Invasion Pattern of Aedes aegypti in the Native Range of Ae. albopictus in Vietnam Revealed by Biogeographic and Population Genetic Analysis

Outline-based geometric morphometrics: Wing cell differences for mosquito vector classification in the Tanaosri mountain range, Thailand

Recent studies have revealed taxonomic signals within the wing cells of certain mosquito species. In our study, wing cell differentiation among mosquito vectors from the Tanaosri mountain range in Thailand was evaluated using the outline-based geometric morphometric (GM) approach. Our focus was on four specific wing cells for GM analysis: the wing contour (external cell), the second submarginal cell (internal cell 1), the first posterior cell (internal cell 2), and the third posterior cell (internal cell 3). Before proceeding with the GM approach, the identity of seven mosquito genera and 21 species was confirmed using molecular techniques. Our validated classification tests demonstrated that the performance of mosquito species classification varies according to genus. Notably, three Aedes species exhibited the highest accuracy for both internal cell 2 and internal cell 3, each registering a score of 93.20 %. In the case of two Mansonia species, the wing contour displayed a remarkable accuracy of 98.57 %. Consequently, we suggest the use of the outline-based GM approach, particularly focusing on the wing contour, for differentiating Mansonia annulifera and Mansonia uniformis. In contrast, the highest accuracy for classifying Culex species was found in internal cell 1, at 75.51 %, highlighting the challenges due to similarities in wing cells within this genus. These findings provide a guideline for future applications of the outline-based GM approach, focusing on wing cells, as an alternative method to classify mosquito vector species.

Genetic diversity of Aedes aegypti and Aedes albopictus from cohabiting fields in Hainan Island and the Leizhou Peninsula, China

BACKGROUND

Aedes aegypti and Ae. albopictus are important human arbovirus vectors that can spread arboviral diseases such as yellow fever, dengue, chikungunya and Zika. These two mosquito species coexist on Hainan Island and the Leizhou Peninsula in China. Over the past 40 years, the distribution of Ae. albopictus in these areas has gradually expanded, while Ae. aegypti has declined sharply. Monitoring their genetic diversity and diffusion could help to explain the genetic influence behind this phenomenon and became key to controlling the epidemic of arboviruses.

METHODS

To better understand the genetic diversity and differentiation of these two mosquitoes, the possible cohabiting areas on Hainan Island and the Leizhou Peninsula were searched between July and October 2021, and five populations were collected. Respectively nine and 11 microsatellite loci were used for population genetic analysis of Ae. aegypti and Ae. albopictus. In addition, the mitochondrial coxI gene was also selected for analysis of both mosquito species.

RESULTS

The results showed that the mean diversity index (PIC and SI values) of Ae. albopictus (mean PIC = 0.754 and SI = 1.698) was higher than that of Ae. aegypti (mean PIC = 0.624 and SI = 1.264). The same results were also observed for the coxI gene: the genetic diversity of all populations of Ae. albopictus was higher than that of Ae. aegypti (total H = 45 and Hd = 0.89958 vs. total H = 23 and Hd = 0.76495, respectively). UPGMA dendrogram, DAPC and STRUCTURE analyses showed that Ae. aegypti populations were divided into three clusters and Ae. albopictus populations into two. The Mantel test indicated a significant positive correlation between genetic distance and geographic distance for the Ae. aegypti populations (R2 = 0.0611, P = 0.001), but the correlation was not significant for Ae. albopictus populations (R2 = 0.0011, P = 0.250).

CONCLUSIONS

The population genetic diversity of Ae. albopictus in Hainan Island and the Leizhou Peninsula was higher than that of Ae. aegypti. In terms of future vector control, the most important and effective measure was to control the spread of Ae. albopictus and monitor the population genetic dynamics of Ae. aegypti on Hainan Island and the Leizhou Peninsula, which could theoretically support the further elimination of Ae. aegypti in China.