M.A. dissertation, University of Hong Kong, 1974. / Typescript.

Thesis--M. Phil., University of Hong Kong, 1987.

No description available.

Abstract Lion populations in West and Central Africa are small and fragmented. In areas where park management is weak, threats will likely facilitate the extinction of the lion. Wildlife management requires knowledge of the population estimate. The population of lions in Waza National Park (Waza NP) was assessed by individual identification of members in the population. The population was assessed to comprise of 14–21 adult individual lions. The age structure was skewed towards adults; cubs comprised 22% of all lions identified while the sex ratio was 1 : 3. Two out of four collared lions were lost to illegal, retaliatory killings within 1 year; and probably two more males and one more female were also killed during this period. The lion population appears to have declined during the last 5 years with six lions dying per year, which is at a much higher rate than observed in the previous decades. Human-livestock pressure has increased tremendously in this period, resulting to frequent human-lion conflicts. To ensure the survival of the lion in Waza NP and in the entire region, management needs to intensify efforts to mitigate the pressure from humans and their livestock.

The serpentine endemic, Mimulus nudatus, lives sympatrically on the serpentine soils of Lake County, California, with its probable progenitor, the bodenvag species M. guttatus. This thesis examined the mechanisms which enable M nudatus and M guttatus to coexist in sympatry. In addition, it sought to determine the genetic basis of the postzygotic reproductive isolating barrier between M nudatus and M guttatus, in order to distinguish between the classical allopatric and the ecotypic models of speciation. The postzygotic barrier achieving reproductive isolation between the species was at the seed provisioning stage and was strong for both local and distant populations of M guttatus. In addition, there was some evidence for premating pollinator isolation, since honey bees preferentially visited M guttatus and Dialictus preferred M. nudatus. In spite of the majority of pollinator visits being intra-specific, M nudatus still suffered a reduction in fertility caused by interspecific crossing, although M guttatus experienced no such reduction. To avoid M nudatus being outcompeted into extinction, the two species must thus be sufficiently ecologically different. In the field and in the greenhouse, whilst M guttatus experienced a reduction in fitness as calcium levels decreased, the fitness of M nudatus was independent of calcium levels. Therefore one hypothesis suggested for the ecological differentiation of the two species, was that M nudatus had evolved greater tolerance to calcium deficient soils. The genetic basis of the postzygotic reproductive isolating barrier between M nudatus and M guttatus was investigated by using crosses to a third species, M cupriphilus, which was used since it gave fertile hybrids with both species. It was not possible to determine the genetic basis of the postzygotic reproductive isolating barrier between M nudatus and M guttatus since the results in the crossing program were contradictory. Some results supported the simple two gene complementary interaction system previously found for populations of M guttatus, but others did not. Hence no distinction could be made between the allopatric and ecotypic models of speciation.

published_or_final_version / Comparative Asian Studies / Master / Master of Arts

published_or_final_version / Statistics and Actuarial Science / Master / Master of Philosophy

No description available.

The concept of inclusive fitness plays a key role in much of sociobiology. Yet most theoretical studies concerning the evolution of social behavior circumvent inclusive fitness by mobilizing the concept of frequency dependent individual fitness. Given certain assumptions, it is shown that models based on these two different concepts are dynamically equivalent. The models do differ, however, in bookkeeping methods which are advantageous under different circumstances. A knowledge of these circumstances should prove of value to students of social behavior. It is then shown that evolution acts according to an adaptive landscape based on Hamilton's inclusive fitness in the absence of strong selection and inbreeding. This yields an inclusive fitness analogue to much of traditional population genetics. For example, heterozygote superiority in inclusive fitness yields stable polymorphisms, while intermediate dominance results in fixation of one of the alleles. When individuals do not affect one another's fitnesses, the inclusive fitness topography collapses to one based on individual fitness. A general rule for the evolution of social behavior under intermediate dominance is shown to yield Hamilton's Rule as a special case. Next, a general model for examining the evolution of social behavior is developed which, unlike inclusive fitness models, does not require that benefits received be linear functions of the number of social donors encountered. The subsocial route for the evolution of eusociality in haplodiploid organisms is then examined within the context of this model. Nonlinearities render conditions for frequency independent fixation or loss of sister-helping alleles more stringent than expected from models based on the assumption of linear benefits. In particular, both stable polymorphisms and frequency dependent selective thresholds for sister-helping behavior may commonly obtain.

Using standard procedures of demographic methodology, analysts working with mortality data are faced with a choice between large, unwieldy arrays of age-specific rates (or equivalent sets of life table entries), or one or more of a summary measures set, such as life expectancies and standardized rates, which does not retain all of the available information. This dissertation describes the development and preliminary testing of a mathematical model derived from elementary considerations of mortality mechanisms in the life table population. The model as developed postulates a Gompertz specification to account for mortality rates increasing with age among adults. Also, a proportion of the population was posited to be subject to a competing constant risk, to account for the declining mortality rates in early childhood. The motivation for this model is that its parameters, estimated for particular populations via nonlinear regression procedures, might be used as more efficient mortality summaries than those routinely used, without loss of conceptual interpretability. In testing life tables for male and female populations of 47 selected nations during the 1960s, the model was shown to be substantially more efficient for reproducing the original life tables than were any of the traditional measures considered.