Biol Invasions (2013) 15:1155–1168 DOI 10.1007/s10530-012-0358-y ORIGINAL PAPER Behavioural and genetic interactions between an endangered and a recently-arrived hummingbird Wouter F. D. van Dongen • Ilenia Lazzoni • Hans Winkler • Rodrigo A. Va´squez • Cristia´n F. Estades Received: 5 March 2012 / Accepted: 19 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract The invasion or expansion of non-native other ecological or anthropogenic processes. Potential species into new geographic areas can pose a major interactions can include both competition for scarce threat to the conservation of biodiversity. These threats resources and reproductive interference, including are augmented when the newly-arrived species inter- hybridisation. Understanding the dynamics of these acts with native species that are already threatened by interactions forms a crucial component of conservation management strategies. A recent contact zone occurs in the north of Chile between the endangered Chilean Electronic supplementary material The online version of woodstar (Eulidia yarrellii) and the closely-related and this article (doi:10.1007/s10530-012-0358-y) contains recently-arrived Peruvian sheartail (Thaumastura supplementary material, which is available to authorized users. cora), which expanded its range from Peru into Chile W. F. D. van Dongen (&) Á H. Winkler during the 1970s. We characterised the interactions Konrad Lorenz Institute of Ethology, Department of between the species by combining population size Integrative Biology and Evolution, Veterinary University estimates with molecular, morphological and behav- of Vienna, Vienna, Austria e-mail: [email protected] ioural data. We show that a low degree of hybridisa- tion, but not introgression, is occurring between the W. F. D. van Dongen Á H. Winkler two species. Despite interspecific morphological sim- Konrad Lorenz Institute of Ethology, The Austrian ilarities, behavioural observations indicate that food Academy of Sciences, Vienna, Austria niche overlap between the species is relatively low, and W. F. D. van Dongen Á R. A. Va´squez that the dietary breadth of sheartails is larger, which Departamento de Ciencias Ecolo´gicas, Facultad de may have aided the species’ range expansion. Finally, Ciencias, Universidad de Chile, Las Palmeras 3425, woodstars dominate the sheartails in male–male terri- N˜ un˜oa, Santiago, Chile torial interactions. However, potentially increased I. Lazzoni Á C. F. Estades energetic costs for woodstars associated with frequent Laboratorio de Ecologia de Vida Silvestre, Departamento territorial chases and courtship displaying with shear- de Gestio´n Forestal y Medio Ambiente, Facultad de tails may exacerbate the effects of other threats on Ciencias Forestales y Conservacio´n de la Naturaleza, Universidad de Chile, Av. Santa Rosa 11315, La Pintana, woodstar viability, such as human-induced habitat Santiago, Chile modification. This study highlights the value of implementing multidisciplinary approaches in conser- R. A. Va´squez vation biology to gain a more complete understanding Instituto de Ecologı´a y Biodiversidad, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, of interactions between recently-arrived and endan- N˜ un˜oa, Santiago, Chile gered species. 123 1156 W. F. D. van Dongen et al. Keywords Contact zones Á Eulidia yarrellii Á via either resource competition or reproductive inter- Hummingbirds Á Hybridisation Á Resource competition Á ference (MacDougall and Turkington 2005; Thaumastura cora Hochkirch et al. 2007; Sol et al. 2012). Resource competition can occur when there is high niche overlap between the species, for example when similar Introduction food resources are exploited that are not abundant in the environment (Petren and Case 1996; Byers 2000; A major threat to the conservation of biodiversity is the Fox 2002; Vogel and Pechmann 2010). In contrast, invasion or expansion of non-native species into areas reproductive interference involves any interactions inhabited by endangered species. Recently-arrived spe- between species associated with their mating system cies can threaten native species in areas of sympatry that are caused by incomplete species recognition (known as contact zones) via various processes, includ- systems (Seehausen 2004; Hochkirch et al. 2007). It ing competition for scarce resources or reproductive can result in wasted energy and gametes courting and interference and hybridisation (Allen et al. 2004;Strayer mating with heterospecifics, and can ultimately lead to et al. 2006;Mun˜oz-Fuentes et al. 2007; Steeves et al. hybridisation. These hybridisation events can have 2010). In recent times, the frequency of such contact diverse effects, either promoting reproductive isola- zones