Invasiveness in introduced Australian acacias: The role of species traits and genome size

Aim To assess associations between invasiveness, genome size and species traits in Australian Acacia species introduced outside their native range. Location Global. Methods Holoploid genome size was determined by flow cytometry for 92 species in Acacia subgenus Phyllodineae native to Australia. These data were used to test whether genome size was significantly different for invasive (n=21; species known to be established and spreading in foreign environments) and non-invasive (n=71; species that have been introduced to foreign environments but which are not known to be spreading) species. Data for five functional traits [seed mass, specific leaf area (SLA), relative growth rate (RGR), maximum height and dispersal mode] and three characteristics of native range (size, temperature range and precipitation range) were used to test for univariate and multivariate relationships between (1) invasiveness and traits and (2) genome size and traits. Results Genome size ranged from 1.20 to 2.13pg/2C and was not significantly smaller in invasive compared with non-invasive acacias. However, invasive acacias were found to be taller and possess a larger native range size and a wider range of annual precipitation when compared with non-invasive acacias. Multivariate analyses revealed significant differences between invasive and non-invasive acacias (PERMANOVA; P<0.01) driven largely by differences in native range characteristics. We detected a positive relationship between genome size and SLA (P=0.02) and elaiosome dispersal mode (P<0.01) in analyses across species, but these findings were not supported by evolutionary divergence analyses. Main conclusions Genome size variation does not underpin variation in traits associated with the invasive/non-invasive dichotomy in introduced acacias, probably because of the very small DNA values in the Acacia species studied. Acacias introduced into new environments are most likely to become invasive if they are tall shrubs or trees and are widely distributed in their native range.