Sand fly (Phlebotominae) activity and abundance in vertical strata in a tropical dry forest in the Yucatan Peninsula, Mexico

The study of population dynamics in a vertical forest gradient provides basic information on the aspects of insect vector natural history that influence the rate of pathogen transmission. In Mexico, these studies are remarkably limited for sand flies recognised as Leishmania vectors. This study analyses the temporal dynamics of sand fly species (Diptera: Psychodidae) along vertical strata of a tropical dry forest in Yucatán, Mexico, an area previously identified as a transmission hotspot for Leishmania mexicana. Bimonthly samplings were conducted over 1 year by using six CDC light traps in the understory and six traps in the canopy. During the collection period, forest attributes and environmental data (temperature and relative humidity) were recorded for each ecotope. In total, 630 individuals were sampled, of which 68% were collected in the understory and 32% in the canopy. No significant differences in species diversity and abundance were detected between the two ecotopes. Psathyromyia shannoni (Dyar) and Dampfomyia deleoni (Fairchild and Hertig) were the only species structured in the vertical dimension. Observed diversity in both strata responds similarly across both monthly and seasonal time scales. Data analyses indicated that relative humidity influenced the vertical distribution of P. shannoni and D. deleoni, although the magnitude and direction of this effect varied by species. Psathyromyia shannoni exhibited contrasting responses to relative humidity between the canopy and the understory, independent of sex, suggesting that additional environmental factors not assessed in this study may modulate its vertical distribution. Despite the limitations of our work, these findings contribute to the knowledge on the population dynamics of sand flies in the tropical forests of the Yucatán Peninsula.