Flowering, seed production, predation and recruitment of Posidonia australis

The drivers and bottlenecks of sexual reproduction in seagrasses are a
crucial element in their conservation and restoration, determining
resilience over ecological and evolutionary timescales. We collected
flowering, seed production, and seedling establishment data for the
seagrass Posidonia australis annually between 2013-2018 in meadows at six
locations around Rottnest Island, Western Australia. We present data on
inflorescence and vegetative shoot density, reproductive effort, flower
and seed density, seed to ovule ratio, seed predation, and seedling
survival. We found variable annual rates of flowering and seed production
among meadows and between years. Some meadows, however, flowered more
intensely and produced more seeds across the years of the survey.
Inter-site and inter-annual variation in seed production, the stochastic
nature of weather during seed release, and the large, but variable, impact
of seed predation are likely the principle drivers of successful
recruitment into established meadows and in colonising unvegetated sands.
We propose that for the long-lived and persistent P. australis, variable
annual reproductive investment increases the probability of low levels of
continuous recruitment from seed in this seagrass, despite high rates of
abiotic and biotic disturbance at seedling, shoot and patch scales.