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- 2.3.4 GENETIC DIVERSITY
Source: Shrestha and Joshi 1996 Altogether, 27 mammal species are listed as threatened by IUCN: eight as Endangered, ten as Vulnerable, four as Indeterminate, and five as Insufficiently Known. Additionally, 22 bird species, nine reptile species (one Endangered, two Vulnerable, one Rare, four Indeterminate and one Insufficiently Known), and two insect species are listed under IUCN’s Red List (1995) (Table 2.28). Nine species of birds are regarded as threatened in Nepal. One rodent species, the Himalayan field mouse (Apodemus gurkha), which is found in central Nepal between 2,200-3,600m, is endemic to Nepal. Two species of mammals, the pigmy hog (Sus salvanius) and the Indian Chevrotain (Moschiola meminna), have probably become extinct in Nepal (IUCN-Nepal 1995a). Table 2.28 Nepal’s Threatened Animals in the IUCN Red List, 1994
Source: IUCN-Nepal 1995a. Endangered Wildlife - Nepal’s threatened animals in the IUCN Red list 1994 A summary of all threatened plants and animals in Nepal is given below in Table 2.29. Table 2.29 Numbers of threatened plant and animal species in Nepal
Source: IUCN (1995 a, b); BPP (1995a, b, c, d, e, f, g, h, i) Endemic species Altogether, 342 plant species and 160 animal species have been reported as being endemic to Nepal (Table 2.30). Table 2.30 Endemic species in Nepal
(* Possible endemic taxa). Oberonia nepalensis is a recently reported endemic species of angiosperm (Shakya & Chaudhary 1999) Tomoptera maskeyi is an endemic amphibian species. 2.3.4 GENETIC DIVERSITYGenetic diversity is the basis of heritable variation within and between populations of organisms. Ultimately, this diversity resides in the variations in sequences of the four, nucleotide base pairs, which constitute the genetic code. Farmers have used genetic diversity for thousands of years in agriculture. Hundreds of plant and wild animal species have been domesticated and have been bred for desirable characteristics such as size, disease resistance, taste, and productivity. Modern breeders also take advantage of genetic diversity. For example, a few plants from one tiny population of wild rice provided the gene for resistance to the grassy stunt virus, and so the Asian hybrid rice crop whose genotype made it susceptible to disease has flourished (Glowka et al. 1994). Until recently, genetic diversity was only given consideration amongst domesticated species and populations held in zoos or botanical gardens (Raven 1992). However, because of habitat destruction and degradation, the number of plant and animal species is decreasing and their genetic diversity is threatened, and conservation of genetic diversity has become a major issue today. Molecular techniques and screening of genes is being applied for the preservation of wild species. Hence, knowledge of how much genetic variation exits within a species, how variation is partitioned between and within populations, and where the species has its centres of diversity is fundamental to applied conservation (Rowe & Cronk 1995). Genetic diversity can be identified by determining allozyme variation, the amount of DNA, and the structures and numbers of chromosomes of any cell of an organism (WCMC 1992). Allozyme variation is a common method of assessing genetic diversity. Allozymes that differ by one or a few amino acids have different overall electrical charges, which can be assessed using electrophoresis. Methods such as Restriction Fragment Length Polymorphism and DNA amplification using Polymerase Chain Reaction thermocycler are being applied to individual organisms to identify variations (Smith 1994; Gillings & Briscoe 1996). Knowledge of the genetic diversity of plants in Nepal is poor. The very few studies that have been done using modern techniques include analyses of the genetic diversity in rice using Rubisco (Ribulose biphosphate carboxylase/oxygenase), Restriction Fragment Length Polymorphism, DNA fingerprinting using Randon Amplified Polymorphic DNA, and DNA amplification using Polymerase Chain Reaction (PCR) (Shakya et al. 1993; Agrawal & Agrawal 1994). Kataloq: doc -> world world -> Total no of Botanic Gardens recorded in Hungary: 22 world -> Antigua and Barbuda’s First National Report world -> Total no of Botanic Gardens recorded in Tanzania: 4 world -> - world -> Total no of Botanic Gardens recorded in Belize: 2 world -> Programa de Nações Unidas para Desenvolvimento world -> Quatrieme rapport national sur la diversite biologique world -> Os Recursos Biológicos constituem potenciais fontes de rendimento com grandes benefícios para a população, se forem geridos de forma sustentável world -> Acknowledgements 5 Glossary 6 List of Tables 8 List of Figures 9 List of Boxes 10 Pakistan Fact Sheet 11 Executive Summary 12 world -> Total no of Botanic Gardens recorded in Sri Lanka: 6 Yüklə 1,16 Mb. Dostları ilə paylaş:
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