International Journal of Molecular Zoology, 2025, Vol.15, No.2, 58-68 http://animalscipublisher.com/index.php/ijmz 63 Castillo et al. (2025) selected Cali City in southwestern Colombia as a case. During the period, from May 2023 to April 2024, 578 samples were collected from 22 urban districts and typed using the 16S rRNA gene sequence. The result is quite simple - only two haplotypes were found: Type C accounts for 11% and Type D accounts for 89%. In terms of spatial distribution, the D-type pattern holds an absolute advantage in most urban areas, and in some places, it even reaches 100%. Type C can only be seen in a few urban areas (such as urban areas 3 and 5), and the proportion is relatively balanced (Figure 2). The Tajima's D index of the population is -2.41, combined with a relatively low nucleotide diversity (π = 0.00124), suggesting that these snails may have undergone recent expansion, or positive selection, resulting in an increase in low-frequency variations. Interestingly, time series analysis has found that during the long-term drought caused by El Nino, the proportion of type D has been rising in most regions, while that of type C has decreased significantly and even disappeared completely in some places. This is very likely because Type D is more resistant to dry heat, while Type C may temporarily "disappear" through summer sleep during the dry season. It also pointed out that human activities and urban environments - like waste dumping and landscaping - provide these snails with abundant food and hiding places, and also enable them to spread faster. Figure 2 The median-joining haplotype network of L. fulica (23 haplotypes) based on 16 sRNA gene sequences (255 bp). The size of each circle indicates the frequency of the corresponding haplotype, while the colors of the circles represent the 22 urban areas (communes) in the city of Cali where each haplotype was recorded. Additionally, the frequencies of haplotypes C and D are shown across the three time intervals during which the snails were collected (Adopted from Castillo et al., 2025) 6.2 Identification of two species of African giant Snails in Shenzhen, China In the field investigation conducted in Shenzhen City, Zhang et al. (2024) collected field samples of the common African giant snail (Achatina fulica) and the spotted African giant snail (Achatina immaculata). To accurately determine species affiliation, the research team constructed a phylogenetic tree in combination with the COX1 gene sequence and compared morphological features such as shell shape, shell color and lip color. The results
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