Master of Science / Department of Biology / Michael Tobler / Natural selection drives the evolution of traits to optimize organismal performance, but optimization of one aspect of performance can often influence other aspects of performance. Here, we asked how phenotypic variation between locally adapted fish populations affect locomotion and ventilation, testing for functional trade-offs as well as trait-performance correlations. Specifically, we investigated two populations of livebearing fish (Poecilia mexicana) that inhabit distinct habitat types (hydrogen-sulfide-rich springs and adjacent nonsulfidic streams). For each individual fish, we quantified different metrics of burst-start swimming during simulated predator attacks, steady swimming, as well as gill ventilation. Coinciding with theoretical predictions, we documented significant population differences in all aspects of performance, with fish from sulfidic habitats exhibiting higher steady swimming performance and higher ventilation capacity but slower burst-starts. There was a significant functional trade-off between steady and burst-speed swimming, but not between different aspects of locomotion and ventilation, indicating modularity of traits associated with either aspect of function. While our findings about population differences in locomotion performance largely parallel the results from previous studies, we provide novel insights about how morphological variation might impact ventilation and ultimately oxygen acquisition. Overall, our analyses provided insights into the functional consequences of previously documented phenotypic variation, which will help to disentangle the effects of different sources of selection that may coincide along complex environmental gradients.

Mobility of the vertebral column is important for many ecological aspects of vertebrates, especially in the cervical series, which connects the head to the main body. Thus, fusion within the cervical series is hypothesized to have ecological and behavioural implications. Fused, anterior cervical vertebrae have evolved independently over 20 times in ecologically disparate amniotes, most commonly in pelagic, ricochetal, and fossorial taxa, suggesting an adaptive function for the ‘syncervical.’ Fusion may help increase out-force during head-lift digging or prevent anteroposteriorly shortened vertebrae from mechanically failing during locomotion, but no hypothesis for syncervical function has been tested. The syncervical of neoceratopsian dinosaurs is hypothesized to support large heads or aid in intraspecific combat. Tests of correlated character evolution within a ceratopsian phylogeny falsify these hypotheses, as the syncervical evolves before large heads and cranial weaponry. Alternative functional hypotheses may involve ancestral burrowing behaviour or unique feeding ecology in early neoceratopsians.

Mobility of the vertebral column is important for many ecological aspects of vertebrates, especially in the cervical series, which connects the head to the main body. Thus, fusion within the cervical series is hypothesized to have ecological and behavioural implications. Fused, anterior cervical vertebrae have evolved independently over 20 times in ecologically disparate amniotes, most commonly in pelagic, ricochetal, and fossorial taxa, suggesting an adaptive function for the ‘syncervical.’ Fusion may help increase out-force during head-lift digging or prevent anteroposteriorly shortened vertebrae from mechanically failing during locomotion, but no hypothesis for syncervical function has been tested. The syncervical of neoceratopsian dinosaurs is hypothesized to support large heads or aid in intraspecific combat. Tests of correlated character evolution within a ceratopsian phylogeny falsify these hypotheses, as the syncervical evolves before large heads and cranial weaponry. Alternative functional hypotheses may involve ancestral burrowing behaviour or unique feeding ecology in early neoceratopsians.

Pterotocrinus is an echinoderm of the class Crinoidea that is restricted to the Chesterian Series (Chestnut and Ettensohn, 1988; Sutton, 1934). The most identifiable and best preserved remains of Pterotocrinus are the wing plates (Welsh, 1978). These wing plates are specialized tegmen plates that give Pterotocrinus its name (from pteron, Greek for "wing") (Welsh, 1978). This study questions whether or not wing plates can be used for biostratigraphy throughout the Chesterian Series, as well as what the functions of the wing plates were. New morphologies of Pterotocrinus found within the Menard Limestone during this study bring into question the biostratigraphical usefulness of many of the morphologies of Pterotocrinus wing plates. Certain species of Pterotocrinus appear to remain valuable index fossils within the Menard Limestone and the Kinkaid Formation. Four new morphologies were collected within the Menard Limestone during this study. These new finds draw questions about our knowledge of this genus. This study also attempted to explain the function of the wing plate, and how it may have changed over time. Pterotocrinus wing plates evolved rapidly during the Chesterian Series developing vastly different morphologies from the time the Menard Limestone was deposited to the time when the Kinkaid Formation was deposited. This study suggests a functional shift over time, with the wing plates of the Menard Limestone acting as rudders to orient the calyx to either assist in feeding or reduce stress on the calyx, and the wing plates of the Kinkaid Formation acting as an antipredatory defense mechanism. This study presents new conclusions and new questions regarding the wing plates of Pterotocrinus.

