Biology Commons^™

Is There A Link Between Male Gonopodium Size And Mating Strategies Amongst Fish In The Family Poeciliidae?, Ryen Hunsaker, Jerald B. Johnson

Library/Life Sciences Undergraduate Poster Competition 2023

Have different male mating strategies led to evolutionary changes in male gonopodium size?

Natural selection should act strongly on any traits that affect successful reproduction. Fish species in the family Poeciliidae (livebearers) have a unique form of reproduction.

Life History Divergence In Livebearing Fishes In Response To Predation: Is There A Microevolution To Macroevolution Barrier?, Mark C. Belk, Spencer J. Ingley, Jerald B. Johnson

Faculty Publications

A central problem in evolutionary biology is to determine whether adaptive phenotypic variation within species (microevolution) ultimately gives rise to new species (macroevolution). Predation environment can select for trait divergence among populations within species. The implied hypothesis is that the selection resulting from predation environment that creates population divergence within species would continue across the speciation boundary such that patterns of divergence after speciation would be a magnified accumulation of the trait variation observed before speciation. In this paper, we test for congruence in the mechanisms of microevolution and macroevolution by comparing the patterns of life history divergence among three …

Does Negative Frequency-Dependent Selection Maintain Gonopodial Asymmetry In A Livebearing Fish?, Mary-Elise Johnson

Undergraduate Honors Theses

How genetic variation is maintained in the face of strong natural selection is an important problem in evolutionary biology. Selection should erode genetic diversity, leading to more and more homogeneous populations. Yet in nature, we commonly see high degrees of genetic variation, even for traits that are important to fitness. Negative frequency-dependent selection, a balancing selective force that favors traits when they are rare but not when they are common, is a mechanism proposed to maintain polymorphisms in a population. However, there is little empirical data to demonstrate how negative frequency-dependent selection sustains variation. Xenophallus umbratilis is a bilaterally symmetrical …

Anal Fin Pigmentation In Brachyrhaphis Fishes Is Not Used For Sexual Mimicry, Kandace Mary Hugentobler

Theses and Dissertations

Pigmentation patterns can be used as a communication signal in a variety of taxa, and can convey information relative to sexual selection, dominance, and species identification. Pigmentation is also sometimes used in mimicry to deceive the signal receiver into thinking the signaler is something other than itself. Mimicry can occur in several contexts, including sexual interactions, where one sex mimics another. There are relatively few examples of species with females that mimic males. Proposed hypotheses to explain female mimicry of males are that mimicry is used to reduce male harassment or that mimicry is used to display dominance over other …

Understanding The Diversification Of Central American Freshwater Fishes Using Comparative Phylogeography And Species Delimitation, Justin C. Bagley

Theses and Dissertations

Phylogeography and molecular phylogenetics have proven remarkably useful for understanding the patterns and processes influencing historical diversification of biotic lineages at and below the species level, as well as delimiting morphologically cryptic species. In this dissertation, I used an integrative approach coupling comparative phylogeography and coalescent-based species delimitation to improve our understanding of the biogeography and species limits of Central American freshwater fishes. In Chapter 1, I conducted a literature review of the contributions of phylogeography to understanding the origins and maintenance of lower Central American biodiversity, in light of the geological and ecological setting. I highlighted emerging phylogeographic patterns, …

Generality Of The Terminal Investment Hypothesis: Effects Of Extrinsic Mortality And Resource Availability On Age-Related Reproductive Investment, Allystair Jones

Theses and Dissertations

A central question in life history theory is, what combination of traits and behaviors will lead to the highest reproductive success throughout a lifetime. The trade-off between current and future reproduction is central to the lifetime reproductive success of an organism. If there is a cost to reproduction, then allocation of energy to current reproduction will come at a cost to future reproduction. We expect young individuals to favor future reproduction over current reproduction and that balance shifts to current reproduction as they age (i.e. terminal investment hypothesis). However, how this transition from an emphasis on future reproduction to emphasis …

Changes In Life History Within An Individual's Lifetime, Eric J. Billman

Theses and Dissertations

A central goal of life history theory is to understand the selective factors that generate the diversity of reproductive patterns observed in nature. Within lifetime changes in reproductive investment will determine an organism's fitness; however, this area of life history theory has received less attention than comparisons among population that characterize life history traits as a single population mean. Reproductive allocation can be affected by multiple cues; the integration of these cues across an organism's lifetime generates the diversity in life history strategies observed in nature. Life history studies should examine the interacting effects of multiple cues on life history …

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 …

Co-Occurrence With A Congeneric Species Predicts Life History And Morphological Diversification In The Mexican Livebearing Fish Poelicopsis Baenschi, Laura E. Scott

Theses and Dissertations

Understanding why some species coexist and others do not remains one of the fundamental challenges of ecology. While several lines of evidence suggest that closely related species are unlikely to occupy the same habitat because of competitive exclusion, there are many cases where closely related species do co-occur. Research comparing sympatric and allopatric populations of co-occurring species provides a framework to understand the role of phenotypic diversification in species coexistence. In this study I focus on the livebearing fish Poeciliopsis baenschi and ask if differences in phenotypic traits among populations can be explained by the presence or absence of the …

Biogeography Of The Livebearing Fish Poecilia Gillii In Costa Rica: Are Phylogeographic Breaks Congruent With Fish Community Boundaries?, Jared Benjamin Lee

Theses and Dissertations

One of the original goals of phylogeography was to use genetic data to identify historical events that might contribute to breaks among biotic communities. In this study, we examine the phylogeography of a common livebearing fish (Poecilia gillii) from Costa Rica. Our goal was to see if phylogeographic breaks in this species were congruent with previously-defined boundaries among four fish community provinces. We hypothesized that if abiotic factors influence both community boundaries and genetic structuring in P. gillii then we would find four monophyletic clades within our focal species that were geographically separated along community boundary lines. Similarly, we expected …