The comparison of dispersal rate between invasive and native species varied by plant life form and functional traits

Abstract

A long dispersal distance is widely used to indicate high invasiveness, but it ignores the temporal dimensions of plant invasion. Faster dispersal rates (= distance/time) of invasive species than native ones have been widely used in modeling species invasion and planning control management. However, the comparison of dispersal rate between invasive and native plants, particularly for dispersal on a local or landscape scale, has not been tested with a comprehensive dataset. Moreover, both the effects of plant functional traits on the dispersal rate and variation in the functional-trait effects between invasive and native plants remain elusive. Compiling studies from 30 countries globally, we compared seed dispersal rates (km/year) on a local or landscape scale between 64 observations of invasive and 78 observations of native plants given effects of plant life forms, disturbance levels, and measurement methods. Furthermore, we compared the effects of functional traits on dispersal rate between invasive and native species. We found that: (1) Trait values were similar between the invasive and native plants except for the greater height of woody native plants than woody invasive ones; (2) Compared within the same plant life form, the faster dispersal rates of invasive species were found in herbaceous plants, not in woody plants, and disturbance level and measurement methods did not affect the rate comparison; (3) Plant height and seed length had significant effects on dispersal rates of both invasive and native plants, but the effect of leaf dry matter content (LDMC) was only significant on herbaceous invasive plants. The comparison of dispersal rate between invasive and native plants varied by plant life form. The convergent values but divergent dispersal effects of plant traits between invasive and native species suggest that the trait effects on invasiveness could be better understood by trait association with key factors in invasiveness, e.g., dispersal rate, than the direct trait comparison between invasive and native plants.

Keywords: Dispersal rate; Leaf dry matter content; Longevity; Plant height; Plant life form; Seed length; Species invasion.

Fig. 1

Partial residual plots showing the dispersal rate comparison by plant groups (A), plant life forms (B), disturbance groups (C), and measurement methods (D). Boxplots denote the median (centerline) and interquartile range (box), with upper and bottom whiskers (or error bars) extending to 1.5 × interquartile range measured out from upper and bottom sides of the box, respectively. Statistical significances of the comparisons were denoted by the p values calculated by the linear mixed model. The different letters indicate significant differences (p < 0.05)

Fig. 2

Structural Equation Model assesses the direct and indirect effects of functional traits on standardized dispersal rate (standardized D_rate) among the four plant types: woody invasive, woody native, herbaceous invasive, and herbaceous native plants. The solid lines denote similar effects, but the dashed lines denote significantly different effects among the four plant types. The values on the solid and dashed lines are regression coefficients (or slopes), and the values in the parentheses are standard errors of the regression coefficients. Height: whole plant height (m); LDMC: leaf dry mass per leaf fresh mass (mg g⁻¹); Seed length (mm); Seed mass (mg); Plant longevity (year)

Fig. 3

Comparison of A Longevity (year), B Plant height (m); C LDMC: leaf dry mass per leaf fresh mass (mg/g) and D Seed length (mm) among the four plant types. All other variables are as previously defined. The asterisk sign indicates the significant difference between invasive and native plants within a plant life form