International Journal of Molecular Zoology, 2025, Vol.15, No.2, 58-68 http://animalscipublisher.com/index.php/ijmz 62 5 Evolutionary Insights from SV and Genome Analysis of Giant African Land Snail (Lissachatina fulica) 5.1 SVs and rapid adaptation in invasive environments Structural variations (SV), including gene duplications, deletions and rearrangements, are regarded as an important driving force for the rapid adaptation of invasive species. In Lissachatina fulica, genome-wide analysis revealed that a shared genome-wide replication (WGD) event with Achatina immaculata provided it with a legacy of genomic plasticity, which helps adapt to the terrestrial environment. And it may promote the successful invasion of snails (Sirbu et al., 2022). The expansion of gene families related to mucus secretion, immune defense and stress tolerance, many of which are produced or retained after WGD, and these genes are involved in water retention, wound healing and protection against reactive oxygen species (Sirbu et al., 2022; Alcaraz et al., 2025). These structural variations, by increasing gene dose and functional redundancy, enable the phenotype to change rapidly and maintain plasticity, thereby supporting snail colonization in new environments and coping with environmental stress (Sirbu et al., 2022; Bentley et al., 2024). Studies on other invasive mollusks and snails also support the role of structural variations in promoting rapid adaptation, mainly through the expansion of gene families related to metabolism, osmotic regulation and defense (Koch et al., 2021). 5.2 Comparative evolutionary rates of SV vs. SNP From the perspective of comparative genomics, structural variations often exert a faster, and more direct driving force on evolution than single nucleotide polymorphisms (SNPS). SNPS usually accumulate gradually and have subtle effects. Structural variations sometimes can cause extensive alterations, at the genetic content and regulatory levels, with just one mutation event, directly resulting in significant phenotypic differences (Koch et al., 2021; Gompert et al., 2025). This difference was more pronounced in L. fulica and related mollusks - even in cloned or asexual reproduction populations, changes in DNA content due to structural variations and higher levels of gene family expansion could be observed (Sirbu et al., 2022). Many studies have also pointed out that, certain types of structural variations, especially gene duplications and inversions, are often associated with adaptive traits and can even promote ecological differentiation in a short period of time. This change is particularly important in the context of invasive species (Koch et al., 2021; Castillo et al., 2023). 5.3 SVs as phylogenetic and biogeographic markers Structural variations are rarer and more stable than SNPS and are powerful phylogenetic and biogeographic markers. In L. fulica, mitochondrial and nuclear genomic analyses have identified specific haplotypes and structural variations corresponding to different invasive populations in Asia, West Africa and other regions (Lai et al., 2025). These structural variations can be used to reconstruct invasion paths, infer multiple introduction events, and track the global spread of the species (Bentley et al., 2024; Lai et al., 2025). Comparative studies of mollusks have also shown that structural variations such as rearrangement and duplication of gene sequences can provide strong signals for solving phylogenetic relationships and understanding evolutionary transitions (e.g., the transition from aquatic to terrestrial) (Bitter et al., 2019; Sirbu et al., 2022). 6 Case Studies 6.1 Genetic structural variations of the L. fulica that invaded Africa in Colombia About a decade or so ago, Colombia introduced L. fulica for its cosmetics industry. It wasn't long before this kind of snail took root in many places across the country. The local tropical climate, combined with the urban environment, has almost become a breeding ground for their spread. Researchers have found that structural variation (SV) can well distinguish populations of different origins, especially those that fall in regulatory and coding regions. It can reveal the genetic differentiation between Asian and African populations and also reflect their respective invasion histories and local adaptations (Catanach et al., 2019; Merot et al., 2020).
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