Invasion syndromes: hypotheses on relationships among invasive species attributes and characteristics of invaded sites

Abstract

As invasion science accepts that there is no single causal factor for biological invasion, the identification of groups of traits that are often associated, or “syndromes”, is a logical move forward. Invasion syndromes are proposed to identify suites of site conditions (biotic and environmental) that render a site vulnerable to invasion by different types of invaders. This paper proposed four invasion syndromes which relate invader attributes (competitive ability, niche construction, phenotypic plasticity, and phenological niche separation) to the biotic characteristics (biodiversity and enemies) and environmental conditions (resource abundance and fluctuation) of invaded sites. The four invasion syndromes described in this paper are a development of hypotheses of how the many factors that influence species invasion might be associated. Invasion Syndrome 1 proposes that sites with relatively high resource abundance and high diversity should be vulnerable to invasion by species with high competitive ability. Invasion Syndrome 2 hypothesizes that sites with relatively low resource abundance and low diversity should be vulnerable to invasion by species with niche construction ability. Invasion Syndrome 3 postulates that sites with moderate or fluctuating resources and moderate diversity should be vulnerable to invasion by species with high phenotypic plasticity. Invasion Syndrome 4 hypothesizes that species introduced into a site where it has phenological niche separation from natives will not have to contend with interference from the biotic community at a site (diversity or natural enemies) and may invade where ever site environmental conditions suit its life history. Further work is needed to support, contradict, or refine these hypotheses and almost certainly will identify more invasion syndromes.