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EVOLUTION OF DOMESTIC PLANTS AND ANIMALS Wilson Nandolo | Timothy Gondwe Aim of this topic Aim of the topic To equip students with knowledge of evolution of genetic diversity and potential losses that occur Objectives of the topic By the end of the topic, you should be able to Describe origin of genetic diversity Describe the role of mutation, trade and migration in genetic diversity creation Describe the Darwin Theory of Natural Selection Describe the process of livestock domestication as component of genetic diversity Discuss causes of decline in numbers and diversity Diversity from wild Huge variety of animals and other species has arisen from earliest, primitive form of life Mutation has taken place on original genes due to reaction to different environment, leading to creation of new alleles ~ hence variation This chance variation has occurred in size, shape and functioning of animals, over the course of million years And the variation has allowed animals to adapt to particular environments or niches Mutation, therefore, lead to creation of new genetic variation Creation of new breeds with domestication and migration The process of domestication began some 12 14 thousand years ago Both the process and the domesticated stock produced by it have been carried by migrating humans to most remote regions of the earth In each region and local area, domestic populations adapted and evolved in response to a great range of selection pressures Creation of new breeds with domestication and migration In each case the primary factors contributing to the final population were complex and included founder affects migration mutation natural selection and selection by man Founder Group The genetic make-up of each and every breed or population is largely dependent upon the genetic make-up of its founder group This foundation group was in turn dependent upon the selection pressures it had previously encountered and upon the genetic make-up of its own founder group Thus, as tribes of people migrated across the globe they took samples of their own livestock with them to their new homes Founder Group In each location the people and their livestock would adapt through selection which is the survival of those individuals genetically suited, or able to adapt to the new environment A sample of this population would then be taken with the next human migration to be the founders of a new community in a slightly different situation. Spread of farming with domestication and human migration Source: FAO (2007): The SOW AnGR for Food and Agriculture, Rome, page 5 In-flow of genes The migration of people and livestock has not generally been in one continuous direction In most regions there has been fairly constant trade in livestock from one community to the next throughout human history When animals arose through mutation or trade that had better survival or production characteristics than those found in the local population more of their adapted progeny would survive and the enhanced characteristics would soon become common or even fixed within the group In-flow of genes and AnGR diversity Thus, other than geographically isolated situations, a gradual inflow of genes has modified every population that exists today Thousands of years of natural and human selection Genetic drift Inbreeding and crossbreeding Have Contributed to AnGR diversity And allowed livestock keeping to be practiced in variety of environments and production systems Natural selection ~ Darwin’s Theory Natural selection is the term used to describe all the environmental pressures acting on an individual which will result in it succeeding or failing to survive and to reproduce Only successful individuals will pass their genes onto the next generation Natural selection ~ Darwin’s Theory The principal aspects of natural selection are nutrient supply Climate parasites and predators and competition within the species Natural selection ~ Darwin’s Theory Darwin’s Theory of natural selection states that species can change over time And that their survival or success depends on how well they fit their environment Termed ‘survival of the fittest’ The key to this process is variation between individuals Which has developed over years And allowed individuals to adapt to particular environments or niches Natural selection ~ Darwin’s Theory Darwin’s work is usually linked to evolution and natural selection of wild animals But he also recognized changes in domestic animals brought about by artificial selection of early livestock breeders Domestication of animals Domesticated animals are considered to be those species that are bred in captivity and modified from their wild ancestors to make them more useful to humans who control their reproduction (breeding), care (shelter, protection against predators) And food supply Domestication is different from taming wild-borne animals Domestication includes the following steps initial association with free breeding confinement confinement with breeding in captivity selective breeding and breed improvement Domestication included transition from hunting and gathering to farming Causes of domestication During hunter – gathering periods, the following occurred Unpredictable climate Decline in big-game species Increased human occupation of available habitats These led to risks of unpredictable variation in food supply Domestication was a way to broaden human diets Discovery of domestication history Archaeologists and animal geneticists use various means to unravel the history of domestication