assume that they are different species when they are really the same.
Organs scale with body size according to Y = bxα. Alpha is the ratio between body size (x) and organ size (y). Usually this ratio is negative, meaning that larger specimens usually have organs that are larger than the organs of smaller specimens, but the organs of smaller specimens are relatively larger when you compare it to their own body size.
Insulin-like peptides (nutrition), ecdysone (nutrition), and temperature can all have effects on body and organ size. What was interesting to me about this study is that it used the compound eyes of wood ants to demonstrate that the rules that govern scaling at the organ and cellular levels can differ even within a single population.
Eye facet size and facet number both change across differently sized eyes. However, the allometric relationship is not the same between different conspecific nests. There were also subsets of ants within each nest whose allometric relationships differed from their nest mates. So sometimes a large ant has a large eye because its facets are huge, and sometimes it is becuase it has a huge number of facets. And sometimes still it is because it has a greater number of bigger facets.
Paul Dessart, who has worked extensively on the taxonomy of Ceraphronoidea, mentions that many defining/useful characters for megaspilids are much easier to see on larger specimens. Assuming that Ceraphronoidea also exhibit negative allometric relationships, the larger the specimens, the relatively smaller the feature. I’m going to have to keep this in mind as I continue to look at specimens and develop my species concepts.
Jonah: Camiletti and Thompson (2016) examined the genetic underpinnings of social behaviour, especially for altruistic brood care. Drosophila was induced with different pheromones from queen honey bees to see how a non social insect would react to genetic social cues. This is a major point of study in sociobiology and gives a foundation for understanding nature vs nurture on an evolutionary scale.
István: Nijhout and Callier (2015) thoroughly review studies aimed at understanding processes that control body size and relative size of organs in insects. It is a must read for insect taxonomists since it provide basic information about the development of imaginal disks that give rise the adult integument, the subject of taxonomic descriptions.
Andy: My readings this week focused on three totally unrelated events: writing a letter of support, participating in a candidacy exam, and harvesting stone from our forest to build a stone wall. First, the letter. I’ve always been proud of my letters of support and recommendation, which I’d describe as comprehensive, accurate, and well-written. But do I introduce bias depending on the gender of the subject? I don’t think so, but stranger things have happened. I decided to revisit a couple of research papers on this topic—first Schmader et al. (2007), then Trix and Psenka (2003)—which re-raised my awareness (and made me feel better about my letters). I definitely need to read Trix and Psenka (2003) again.
One of our medical entomology students had her candidacy exam this week. She works on malaria and its vectors, so I had to read up. To become a PhD candidate one must critique (oral and written) an article of the committee’s choice. This student critiqued a 2013 paper that was an attempt to build a new ecological model to predict epidemics. All I can say is we need a WHOLE HELL OF A LOT MORE data about Anopheles physiology and natural and phylogenetic history if we want to have any hope of controlling this incredible important disease. Papers I read include: Harbach and Kitching (2016), Harbach (2004), Mordecai et al. (2013). Seriously, it’s shocking what we don’t know—even basic information—about the biology of such important vectors.
I spent two days hauling stones out of our forest (see above), so that we can build a 34 m rock wall that lines part of our driveway. My body feels old and broken, but the exercise got me thinking about the geology of Pennsylvania and the potential for fossils on our property. (Certainly some awesome vertebrates—Hynerpeton, for example—have been discovered relatively close by!) Wikipedia describes my rocks as “grayish-red to greenish-gray, thin- to thick-bedded siltstone, shale, and very fine to medium-grained crossbedded sandstone or subgraywacke and protoquartzite with interbedded conglomerate” (see Juniata formation entry), and they’re likely Ordovician in age. Arthropods were just starting to radiate on land, and insects likely didn’t even exist yet. I don’t think my rock wall will yield any insights into arthropod evolution, sadly, but having this knowledge makes the wall’s construction much more meaningful. Davies et al. (2010) was one of my reads about this formation.
