Data from: Evolutionary change in flight-to-light response in urban moths comes with changes in wing morphology
Data files
Mar 19, 2024 version files 125.04 KB
Abstract
Moths and other insects are attracted by artificial light sources. This flight-to-light behaviour disrupts their general activity focused on finding essential habitat resources, such as mating partners, and increases predation risk. It thus has substantial fitness costs. In illuminated urban areas, spindle ermine moths Yponomeuta cagnagella were reported to have evolved a reduced flight-to-light response. Yet, the specific mechanism remained unknown, and was hypothesized to involve either changes in visual perception or general flight ability or overall mobility traits. Here, we test whether spindle ermine moths from urban and rural populations—with known differences in flight-to-light response—differ in flight-related morphological traits. Urban individuals were found to have on average smaller wings than rural moths, which in turn correlated with a lower probability of being attracted to an artificial light source. Our finding supports the reduced mobility hypothesis, which states that reduced mobility in urban areas is associated with specific morphological changes in the flight apparatus.
README: Data from: Evolutionary change in flight-to-light response in urban moths comes with changes in wing morphology
https://doi.org/10.5061/dryad.qz612jmp5
The dataset "Yponomeuta2.csv" contains data on the origin, flight-to-light response and flight-related morphology of Yponomeuta cagnagella moths. Young larvae of this species were collected from multiple populations (several families per population) at sites that were either located in light-polluted, urban areas or prstine dark, rural areas. They were then reared in a common-garden setting in the lab. Resulting adults received an individual colour code with a unique number linked to it before being subjected to an experimental test. At night, groups of moths were released at one side of a flight cage with at the other end a Heath light trap (actinic 6 W). After 8 h, it was noted whether a specimen was caught in the light trap or not. The specimens were stored in the freezer awaiting measurements of flight-related morphology.
Moths were oven-dried before total body mass (without antennae and legs), thorax mass and abdomen were measured. From these measurements, relative thorax and abdomen mass were calculated. The ventral side of the was then photographed in a standardized way. From these pictures, we measured forewing length, width and area using ImageJ software. Further, aspect ratio and wing loading were calculated using these raw measurements. We used this dataset to verify whether (1) there are differences in flight-related morphology between moths originating from urban and rural areas (2) flight-related morphology is related to the observed differences in flight-to-light response between urban and rural moths.
Description of the data and file structure
Yponomeuta.csv: This dataset contains all data used for our analyses in the R-script ("Yponomeya_script.R"). It contains the individual numeric code, the origin of the specimens, the flight-to-light response and the flight-related morphological traits. Missing values are given by "NA" and are a result of severe wing damage in both forewings.
- Nr: individual numeric code of the moth specimen
- L: indicates whether the moth specimen originated from a light-polluted, urban area (Light) or a dark, rural area (Dark)
- Pop: population from which the moth specimen originated; nested in L
- Fam: family from which the moth specimen originated; nested in Pop
- ftl(2): flight-to-light response; indicates whether the moth specimen was caught in the light trap at the end of the experiment (yes = 1, no = 0)
- fwl1: forewing length (1st measurement) (mm)
- fwl2: forewing length (2nd measurement) (mm)
- fwl: forewing length (mean of fwl1 and fwl2) (mm)
- fww1: forewing width (1st measurement) (mm)
- fww2: forewing width (2nd measurement) (mm)
- fww: forewing width (mean of fww1 and fww2) (mm)
- shape: forewing aspect ratio calculated as 4 x fwl²/fww
- area: forewing area (mm²)
- wl: forewing wing loading calculated as mtot/area (mg/mm²)
- mtot: total body mass (mg)
- mth: thorax mass (mg)
- mab: abdomen mass (mg)
- relmth: relative thorax mass calculated as mth/mtot
- relmab: relative abdomen mass calculated as mab/mtot
- relmthab: calculated as relmth + relmab
Code/Software
Yponomeuta_script.R: This R-script was used to perform all analyses in our study. The used dataset ("Yponomeuta2.csv") has to be put in the same working directory as the R-script. Analyses were performed in R 4.2.2
- Packages: afex, car, effects, ggplot2, ggthemes, lme4, export, ggeffects
Functions:
- sumSE: function to calculate group means and standard errors. These are also used to produce the graphs.
- Create pairs: function to visualize correlation between the different morphological traits; used for data exploration.
- LMM: Morphology ~ L: contains the linear mixed models used to investigate differences in morphological traits between urban and rural areas. To analyze models for the other sex, change "male" to "female".
- GLMM FTL: contains the generalized linear mixed models used to investigate relations between the morphological traits and flight-to-light response. To analyze models for the other sex, change "male" to "female".
- GLMM FTL ~ Morphology (rural-urban): contains the generalized linear mixed model used to investigate whether the found relation between wing area and flight-to-light response was more pronounced in rural or urban areas. To analyze the model for the other sex, change "male" to "female". To analyze models for the other origin, change "Light" to "Dark".
- Figures model output: contains the script to produce the graphs based on the model output.
- Figures raw data: contains the script to produce the graphs based on the raw data.
Methods
Caterpillars of the moth Yponomeuta cagnagella were collected from different populations (with multiple families per population) at either light-polluted, urban sites or pristine dark, rural areas. They were grown under common-garden conditions in the lab. Obtained adults received an individual code before they were subjected to an experimental test. In this test, moths were released at one side of a flight-cage and at the other end of the cage there was a Heath actinic (6 W) light trap. After 8h, it was recorded whether the moths were captured in the light trap or not (i.e., the flight-to-light response). Moths were stored in the freezer (-20 °C) after the experiment.
Thorax and abdomen mass – Dead adult moths were oven-dried at 60 °C for 4 h. Remaining antennae and legs were systematically removed in all individuals prior to measuring total dry body mass (mtot). Head, thorax, abdomen and wings were carefully separated. For each individual, thorax (mth) and abdomen mass (mab) were also measured. All mass measurements were done with a microbalance (precision ± 0.001 mg). From these data, relative thorax (mth,rel) (mth/mtot) and abdomen mass (mab,rel) (mab/mtot) were calculated.
Wing morphology - For each individual, we took standardized pictures of the ventral side (clear difference between wing surface and fringe) of the right forewing (Fig. 1). In case of significant wing damage, the left forewing was used instead. Forewing length (FWL), forewing width (FWW) and forewing area (A) were measured using ImageJ software (https://imagej.net/ij/index.html) on size-calibrated pictures. Length and width were measured twice and the mean value was used in the analyses. Based on these wing measures, we also calculated aspect ratio (AR) (4 ∙ FWL²/FWW) and wing loading (WL) (mtot/A).