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Diversification Process (diversification + process)
Selected AbstractsDiversification of rural livelihood strategies and its effect on local landscape restoration in the semiarid hilly area of the Loess Plateau, ChinaLAND DEGRADATION AND DEVELOPMENT, Issue 5 2010L. Wang Abstract This study is about the diversification of livelihood strategies and the interaction of farmers' livelihood with landscape change in Zhongzhuang small watershed, Pengyang County in Ningxia Autonomous region located in the Loess Plateau, western China. Farmers' livelihoods and landscape patterns during 1978,2007 in Zhongzhuang were analysed. In different stages, diverse limiting factors were discovered behind the diversification process of livelihood strategies. Before 1978, ,planned economy', ,production team organization', strict ,household registration system' and the scarcity of livelihood assets were the main factors restricting the diversification of livelihood strategies. From 1978 to 1993, the reform and open policy provided opportunities for local people to diversify their livelihood strategies, but livelihood strategies based on crop production still took an important role in their life. From 2000 to 2007, national policies brought assistance to help local farmers diversify their agricultural activities. However, the insufficient and incomplete credit and insurance market and lack of skill were the main factors constraining non-farm activity diversification. Meanwhile, through analysis of the links between livelihood strategies diversification and landscape pattern change, we found that diversification of farmers' livelihoods contributed to the recovery of the landscape. Finally, using this relationship, steps for future landscape restoration is proposed, which provide a new view of landscape restoration research in the Loess Plateau. Copyright © 2010 John Wiley & Sons, Ltd. [source] Commodity trading advisors' leverage and reported margin-to-equity ratiosTHE JOURNAL OF FUTURES MARKETS, Issue 10 2003Fernando Diz We investigate the effect of leverage on Commodity Trading Advisors' (CTAs) performance measurement. We find that leverage has important effects on the cross section of CTA returns, volatility, and survival experience. On average, a 100-basis points increase in leverage is associated with a 27-basis points increase in returns. After performance is adjusted for leverage, volatility, and survival experience, CTAs' style variables have no significant effect on performance. The amount of leverage used by a CTA is found to reduce the likelihood of survival. However, the total effect of leverage on survival is much smaller than its partial effect. Contrary to common beliefs, we find that CTA diversification leads to higher levels of leverage and volatility. This apparent contradiction is related to how the diversification process affects the use of leverage. The findings in this study have implications for measuring and comparing managers' performance track records. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:1003,1017, 2003 [source] Evolutionary and ecological implications of genome size in the North American endemic sagebrushes and allies (Artemisia, Asteraceae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2008S̉NIA GARCIA The genome size of 51 populations of 20 species of the North American endemic sagebrushes (subgenus Tridentatae), related species, and some hybrid taxa were assessed by flow cytometry, and were analysed in a phylogenetic framework. Results were similar for most Tridentatae species, with the exception of three taxonomically conflictive species: Artemisia bigelovii Gray, Artemisia pygmaea Gray, and Artemisia rigida Gray. Genome size homogeneity (together with the high morphological, chemical, and karyological affinities, as well as low DNA sequence divergence) could support a recent diversification process in this geographically restricted group, thought to be built upon a reticulate evolutionary framework. The Tridentatae and the other North American endemic Artemisia show a significantly higher genome size compared with the other subgenera. Our comparative analyses including genome size results, together with different kinds of ecological and morphological traits, suggest an evolutionary change in lifestyle strategy linked to genome expansion, in which junk or selfish DNA accumulation might be involved. Conversely, weed or invasive behaviour in Artemisia is coupled with lower genome sizes. Data for both homoploid and polyploid hybrids were also assessed. Genome sizes are close to the expected mean of parental species for homoploid hybrids, but are lower than expected in the allopolyploids, a phenomenon previously documented to be related with polyploidy. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 631,649. [source] Phylogeny and the modalities of acoustic diversification in extant Eneopterinae (Insecta, Orthoptera, Grylloidea, Eneopteridae)CLADISTICS, Issue 3 2004Tony Robillard Calling with a tegminal stridulatory apparatus is widespread in crickets. However, the evolution of cricket stridulums has been poorly studied and then only on the basis of prephylogenetic models, which are unable to account for the huge diversity recently documented for acoustic features in crickets. The present paper focuses on the evolution of acoustic devices in the subfamily Eneopterinae. This is the first attempt to reconstruct the phylogeny of a large and diverse cricket clade in order to analyze the evolution of emitting structures using precise homology statements. In the first step, we reconstruct the phylogeny of this clade using a morphological data set of 193 characters and 45 taxa. The resultant phylogeny supports the monophyly of the subfamily and that of the 13 genera represented by at least two species in our taxonomic sample. Phylogenetic relationships within the subfamily also support the definition of five tribes: Eurepini, Eneopterini, Nisitrini, Xenogryllini and Lebinthini. In the second step, the evolution of acoustic devices is studied by optimization of venation characters defined on precise homology statements. As hypothesized by previous authors, losses of acoustic communication occur independently in the course of eneopterine evolution; however, they happen abruptly with no intermediate state. Our results also document for the first time the modalities of forewing evolution: the diversification of male forewing venation originates from two processes, a continuous and regular modification process, responsible for slight venation change; and an irregular, more intense punctuated process, allowing the emergence of different venations. This diversification process with sudden changes could be related to the occurrence of acoustic novelties in advertisement calls. [source] Parasitoid fig-wasp evolutionary diversification and variation in ecological opportunityMOLECULAR ECOLOGY, Issue 7 2010M. J. MCLEISH Abstract Ecological processes are manifest in the evolution and form of phenotype diversity. The great abundance of parasitoid species has led to speculation whether rates of speciation and extinction are dependent on parasitoid diversity. If these factors are mutually exclusive, species diversity should fluctuate instead of remaining relatively constant over time. It is not known whether radiations constrained by coevolutionary interactions conform to density-dependent diversification processes. Here we test the prediction that parasitoid fig wasp diversification responds to changes in ecological opportunity and density-independent processes. A phylogenetic approach is used to estimate relative divergence times and infer diversification rate changes using ,-statistics. Monte Carlo constant rates tests that accommodate incomplete sampling could not reject constant rates diversification. Parasitoid fig wasp diversification is consistent with a more complex explanation than density-dependent cladogenesis. The results suggest contemporary African parasitoid fig wasp diversity remains a legacy of an ancient ecological opportunity facilitated by fig tree diversification following the breakup of Pan-African forests and evolution of the savanna biome over the last 55 Ma and the more recent aridification of the African continent in the last 5 Ma. These results imply that amplified phenotypic differentiation of specialist insects coevolving with plants is coupled to evolutionarily infrequent changes in ecological opportunity. [source] Gene duplications and the time thereafter , examples from plant secondary metabolismPLANT BIOLOGY, Issue 4 2010D. Ober Abstract Gene duplications are regarded as one of the central mechanisms for the origin of new genes. Recent studies in plant secondary metabolism have provided several examples of genes that originated by duplication with successive diversification. In this review, the mechanisms of gene duplication are explained and several models discussed that suggest the way that gene duplicates develop into genes with new functions. Signatures of gene duplication and diversification processes are discussed using the biosynthesis of benzoxazinones and of pyrrolizidine alkaloids as examples. [source] | ||||||||||