Plant regeneration trait syndromes, tradeoffs, and linkages to adult abundance for native and exotic grassland plants

Abstract

Recruitment is the most sensitive plant life stage to environmental filters. Yet, most research linking functional traits to environmental filters has focused on adult plants with little known about early plant traits, their interactions with environmental filters, or their relation to species abundance. Likewise, how such relationships might vary between native and exotic species or influence plant invasion outcomes is unclear. We quantified regeneration traits for 12 native and 12 exotic (naturalized and invasive) forbs and evaluated trait relationships and their associations with species abundance across an environmental gradient in semi-arid grasslands. Species differentiated along two orthogonal trait axes suggestive of two distinct trait syndromes. The first trait syndrome, likely associated with competitive ability, was correlated with seed mass and growth-related seedling traits. Conversely, the second trait syndrome revealed a tradeoff between traits related to development and growth and traits related to resource management. This syndrome may reflect different approaches for seedling stress tolerance and avoidance. Neither trait syndromes nor mean trait values differed between native and exotic species, whether exotics were invasive or naturalized. Two traits and one trait syndrome were significantly associated with adult species abundance on the landscape. First, species with faster seedling maturation were generally more abundant. Naturalized exotic species with lower specific leaf area were also more abundant, suggesting a possible link between lower specific leaf area and greater drought survival. Abundance of native and invasive exotic species was greater for taxa with faster development and growth and thin, carbon-rich leaves, traits associated with stress avoidance. Importantly, the greater abundance of invasive exotics over other taxa was not accounted for by differences in regeneration traits. Evidence of regeneration trait syndromes and tradeoffs points to important selective forces shaping early plant life-history strategies. Linkages between some of these traits and adult plant abundance also suggest a significant role in recruitment success. Better elucidating these traits and their connections to species abundance—particularly across life stages—can help improve our understanding of plant community assembly.