Seed dispersal networks in an urban novel ecosystem

Abstract

The conflict resulting from the expansion of human activities into natural habitats affects the structure and functioning of ecosystems. Similarly, the anthropogenic redistribution of many species all over the world affects the composition of biological communities, possibly altering their capacity to sustain key ecological functions, such as seed dispersal. Urban parks are extreme examples of such novel ecosystems resulting from the anthropogenic redistribution of species in a new ecological framework. Here, we describe the avian seed dispersal network in an urban recreational woodland in central Portugal (c.79 ha). Four quantitative seed dispersal networks were assembled by identifying intact seeds in the droppings of mist-netted birds throughout the year. Overall, 1,244 seeds were identified, representing 33 links between 15 plant species and 11 bird species. Most birds dispersed alien seeds, but these represented a small proportion of the overall network (20 % of the seeds and 13 % of the droppings). Blackcap (Sylvia atricapilla) was the main disperser of native and alien seeds in all seasons, particularly those of the invasive Phytolacca americana. Fleshy fruits were more abundant in summer, but were more consumed in winter, presumably when other foods were difficult to find. Our study suggests that even in a highly managed urban park, seed dispersal networks can be temporally complex and variable and that a network approach can be an important monitoring tool to detect the status of crucial ecosystem functions in rapidly changing habitats such as urban parks. Keywords Birds Á Ecosystem services Á Frugivory Á Novel ecosystems Á Urban parks Á Sylvia atricapilla Communicated by A. Weiskittel.

Moving from frugivory to seed dispersal: Incorporating the functional outcomes of interactions in plant–frugivore networks

“…Great tit) and seed predators (e.g. Chaffinch Fringilla coelebs ) have been reported to disperse seeds of fleshy fruits internally, through endozoochory (Cruz, Ramos, da Silva, Tenreiro, & Heleno, ). However, evidence from the gut content of road‐killed (Debussche & Isenmann, ) and mist‐netted birds (Olesen et al., ), and more recently from DNA barcoding applied to dispersed seeds (González‐Varo, Arroyo, & Jordano, ), demonstrates that seed predators and pulp peckers are virtually absent from true seed dispersal networks.…”

Non-native species in urban environments: patterns, processes, impacts and challenges

“…Many urban areas are situated along waterways which provide corridors for dispersal of non-native species (Säumel and Kowarik 2010;Meek et al 2010). Most urban ecosystems have effective networks of seed dispersers (Cruz et al 2013), pollinators (Winfree et al 2011;Baldock et al 2015), and other facilitators for the integration of many non-native plants. Although these factors have been well studied in some urban environments, general principles on how biotic and abiotic factors interact to mediate invasibility are lacking.…”

Evaluating the efficacy of restoration plantings through DNA barcoding of frugivorous bird diets

“…); and it is one of the most active seed dispersers due to its propensity to explore all the available plant resources (Cruz et al. ).…”

“…To assess the suitability of DNA barcoding to characterize plant residues in bird droppings and to evaluate the effects of restoration plantings on bird diets, we selected the Eurasian Blackcap (Sylvia atricapilla) as a bioindicator because it is one of the most abundant species of European passerines with a well-known stopover ecology (Aamidor et al 2011); during the autumn migration it becomes a generalist consumer of fruits and its trophic preferences resemble those of rarer species that would be more difficult to sample (Gonzàlez-Varo et al 2014); and it is one of the most active seed dispersers due to its propensity to explore all the available plant resources (Cruz et al 2013).…”