Fig 1.
(a) South America and the Galapagos Islands (red square). (b) Galapagos Islands with Santa Cruz (red square). (c) Santa Cruz with study site indicated in red and sketch of the sampling design. Projection: WGS 84 EPSG 4326.
Fig 2.
Mature Scalesia pedunculata trees in 2019 with saplings and young trees in the understory in a 6 ha study area in which invasive plant species, especially Rubus niveus, had continuously been removed by the Galapagos National Park Directory since 2014.
The plant cover on the forest floor mainly consisted of the invasive carpet-forming Tradescantia fluminensis.
Fig 3.
(a) Number (within bars) and percent (top row) of surviving S. pedunculata saplings and young trees over 5 years. The mortality rate over five years was 95%. (b) Height of the S. pedunculata saplings and young trees over time. The boxplots display the median and the interquartile range (25th to 75th percentile), whiskers indicate the variability outside upper and lower quartiles and outliers are displayed. Mean height is given on top of the boxplots.
Fig 4.
Percent canopy shade was significant in explaining S. pedunculata saplings mortality (a, GLM with binomial distribution and logit link function) and growth (b, GLM with a Gaussian distribution) after the first year.
Boxplots (a) display the median, interquartile range (25th to 75th percentile), variability outside upper and lower quartiles (whiskers) and outliers. Significance levels are reported as: [*] p < 0.05; [***] p < 0.001.
Table 1.
Scalesia pedunculata sapling and young tree mortality was significantly correlated with percent canopy shade and distance to the next S. pedunculata tree, while percent cover of surrounding vegetation did not have a significant explanatory power.