Invasive plant species are the second most important threat to global biodiversity loss after land-use change. Invasive species can modify native community composition, deplete species diversity and affect ecosystem processes. The Caatinga is one of the most human-affected Brazilian ecosystems owing to non-sustainable use of its natural resources. Prosopis juliflora is an important invasive plant species in the Caatinga ecosystem. Seed germination is a critical stage in plant life cycles and is a major factor in the establishment and success of invasive plant species. Among the factors that affect seed germination and dormancy, coat-imposed seems to be the most important for P. juliflora. In Prosopis species, the ingestion of fruits by wild and domestic animals may promote and accelerate germination, enhancing the dispersal of seeds and fruits of these species. We investigated the germination capacity of P. juliflora seeds after artificial mechanical and chemical scarification and analyzed the changes in seedling vigor caused by the scarification treatments. Germination rate, germination time (TMG) and germination synchrony (E) differed significantly with the length of the scarification treatments in H2SO4 for both seeds with endocarps and seeds without endocarps (non-endocarp seeds). Sulfuric acid affected plant survival more strongly than germination rate, particularly in non-endocarp seeds.

Urbanization has rapidly increased in recent decades and the negative effects on biodiversity have been widely reported. Urban green areas can contribute to improving human well-being, maintaining biodiversity, and ecosystem services (e.g. pollination). Here we examine the evolution of studies on plant-pollinator interactions in urban ecosystems worldwide, reviewing also research funding and policy actions. We documented a significant increase in the scientific production on the theme in recent years, especially in the temperate region; tropical urban ecosystems are still neglected. Plant-pollinator interactions are threatened by urbanization in complex ways, depending on the studied group (plant or pollinator [generalist or specialist]) and landscape characteristics. Several research opportunities emerge from our review. Research funding and policy actions to pollination/pollinator in urban ecosystems are still scarce and concentrated in developed countries/temperate regions. To make urban green spaces contribute to the maintenance of biodiversity and the provision of ecosystem services, transdisciplinary approaches (ecological-social-economic-cultural) are needed.

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