DOI: 10.5061/dryad.w3r2280pm
title: Dead litter of resident species first facilitates and then inhibits sequential life stages of range-expanding species

description: 1. Resident species can facilitate invading species (biotic assistance) or
 inhibit their expansion (biotic resistance). Species interactions are
 often context-dependent and the relative importance of biotic assistance
 versus resistance could vary with abiotic conditions or the life stage of
 the invading species, as invader stress tolerances and resource
 requirements change with ontogeny. In northeast Florida salt marshes, the
 abundant dead litter (wrack) of the native marsh cordgrass, Spartina
 alterniflora, could influence the expansion success of the black mangrove,
 Avicennia germinans, a tropical species that is expanding its range
 northward. 2. We used two field experiments to examine how S. alterniflora
 wrack affects A. germinans success during 1) propagule establishment and
 2) subsequent seedling survival. We also conducted laboratory feeding
 assays to identify propagule consumers and assess how wrack presence
 influences herbivory on mangrove propagules. 3. S. alterniflora wrack
 facilitated A. germinans establishment by promoting propagule recruitment,
 retention, and rooting; the tidal regime influenced the magnitude of these
 effects. However, over time S. alterniflora wrack inhibited A. germinans
 seedling success by smothering seedlings and attracting herbivore
 consumers. Feeding assays identified rodents – which seek refuge in wrack
 – as consumers of A. germinans propagules. 4. Synthesis: Our results
 suggest that the deleterious effects of S. alterniflora wrack on A.
 germinans seedling survival counterbalance the initial beneficial effects
 of wrack on A. germinans seed establishment. Such seed-seedling conflicts
 can arise when species stress tolerances and resource requirements change
 throughout development and vary with abiotic conditions. In concert with
 the tidal conditions, the relative importance of positive and negative
 interactions with wrack at each life stage can influence the rate of local
 and regional mangrove expansion. Because interaction strengths can change
 in direction and magnitude with ontogeny, it is essential to examine
 resident-invader interactions at multiple life stages and across
 environmental gradients to uncover the mechanisms of assistance and
 resistance during invasion.
description: This dataset includes all data necessary to re-create the figures
 and analysis in R.S. Smith, J.A. Blaze, and J. E. Byers. Dead litter of
 resident species first facilitates and then inhibits sequential life
 stages of range-expanding species. Journal of Ecology. 2021. These data
 represent measures collected during two field experiments – 1) propagule
 establishment experiment and 2) seedling survival experiment – and a
 series of laboratory invertebrate and rodent ‘no-choice’ and ‘choice’
 feeding assays. All data was collected by R.S. Smith and J.A. Blaze. All
 data processing and analysis were performed in the statistical program R
 and are described in the manuscript text. Columns that contain emergent
 data have been defined with reference to the component columns in the
 associated meta-data.