Rapid increase in growth and productivity can aid invasions by a non-native tree.

Guilherme Sena,Rafael Dudeque Zenni,Wanderson Lacerda da Cunha

doi:10.1093/aobpla/plw048

Abstract

Research on biological invasions has produced detailed theories describing range expansions of introduced populations. However, current knowledge of evolutionary factors associated with invasive range expansions, especially those related to rapid evolution of long-lived organisms, is still rudimentary. Here, we used a system of six 40-year-old invasive pine populations that originated from replicated introduction events to study evolution in productivity, growth, and chemical defence traits. We tested the hypotheses that invasive populations were undergoing rapid phenotypic change as populations spread, that populations exhibit trade-offs between evolution in growth and chemical defences, and that rates of rapid evolution in plant growth and productivity effect rates of invasion. Although all invasions started from replicated pools of genetic material and equal propagule pressure, we found divergence in mean values for the six invasive populations in the six traits measured. Not only were there between-population variations but also invasive populations were also rapidly changing along each invasive population expansion. Two populations displayed greater leaf areas (LAs) and smaller specific LAs (SLAs) during range expansion. Four populations had faster growth rates at the leading edge of the invasion front in comparison with plants at the rear edge. In terms of total plant defences, non-volatile resin increased in plants along one invasion gradient and decreased in a second, total needle phenolics increased in plants along one invasion gradient and total wood phenolics increased in plants along the one invasion gradient and decreased in a second. We found no trade-offs between investments in growth and chemical defence. Also, faster rates of change in growth rate and LA were positively associated with greater dispersal distances of invasive populations, suggesting rapid evolution may increase invasiveness. Understanding the roles of both natural and human-mediated ecological and evolutionary processes in population-level dynamics is key to understanding the ability of non-native species to invade.

Highlights

Biological invasions are a leading cause of environmental degradation, are a main focus of concern for conservation practitioners and provide important insights on species responses to climate change (Pysek et al 2012; Caplat et al 2013; Moran and Alexander 2014; Kuebbing and Simberloff 2015)
All invasions started from replicated pools of genetic material and equal propagule pressure (Zenni et al 2014), we found divergence in mean trait values in the six invasive populations for the six traits measured (Fig. 2 and Table 1): leaf areas (LAs) (F5,273 1⁄4 16.69, P < 0.001), specific LAs (SLAs) (F5,273 1⁄4 7.976, P < 0.001), mean annual growth (MAG; F5,276 1⁄4 15.56, P < 0.001), non-volatile resin content (F5,273 1⁄4 9.945, P < 0.001), needle total phenolic content (F5,273 1⁄4 19.36, P < 0.001) and wood total phenolic content (F5,264 1⁄4 16.63, P < 0.001)
While LA and SLA were smaller in hotter and wetter locations, MAG was higher in locations with higher annual precipitations

Summary

Introduction

Biological invasions are a leading cause of environmental degradation, are a main focus of concern for conservation practitioners and provide important insights on species responses to climate change (Pysek et al 2012; Caplat et al 2013; Moran and Alexander 2014; Kuebbing and Simberloff 2015). Invasive organisms alter ecosystem properties and community dynamics, impacting native species and ecosystem functioning (Wardle et al 2011; Yelenik and D’Antonio 2013). Driving the spread and impact of non-native populations are dynamic ecological and evolutionary processes acting at levels ranging from genes to global scale (Zenni 2014; Zenni et al 2014; Zenni and Hoban 2015b). Several decades of ecological research have produced detailed frameworks and theories describing range expansions of introduced populations Researchers started to disentangle the evolutionary mechanisms driving spread of nonnative populations and to incorporate them into invasion theory (Parker et al 2003; Prentis et al 2008; Sargent and Lodge 2014). The role of contemporary evolution in invasive range expansions is still poorly understood (Colautti and Barrett 2013; Zenni et al 2014), especially for long-lived organisms such as trees

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