DUGi

Wildfire and time since fire effects on length and asymmetry of Cicada orni (Cicadidae) nymphs

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@28554

The Mediterranean Basin has a long history of wildfires, thus many species have coevolved with these disturbances. However, recent shifts in the fire regime could threaten the resilience of Mediterranean ecosystems. Cicadas spend their entire nymph stage belowground, feeding on xylem fluids from roots, emerging only to molt one last time and become adults. This unique life cycle makes them important contributors to ecosystem functioning both below and above ground, but it could also make them vulnerable to root degradation due to fire disturbances. The aim of this study is to investigate whether wildfires can be detrimental to the development of cicada nymphs using body, wing, and foreleg length, as well as wing and foreleg asymmetry as indicators of growth. We also analyzed how these traits vary across time since fire. The research was conducted by photographing the final instar exuviae (i.e., the sheds from the last molt that preserve nymph morphology) and measuring the length of body structures using ImageJ software. A sample of 456 exuviae of Cicada orni males was selected from burned and unburned sites at 5 different study areas in Spain and for 1, 2, 3, 6, and 11-12 years since fire. We analyzed the data using ANOVA, GLM, GLMM, and Kruskal-Wallis tests. We expected body, wing, and foreleg lengths to be shorter in burned sites, while asymmetry would be lower in unburned sites. Moreover, we hypothesized that there would be changes throughout the years since fire. Our results show a significantly longer body, wing and foreleg length in unburned sites. However, only body length exhibited a consistent post-fire temporal trend, increasing in the third year after the disturbance. These parameters were also significantly influenced by the study area. The wing asymmetry index was not significantly different between treatments and over time since fire, whereas the foreleg asymmetry index showed a higher asymmetry in unburned sites possibly due to an unknown stressor. Our results suggest that cicada size is negatively affected by wildfires, probably caused by nutritional constraints. Further research is needed to better understand the potential correlation with time since fire and the effects on asymmetry

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