The preferential grazing of an organism on certain particles from the environment (selective feeding) impacts particle compositions and distributions in aquatic systems. Historically, selective feeding has been examined almost exclusively through the lens of particle size. In this dissertation, I investigated size-based selection alongside particle shape, adhesive interactions, and the mechanical operation of the filter to characterize the selective-feeding capabilities of marine mucous-mesh filter-feeders (the planktonic appendicularian Oikopleura dioica and the benthic ascidians Herdmania momus and Styela plicata). I used high-speed videography to describe the feeding-filter mechanics of O. dioica and tested its capacity for size-based particle selection. I show for the first time how pulsatile flow coupled with elasticity of the filter facilitates prey detachment. Using synthetic beads, I showthat the food-concentrating filter selectively retains smaller particles because of their increased adhesion. Appendicularian houses may therefore retain particles size-selectively, which counters the historically-held assumption that appendicularians are non-selective grazers. I synthesized ellipsoidal microbeads to test the effect of particle length-to-width ratios on the capture efficiency of O. dioica and S. plicata. Both grazers retained ellipsoidal particles according to their minimum diameter. I identified the kinematic mechanism for retention patterns of ellipsoidal particles using high-speed videography and endoscopy of particle interactions with the mucous filters of O. dioica and H. momus, respectively. In the filters of both animals, ellipsoids oriented parallel to fluid streamlines and the minimum dimension of the particle intercepted the filters. I provide the first mesh-scale observations of particle capture by H. momus, show how particle shape influences hydrosol filtration by S. plicata, and suggest that ascidian filtration may not be adequately described by simple sieving.

Gorgonocephalus eucnemis, Ophiothrix suensonii and Ophiothrix spiculata are aerobic Echinoderms. Previous observations on the anatomy of these two genera state five pairs of radial shields and genital plates are responsible for regulating the position of the roof of the body disc and the flushing of water in and out of the bursae. Rates of bursal ventilation increase by an average 60-64% when the ophiuroid is exposed to an increase in food or a decrease in dissolved oxygen in Gorgonocephalus. When exposed to hypoxic oxygen concentrations O. suensonii and O. spiculata increased bursal-ventilation rates by (means of) 35% and 28%. Measurements of DO from inside and outside the bursae show that DO is being absorbed during bursal-ventilations. These findings suggest bursal ventilation is a means of respiration and increased rates of bursal-ventilation may help meet increased oxygen demands during feeding and some periods of hypoxia. This dissertation includes unpublished, co-authored material.

<p>Functional morphology analyzes the relationships between form and function in organisms. However, a comprehensive analysis of any organic structure requires an integrated approach to morphology. For this purpose constructional morphology was developed, where function, phylogeny and construction together explain form. This thesis investigates functional and constructional aspects of gastropods and bivalves; two groups of molluscs which are among the most common shell-bearing invertebrates. Their shell protects the soft parts and different morphologic specializations enhance this function. Morphology and mode of life are often closely coupled. </p><p>Comparison of the distantly related cardiid bivalves <i>Cardium</i> <i>costatum</i> and <i>Budmania</i> spp. reveals similar shell modifications. Both have prominent keels functional in anchoring the shell within the sediment. The straight keels in <i>C. costatum</i> indicate an additional strengthening function, whereas the keels in <i>Budmania</i> spp. often are deformed and do not. Other shell modifications include secondary resorption of shell material and hollow keel interiors, reducing shell weight. These similarities are explained by parallel evolution and a common cardiid <i>Bauplan</i>.</p><p>Morphological shell characters in cerithiform gastropods have evolved independently in different taxonomic groups and multiple times within the same group. Shell characters are adaptive within five functional areas: defence from shell-peeling predators, burrowing and infaunal life, clamping, stabilization, and righting of the shell. Most characters are made feasible by determinate growth and a count-down programme.</p><p>In most environments predators that crush, peel and bore shells are present. As bivalves and gastropods grow by marginal accretion, and are able to replace lost shell material, traces of unsuccessful predation are preserved as scars. Experiments on the snail <i>Nucella lamellosa</i> show that repaired shells are just as strong as shells without damage. However, new scars follow old scar lines in 43% of tested specimens. This might be due to a higher organic content in this area.</p>