including study of morphological changes to the teeth, cranium and skeleton and the construction of demographic age and sex curves which allow the identification of patterns indicative of domestication Livestock domestication process Very few animal species have been successfully domesticated among the world’s 148 non-carnivorous species weighing more than 45 kg only 15 have been domesticated only six have become widespread on all continents (cattle, sheep, goats, pigs, horses, and donkeys) while the remaining nine (dromedaries, Bactrian camels, llamas, alpacas, reindeer, water buffalo, yaks, Bali cattle, and mithun) are important in more limited areas of the globe Domestication was a complex and gradual process which altered the behavior and morphological characteristics of the ancestral animals Some localized domesticated species Livestock domestication process ~ Birds Only ten species (chickens, domestic ducks, Muscovy ducks, domestic geese, guinea fowl, ostriches, pigeons, quails, and turkeys) Are currently domesticated out of around 10 000 avian species Wild ancestors and relatives of livestock With the exception of the wild boar (Sus scrofa) The ancestors and wild relatives of major livestock species are either extinct or highly endangered As a result of hunting, changes to their habitats, and in the case of the wild red jungle fowl, intensive cross-breeding with the domestic counterpart This is unlike crop species that have their wild ancestors found at their centres of origin And hence, an important source of variation and adaptive traits for future breeding programs Essential elements for domestication to take place Important or essential characteristics for successful domestication include behavioral traits such as a lack of aggression towards humans a strong gregarious instinct Including “follow the leader” dominance hierarchies which allow the possibility of a human substitute as leader a tendency not to panic when disturbed Comparison between domesticated wild animals and their wild counterparts Source: Diamond J (2002). Nature/Vol 418. Major centres of livestock domestication Source: FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 10 Origin and domestication of livestock species (FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 7 - 8) Origin and domestication of livestock species (FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 7 - 8) Origin and domestication of livestock species (FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 7 - 8) Origin and domestication of livestock species (FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 7 - 8) Domestication took place at different time period Species domesticated Time frame (years ago) Purposes Dog 14000 Hunting and watchdogs Goats 10000 Sheep 8000 – 9000 Pigs 9000 Cattle 7000 – 9000 Chickens 5000 – 7000 Source: FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 11 - 14 Origin and migration of domestic cattle in Africa Source: FAO (2007): The SOW AnGR for Food and Agriculture, Rome. Page 16 Essential elements for domestication to take place the ability to breed in captivity Physiological traits such as a diet that can easily be supplied by humans a rapid growth rate Relatively short intervals between births and large litter size The rest of animal species do not have these characteristics, hence fail to be domesticated Transformation following domestication Mutation, selective breeding, and adaptation have shaped the diversity of livestock populations The domestication process resulted in many changes some are still ongoing Particularly important have been morphological changes However, the world’s livestock diversity is currently shrinking with rapid and uncontrolled loss of unique and often uncharacterized AnGR. Transformation following domestication Transition from hunting and gathering to farming resulted into More work Lower adult stature Worse nutritional conditions Heavier disease burdens Evolutionary relationship of mammalian species used for food and agriculture FAO (2004) FanGR : Safeguardin g national assets … CD Causes for declining numbers of livestock Previous breed improvement programs Especially crossbreeding with more popular exotic breeds Local breeds have been crossed with exotics e.g. In Malawi BA and LC Boar goat and Local Brahman and Zebu Causes for declining numbers of livestock Unfortunately such programs have gone with unplanned and non-regulated breeding strategies And no record keeping Resulting in uncontrolled (non-systematic) random mating With this, replacement of local breeds may occur And blood gets diluted Causes for declining numbers of livestock Small herds or populations Most animals are kept in small herds or flocks This creates difficulties in maintaining their genetic constitution Resulting in high chances of inbreeding Since in small populations, there is increased chances of mating between related individuals The smaller the number of animals used in breeding (N), the greater the probability of inbreeding 1 Δ𝐹 = 2𝑁 ΔF is increase in inbreeding per generation Small herds or populations Where number of males and females are different, effective population size (Ne) is used This is the case for many species and breeds 4𝑁𝑚 ∗ 𝑁𝑓 𝑁𝑒 = 𝑁𝑚 + 𝑁𝑓 Where Nm, Nf are number of breeding males and females, respectively Increase in inbreeding is calculated as 1 Δ𝐹 = 𝑁𝑒 Optimal Ne is around 50 Causes for declining numbers of livestock Preference for fewer breeds to others Due to feeling of others being less productive And concentrating on few breeds only This results in others being neglected And