Relationship between aesthetic traits of woody ornamental plants and their origin

Abstract

Urban green spaces provide valuable ecosystem services and benefit biodiversity. Yet, the use of ornamental plants in public gardens is also the main pathway for the introduction of exotic species in natural habitats. Understanding which are the plant traits that influence the introduction of exotic species is key for preventing their invasion. In this study, we compared aesthetic traits of woody ornamental plant based on whether they are native or exotic in Spain; and according to their invasion status (i.e. non-established, naturalized and invasive). For this purpose, we gathered data on 12 aesthetic traits related to colour, shape, texture and type of aerial organs from 342 ornamental woody species, cultivated in 59 parks belonging to 27 cities across peninsular Spain. We did not find any differences for colour and type traits, except for invasive species having more bipinnated leaves and less simple leaves than the rest. Nevertheless, exotic species differ from natives according to the shape of their flowers, fruits and canopies, and to the texture of their barks. Among exotic species, non-established species differ from the naturalized ones on the shape of their leaves and the texture of their barks. In conclusion, our study demonstrates the existence of traits influencing the choice for ornamental exotic plants. However, these traits might not be useful for distinguishing their invasive potential.