DOI: 10.2478/s11686-010-0055-x © W. Stefan´ski Institute of Parasitology, PAS Acta Parasitologica, 2010, 55(4), 297–303; ISSN 1230-2821 Low prevalence of haemosporidian parasites in the introduced house sparrow (Passer domesticus) in Brazil Marcos Robalinho Lima 1,2 *, Lucy Simpson 2 , Alan Fecchio 3 and Cynthia M. Kyaw 4 1 Departamento de Ecologia-IB, Pós-Graduação em Ecologia, Universidade de Brasília, Brasília, DF, 70910-900 Brazil; 2 Centre of Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Treliever Road Penryn, Cornwall, UK, TR10 9EZ; 3 Instituto de Ciências Biológicas, Pós-Graduação em Biologia Animal, Brasília, DF, 70919-970, Brazil; 4 Departamento de Biologia Celular-IB, Laboratório de Microbiologia, Universidade de Brasília, Brasília, DF, CEP 70910-900, Brazil Abstract Species that are introduced to novel environments can lose their native pathogens and parasites during the process of intro- duction. The escape from the negative effects associated with these natural enemies is commonly employed as an explanation for the success and expansion of invasive species, which is termed the enemy release hypothesis (ERH). In this study, nested PCR techniques and microscopy were used to determine the prevalence and intensity (respectively) of Plasmodium spp. and Haemoproteus spp. in introduced house sparrows and native urban birds of central Brazil. Generalized linear mixed models were fitted by Laplace approximation considering a binomial error distribution and logit link function. Location and species were con- sidered as random effects and species categorization (native or non-indigenous) as fixed effects. We found that native birds from Brazil presented significantly higher parasite prevalence in accordance with the ERH. We also compared our data with the lit- erature, and found that house sparrows native to Europe exhibited significantly higher parasite prevalence than introduced house sparrows from Brazil, which also supports the ERH. Therefore, it is possible that house sparrows from Brazil might have experienced a parasitic release during the process of introduction, which might also be related to a demographic release (e.g. release from the negative effects of parasites on host population dynamics). Keywords Plasmodium, Haemoproteus, nested PCR, enemy release hypothesis, invasive species, house sparrow Introduction Invasive species are responsible for great ecological and eco- nomic impacts and are considered one of the major causes of global biodiversity loss (Wilcove et al. 1998, Mack et al. 2000, Sala et al. 2000), alongside human environmental al- teration (e.g. habitat destruction and global warming). This has prompted extensive research into invasion biology in order to understand why some introduced species establish them- selves and become widespread, while other species do not (Kolar and Lodge 2001, Sakai et al. 2001, Duncan et al. 2003, Hufbauer and Torchin 2007). The enemy release hypothesis (ERH) is frequently sum- moned as an explanation for the success of introduced species in their non-native range (Torchin et al. 2001, 2003; Mitchell and Power 2003; Torchin and Mitchell 2004; Lafferty et al. 2005). It postulates that the release from natural coevolved en- emies such as parasites, pathogens, predators and competitors is responsible for the success of introduced species. However, Colautti et al. (2004) argued for the need of more critical test- ing. They suggested, for example, that release from regulatory parasites should have a stronger and therefore substantial ef- fect, when compared with release from compensatory para- sites. This is because for the latter there is a time lag, as hosts with costly defences are selected against hosts that re-allocate their limiting resources into other important biological func- tions (e.g. reproduction and growth), therefore away from costly defences (Colautti et al. 2004). Blood parasites are an interesting model to test the ERH since they can be considered regulatory parasites when para- sitemia is high enough to eliminate individuals from the pop- ulation (directly or indirectly). For example, avian malaria was a major cause of native bird species decline in Hawaii (Warner 1968, van Riper et al. 1986), therefore manifestation of avian malaria and other haemosporidia can remove weak individu- als from wild populations (Valkiūnas 2005). Blood parasites can also be considered compensatory parasites during chronic infections (i.e. low parasitemia) by reducing hosts’ reproduc- *Corresponding author: robalinho.lima@googlemail.com