Can demographic rates of early development stages justify invasion success among three pine species in the Cerrado biodiversity hotspot?

Abstract

Recognising which life-history factors can potentially explain the success of biological invasions is essential to understand why certain exotic species are more successful to invade a given system than others, and also to better predict invasion outcomes. We focused on the three most planted pine tree species in Southern Brazil -Pinus elliottii, P. caribaea and P. oocarpaas a natural system to test the hypothesis that some key vital attributesfecundity (number of seeds produced), seed viability, germinability, seedling growth vigour (biomass and stem length)could be driving the greater invasion of P. elliottii in the region. We collected seeds of P. elliottii var. elliottii, P. caribaea subsp. hondurensis and P. oocarpa in two sites of similar climate and soil in the Cerrado biodiversity hotspot. Seeds were tested for viability and germinability, and seed production was estimated. Under laboratory conditions, we evaluated seedling survival, stem and root development, biomass production and mortality for each species. Although P. elliottii is regarded as the most successful invasive pine species in the Cerrado, it did not outperform the other pines in terms of seed viability, germinability and seedling survival, and it had the slowest growth. P. elliottii did produce, however, at least twice as many seeds as the other species. P. caribaea revealed high seed viability and seedling survival, the fastest seedling development, but low seed production. P. oocarpa showed the lowest seed viability, but fast root growth and very low seedling mortality. Our results suggest seed production is a key factor for P. elliottii invasion success. However, given the strong performance of P. caribaea and P. oocarpa for germinability and growth, we emphasise the risk of both species also becoming successful invaders in the Cerrado. We highlight the need for constant monitoring of emerging pine individuals in native ecosystems to avoid future invasions.

Competition–colonisation trade‐offs are found among but not within wind‐dispersed Pinus species

“…Finally, smaller seeded species also typically produce larger numbers of seeds per parent than the larger seeded species, which may further contribute to their invasive success (Miashike et al., 2021; Rejmánek & Richardson, 1996) and compensate for their lower per‐seed establishment success (Eriksson & Jakobsson, 1999). Future work could extend our analysis here by considering the potential relationships between seed number per parent, dispersal traits of the seeds, release height, and seedling performance for parent trees in common garden conditions.…”