Environmental drivers of parasite load and species richness in introduced parakeets in an urban landscape

Abstract

Introduced species represent a threat to native wildlife worldwide, due to predation, competition, and disease transmission. Concurrent introduction of parasites may also add a new dimension of competition, i.e. parasite-mediated competition, through spillover and spillback dynamics. Urban areas are major hotspots of introduced species, but little is known about the effects of urban habitat structure on the parasite load and diversity of introduced species. Here, we investigated such environmental effects on the ectoparasite load, richness, and occurrence of spillback in two widespread invasive parakeets, Psittacula krameri and Myiopsitta monachus, in the metropolitan area of Rome, central Italy. We tested 231 parakeets and found that in both species parasite load was positively influenced by host abundance at local scale, while environmental features such as the amount of natural or urban habitats, as well as richness of native birds, influenced parasite occurrence, load, and richness differently in the two host species. Therefore, we highlight the importance of host population density and habitat composition in shaping the role of introduced parakeets in the spread of both native and introduced parasites, recommending the monitoring of urban populations of birds and their parasites to assess and manage the potential occurrence of parasite-mediated competition dynamics as well as potential spread of vector-borne diseases.

A protective nesting association with native species counteracts biotic resistance for the spread of an invasive parakeet from urban into rural habitats

“…Contrarily to the secondary cavity-nesting rose-ringed parakeet, which competes with native species for nest holes [52], monk parakeets are unique among parrots as they build their own nests using wood sticks on trees and artificial substrates such as power pylons and roofs [65,95], thus avoiding competition for nest sites. Regarding parasite release, monk parakeets gain novel parasites from the recipient community in its invaded range while also maintain parasites from its native range [7,19,70].…”

First record of Ornithonyssus bursa (Berlese, 1888) (Mesostigmata: Macronyssidae) parasitizing invasive monk parakeets in Santiago, Chile

“…Furthermore, in their invasive distribution, monk parakeets are also capable of acquiring local parasites. Consequently, it was found in Rome, Italy, that monk parakeets harbored not only the invasive parasites P. fulvofasciatum and O. bursa, but also the flies Crataerina pallida and Ornithophila metallica (Diptera: Hippoboscidae) and the louse Columbicola columbae (Phthiraptera: Philopteridae) (Ancillotto et al, 2018).…”

Investigating the role of urbanisation, wetlands and climatic conditions in nematode parasitism in a large Australian elapid snake

“…Urbanisation can either increase, decrease or have no detectable impact on host parasite infection (Ancillotto et al, 2018; Giraudeau et al, 2014). An increased level of parasite infection in urban areas has commonly been attributed to a reduced host immunocompetence from external stressors; for example, increased stress levels and/or host exposure to contaminants can result in a suppressed immune system in anurans (Linzey et al, 2003; Rohr et al, 2008) and reptiles (Day, 2003).…”