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Predators As Agents Of Selection And Diversification, Jerald B. Johnson, Mark C. Belk
Predators As Agents Of Selection And Diversification, Jerald B. Johnson, Mark C. Belk
Faculty Publications
Predation is ubiquitous in nature and can be an important component of both ecological and evolutionary interactions. One of the most striking features of predators is how often they cause evolutionary diversification in natural systems. Here, we review several ways that this can occur, exploring empirical evidence and suggesting promising areas for future work. We also introduce several papers recently accepted in Diversity that demonstrate just how important and varied predation can be as an agent of natural selection. We conclude that there is still much to be done in this field, especially in areas where multiple predator species prey …
Density And Distribution Of Piscivorous Fishes In The Sacramento – San Joaquin Delta, Christopher M. Loomis
Density And Distribution Of Piscivorous Fishes In The Sacramento – San Joaquin Delta, Christopher M. Loomis
Cal Poly Humboldt theses and projects
Predatory fishes, including numerous introduced species, are common to the Sacramento – San Joaquin Delta, but abundance data for most species is insufficient to determine the Delta-wide distribution and ecological impacts of these species. Predatory fishes (e.g. Striped Bass, Largemouth Bass have long been suspected of contributing to the decline of native species, including salmonids, but data has been insufficient to investigate this hypothesis. In this study, I present a novel method to assess predator fish populations across the southern Delta using DIDSON acoustic cameras and analyze the environmental associations that form the landscape and fine-scale distribution of predatory fishes. …
Presence And Function Of Tetrodotoxin In Terrestrial Vertebrates And Invertebrates, Amber N. Stokes
Presence And Function Of Tetrodotoxin In Terrestrial Vertebrates And Invertebrates, Amber N. Stokes
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Tetrodotoxin (TTX) is a potent neurotoxin found in a variety of species. This toxin has long been of concern to human health as it is found in puffer fish, which are a delicacy in Japan. Since the distribution of this toxin is so great, there are many questions regarding the evolution and ecology of organisms that have TTX. My research has focused on further investigating three topics with this research: production, predation, and identification of novel TTX bearing taxa. In order to perform this research I first refined a Competitive Inhibition Enzymatic Immunoassay methodology to quantify levels of TTX in …
Propulsion In Cubomedusae: Mechanisms And Utility, Sean Colin, John H. Costello, Kakani Katija, Jamie Seymour, Kristen Kiefer
Propulsion In Cubomedusae: Mechanisms And Utility, Sean Colin, John H. Costello, Kakani Katija, Jamie Seymour, Kristen Kiefer
Arts & Sciences Faculty Publications
Evolutionary constraints which limit the forces produced during bell contractions of medusae affect the overall medusan morphospace such that jet propulsion is limited to only small medusae. Cubomedusae, which often possess large prolate bells and are thought to swim via jet propulsion, appear to violate the theoretical constraints which determine the medusan morphospace. To examine propulsion by cubomedusae, we quantified size related changes in wake dynamics, bell shape, swimming and turning kinematics of two species of cubomedusae, Chironex fleckeri and Chiropsella bronzie. During growth, these cubomedusae transitioned from using jet propulsion at smaller sizes to a rowing-jetting hybrid mode …
Morphological Convergence During Pregnancy Among Predator And Nonpredator Populations Of The Livebearing Fish Brachyrhaphis Rhabdophora (Teleostei: Poeciliidae), Jeff S. Wesner, Eric J. Billman, Adam Meier, Mark C. Belk
Morphological Convergence During Pregnancy Among Predator And Nonpredator Populations Of The Livebearing Fish Brachyrhaphis Rhabdophora (Teleostei: Poeciliidae), Jeff S. Wesner, Eric J. Billman, Adam Meier, Mark C. Belk
Faculty Publications
Predation can drive morphological divergence in prey populations, although examples of divergent selection are typically limited to nonreproductive individuals. In livebearing females, shape often changes drastically during pregnancy, reducing speed and mobility and enhancing susceptibility to predation. In the present study, we document morphological divergence among populations of nonreproductive female livebearing fish (Brachyrhaphis rhabdophora) in predator and nonpredator environments. We then test the hypothesis that shape differences among nonreproductive females are maintained among reproductive females between predator and nonpredator environments. Nonreproductive females in predator environments had larger caudal regions and more fusiform bodies than females in nonpredator environments; …
Differential Mortality Drives Life-History Evolution And Population Dynamics In The Fish Brachyrhaphis Rhabdophora, Jerald B. Johnson, J. Jaime Zuniga-Vega
Differential Mortality Drives Life-History Evolution And Population Dynamics In The Fish Brachyrhaphis Rhabdophora, Jerald B. Johnson, J. Jaime Zuniga-Vega
Faculty Publications
Life-history theory predicts that populations experiencing different levels of extrinsic mortality will evolve divergent reproductive strategies. Previous work in the live bearing fish Brachyrhaphis rhabdophora shows that individuals from populations that occur with piscivorous fish mature earlier and at smaller sizes and have more and smaller offspring than fish from populations without predators. However, until now, there have been no data to demonstrate that differences in mortality rates actually exist between predator and predator free sites. Here we present the results of a serial mark-recapture field study designed to estimate mortality rates in natural populations of B. rhabodophora from Costa …
The Impacts Of A Nonindigenous Marine Predator In A California Bay, Edwin D. Grosholz, Gregory M. Ruiz, Cheryl A. Dean, Kim A. Shirley, John L. Maron, Peter G. Connors
The Impacts Of A Nonindigenous Marine Predator In A California Bay, Edwin D. Grosholz, Gregory M. Ruiz, Cheryl A. Dean, Kim A. Shirley, John L. Maron, Peter G. Connors
Biological Sciences Faculty Publications
Coastal marine ecosystems worldwide are being altered rapidly by the invasion of nonindigenous species. Unlike terrestrial and freshwater systems, the impacts of an invading species have never been quantified on multiple trophic levels for a marine food web. We measured the impact of the nonindigenous green crab, Carcinus maenas, on a coastal marine food web in central California and found that this predator exerted strong “top-down” control, significantly reducing the abundances of several of the 20 invertebrate species monitored over a 9-yr period. Densities of native clams, Nutricola tantilla and Nutricola confusa, and native shore crabs, Hemigrapsus oregonensis, showed 5-fold …