P H Y L O G E N Y

E V O L U T I O N

How did this behavior develop throughout the history of the species?

What selective pressures have shaped this behavior in the history of the species?

Aposematism in Granular Poison Frogs:

Figure 4 from Darst et al., 2006. Retrieved November 29th, 2015 from www.pnas.org

Several theories have been generated to explain phenotypic variation in aposematic coloration. The most prevailing theory posits that aposematic coloration evolved in tandem with toxicity so that the development of increased toxicity will coincide with more conspicuous coloration (Speed & Ruxton,2007). However, the coupling between increased aposematism and higher levels of toxicity has been challenged recently as studies have displayed an inverse relationship between conspicuousness and toxicity (Wang, 2011). One explanation for the inverse relationship between these functions is that the energetic costs of producing toxins and bright color pigments lead to potential trade-offs between toxicity and bright coloration, as illustrated in the supplemental image provided below(Darst et al., 2006). Researcherís postulate that in this case once aposematism has been secured within a species, toxicity and conspicuousness may become unlinked and individuals can acquire protection by evolving either increased conspicuousness or increased toxicity independent from one another (Darst et al., 2007). In addition to this, environmental differences may drive variation in toxicity and coloration in this species (Wang, 2011). Two biogeographic scenarios that have been suggested for facilitating such variation have been that 1)populations may have colonized areas with greater toxin availability and evolved reduced conspicuousness as a response, or 2) this species may have expanded into regions where toxin sequestration is more limited and evolved greater conspicuousness to compensate for a loss of toxicity (Wang, 2011). These findings suggest that ecological differences, as well as inherent trade-offs, play an important role in phenotypic variation in aposematism in this species, and that increased aposematism does not always evolve congruently with toxicity.

Stotting:

[lamb stotting] retrieved November 29, 2015 from: http://tragos.tumblr.com/post/1701309464/failureinsmallincrements-stotting-also

The main evolutionary question regarding stotting is how it developed despite it requiring more energy than just escaping the predator. FitzGibbon et al. (1988) found that stotting Thomson's gazelles that stotted more frequently had a higher rate of survival. They also found that it had to be an honest signal, as the behavior is too energetically consuming to evolve as a deceit, as the risks of being spotted without having the strength to escape outweigh the possible chance of fooling the predator. Furthermore, stotting individuals will have higher chances of finding mates as they can display their fitness to a mate and prove that in case of predation they will have the ability to distract the predator from the kin, suggesting that one possible factor by which this behavior has evolved is kin selection (Pitcher, 1979). The fact that this behavior is found in a wide range of species suggests that it has been effective in dealing with a variety of selective pressures.

[Amazing display of a springbok in the Karoo, South Africa.] retrieved November 29, 2015 from: https://500px.com/photo/96030461/pronking-by-charles-jorgensen