Functional morphology analyzes the relationships between form and function in organisms. However, a comprehensive analysis of any organic structure requires an integrated approach to morphology. For this purpose constructional morphology was developed, where function, phylogeny and construction together explain form. This thesis investigates functional and constructional aspects of gastropods and bivalves; two groups of molluscs which are among the most common shell-bearing invertebrates. Their shell protects the soft parts and different morphologic specializations enhance this function. Morphology and mode of life are often closely coupled. Comparison of the distantly related cardiid bivalves Cardium costatum and Budmania spp. reveals similar shell modifications. Both have prominent keels functional in anchoring the shell within the sediment. The straight keels in C. costatum indicate an additional strengthening function, whereas the keels in Budmania spp. often are deformed and do not. Other shell modifications include secondary resorption of shell material and hollow keel interiors, reducing shell weight. These similarities are explained by parallel evolution and a common cardiid Bauplan. Morphological shell characters in cerithiform gastropods have evolved independently in different taxonomic groups and multiple times within the same group. Shell characters are adaptive within five functional areas: defence from shell-peeling predators, burrowing and infaunal life, clamping, stabilization, and righting of the shell. Most characters are made feasible by determinate growth and a count-down programme. In most environments predators that crush, peel and bore shells are present. As bivalves and gastropods grow by marginal accretion, and are able to replace lost shell material, traces of unsuccessful predation are preserved as scars. Experiments on the snail Nucella lamellosa show that repaired shells are just as strong as shells without damage. However, new scars follow old scar lines in 43% of tested specimens. This might be due to a higher organic content in this area.

All living hominoids are characterized by taillessness and adaptations to orthograde (upright) trunk posture. Accordingly, these features have importance for our understanding of ape origins, evolutionary relationships and positional behaviors. Despite extensive study of the hominoid postcranial skeleton, researchers continue to face difficulty identifying taillessness and orthogrady from fossil material. In part, difficulties persist because although the Miocene fossil record indicates that the evolution of tail loss and orthogrady was decoupled, previous research has focused primarily on how the skeletal anatomy of extinct apes resembles that of living apes, in which these traits appear in conjunction. The remarkable diversity in tail lengths and positional behaviors exhibited by other mammals presents a valuable opportunity to employ the strength of the comparative method for testing functional hypotheses. The goal of this dissertation is to identify anatomical correlates of tail length and positional behaviors from sacral and caudal vertebral morphology among primates and other mammals in three studies. The first study examines the relationship between trabecular structure in the first sacral vertebra and positional behaviors (N= 78 primates). The second study quantifies aspects of internal (N=78 primates) and external (N= 472 mammals) sacral anatomy for correlates of relative tail length. The third study evaluates the functional morphology of caudal vertebrae among nonprehensile-tailed primates and other mammals that vary in relative tail length, offering additional insight into the anatomy associated with tail loss (N=333). The relationship between trabecular structure in the proximal sacrum and positional behaviors among living primates is somewhat unclear. Some trabecular parameters in the distal sacrum appear to have a relationship with tail length. Results support the functional links between previously and newly defined metrics from the external morphology of sacra and caudal vertebrae, and relative tail length, among primates and other mammals. Identified anatomical correlates from the extant primate sample are used to reconstruct the tail lengths of extinct primates. From the sacral data, Proconsul is reconstructed as tailless, Archaeolemur likely possessed a long tail, and Palaeopropithecus, Megaladapis and Epipliopithecus had short tails. From the caudal vertebrae data, Archaeolemur is reconstructed as possessing a long tail and Palaeopropithecus is reconstructed as having a short tail. / text

xvi, 169 p. ： ill. (some col.) / This dissertation describes the postcranial functional morphology of Theropithecus brumpti , a fossil cercopithecoid primate from the Plio-Pleistocene of East Africa. Theropithecus is often used as an analogue for human evolution, but much of our understanding of its paleobiology is based on the grassland adapted Theropithecus oswaldi , masking potential morphological and ecological breadth within the genus and limiting its use as an ecological comparator. To better understand the evolutionary history and ecological breadth of the genus, an analysis of the woodland associated T. brumpti is presented. All available T. brumpti postcranial material is included, along with comparative data on T. oswaldi and a large extant sample. Skeletal elements were metrically described using 125 postcranial measurements believed to have functional relevance. Measurements were transformed into 46 ratios to reflect shape and the functional lengths over which muscles act and to reduce the effects of differences in scale among individuals and species. Contrary to previous findings, there is no evidence T. brumpti was arboreal; rather it is clearly a terrestrial papionin. While T. brumpti retains a degree of flexibility (at the shoulder, elbow, hip, knee and ankle), this is not exceptional when compared to other members of the genus, notablyT. oswaldi . Not only are traits similar in both species, but there is a wide range of variation and overlap in both. Features historically used to reconstructT. brumpti as more arboreal are interpreted here as part of a suite of traits that characterize early Theropithecus . This suite of traits may instead be adaptations to manual terrestrial foraging, in particular adaptations related to forest floor locomotion and gleaning, which may be primitive for Theropithecus and possibly for papionins. This interpretation of the paleobiology of T. burmpti compared to that of T. oswaldi offers a parallel with hominins. New fossil evidence suggests use of terrestrial substrates in more woodland habitats for late Miocene to early Pliocene hominins, in contrast to more open habitats associated with later hominins. Therefore, this dissertation develops a framework for understanding the woodland to grassland transition among large bodied primates including hominins. / Committee in charge: Stephen Frost， Chairperson； Frances White， Member； John Lukacs， Member； Samantha Hopkins， Outside Member