The giant panda (Ailuropoda melanoleuca) subsists on bamboo, but lacks gastrointestinal modifications for fiber digestion. Pandas display dietary selectivity for certain plant parts; however, cues for selection are unknown, and few have examined panda feeding behavior and bamboo nutrient composition simultaneously. Bamboos are clonal plants, with seasonal cycles of nutrient accumulation related to peak photosynthesis and recruitment. These cycles can be destabilized by aboveground disturbance; however, effects of disturbance on nutritional quality and sustainability of bamboo for primary consumers have not been studied. I examined 4 factors that may contribute to bamboo nutritional quality or sustainable harvest: season, ramet maturity and age, and disturbance. I conducted a 3-year study with Phyllostachys aureosulcata (PLLAU), P. glauca (PLLGL), and P. rubromarginata (PLLRU), at the Shelby County AgriCenter, Memphis TN, applying 3 disturbance treatments in a replicated split-plot design: control, 3% and 20% annual removal of biomass. Bamboo was sampled 8 times/year and divided into shoot, leaf, and culm (central stem) for analysis of crude protein (CP), neutral- and acid-detergent fiber (NDF and ADF), ash, lipid, minerals, and acid-insoluble ash (AIA). I quantified bamboo-stand production, maturity, recruitment and mortality. Biomass removed from PLLAU was used in diet-selection trials with 2 giant pandas, observing consumption of plant parts and bamboo from different disturbance treatments, and sampling bamboo for allelochemical and starch analysis. Disturbance effects were evident only for branch and culm dry mass in PLLRU. In Year 2, drought conditions and peak roosting blackbird populations confounded results. Defoliation and guano deposition preceded changes to soil chemistry, bamboo composition, and stand structure; recruitment increased for PLLRU. After accounting for confounding factors, less-mature bamboo had greater concentrations of most nutrients, but less NDF, ADF, and K. Two-year-old ramets had greater CP, NDF, lipid, P, K, S, and Cu, but less Ca and Fe, than 1-year-old ramets. I confirmed seasonal plant-part selection by pandas, but found no correlation between leaf consumption and AIA concentration. Culm starch analyses were insufficient to establish a clear pattern. I recommend further investigation of non-structural carbohydrates in bamboo, and palatability testing of undisturbed versus disturbed bamboo, which I was unable to examine.

Background: Clonal competition in cancer describes the process in which the progeny of a cell clone supersedes or succumbs to other competing clones due to differences in their functional characteristics, mostly based on subsequently acquired mutations. Even though the patterns of those mutations are well explored in many tumors, the dynamical process of clonal selection is underexposed. Methods: We studied the dynamics of clonal competition in a BcrAbl-induced leukemia using a γ-retroviral vector library encoding the oncogene in conjunction with genetic barcodes. To this end, we studied the growth dynamics of transduced cells on the clonal level both in vitro and in vivo in transplanted mice. Results: While we detected moderate changes in clonal abundancies in vitro, we observed monoclonal leukemias in 6/30 mice after transplantation, which intriguingly were caused by only two different BcrAbl clones. To analyze the success of these clones, we applied a mathematical model of hematopoietic tissue maintenance, which indicated that a differential engraftment capacity of these two dominant clones provides a possible explanation of our observations. These findings were further supported by additional transplantation experiments and increased BcrAbl transcript levels in both clones. Conclusion: Our findings show that clonal competition is not an absolute process based on mutations, but highly dependent on selection mechanisms in a given environmental context.

Background: Clonal competition in cancer describes the process in which the progeny of a cell clone supersedes or succumbs to other competing clones due to differences in their functional characteristics, mostly based on subsequently acquired mutations. Even though the patterns of those mutations are well explored in many tumors, the dynamical process of clonal selection is underexposed. Methods: We studied the dynamics of clonal competition in a BcrAbl-induced leukemia using a γ-retroviral vector library encoding the oncogene in conjunction with genetic barcodes. To this end, we studied the growth dynamics of transduced cells on the clonal level both in vitro and in vivo in transplanted mice. Results: While we detected moderate changes in clonal abundancies in vitro, we observed monoclonal leukemias in 6/30 mice after transplantation, which intriguingly were caused by only two different BcrAbl clones. To analyze the success of these clones, we applied a mathematical model of hematopoietic tissue maintenance, which indicated that a differential engraftment capacity of these two dominant clones provides a possible explanation of our observations. These findings were further supported by additional transplantation experiments and increased BcrAbl transcript levels in both clones. Conclusion: Our findings show that clonal competition is not an absolute process based on mutations, but highly dependent on selection mechanisms in a given environmental context.