Wing Metric Variation in Aedes aegypti Effect of Altitude on Wing Metric Variation of Aedes aegypti (Diptera: Culicidae) in a Region of the Colombian Central Andes

In mosquitoes of medical importance, wing shape and size can vary with altitude, an aspect that can influence dispersion and, consequently, their vector capacity. Using geometric morphometry analysis, Aedes aegypti wing size and shape variation of males and females was studied in four altitudes in the second-smallest department in Colombia: 1.200 m (Tebaida), 1.400 m (Armenia), 1.500 m (Calarcá), and 1.700 m (Filandia). Wing shape in males (P < 0.001) and females (P < 0.001) was significantly different through the altitudinal gradient; in turn, wing size in males followed the altitudinal gradient (Males R2 = 0.04946, P = 0.0002), Females (R2 = 0.0011, P = 0.46). Wing allometry for males (P < 0.001) and females (P < 0.001) was significant. Likewise, the shape and size of the wings of males (P < 0.001) and females (P < 0.001) had significant fluctuating asymmetry. It is concluded that, in a small scale with an altitudinal variation of 500 meters, it is detected that the size and shape of the wings varied in A. aegypti, principal vector of dengue, chikungunya, and Zika. The fluctuating asymmetry is present in the individuals studied and could be associated with environmental effects caused by vector control campaigns present in some sampling locations.


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Aedes (Stegomyia) aegypti (Linnaeus, 1762) is an urban anthropophilic mosquito from 44 Africa, distributed in the world's tropical and sub-tropical regions [1]. In the Americas, 45 this mosquito is present in almost every country, considered the principal vector of 46 dengue (DENV), Zika fever (ZIKV), and chikungunya (CHIKV) [2][3][4]. In Colombia,A. 47 aegypti is registered in 80% of the country up to 2.300 m [5]. Nevertheless, still 48 unknown is the epidemiological impact altitude exerts on the population dynamics of A. 49 aegypti in areas, like the Andean region. It has been observed that the altitude in the 50 zones where the mosquito inhabits has a direct impact on the abundance, geographic 51 distribution, vector capacity, epidemiology, and pathogenicity of the mosquitoes [6]. 52 Additionally, in culicids, the range of altitudinal distribution may be modified by 53 increased global temperature [7], a phenomenon observed in the natural populations of 54 A. aegypti of the Americas, including Colombia [5]. 55 In A. aegypti, the size of the individuals has been associated with components of the 56 reproductive success [8,9] [9]. Bigger A. aegypti individuals (per se, bigger wingspan) 57 could be more involved in the transmission of arthropod-borne virus (arbovirus), like 58 dengue, than smaller ones [10]. In addition, bigger individuals have been associated 59 with a higher frequency of feeding from blood in human hosts [11], greater survival, 60 and fertility [12]. On the contrary, smaller mosquitoes (hence, with smaller wingspan) 61 may have a higher number of feeding events throughout their lives, which can increase 62 infection levels and arbovirus dissemination [9,13,14]. Furthermore, the biological 63 shape is an outstanding aspect of the phenotype of an organism and provides a link 64 between the genotype and the environment [15]. Said shape has been studied in insects, like butterflies and fruit flies, with emphasis on the wings, which are a trait associated 66 with load capacity and dispersion [16,17]   The adults were collected through mechanical aspiration through an electric aspirator.

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After collection, the individuals were sedated and sacrificed with acetone. All 113 collections were made under the framework permit from the Corporación Autónoma 114 Regional del Quindío (CRQ) N° 240 issued for the department of Quindío, Colombia. 115 Thereafter, the specimens were identified at species level by using the dichotomous 116 keys by [38] and [39]. Fig 1 shows the location, as well as the total number of 117 mosquitoes by altitude and sex used in this work.

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Information from the right wing was used to analyze the shape and size variation in the 148 altitudinal gradient for both sexes. The CS for each sex and altitude was evaluated by 149 using the Kruskal-Wallis non-parametric test. When differences were significant, a pair-150 wise Mann-Whitney U-test was used, and it was visualized by using a box diagram and  and females had significant differences (Gl = 1, P < 0.05), being higher in females (4.19 177 ± 0.38) than in males (3.29 ± 0.30); (Fig.3). In turn, the CS variation in function of the 178 altitudinal gradient for wings from males (Gl = 3, P < 0.05) and females (Gl = 3, P <  (Fig 4B)).  The allometry test indicated that the contribution of CS wing shape variation was 196 significant for both sexes (Males P < 0.001, Females P < 0.001), where the percentage 197 of wing shape variance explained by the size was 4.9% for males and 2.5% for females.

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The PCA in total explained 53.1% of data variation (PC1 = 43.8%, PC2 = 9.3%). The The CVA for each sex showed differences in wing shape among mosquitoes located at 210 different altitudes. In males, CV1 and 2 explain -in total -85.3% of the wing shape  The bilateral symmetry test for shape indicated no significant variation between the left 222 and right sides for males (Side P = 0.157) and females (Side P = 0.157) of A. aegypti.

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On the contrary, the variation among individuals and its interaction with the wing side, 224 was indeed significant for males (Individuals P = 0.001, Side*Individual P = 0.001; 225   theileri, it was found that wing size and altitude are correlated positively, while in A. 242 vexans, these differences were observed for wing size and shape through the altitudinal 243 gradient. Additionally, in C. theileri and A. vexans, these differences were noted in 244 altitudinal gradients from 808 to 2,130 m (with a difference of 1,322 m) and 808 to 1.620 245 m (with a difference of 812 m), respectively. Curiously in our case, said difference was 246 observed within an altitudinal range from 1.200 to 1.700 m with a difference of 500 m.

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For both species, the differences observed regarding wing shape or size could be 248 attributed to variables, like relative humidity and temperature. In turn, in A. aegypti, the 249 wing shape and size variation observed may be due to the influence of temperature. In , hence, expecting that with a higher larval density, mosquitoes will have a 264 smaller wing size, and with greater availability of food, there will be bigger individuals.