Interactions between the autochthonous deer ked <i>Lipoptena cervi</i> and the alien <i>L. fortisetosa</i> (Diptera: Hippoboscidae) ectoparasites of <i>Cervus elaphus</i> in Italy: coexistence or competition?

The autochthonous <i>Lipoptena cervi</i> and the allochthonous <i>Lipoptena fortisetosa</i> in <i>Cervus elaphus</i> in Central/Northern Italy were studied during autumn and winter 2018-2020 in order to evaluate the possible interactions between the two parasite species and the possible influence of geographical parameters on their abundance. This survey could help disentangling whether the coexistence between the two species will be possible or the competitive exclusion of <i>L. cervi</i> is to be expected. The results show that <i>L. cervi</i> is influenced by host sex and age and is more abundant at higher altitudes, while <i>L. fortisetosa</i> is more abundant in lower altitudes and in southern/eastern areas. The interaction between the two species is evident and symmetrical but mild at the component community level, while at the infracommunity level an asymmetric competition has been evidenced by the displacement of <i>L. cervi</i> when <i>L. fortisetosa</i> is present in the same body location. Geographical clusters of <i>L. fortisetosa</i> are evident in plains near urbanized areas, while <i>L. cervi</i> distribution appeared more scattered in all the Apennine ridge. Our observations indicate that the two deer ked species not only can coinfect the same host population but also the same host individual, avoiding strong direct interaction and competitive exclusion. All the observed patterns reflect different adaptations to environmental conditions and possible strategies to minimize competition. However, longitudinal surveys are needed to evaluate if the observed pattern is a constant feature or a result of the sampling seasons.