Predation on artificial caterpillars following understorey fires in human-modified Amazonian forests
Data files
Oct 04, 2024 version files 268.47 KB
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README.md
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rossi_et_al_predation.data.csv
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Abstract
Tropical forests are facing several impacts from anthropogenic disturbances, climate change and extreme climate events, with potentially severe consequences for ecological functions, such as predation on folivorous invertebrates. Folivory has a major influence on tropical forests by affecting plant fitness and overall seedling performance. However, we do not know whether predation of folivorous arthropods by birds, mammals, reptiles and other arthropods is affected by anthropogenic disturbances such as selective logging and forest fires. We investigated the impacts of both pre-El Niño human disturbances and the 2015-2016 El Niño understorey fires on the predation of 4,500 artificial caterpillars across 30 Amazonian forest plots. Plots were distributed in four pre-El Niño forest classes: undisturbed, logged, logged-and-burned and secondary forests, of which 14 burned in 2015-16. We found a higher predation incidence in forests that burned during the El Niño in comparison to unburned ones. Moreover, logged-and-burned forests that burned again in 2015-16 were found to have significantly higher predation incidence by vertebrates than other forest classes. However, overall predation incidence in pre-El Niño forest disturbance classes was similar to undisturbed forests. Arthropods were the dominant predators of artificial caterpillars, accounting for 91.5% of total predation attempts. Our results highlight the resilience of predation incidence in human-modified forests, although the mechanisms underpinning this resilience remain unclear.
forest_class
The ‘forest_class’ column categorizes the forest plots based on four types of pre-El Niño human-modified forest conditions. These classifications are as follows:
- UF (Undisturbed Forests): Forests that have not been subjected to human disturbance.
- LF (Selective Logged): Forests that have experienced selective logging, where only certain trees were removed.
- LBF (Logged-and-Burned): Forests that have undergone both logging and subsequent burning.
- SF (Secondary Forests): Forests that have regrown following a disturbance, such as logging or agriculture, and are in the process of ecological succession.
These classifications are used to assess the impact of different disturbance levels on forest ecosystems.
fire_2015
The ‘2015–2016 El Niño affected forests’ classification differentiates forest plots based on whether they were affected by fires during the 2015–2016 El Niño event. Here’s the description:
- 0 (Unburned Forests): Forests that did not burn during the 2015–2016 El Niño event.
- 1 (Burned Forests): Forests that burned during the 2015–2016 El Niño event.
trans_code
The ‘trans_code’ column represents the unique code assigned to each of the 30 forest study plots. Each code identifies a specific plot used in the research.
trans_code_sp
The ‘trans_code_sp’ column represents the codes assigned to sub-plots within each forest plot. Each of the 30 forest plots measures 250 x 10 meters (0.25 hectares) and contains five sub-plots, each measuring 20 x 5 meters. The codes in this column follow a pattern based on the distance from the start of the forest plot, with the number reflecting the center point of each sub-plot (measured in meters).
Here’s the breakdown of the sub-plot codes:
- SP25: Sub-plot centered at 25 meters
- SP75: Sub-plot centered at 75 meters
- SP125: Sub-plot centered at 125 meters
- SP175: Sub-plot centered at 175 meters
- SP225: Sub-plot centered at 225 meters
These codes help to precisely locate and differentiate the sub-plots within each forest plot.
number
The ‘number’ column refers to the unique identifier assigned to each caterpillar within the forest plots, ranging from 1 to 150. This numbering system helps track individual caterpillars.
caterpillar_cod
The ‘caterpillar_cod’ column represents a unique identifier for each caterpillar, created by combining three elements:
- trans_code: The code for the forest plot.
- trans_code_sp: The code for the sub-plot within the forest plot.
- number: The individual caterpillar’s number within that plot.
This combination ensures that each caterpillar in the study has a distinct code, making it possible to accurately track and reference caterpillars across different plots and sub-plots.
predation
The ‘predation’ column indicates the presence or absence of predation marks on the caterpillars. The values are coded as follows:
- 0 (Absence): No predation marks were observed on the caterpillar.
- 1 (Presence): Predation marks were observed on the caterpillar.
arthropod
The ‘arthropod’ column indicates whether caterpillars were predated by arthropods. The values are coded as follows:
- 0 (Absence): No evidence of predation by arthropods.
- 1 (Presence): Evidence of predation by arthropods was observed.
vertebrate
The ‘vertebrate’ column indicates whether caterpillars were predated by vertebrates, including birds, mammals, and reptiles. The values are coded as follows:
- 0 (Absence): No evidence of predation by vertebrates.
- 1 (Presence): Evidence of predation by vertebrates was observed.
bird
The ‘bird’ column indicates whether caterpillars were predated by birds. The values are coded as follows:
- 0 (Absence): No evidence of predation by birds.
- 1 (Presence): Evidence of predation by birds was observed.
mammal
The ‘mammal’ column indicates whether caterpillars were predated by mammals. The values are coded as follows:
- 0 (Absence): No evidence of predation by mammals.
- 1 (Presence): Evidence of predation by mammalswas observed.
reptile
The ‘reptile’ column indicates whether caterpillars were predated by reptiles. The values are coded as follows:
- 0 (Absence): No evidence of predation by reptiles.
- 1 (Presence): Evidence of predation by mammalswas reptiles.
lost and excluded
The ‘lost and excluded’ column refers to caterpillars that were removed from the analyses due to being unrecovered or lost during the study.
Predation experiments were conducted between April 10 and June 15 2019, corresponding to the middle-end of the wet season. All artificial caterpillars were green, made from odourless non-toxic coloured plasticine (Lewis NewplastTM) mixing an equal portion of dark and light green to create medium green coloured caterpillars. Artificial caterpillars were crafted to mimic cryptic Lepidoptera larvae. We fixed the caterpillars to the vegetation by passing a wire longitudinally through them. When placing caterpillars in the field, we removed all handling marks to avoid misidentifying them with predator’s marks.
We established five 20 × 5 m sub-plots within each of the 30 forest plots. We placed 30 caterpillars in each sub-plot, totalling 150 caterpillars per forest and 4,500 caterpillars across the experiment. All caterpillars were installed on understorey vegetation branches, between 1.0 – 4.5 m from the ground, separated by at least 1 m from each other. We evaluated predation in the understorey due to the difficulties of placing caterpillars in the tall canopy (i.e., 30-50 m). After 14 days of field exposure, a single observer (LCR) recovered all caterpillars and assessed whether they had been predated, attributing predation marks to different predator groups. The identification of predation marks on recovered caterpillars was based on the beak, mandibular tooth or radula marks. The predation marks were attributed to one of four predator groups: arthropods, birds, reptiles and mammals. Multiple marks made by the same type of predator on a single caterpillar were categorized as a single predation event.