Differences in life‐cycle stage components between native and introduced ranges of five woody Fabaceae species

Abstract

Understanding differences in the components of life-cycle stages of species between their native and introduced ranges can provide insights into the process of species transitioning from introduction to naturalization and invasion. We examined reproductive variables of the germination (seed predation, seed viability, time to germination), seed output (crown projection, seed production, seed weight) and dispersal (seed weight, dispersal investment) stages of five woody Fabaceae species, comparing native and introduced ranges. We predicted that each species would differ in reproductive variables of at least one life-cycle stage between their native and introduced ranges, thus allowing us to determine the life-cycle stage most associated with invasion success in the introduced range. Acacia melanoxylon and Paraserianthes lophantha had reduced seed predation in their introduced ranges while P. lophantha also had higher seed viability indicating that the germination life-cycle stage is most strongly associated with their invasion success in the introduced range. Only Acacia longifolia varied between ranges for the seed output stage due to larger plant size, greater seed production and smaller seed size in its introduced range. Similar to A. longifolia, Acacia cyclops had smaller seed size in its introduced range but did not have any other variable differences between ranges suggesting that the dispersal stage is best associated with its invasion success in the introduced range. Surprisingly, Acacia saligna was the only species without a clear life-cycle stage difference between ranges despite it being one of the more invasive acacia species in Australia. Although we found clear differences in reproductive variables associated with life-cycle stages between native and introduced ranges of these five species, these differences were largely species-specific. This suggests that a species invasion strategy into a novel environment is complex and varies among species depending on the environmental context, phenotypic plasticity and genotypic variation in particular traits.

Lack of fire and insect herbivory constrain recruitment in a rare legume from Western Australia

“…; Harris et al . ). Whilst seeds of the study species were highly viable, the longevity of the seed reserve is unknown and the impact of post‐dispersal seed predation, though not quantified, can be a limiting factor for persistence for many species (Auld & Myerscough ).…”

Diminishing importance of elaiosomes for acacia seed removal in non-native ranges

“…A recent study comparing seed and elaiosome size of A. longifolia and A. dealbata from Portugal and Australia showed a significant increase in seed size in Portugal, and a trend towards reducing the proportion of biomass allocated to elaiosomes (Correia et al 2016). Another study comparing A. longifolia from native and non-native ranges within Australia found that this species allocated proportionally less resources to elaiosomes in the non-native ranges than in the native ones (Harris et al 2016). The present study sheds light on one of the potential selective forces that might be responsible for a shift in resource allocation trade-offs, since our observations of seed removal showed that the difference in removal rates of elaiosome-bearing and elaiosome-removed seeds was proportionally lower in Portugal than in Australia, particularly in the high-density acacia stands in Portugal.…”

Large generative and vegetative reproduction independently increases global success of perennial plants from Central Europe

“…Exploring native range characteristics of species with varying global success is a relevant approach that has been used previously (e.g.,Schlaepfer et al., ). Though traits and demographic components and their relationships can change during the transition from native to exotic ranges (Beckmann et al., ; Buckley et al., ; Harris et al., ), multiple studies have also demonstrated that species can be pre‐adapted for their success elsewhere already in a native range (e.g.,Van Kleunen et al., ). This finding is also supported by our study.…”

“…() showed that some invasive species are characterized by a unique combination of long lifespan and high sexual reproduction. Though Van Kleunen, Dawson, and Maurel () argued that it is rather unlikely to find a species that is superior in any trait and in all possible environmental contexts, the idea that invasiveness of plant species can be related to relaxed life‐history trade‐offs remains rarely examined (Beckmann et al., ; Harris, Manea, Moles, Murray, & Leishman, ; Molina‐Montenegro et al., ).…”

“…On the other hand, larger seed size promotes better establishment in suboptimal conditions, for example under competition (Jakobsson & Eriksson, ; Leishman, Wright, Moles, & Westoby, ; Turnbull, Rees, & Crawley, ). Therefore, no clear pattern has yet emerged for the association between seed size and invasion success (discussed by Van Kleunen & Johnson, or by Harris et al., ). Rather than by seed size or seed output per se, invasiveness can be determined by a weaker negative association of the two traits: more successful species are hypothesized to produce more and larger seeds compared to less successful plants.…”