The hypothesis that emigration of individuals in excess of resource carrying capacity acts as a population regulatory mechanism was tested experimentally using the desert pupfish (Cyprinodon macularius). When emigration was prevented, four pupfish populations monitored from May 1982 to March 1984 were unable to regulate numbers to resources. Numbers increased to a mean peak size 1.4 times greater than four pools open to emigration, followed by high mortality, a decline in body condition, reduced recruitment, and stunting. The pattern of overpopulation was similar to that observed in fenced populations of rodents. In contrast, pupfish in open pools had lower numbers, higher recruitment, better condition and growth, and higher total production. Emigration patterns were similar in all four open pools. Population size, rate of increase, and temperature affected emigration rates. Nearly twice as many males than females emigrated. Emigrant pupfish usually had poorer condition factors than residents. Pupfish showed a rapid and uniform increase in emigration when resources were reduced. Nearly one-half (42.2 and 41.8%) of pupfish populations emigrated from two open pools wherein resources were suddenly reduced by 50%. Many fewer fish emigrated from undisturbed control pools (15.2 and 16.0%). The results suggest that residency-emigratory behavior of pupfish can reliably and precisely effect changes in numbers to be in consonance with resources. They support emigration as sufficient to regulate pupfish numbers to resources in open systems without the need for other factors or mechanisms.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 4, 2008) Vita. Includes bibliographical references.

Cyprinodon variegatus is a pupfish that inhabits the Atlantic coast of North America, nearly continuously, from Massachusetts to Belize. This research attempts to resolve the phlylogeography of C. variegatus by investigating the genetic sequence structure of the mitochondrial control region (D-loop, non-coding origin of replication) and cytochrome-b gene for evidence of northern and southern subspecies within the Atlantic Coast of the eastern United States. Additionally, it will be may be possible to determine if secondary hybrid zones developed as a result of the last retreat of ice from North America during the Pleistocene, about 17,000 years ago. A definitive monophyletic northern clade was found using parsimony, distance, and maximum likelihood phylogenetic methods to analyze the control region data. The cytochrome-b sequence data supported this monophyletic northern clade, although their utility for this analysis is marginal. Little evidence was found for the existence of a hybrid zone. More thorough sampling will be needed to make more accurate determinations regarding the existence of such a zone. / Master of Science

Varying numbers of adult desert pupfish (Cyprinodon macularius) and mosquitofish (Gambusia affinis) were introduced separately into experimental habitats open to egress to determine resource requirements for each species and the relation between numbers and resources. Laboratory environments in which "voluntary" colonization was achieved, were created for both species. Results indicated that both species have the innate ability to regulate numbers in their respective populations to available resources via emigration. The number of resident fish varied directly with experimental reductions of cover. When adult mosquitofish were introduced into open tanks with established populations of adult desert pupfish in habitats containing constant resources, there was no significant change in population size for either species as compared to single species populations over a 5-day period. Adult desert pupfish and mosquitofish are able to coexist successfully in habitats open to egress for 5 days because they utilize available resources in very different ways and the number of fish that become residents do not go beyond resource limits. These data suggest that replacement of desert pupfish by mosquitofish in the American Southwest is a phenomenon that is the result of more long-term interactions between all life stages of the species and may be more likely to occur in environments of low complexity and closed to egress.

Drastic alterations to the North American Southwest’s hydrology have highly influenced resident fish communities. In New Mexico and Texas, the Pecos River has been severely altered as a result of water manipulation, isolating backwaters and various habitats that were once connected to the main river. Cyprinodon pecosensis (Pecos pupfish) has been highly impacted due to the effects of anthropogenic water manipulation, as well as species introductions. Cyprinodon pecosensis populations have become isolated and scattered, residing in sinkholes, remnant lakes, and static backwaters, thus creating numerous micropopulations. The purpose of this study was to assess the morphological variation in cranial features that occur in response to varied habitats, especially in terms of environmental factors and species co-occurrence. Landmark-based geometric morphometrics was used to assess shape variation across the aforementioned micropopulations comprising four general habitat types and 27 different localities, each with varied community structure and salinity. Results from this study suggest that head and mandible morphology vary temporally, with year to year variation, as well as among different localities. The head morphology of C. pecosensis was most heavily influenced by habitat type and localities within habitat types, but was largely canalized with the exception of localities classified as deep sinkholes. Year to year variation and localities among habitat types were the most influential factors associated with mandible morphology, but there was strong overlap among the convex hulls that defined regions of morphospace for habitat types. As C. pecosensis is a threatened species, this research has important implications for future conservation and management. Additionally, these results could further aid in the understanding of preserving species in fragmented landscapes.

No description available.

<p dir="ltr">In a rapidly changing world, human actions and natural events are reshaping ecosystems and presenting new challenges for conservation efforts. Within this context, unraveling the recent ecosystem transformations and their implications on a fine scale is required. The impacts of such changes are not always sudden but often gradual and sometimes as a result of historical events. With the recent advancement in technologies, the resolution of information by genome sequences spans from millions of years ago (hindcasting) to future generations (forecasting). Aquatic ecosystems pose their own challenges when it comes to ecosystem changes and the types of data required to assess impact and help inform conservation efforts. My dissertation comprises three chapters focused on using genomic techniques to generate data valuable for the conservation and management of aquatic ecosystems. Each of the three chapters is a distinct manuscript in terms of scientific publications, where Chapter 1 has already been published, Chapter 2 has been submitted to a journal, revised, and is now awaiting publication, and Chapter 3 is in preparation for submission to a peer-reviewed journal. In Chapter 1, dietary DNA from harvested North American river otter (<i>Lontra canadensis</i>)<i> </i>was used to determine whether metabarcoding of stomach content could be used to identify fish prey species consumed. In Chapter 2, DNA sequencing of endangered pupfish species in the Tularosa Basin of New Mexico was studied; before my work, it was nominally comprised of a single species, the White Sands pupfish (<i>Cyprinodon tularosa</i>). The results indicate a rapid speciation event occurred within about the last ~5000 years, driven primarily by genetic drift. Chapter 3 extends Chapter 2 by assessing the dynamics of genomic diversity over space and time while evaluating the short-term evolutionary dynamics (~18 generations) of the two native pupfish populations. This temporal study aimed to determine if the extraordinarily rapid evolution over the last ~5000 years (observed in Chapter 2) could be detected over timescales more relevant to conservation and management efforts. Overall, this dissertation used genomic sequence data from metabarcoding of the COI gene region in the otter stomach content as well as pool sequencing and whole genome resequencing of pupfish to provide key biological insights into the conservation of these aquatic species. This dissertation also provides insights into avenues for further study and highlights the significant role that conservation genomics can play in the future. The findings presented in the three chapters are discussed within the context of species’ conservation and management.</p>