their numbers to decline Boer Goat Preferred to Causes for declining numbers of livestock Genetic drift This is a change in genetic constitution of breeds in a population This results in changes in gene frequency Possible loss of some alleles Or fixation of others Genetic drift is common in small populations Leads to uniformity within and diversity between populations Causes for declining numbers of livestock Direct replacement of local breeds by exotic popular breeds Local or indigenous breeds do not provide good returns Owners develop little incentives to keep local breeds for commercial purposes They therefore replace with common breeds This has been the case for many breeds in Malawi However, the problem has been due to improper comparison of the two breeds Using conventional western methodologies And without dual consideration for adaptation Local pigs replaced by exotic breeds for commercial purposes Causes for declining numbers of livestock Bottlenecks such as Floods Wars Draughts Theft cases etc Some Terminologies in AnGR Agro-biodiversity Means agricultural biological diversity This is a component of biodiversity that contributes to food and agricultural production, and goods and services Encompasses diversity of cultivated plants and domestic animals Includes Within species diversity Between species diversity Ecosystem diversity Some Terminologies Biodiversity or Biological diversity Means a variety of life of all forms, levels and combinations Encompasses Genetic diversity Species diversity (Zebu, Brahman, Freisian etc) (Chickens, ducks, pigeons etc) Ecosystem diversity (Upland, lowlands, high rainfall, semi-arid, desert etc) Some Terminologies Diversity A set of two or more things that differ •If one of the sets is removed, then there is reduced or decline in diversity •On the other hand, an addition of sets that are different means an increase in diversity Some Terminologies Domestic or Farm Animal Diversity A spectrum of genetic differences within each breed, between breeds within each domestic animal species Between species Within diversity falls biological diversity Within biological diversity falls animal diversity Within animal diversity falls farm animal diversity (domestic livestock) All the different livestock are available for sustainable intensification of food and agricultural production Species and breed diversity Which diversity can we claim to identify with certainty here? Breed diversity Within breed diversity Within breed diversity Some Terminologies Breed conservation To maintain breeds of livestock for which numbers have greatly declined and may continue to do so to the point of extinction if not rescued This may be for present or future use Animal Genetic Resources Management Sustainable utilisation of different species and breeds within species for present use without jeopardising future use Includes aspects of conservation, improvement and utilisation of breeds and species of livestock Why Breed conservation? The world had different species and breeds of livestock, including wild ancestors That developed and adapted to different ecosystems And providing a variety of uses, specific ecosystem and cultural or tribal Unfortunately many have become extinct Some have declined in numbers, putting then in danger of extinction Why Breed conservation? Current status There are about 40 + domestic livestock species Only 14 % are used and contribute directly or indirectly to food and agricultural production These have been domestic and evolved into separate and genetically unique breeds These have adapted to their local environments and community requirements Some of these have declined Currently about 6000 – 7000 breeds remain And comprise the world’s animal genetic resources important to food and agricultural production Why Breed conservation? Africa status Several livestock local breeds exist Have remained undescribed and neglected Have their numbers declining The same applies to Malawi The future of these breeds is very insecure if there is no action to conserve them Others are in danger of extinction if nothing is done Hence the need to conserve them Role of animal production in agriculture Global livelihood for 1.96 billion people Over 50 % of these living in pastoralists and agro-pastoralists Contributes to GDP and GNP of the country Malawi has 7 % of GDP; 2 % of GNP from livestock Organic fertilisers Draught power Fibre for clothing, leather etc Cultural significance Employment for villagers Cash reserves, moving savings bank Contributes to risk management eg during hunger Contributes to agricultural integration Role of animal production in agriculture All these functions and uses can not be fulfilled by one species Having a broad range of animal species is essential to meet all the functions And for the many mixed farming systems That are more sustainable than in monoculture Hence the need to conserve the species Purpose for conservation of FAnGR To meet present and future needs To meet future adverse conditions in case of diverse but changing environment, climate, feeds, diseases, etc To have a storehouse for genetic variation that is needed in breed improvement programs eg. Selection Keeping more and diversity spread risks among farmers To meet the increasing and broad demand for locally and globally livestock products To maintain sustainable production based on diverse environment that requires different genetic types To maintain cultural affiliation as different breeds are integral part of human heritage and are therefore to be nurtured for future generations End of presentation