In many applications of population genetics, particularly in the field of conservation biology, estimates of molecular diversity are used as surrogate indicators of less easily acquired measures of ...genetic variation for quantitative traits. The general validity of this approach to inferring levels of quantitative genetic variation within populations is called into question by the demonstration that estimates of molecular and quantitative-genetic variation are essentially uncorrelated in natural populations of Daphnia, one of the few organisms for which multiple estimates of both quantities are available. On the other hand, molecular measures of population subdivision seem to give conservatively low estimates of the degree of genetic subdivision at the level of quantitative traits. This suggests that although molecular markers provide little information on the level of genetic variation for quantitative traits within populations, they may be valid indicators of population subdivision for such characters.PUBLICATION ABSTRACT
Thesis (Ph.D.)--Utah State University, 2010.
Title from title screen (viewed June 10, 2010). Department: Biology. Includes vita. Includes bibliographical references. Archival copy available in print.
Abstract Background Introduced species can have profound effects on native species, communities, and ecosystems, and have caused extinctions or declines in native species globally. We examined the ...evolutionary response of native zooplankton populations to the introduction of non-native salmonids in alpine lakes in the Sierra Nevada of California, USA. We compared morphological and life-history traits in populations of Daphnia with a known history of introduced salmonids and populations that have no history of salmonid introductions. Results Our results show that Daphnia populations co-existing with fish have undergone rapid adaptive reductions in body size and in the timing of reproduction. Size-related traits decreased by up to 13 percent in response to introduced fish. Rates of evolutionary change are as high as 4,238 darwins (0.036 haldanes). Conclusion Species introductions into aquatic habitats can dramatically alter the selective environment of native species leading to a rapid evolutionary response. Knowledge of the rates and limits of adaptation is an important component of understanding the long-term effects of alterations in the species composition of communities. We discuss the evolutionary consequences of species introductions and compare the rate of evolution observed in the Sierra Nevada Daphnia to published estimates of evolutionary change in ecological timescales.
The hierarchy of biological organization, from molecules to ecosystems, describes the relationships among various biological systems. Of particular interest is assessing how the factors that ...primarily determine the nature of one hierarchical level also have transcendent qualities that affect the ecology and evolution of higher hierarchical levels. The goal of this dissertation was to use a bottom-up approach to examine the transcendent effects of two factors that strongly determine the nature of their associated level of biological organization. The first, phenotypic plasticity, is a primary factor that determines the phenotype of an individual. The second factor, genetic diversity, largely determines the phenotypic distributions associated with populations. Controlled laboratory experiments on taxa from a freshwater tri-trophic food web were employed to examine the transcendent effects of phenotypic plasticity and genetic diversity on the biological hierarchy because relationships between individuals and populations from different trophic levels are well documented for numerous freshwater species. The results show that phenotypic plasticity can induce changes in population means and variances that promote population persistence and evolvability, and that plasticity provides a mechanistic explanation of community stability in response to changing environments. Similarly, genetic diversity may act as a signal that induces phenotypic plasticity in individuals, modulates community richness and ecosystem properties, and suggests a potential mechanism for the changes in biodiversity. Thus, results from this dissertation show that plasticity and genetic variation can shape the attributes of other biological groups higher in the biological hierarchy, and, in some cases, may also provide a mechanistic explanation for variability observed in higher levels of the biological hierarchy. These results highlight the importance of integrating traditionally disparate biological disciplines and may help to unify biology as a field.
Purpose
Palmar-plantar erythrodysesthesia (PPE) is a common chemotherapy and anti-VEGF multi-kinase inhibitor class-related toxicity that often results in debilitating skin changes and often limits ...the use of active anti-cancer regimens. Mechanistic and anecdotal clinical evidence suggested that topical application of sildenafil cream may help reduce the severity of PPE. Therefore, we conducted a randomized, double-blind, placebo-controlled pilot study to evaluate the feasibility, safety and efficacy of topical sildenafil cream for the treatment of PPE.
Methods
Eligible subjects were required to have grade 1–3 PPE associated with either capecitabine or sunitinib. Subjects were randomized to receive 1 % topical sildenafil cream to the left extremities or right extremities and placebo cream on the opposite extremity. Two times per day, 0.5 mL of cream was applied to each affected hand/foot. The primary endpoint was improvement in PPE grading at any point on study. Clinical assessments were evaluated by NCI-CTC 4.0 grading and patient self-reported pain.
Results
Ten subjects were enrolled, nine were evaluable for safety and efficacy. Five of nine subjects reported some improvement in foot pain and three of eight subjects for hand pain improvement. One of these subjects noted specific improvement in tactile function. No treatment-related toxicities were observed.
Conclusions
In this limited, single-center study, topical cream containing 1 % sildenafil is feasible to administer, is well-tolerated, and may mitigate PPE-related symptoms due to anti-cancer therapeutic agents. Further validation is necessary.
PDF
