Biogeographical contrasts to assess local and regional patterns of invasion: a case study with two reciprocally introduced exotic maple trees

Abstract

Quantitative comparisons of distribution and abundance of exotic species in their native and non-native ranges represent a fi rst step when studying invaders. However, this approach is rarely applied Ϫ particularly to tree species. Using biogeographical contrasts coupled with regional dispersal surveys, we assessed whether two exotic maple tree species, Acer negundo and Acer platanoides , can be classifi ed as invasive in the non-native regions surveyed. We also examined the importance of biogeography in determining the degree of invasion by exotic species using this reciprocal approach. Local-scale surveys were conducted in a total of 34 forests to compare density, relative abundance, age structure of native and introduced populations, and whether the two introduced maple species negatively aff ected native tree species density. Regional-scale surveys of a total of 136 forests were then conducted to assess distribution in the introduced regions. Introduced populations of A . negundo were denser than populations measured in their native range and negatively related to native tree species density. Age structure did not diff er between regions for this species. At the regional scale, this species has invaded most of the riparian corridors sampled in France. Conversely, the density of A . platanoides introduced populations was similar to that of native populations and was not related to native tree species density. Although seedling recruitment was higher away than at home, this species has invaded only 9% of the forests sampled in southern Ontario, Canada. Although reported invasive, these two exotic maple species diff ered in their relative demographic parameters and regional spread. Acer negundo is currently invasive in southern France while A . platanoides is not aggressively invasive in southern Ontario. Importantly, this study eff ectively demonstrates that biogeography through structured contrasts provide a direct means to infer invasion of exotic species.

A Test for Pre-Adapted Phenotypic Plasticity in the Invasive Tree Acer negundo L.

“…Currently, A . negundo is highly invasive throughout southern, central and eastern Europe [60], [64]. It frequently occurs not only in riparian habitats characterized by high rate of flood disturbance and high soil nutrient level [65], [66] but also under drier conditions along roadsides, industrial wastelands, and dry ruderal sites [52], [67].…”

“The rich get richer” concept in riparian woody species – A case study of the Warta River Valley (Poznań, Poland)

“…Tokarska-Guzik (2005) reconstructed the history of its spread in Poland and found its center of occurrence in riparian ecosystems and ruderal areas in cities, and the high frequency of this species in our study confirms these observations. This species is a serious threat for riparian ecosystems in the whole of Europe (Saccone et al, 2010;Lamarque et al, 2012;Saccone et al, 2013). Another species with similar biology and origin, F. pennsylvanica, not recorded in the valley of Warta River 30 years ago (Jackowiak, 1993), occurred in 45% of grid squares, including fruiting trees and natural regeneration.…”

“…There are species which constitute an extraordinary threat for native vegetation of river valleys, such as Elaeagnus angustifolia and Tamarix spp. in the USA (Cooper et al, 2003;Friedman et al, 2005;Jarnevich and Reynolds, 2011;Bunting et al, 2013) or Acer negundo in the European temperate zone (Saccone et al, 2010(Saccone et al, , 2013Lamarque et al, 2012).…”

Do invasive species perform better in their new ranges?

“…In contrast, other studies show no difference in performance between the native and introduced ranges (The´baud andSimberloff 2001, Firn et al 2011), sometimes despite large differences in biotic conditions (e.g., Adams et al 2009, Lamarque et al 2012. These patterns suggest the alternative hypothesis that invasion success may reflect the inherent properties of certain species rather than novel conditions.…”