Thursday, April 3, 2014

A sticky situation!

Our lab was recently gifted with a fork-leaved sundew Drosera binata. It's first few weeks were a bit touch-and-go (it was chilly outside the day it was brought to us), but as you can see, it has started the Herculean task of catching our rogue flies using its stick trichomes.


Wednesday, March 26, 2014

Direct fitness consequences of male mate size in Drosophila melanogaster

As previously mentioned back in the infancy of this blog, one of the tools we have in our lab is a sieve shaker system, which was originally designed in the Rice Lab at UCSB as a way to quickly sort phenotypic variation in body size in our Drosophila melanogaster populations. Recently (3 weeks ago), Pam (an incoming member of the Long Lab) set up a simple experiment as part of her fly-lab training. We were originally planning to look at differences in mating speed in single females placed into vials along a single male (from one of three treatments: "Large" - flies that had not passes through the holes in the 1420um sieve; "Medium" - flies that had passed through the holes in the 1262um sieve, not through the holes in the 1214um sieve; and "Small" - flies that had passed through the 1079um sieve). 

However, it transpired that the flies were not really co-operating (the subject of a post for another day), so instead we decided to change the assay (on the fly, so to speak) into an examination of how offspring production differed between the three treatments. We left the pairs of flies in the vials for 48h, then flipped the pairs into a second vial for a final 48h before being discarded. The vials were then incubated for 14 days, and then Pam & I counted the number of eclosed vials. Here are the results of this assay:
Right from the start, there is greater fecundity in the first 48h there was a difference in mean offspring production (ANOVA, F=4.5871, df=2,58, p= 0.014), with the lowest reproductive output coming from the Large male treatment, and the greatest from the small male treatment.
This pattern continued in the next 48 period. (ANOVA*, F=5.0757 , df=2,58, p= 0.009)
And not surprisingly, when data from the two 48h are combined (ANOVA*, F=8.0934 , df=2,58, p= 0.0007)

Now observations of this phenomenon is not new. There have been several studies that have shown this pattern including:

Pitnick, Scott, and Francisco García–González. "Harm to females increases with male body size in Drosophila melanogaster." Proceedings of the Royal Society of London. Series B: Biological Sciences 269.1502 (2002): 1821-1828.
and
Friberg, Urban, and Göran Arnqvist. "Fitness effects of female mate choice: preferred males are detrimental for Drosophila melanogaster females." Journal of evolutionary biology 16.5 (2003): 797-811.

..but I should note that in both of these (excellent, by the way) studies, male size was experimentally manipulated by varying the density of competing larvae, or the quality of their food. Our flies, which came from a large, outbred population (IV), had been cultured according to our standard laboratory protocol, so this shows that this phenomenon is something routinely encountered by female flies in the lab population, and not an artifact of the experiment. A the very least, it is a good snapshot of some of the selective pressures resulting for mate choice in this model species, and is a fun introduction to Pam to the world of behavioural ecology/evolutionary genetics.

Future studies will be focusing on more fine-scale variation of this phenomenon, and more importantly see how this aligns with observations on female mating preferences and/or the outcome of male-male competition, and even more importantly in the behaviour and fitness of the offspring. -TAFL
-----------
By the way, I used ggplot to make these graphs. Here is some sample code.

> jpeg("CUMULATIVE_eggs.jpg",quality=100)
> qplot(PAM$TREATMENT, PAM$CUMULATIVE, data=PAM, geom=c("boxplot"), 
+    fill=PAM$TREATMENT,
+    xlab="", ylab="Eggs laid over 96h")+ opts(legend.position = "none")
> dev.off()
Created by Pretty R at inside-R.org

Thursday, February 20, 2014

Happy Valentine's Day from the Long Lab!

Things have been pretty busy these last couple of weeks. Both Ashley and Leah continue to analyze and interpret their results, the experimental torch has been taken up by Emily and Shada who are collaborating on a project that looks at variation in pre-copulatory behaviour and mate perception, and the post-copulatory consequences. One of those consequences is egg production and size, which led to this beautiful (and season appropriate) image of fruit fly eggs! Hope you enjoy!

Saturday, December 28, 2013

Fun with Google Image Search!

I was putting together some slides on female choosiness, and for inspiration for images, I turned to the google. Imagine my suprise to see our own Ashley and Leah smilin' out on the first page! They even beat out peafowl!

Since I have named this screencap "female choosiness", do you think that this picture of a google search will soon show up on google image search when looking for pictures of "female choosiness"?

New Paper published by Long Lab in the Journal of Evolutionary Biology

Hot off the presses (i.e. Early View @ JEB) --> http://onlinelibrary.wiley.com/doi/10.1111/jeb.12305/abstract

Variation in male effects on female fecundity in Drosophila melanogaster 

  • Hannah M. Tennant,
  • Erin E. Sonser &
  • Tristan A. F. Long
  • Abstract
    In many species, males have the capacity to directly influence (either positively or negatively) the fitness of their mates and offspring, not only via parental care contributions and/or precopulatory resource provisioning, but also via the post-copulatory activity of those substances passed on to their mates in their ejaculates. Here, we examine how an individual male's identity may be related to phenotypic variation in short-term female fecundity in the model species, Drosophila melanogaster. The effect of male identity on short-term fecundity stimulation of females was repeatable across time and accounted for over a fifth of the total observed phenotypic variation in fecundity in two independent populations. The functional explanations for these results and the implications for our understanding of the factors that contribute to the adaptive significance of mating preferences and/or sexual conflict are discussed.
    For a copy of the paper, please follow the link above, or email me --> tlong@wlu.ca

    Monday, December 16, 2013

    Second MSc thesis defended in the Long Lab!

    Congratulations to Adam Lounsbury on the receipt of his MSc! As you can see from the Wordle based on his thesis, Adam's work has focused on the role that body size variation plays in shaping the outcome of mating interactions.

    Tuesday, December 10, 2013

    Cut-out Drosophila

    A few weeks back, I had the opportunity to speak to my son's JK class on what behavioural geneticists do. It was tons of fun. We tested hypotheses regarding phototaxis, gravitaxis and food preferences, and discussed the life cycle of Drosophila melanogaster. One of the things I brought with me to enhance the experience were some fruit-fly cut-outs for them to decorate and take home. If you are interested, why not make one yourself? Use brass fasteners to attach the wings.