Ecology-drama and "it's complicated" written all over it

There are so many ways in which ecology becomes complicated.  The last example is a beautiful one-well studied, fairly well understood, and fairly simple.  The cichlid fish example works so beautifully because there happens to be only 2 major selection pressures driving coloration-sexual selection and water clarity.  But what if there was more to it?  What if suddenly a visual predator was introduced to both clear and murky systems?  Or what if there was increased fishing pressure?  More or less plant material?  Stark changes in diet?  Variables can add up very quickly and have enormous effects.

For example, salmon change to a beautiful bright red during breeding season in order to attract mates.  The bright the red, the more likely you are to pair up because you are PERCEIVED to be more fit.  Now a certain type of salmon called Kokanee got landlocked and now live in a lake system.  Most salmon derive their beautiful red color from their food, which contains a carotene for red coloration.  To adapt to their new environment, the Kokanee salmon improved their ability to obtain (sequester) red coloration from their food, which has much less carotene than the ocean available food of their counterparts.  Both Kokanee and "regular" salmon turn red during breeding season but if the regular salmon get into the lake system they are unable to turn red, because they cannot sequester such small amounts of carotene, and therefore are not chosen to breed, regardless of their actual fitness level.  A simple change in diet shifted mate choice based on coloration to a completely different and isolated level!  And of course, we have speciation as well much like the cichlids, which I do want to say is not necessary when these things occur.



Nothing gets this complicated variable idea across more than thinking about how to design an experiment.  For example, a study that aimed at looking at predation on small rodents by their larger, wolf and fox, predators took the home site of the rodents and fenced it off, denying access to the predatory mammals.  It is a tried and true method, good for animals or to protect plants or even insects from their known predators.  It didn't work here though, because the posts along the fence line attracted hawks and small falcons that wanted a perch, thereby increasing predation on the rodents via a predator that usually accounts for a very small amount of predation (if you're going to stop and rest why not grab a snack while you're at it?).  Oops.  So here even though we've removed the predator that based on observation and testing is the primary influence on the rodent life cycle, you see how moving one thing out of a niche (space/resource/habitat used by an animal in relations to others it shares said space with) how easy it is for something else to move into the open slot.



It is because species and their environments are so intermixed that these things happen.  There is no such thing as a food chain, only food webs.  One creature eating only one other species is the exception, not the rule.  Specializing can be good-if the source is available you become very efficient at handling and deriving nutrients from one thing.  However, the environment is shifty and even poor panda probably regrets it's monogamous relationship status with bamboo.  Moreover more than one thing will determine a species or individuals fitness-habitat, shade, food, water, nutrients, substrate, predation, etc.  Then, each of those factors is controlled by any number of additional factors, habitat for example-competition for space, degree of visibility required, predation, hunting, community of plants, nutrients, flooding, fires, access to mates, etc.  You can see how one thing rarely dictates the response of a given species.

To sum this up let's think about how this looks graphically.  You have your species and the response of said species (i.e. weight, survival, food choice, etc).  On the graph you get a huge cloud of points through which you draw a line, which represents your variable.  The line will likely trend the points with an r squared of maybe 0.1 or 0.2.  In other words, your variable can explain the response of the species about 10-20% of the time.  Seems low considering in chemistry you need above 80%.  But makes sense right?  It has to be one serious pressure to make up 80% of the life response of an individual!  Think about what controls your day to day activities?  Some things are certainly more important than others, but no one thing controls you.  Ecology sets out to find the more important things, from which we can glean the most information about that species in that environment.  Hence why the possibilities are endless!!

Stay tuned! Next week I'll talk about what I did my master's work in and how it puts a whole new twist on this complicated relationship!!



"When one admits that nothing is certain one must, I think, also admit that some things are much more nearly certain than others." Bertrand Russell