Search

Prevalence of parasites in wild animals may follow ecogeographic patterns, under the influence of climatic factors and macroecological features. One of the largest scale biological patterns on Earth is the latitudinal diversity gradient; however, latitudinal gradients may also exist regarding the frequency of interspecific interactions such as the prevalence of parasitism in host populations. Dragonflies and damselflies (order Odonata) are hosts of a wide range of ecto- and endoparasites, interactions that can be affected by environmental factors that shape their occurrence and distribution, such as climatic variation, ultraviolet radiation and vegetation structure. Here, we retrieved data from the literature on parasites of Odonata, represented by 90 populations infected by ectoparasites (water mites) and 117 populations infected by endoparasites (intestinal gregarines). To test whether there is a latitudinal and bioclimatic gradient in the prevalence of water mites and gregarines parasitizing Odonata, we applied Bayesian phylogenetic comparative models. We found that prevalence of ectoparasites was partially associated with latitude, showing the opposite pattern from our expectations – prevalence was reduced at lower latitudes. Prevalence of endoparasites was not affected by latitude. While prevalence of water mites was also positively associated with vegetation biomass and climatic stability, we found no evidence of the effect of bioclimatic variables on the prevalence of gregarines. Our study suggests that infection by ectoparasites of dragonflies and damselflies is driven by latitudinal and bioclimatic variables. We add evidence of the role of global-scale biological patterns in shaping biodiversity, suggesting that parasitic organisms may prove reliable sources of information about climate change and its impact on ecological interactions.

Tree trunks and other cylindrical objects, where aggregated insects live, represent a very specific world for predator-prey interactions, which must differ from the situation on a 2D plane. In the present paper, in order to gain a better understanding of the specificity of predator-prey interaction in a cylindrical space, we applied a theoretical approach. Here we introduce a numerical model that allows us to test the effect of different interaction properties between predator and aggregated prey on the plane (2D) and on a cylinder (3D), taking into consideration different abilities of predators to visually detect the prey in these two types of space. The main aim was to test these interactions in an environment, which more realistically reproduces the conditions where aggregated insects usually live. We showed that the aggregation in conjunction with a specific environment may bring additional advantages for the prey. When one prey subgroup aggregates on the other side of the tree trunk and becomes invisible behind the horizon of events for the predator, the subgroup will survive with an extremely high probability. After all, the predator moving along one side of the tree will finally loose the major group completely.

The effects of environmental factors have been considered important for the evolution of morphological complexity in organisms. The water flow exhibits constant disturbance on stream dwellers, independently of their taxonomic group. Thus, we assessed whether two different kinds of organisms (insects and algae) exhibit any ecological similarity by facing stream current. For this, we used several previous studies in order to relate the morphological complexity of insect gills and algal filaments to water velocity, in micro and mesohabitats. The results for micro-scale showed that complex body shape tends to favor taxa that colonize stream areas with lower velocity for both kind of organisms. However, mesohabitats exhibited no relationship between morphology and water velocity. We suggest that morphological complexity in organisms from different lineages (algae and insects) are similarly related to water velocity in stream habitats. Moreover, the methodology of stream samplings must be carefully designed to get more precisely the environmental factors that organisms experience.

Environments with higher complexity harbor a greater biodiversity and can directly influence on certain behaviors of aquatic animals. Here, we tested whether habitat complexity predicts odonate larvae emergence and mortality rates by rearing larvae in aquaria with or without artificial complexity. The results show a shorter emergence time in more complex environments, and a higher mortality rate on less complex habitats.