Bonellia-nervosa Avalos et al 2024
Description
Describes the population structure of 33 individuals of the tropical dry forest species Bonellia nervosa, along with 43 hemispherical photos taken next to each plant and at 10 random points to measure the habitat preferences of B. nervosa regarding canopy structure and light conditions in the dry forests of Santa Rosa National Park in Costa Rica.
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This study was carried out in Santa Rosa National Park, Guanacaste, Costa Rica (10o50’04” N, and 85o36’45” W, 295 masl) in September 2024, along the “Indio Desnudo” trail. We searched for B. nervosa seedlings and adults along the road from the Park Administration to the Indio Desnudo trail, and within 30 m into the forest on both sides of the trail. Most individuals were found along the Indio Desnudo trail. We located 33 B. nervosa plants, ranging in height from 0.15 to 4.86 m, with 14 bearing fruits. We measured height and stem diameter 10 cm above the ground and analyzed the allometric relationship between these variables using ordinary least squares regression. We took hemispherical photographs 1.5 m above the ground, directly above or next to the 33 individual plants, and at 10 random points along the Indio Desnudo trail where B. nervosa was absent. We used a Nikon Coolpix 5000 camera with a fisheye lens, mounted it on a tripod, and aligned each shot with the geographic North. The photos were taken under overcast skies to ensure a clear contrast between the canopy and the sky. We analyzed the images using Gap Light Analyzer (GLA, version 2.0; Frazer et al. 1999) and measured the percentage of visible sky (% sky area), canopy openness (% canopy openness), leaf area index (LAI, measured at zenith angles of 0°-LAI 4- to 60° and 0° to 75° -LAI 5-), and the percentage of direct, diffuse, and total light transmitted through the canopy. To examine the relationships among the seven light and canopy structure variables, we performed a principal component analysis (PCA). We selected the first two components, which explained 82.27% of the variation, and used them as response variables summarizing the canopy structure. We then conducted a one-way ANOVA to compare these components between locations where B. nervosa was present and the randomly selected points where it was absent. We inspected all B. nervosa plants for the presence of fruits and randomly selected 39 fruits. Using a 30253019 Scout Pro Portable Electronic Balance, we weighed the fresh fruits and seeds and calculated the percentage of seed weight relative to the total fruit weight. We measured the relationship between fruit weight and the number of seeds with an ordinary least squares regression. We also recorded the number of fruits eaten by Tortricidae larvae and calculated the percentage of predisposal seed predation. Additionally, we noted the degree of seed maturation.