BIOL 561, Week 4 – Editing a prospectus abstract
The following is the 1st draft of the abstract for a prospectus in my lab. The sea slug, A. willowi
normally lives in seawater but slugs from Los Angeles, near the center of its range (= geographical
distribution), can survive for about 4 hours in freshwater. In contrast, slugs from the northern-most
population near San Francisco can survive 12 hours in freshwater. “Hyposaline” means freshwater,
or water that is much less saline (salty) than normal seawater. We hypothesize that the greater
rainfall in the north has imposed natural selection on these populations, causing the evolution of
superior tolerance for freshwater in San Francisco compared to L.A., which gets 4 times less rain.
This student’s project was going to test whether it was possible to cause experimental populations in
the lab to evolve through artificial selection. Over successive generations, slugs would be exposed
to freshwater for increasingly long periods of time; the survivors in each generation would be
chosen to lay eggs to start the next generation. We expected that over time, offspring of freshwaterselected lines from L.A. would evolve to have 12-hr survival times, like the ones at the northern
range edge.
However, we also hypothesized that the northern slugs were “tapped out” of genetic potential to
evolve, and would not evolve any better tolerance to freshwater, due to genetic constraints –
intrinsic limitations that prevent the evolution of resistance beyond the 12-hr point. An example
would be if due to limited energetic resources, slugs also evolve to be smaller as they are evolving
higher tolerance for freshwater; beyond the 12-hr tolerance point, slugs could become too small to
reproduce, so the population stops evolving once that point is reached.
Constraints (limitations on what is possible) are commonly observed, because traits affect the
expression of other traits during development. For instance, plants can be toxic and slow-growing,
or non-toxic and fast-growing, but they can’t be toxic and fast-growing because there isn’t enough
energy available to produce both toxins and rapid tissue growth. “Trade-offs” is the term when the
presence of one trait prevents the evolution of another.
Can you determine what this abstract is trying to say? Analyze the passage, and identify as many
problems in the writing as you can in an itemized list. Then, try to fix the passage by editing the
writing, using information gleaned from the text above (but not copy-pasting my text!) as necessary
to flesh out your understanding.
Abstract
Artificial selection experiments are of interest because it enables the experimenter to single out and
identify a trait of interest and find if it is impacted by different variables. This can answer questions
pertaining to adaptability, limits, or anything else of interest. Differences between different
populations of Alderia willowi may be adversely affected by trade-offs when exposed to low salt
environments. Although range edge populations are well adapted to this type of environment, it is
unlikely that further adaptation would be possible due to constraints. These constraints cause
possible loss in fitness or reproductive ability in exchange for further adaptation. Range center
populations that are not fully adapted, are able to further adapt to hyposaline conditions, but not
without trade-offs. I will find that range edge populations are inhibited by further adaptation,
whereas range center populations will be able to adapt while experiencing lower fitness.