has increased dramatically due to direct and tion between parental species or promoting speciation indirect human-induced disturbances, including habitat of admixed individuals (Barton 2001). If hybrids are modification, climate change and the deliberate intro- fertile and do not have lower fitness, then introgression duction of species outside their natural distributional can occur and lead to hybrid swarms (Allendorf et al. range (Strayer et al. 2006). The likelihood that a recently- 2001). From a conservation perspective, as hybridisa- arrived species has a negative impact on a native species tion is more common in disturbed habitats and when (and vice versa) is increased when the species are one species is rare (Mayr 1963), it is especially closely-related or occupy similar ecological niches (e.g. problematic for endangered species and can ultimately Edmands 2002; MacDougall et al. 2009). Moreover the result in species declines (Allendorf et al. 2001). negative effects are exacerbated when the native species Therefore, the early detection and characterisation of is already threatened by other human-induced activities reproductive interference and hybridisation is crucial (Allendorf et al. 2001). In the current study, we examine in maintaining the genetic integrity of endangered the interactions between a recently-arrived humming- species. bird and an endangered native hummingbird in a recent The Chilean woodstar (Eulidia yarrellii) is a ‘bee’ contact zone. hummingbird species endemic to northern Chile and The processes driving dominance hierarchies southern Peru (Jaramillo et al. 2003; Schulenberg et al. among species have long been of interest to conserva- 2007). The species was first sighted in Peru in the early tion biologists and ecologists (e.g. Preston 1948; 1980 s (Parker 1982), but has not been recorded in this McNaughton and Wolf 1970; MacDougall et al. region in more recent times and is now considered as 2009). Theory suggests that species that are able to officially extinct in this country (Cruz 2006). In Chile, establish in new environments may dominate native the Chilean woodstar was once locally very common, species via three mechanisms, which need to be but its range and abundance has diminished dramat- disentangled to formulate appropriate conservation ically since the 1970s and the species is now listed as strategies involving recently-arrived or invasive spe- Endangered on the IUCN Red List of Threatened cies. First, the apparent dominance of one species over Species (Estades et al. 2007). Along with increased another may be unrelated to direct interactions between agricultural activity throughout its Chilean distribu- the species, but instead be due to an environmental tion, this drastic decline coincided with the arrival of change which favours the expansion of one species and the Peruvian sheartail (Thaumastura cora), a closely- suppresses the abundance of the second (e.g. anthro- related bee hummingbird (McGuire et al. 2009). The pogenic habitat modifications, MacDougall and Tur- sheartail was absent from Chile before the 1970s, but kington 2005; King and Tschinkel 2006). is now rapidly expanding its population across north- Alternatively, the recently-arrived species may ern Chile (Estades et al. 2007). The two species are directly suppress the abundance of the native species morphologically very similar, with males differing 123 Endangered and a recently-arrived hummingbird 1157 predominantly and conspicuously in their tail mor- salinity resulting in few crops or plantations, but more phology (as well as in song structure: C. Clark, unpub- cattle grazing. lished data). Plumage differences between females of the two species are even more subtle (Jaramillo et al. Abundance estimates 2003). Sheartails may therefore be reducing the viability of the woodstar population either via resource We estimated abundance of both species using fixed- competition (for example, if they share a similar radius point-counts as outlined in detail in Estades foraging niche) or reproductive interference (if mis- et al. (2007). Briefly, at each point we recorded all takes in species recognition occur). We therefore birds seen and heard within and outside a 30 m radius integrate information on abundance, genetics, mor- during a three-minute period. Following Bibby et al. phology and behaviour of both hummingbirds to (1992) records outside the 30 m radius were used to quantify the nature of the interactions between the two correct density estimates for the effect of detectability species and to ascertain whether the population crash using the equation: in woodstars could indeed be caused by the sheartails. Specifically, we first present abundance estimates of n n both species spanning