Plant regeneration trait syndromes, trade-offs, and linkages to adult abundance for native and exotic grassland plants

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 with
traits related to resource management. This syndrome may reflect different
approaches to 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.