Sophie Biehl Term 2 Biomedia Report

African Cichlid Fishes

Summary:

                African Cichlid Fish have a very unique evolution. They are a prime example of adaptive radiation, a term used to describe a group of species that quickly adapt and speciate from a common ancestor. Located in African Great Lakes of the Rift Valley, these fish have evolved, and now are separated into over 1,500 unique species in only around ten million years’ time. There are over 200 species in Lake Victorian alone, which is only around a million years old.  This rapid and enormous speciation speculated scientists, for it seemed like the lakes doesn’t seem to lead species a chance for ecological isolation, a factor important in a lot of speciation occurrences.

                The fish have been successful in the lakes of Africa for several reasons. First, the lakes were relatively uninhabited, and therefore the niches were mostly open. Like Darwin’s finches, the fish had many possible niches to fill, so the ones most suited for a particular niche by variation would fill it. Over time this group would adapt to the niche, and become different enough from the original group that it became its own species. This was helped by the different feeding options in the lake. Now, each species has a different food source, from algae to fish eyes. This difference in food sources let the fish species coexist, because they weren’t competing. It helped speciation because as the population grew, the fish had to find new foods to be able to hold the population size. The individuals who branched off to new sources adapted to them, and therefore grew different from the original species. This happens through morphological specialization. Like Darwin’s finches, the fish adapt certain traits to more easily obtain the food source. They develop key innovations, which are adaptations that allow a lineage to harvest a resource that they couldn’t previously get. For the Cichlid fish, these include both pharyngeal and oral jaws to obtain and break down food easier and the ability to change tooth and skull morphology to fit whatever food is available.

                Another role in the Cichlid evolution is sexual selection. This is when certain individuals in a population have a better chance of reproduction from having traits that attract a mate. For example, since some species of female Cichlid prefer to mate with a colorful male, the traits for the colorfulness are more likely to be passed down. Sexual selection changes a species overtime because certain traits become very popular, while others therefore become rare or even breed out entirely. This happened with the Cichlids, and it effected their evolution.

                The African Cichlid Fish have a very unique and complex evolution, and it still hasn’t been completely figured out as to why they speciated and evolved so fast.

               

Relevance:

                This article connects to our current unit. Like Darwin’s finches, these fish are an example of adaptive radiation. They have speciated from a common ancestor, and now have over 1,500 different species. The article talks about how they evolved into different niches and the way that so many different, but similar, species could evolve from one species. The African Cichlid Fishes article tracks their evolution, which is a topic in discussion now.

Citation:

"African Cichlid Fishes." Animal Sciences. Ed. Allan B. Cobb. New York: Macmillan Reference USA, 2009. Science in Context. Web. 10 Jan. 2015.
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