DOI: 10.5061/dryad.vhhmgqnwz
title: Flowering, seed production, predation and recruitment of Posidonia australis

description: 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.
description: Shoot density, inflorescence density, and seed
 production Investment in sexual reproduction,
 vegetative shoot, inflorescences, flower and fruit (seed) densities were
 determined within P. australis meadows among the six locations before
 fruit release in November between 2013 and 2018. Vegetative shoot density
 in seagrass meadows was assessed using 10 x 0.04 m2 randomly sampled
 quadrats. Inflorescence density was assessed from five replicate 10 m x 1
 m (10 m2) belt transects. Flower and fruit (seed) production per
 inflorescence were determined from the random collection of 12
 inflorescences from transects at each site. Inflorescences consisted of a
 stem (petiole) bearing several spikes (3 - 12) with 3 - 5 hermaphrodite
 flowers on each spike, which ripen and release pollen in late Austral
 winter, July to August. Following successful pollination, fruits develop
 for approximately 12 weeks. For each inflorescence, the number of fully
 developed fruit, undeveloped fruit and remains of flowers that had not
 been pollinated were counted on each spike. Total number of flowers per
 inflorescence were derived from the sum of all fruit, undeveloped fruit
 and remains of flowers. Seed to ovule ratio was determined from the total
 number of mature fruit (1 fruit = 1 seed) divided by the total numbers of
 flowers (1 flower = 1 ovule). Seed predation
 Seed predation was assessed over two distinct time periods
 between 2001 and 2016 (2001, 2003, 2004, and then again in 2013, 2014,
 2016) at Parker Point, Rottnest Island, to determine whether predators may
 limit seed survival. Details on the tether or seed board methods can be
 found in [11] and
 [20],
 respectively. Ten tethered seeds were placed in a continuous meadow of P.
 australis, approximately 2 m apart and one to two meters from the sand
 edge, as well as in sand also 1 - 2 m from the seagrass meadow. Seed
 boards were used at three sites in 2013 and 2014 spaced approximately 20 m
 apart. At each of the three sites, three seed boards were placed 3 m from
 each other at 1 - 2 m from the sand-seagrass edge in each habitat. Seeds
 were assessed for signs of predation every 24 hrs for 7 days and replaced
 if missing or partially eaten. The experiment was conducted for only three
 days in 2016 due to weather and logistical constraints. 
 Recruitment of seedlings In order to quantify
 seedling recruitment and survivorship at Rottnest Island, we surveyed
 sparsely vegetated, 300 m-2 plots adjacent to well-established P.
 australis meadows to track the emergence and survival of recruiting
 seedlings through time. We counted and photo-tagged all seedlings at
 Parker Point, Stark Bay and Thompson Bay in November 2014 and marked their
 position with a Garmin GPS with a position accuracy of approximately 50 cm
 (Garmin Corp. Models GPSmap78 and etrex20). We also counted the number of
 shoots for each seedling to determine shoot and age-based recruitment. We
 returned the following March, 2015, just prior to winter storms, known to
 cause mortality in recruiting seedlings [6], to
 recount and measure all seedlings, including the new four month old 2014
 cohort.  We repeated this process in November 2015 – 2018, and March 2016
 - 2018.
description: # Flowering, seed production, predation and recruitment of Posidonia
 australis
 [https://doi.org/10.5061/dryad.vhhmgqnwz](https://doi.org/10.5061/dryad.vhhmgqnwz) Give a brief summary of dataset contents, contextualized in experimental procedures and results. ## Description of the data and file structure TThe columns in the datasets are described below File = Inflor_shoot_ReprodEffort 2013-2018 Column 1 = locations(text): Catherine Pt, Crayfish Rock, Nancy Cove, Parker Pt, Stark Bay, Thomson Bay Column 2 = year (text): 2013,2014, 2015, 2016, 2017, 2018 Column 3 = date (day/month/year) Column 4 = Trans or Transect number (integer) from 1-5 Column 5 = Total inflorescences m-2 (integer) Column 6 = shoot density m-2 (integer) Column 7 = reproductive effort (floating point) is Total inflorescence /shoot density as a percentage File = Flower_fruit_and ratio_2013-2018 Column 1 = Observation number, a counter for the data rows Column 2 = locations(text): Catherine Pt, Crayfish Rock, Nancy Cove, Parker Pt, Stark Bay, Thomson Bay Column 3 = year (text): 2013,2014, 2015, 2016, 2017, 2018 Column 4 = rep or replicate (integer) Column 5 = Fruit m-2 (integer). 1 seed is produced from 1 fruit Column 6 = Flowers m-2 (integer) Column 7 = fruit to flower ratio (floating point) overwise known as seed to ovule ration is Fruit m-2 / Flowers m-2 File = Recruitment_14_18 Column 1 = Observation number, a counter for the data rows Column 2 = site names (text) Parker Pt, Stark Bay, Thomson Bay Column 3 – Shoot number bins (text): 1, 2, ,8, 16, 32, 64, and &lt;64. These bins represent an annual doubling of shoots. Column 4 = frequency of individuals in each bin Column 5 – percent frequency for comparison among different total frequencies of recruits