Abstract
We compared the helminth communities of 5 owl species from Calabria (Italy) and evaluated the effect of phylogenetic and ecological factors on community structure. Two host taxonomic scales were considered, i.e., owl species, and owls vs. birds of prey. The latter scale was dealt with by comparing the data here obtained with that of birds of prey from the same locality and with those published previously on owls and birds of prey from Galicia (Spain). A total of 19 helminth taxa were found in owls from Calabria. Statistical comparison showed only marginal differences between scops owls (Otus scops) and little owls (Athene noctua) and tawny owls (Strix aluco). It would indicate that all owl species are exposed to a common pool of ‘owl generalist’ helminth taxa, with quantitative differences being determined by differences in diet within a range of prey relatively narrow. In contrast, birds of prey from the same region exhibited strong differences because they feed on different and wider spectra of prey. In Calabria, owls can be separated as a whole from birds of prey with regard to the structure of their helminth communities while in Galicia helminths of owls represent a subset of those of birds of prey. This difference is related to the occurrence in Calabria, but not Galicia, of a pool of ‘owl specialist’ species. The wide geographical occurrence of these taxa suggest that local conditions may determine fundamental differences in the composition of local communities. Finally, in both Calabria and Galicia, helminth communities from owls were species-poor compared to those from sympatric birds of prey. However, birds of prey appear to share a greater pool of specific helmith taxa derived from cospeciation processes, and a greater potential exchange of parasites between them than with owls because of phylogenetic closeness.
Highlights
In the last 30 years a number of papers on helminths of European owls (Strigiformes) have been published [1,2,3,4,5,6,7] including an exhaustive review of endoparasites found worldwide in raptors [8]
Comparison between Owl Species A total of 19 helminth taxa (10 nematodes, 3 acanthocephalans,3 cestodes and 3 digeneans) and 758 helminth individuals were found in the total sample of owls (Table 1)
All helminth taxa were found in the gastrointestinal tract except for a single specimen of Excisa excisiformis which was collected from the trachea of 1 long-eared owl
Summary
In the last 30 years a number of papers on helminths of European owls (Strigiformes) have been published [1,2,3,4,5,6,7] including an exhaustive review of endoparasites found worldwide in raptors [8]. Sanmartın et al [7] concluded that in Galicia (northwest Spain) the helminth community of owls represented basically a ‘‘subset’’ of that observed in the birds of prey (Accipitriformes and Falconiformes) from the same region This observation would agree with the observation that owls and birds of prey, phylogenetically not closely related, have similar ecological niches and food habits, dividing the habitat not spatially but temporally [9]. Their helminth faunas would be expected to be quite similar [10] This prediction is at odds with the observed differences in composition of parasite faunas in geographical regions other than Galicia, i,e., Florida (USA) and Catalonia (northeast Spain), where a sizeable part of the faunas of each raptor group is not shared [6,10,11,12,13,14]. These observations would suggest that host specificity may play a contrasting role in structuring parasite communities in each raptor group depending on the geographical region
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