Abstract

Across the animal kingdom, predation is a ubiquitous and omnipresent selective agent for a variety of traits. I aimed to address gaps in our knowledge pertaining to how predation shapes animal behavior. Many species of fish naturally occur in drainages that differ in the density of predators and exhibit obvious population divergence, making them ideal study organisms to investigate predator-driven behavioral evolution. In Chapter 1, I conducted a systematic review of the literature. The purpose of this review was to determine if predation acted as a stronger or weaker selective agent on particular behavioral traits (e.g., foraging, mating, antipredator etc.) across fish. This review showed that predation does not always drive behavior in predictable ways, and that some behavioral traits more consistently diverge than others. It was evident that antipredator behaviors are extremely variable but were typically measured in response to a visual stimulus. Investigations on intraspecific variation pertaining to how fish acquire, process, and respond to information across other sensory modalities are needed. To address this, I focused on a Neotropical fish, Brachyrhaphis rhabdophora (Poeciliidae), from Costa Rica that occur in distinct predation environments. For Chapter 2, I evaluated whether males and females exhibit differential responses to conspecific chemical alarm cues. Chemical alarm cues are released when a prey is injured by a predator and are an honest indicator of risk. It was clear that B. rhabdophora responded to alarm cues, but that males and females sometimes employed different antipredator strategies depending on what predation environment they were from. However, we know that in group-living species, such as B. rhabdophora, risk information can also be acquired indirectly through social cues. There are tradeoffs associated with relying on direct vs. indirect information, and these sources of information may sometimes conflict. For Chapter 3 I considered how B. rhabdophora integrates conflicting information to elicit antipredator behavior. I again exposed fish directly to chemical alarm cues and measured how their antipredator responses changed when visually observing conflicting or reinforcing social information. I found that individuals integrated personal and social information differently based on their evolutionary history with predators. Further, we found evidence that even a single observer fish is able to influence group behavior. Finally, for Chapter 4, I evaluated sex-specific variation in brain size across predation environments. According to the "expensive-tissue hypothesis" there should only be investment in brain tissue when there is sufficient selection for enhanced cognitive abilities. Prey under elevated selection from predators should invest more in cognitive traits to enhance survival, but how sex interplays with this effect is unclear. I found that females had higher relative total brain volumes than males, but males exhibited more variation across predation environments in the relative volumes for certain brain regions. This work as a whole suggests that, yes, evolutionary history matters for a variety of sensory-related traits in B. rhabdophora.

Degree

PhD

College and Department

Life Sciences; Biology

Rights

https://lib.byu.edu/about/copyright/