International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.4, 196-205 http://ecoevopublisher.com/index.php/ijmec 19 9 2 meters per hour at night. Young snails can crawl a longer distance. Natural forces such as rainfall and runoff can help snails migrate passively. During heavy rain and floods, a large number of snails drift along with surface runoff and may cross the terrain barrier and enter new watersheds and fields (Purnama and Salwiyah, 2022). Wildlife vectors promote the spread to a certain extent. Some birds and amphibians may accidentally eat snail eggs or attach snail larvae to their feet, thus taking them to new locations. However, the contribution of such dissemination is relatively limited. Soil movement can unintentionally transfer snails. Activities such as ploughing farmland, digging at construction sites, and transporting soil to gardens, if the soil contains snails or egg clumps, can also form new infection sites after being transferred to new sites for on-site hatching and growth (Purnama and Salwiyah, 2022). 3.3 Typical global intrusion cases On the global spread map of the African land snail, the invasion process in many regions is representative. South Asia and Southeast Asia were among the earliest regions invaded by A. fulica. India recorded the invasion of this species at the end of the 19th century. At that time, someone introduced it from Mauritius to a private garden in Kolkata, but unexpectedly, it quickly escaped and spread. In the middle of the 20th century, snails had spread throughout most states of India, causing extensive damage to crops and gardens (Rasal et al., 2022). The tropical islands of Oceania, due to their ecological isolation, lack resistance of local terrestrial mollusks to large snails. Once A. fulica invades, it often leads to disastrous consequences. In countries in the South Pacific such as Fiji and Samoa, African snails emerged one after another in the middle of the 20th century, consuming large amounts of crops like sweet potatoes, papayas and bananas on the islands, which dealt a heavy blow to the economies of these island nations that relied on agriculture for their livelihood. The African land snail was introduced to South America at the end of the last century and has spread rapidly in Brazil, Cuba, Ecuador and other countries in recent years (Goldyn et al., 2016). The situation in Brazil is particularly severe: in the late 1980s, merchants introduced it for consumption, but it dissipated into the natural environment within less than ten years. Due to the hot and rainy climate in most parts of Brazil, which is very suitable for snail growth, the population of A. fulica has grown explosively. By the 2010s, this snail had appeared in 23 of Brazil's 26 states and was known as a "national pest". In places such as the state of Sao Paulo in Brazil, the vegetable crops on small farms have been affected and reduced by up to 30%, causing great distress to farmers (Silva et al., 2022). 4 Impacts at the Ecosystem Level 4.1 Competition with native species and loss of biodiversity As a dominant invasive species, A.fulica often lacks natural enemies to control its introduction site, and thus uses various competitive mechanisms to squeeze out local species. First, there is food competition: The terrestrial snails in Africa have an extremely wide diet, consuming a large amount of tender leaves, fruits and organic debris of plants. The food resources that local terrestrial snails and other herbivorous invertebrates (such as slugs, beetle larvae, etc.) originally relied on have been largely consumed by them, resulting in a decline in the population of local species (Raut and Barker, 2002). Secondly, there is spatial competition: The East African giant snail is large in size and numerous in number, occupying many habitats on the ground and in vegetation. Local small mollusks (such as tree snails and flat snails) are more vulnerable to predation or environmental stress due to the inability to find sufficient habitats, and thus gradually disappear (Andreazzi et al., 2017). In addition, A. fulica can secrete A large amount of mucus-labeled domains. The mucus remaining on its activity path may carry pheromones, which interfere with and repel the normal activities and mating of local snails. 4.2 Changes in vegetation and ecosystem structure As a herbivorous invasive species, the African land snail's damage to vegetation directly affects the structural and functional balance of the ecosystem. In the forest floor and farmland ecosystems, A. fulica feeds heavily on the seedlings, tender leaves and fruits of various herbaceous and woody plants. This will lead to an increase in the mortality rate of plant seedlings, impede vegetation renewal, and ultimately alter the species composition and
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