**5. Erosion of diversity of traditional African vegetables and socio-economic implications in Tanzania rural community**

Predominant pattern of agricultural growth has been at expense of eroded biodiversity of plant genetic resources, livestock, insects and soil organisms [21, 42]. Keller et al. [31] found that wild TAVs are under threat of genetic erosion due to increasing urbanization, encouraged the cultivation of exotic vegetables for sale and the disappearance of indigenous knowledge on where and how to collect, cultivate and prepare traditional vegetables. In their review Chaudhary et al. [6] noted that agrobiodiversity loss can be categorized into natural drivers for example specie's ability to tolerate biotic and abiotic stresses, disturbed habitat render inhabitable and anthropogenic drivers such as change in food preferences, market forces, gene manipulation, human response to climate changes and lack of transfer of traditional knowledge. Farmer's in a survey conducted by Keller et al. [31] in Tanzania mentioned threats of traditional vegetables to be the introduction of new vegetable species or cultivar replaced indigenous vegetables varieties, influence of politics on commercialization of exotic vegetables, loss of indigenous knowledge making young generation unable to utilize existing traditional vegetables, changes in food habits, loss of habitat of wild vegetables and climate changes led to excessive drought.

### **5.1 Natural drivers**

Biodiversity is made up of ecosystems, species diversity, and genetic diversity which sustain our lives and to by preserving our culture, well- being, and to economic prosperity. Biodiversity is increasingly subjected to human-induced changes to the environment. To persist, populations continually have to adapt through natural selection to stressful changes including pollution and climate change. Natural selection is the process through which species adapt to their environments. When faced with new stressful conditions and increased selection pressures, organisms can respond in several ways. If they are not able to adapt, they will either go extinct or they have to avoid the stressful conditions: through changes in local behavior [43]. Small relatively isolated populations become increasingly subject to genetic drift and inbreeding, resulting in loss of genetic variation and a decrease in fitness by a process called genetic erosion. The genetic erosion in small populations, owing to fragmentation of natural habitats, is expected to obstruct such adaptive responses through genetic drift which causes a decrease in the level of adaptive genetic variation, thereby limiting evolutionary responses and inbreeding depression which reduces individual fitness and, consequently, the tolerance of populations to environmental stress. Genetic drift causes allele frequencies to fluctuate, which over time leads to random loss and fixation of alleles and an increase in homozygosity. Significantly, inbreeding mostly increases the sensitivity of a population to stress, thereby increasing the extent of inbreeding depression. As adaptation to stress is utmost frequently convoyed by augmented mortality (cost of selection), the rise in the 'cost of inbreeding' beneath stress is anticipated to harshly hinder evolutionary adaptive processes. Inbreeding therefore plays a fundamental part in this process and is anticipated to bound the chance of genetically eroded populations to effectively adapt to stressful environmental situations. Thus, the dynamics of slight fragmented populations may vary substantially from large non-fragmented populations. The resilience of fragmented populations to altering and deteriorating environments is expected to be greatly decreased. Alleviating inbreeding depression, then, is critical to guarantee population persistence.
