DOI: 10.5061/dryad.3r2280gtb
title: Long-term population dynamics of an insect in a simple food web under a changing environment

description: Weather conditions are important for the population dynamics of
 “cold-blooded” animals like insects, with both direct and indirect effects
 (via the food web). How weather, in combination with other factors,
 generates population change, and how such effects change over time, are
 important questions in times of climate change. We monitored an insect
 seed predator population during a 36-year period of changing weather
 patterns. The insect is part of a simple food web dominated by seed
 consumption and lacking natural enemies. Environmental conditions were
 relatively stable during the first half of the study, but patterns changed
 during the latter half. Areas of host plant patches increased, and seed
 production entered a strong bi-annual pattern. Insect abundance was
 measured twice during the yearly life cycle, before and after summer
 reproduction, and seed resources and competitor densities were measured at
 the end of the summer. We fit a population model to abundance data to
 investigate the population dynamics of the insect in relation to changing
 patterns in weather conditions and food resources. There were both direct
 and indirect effects of weather, operating at multiple time scales.
 Abundant sunshine during summer resulted in increased population growth
 during the same period, but it also resulted in increased survival the
 following winter. Population growth further depends on seed set the
 previous summer, which in turn depends on summer rainfall and is likely
 affected by climate change. This implies indirect weather effects at both
 short-term and decadal time scales. The new pattern of seed production
 seems to have led to increased average insect abundance but did not
 otherwise lead to clear changes in the dynamics of the population. This
 can be explained by weak regulation of the dynamics of the insect such
 that short-term environmental variation leads to long, unstable population
 fluctuations. Our study illustrates how insect responses to drastic
 changes in their environment can be subtle, slow, and hard to detect,
 manifested by long-term fluctuations. This highlights the importance of
 long-term data and mechanistic understandings of population dynamics to
 assess consequences of changing weather and climate on insects.
description: # Long-term population dynamics of an insect in a simple food web under a
 changing environment Dataset DOI:
 [10.5061/dryad.3r2280gtb](10.5061/dryad.3r2280gtb) ## Description of the
 data and file structure Dataset
 DOI: [10.5061/dryad.3r2280gtb](https://datadryad.org/submission/10.5061/dryad.3r2280gtb) Field censuses of the insect *Lygaeus equestris,* its competitor *Euphranta connexa,* and their food resource, the fruit of the herbaceous plant *Vincetoxicum hirundinaria.* ## **Description of the data and file structure:** Two files are provided: Patch_data.csv and Yearly_data.csv The patch file contains the mark-recapture data of *Lygaeus equestris* for each separate patch in every year. The yearly data file contains the estimates of *Lygaeus equestris* abundances as well as statistical parameters for these estimates. It also contains the weather data used in the analysis as well as counts of *Vincetoxicum hirundinaria* seed pods not attacked by *Euphranta connexa* and the total number of pods. #### **File “Patch data”** patch = Code for each patch in the study area yr = year sampled n1.P = Number of bugs marked on first visit in early summer n2.P = Total number of bugs found on the second visit in early summer m2.P = Number of marked bugs found on second visit in early summer n1.F = Number of bugs marked on first visit in late summer n2.F = Total number of bugs found on second visit in late summer m2.F = Number of marked bugs found on second visit in late summer V = Number of last instar nymphs observed on a second visit in late summer perad = The number of adults observed at the same time as nymphs was counted NA = data not available (=missing data) #### **File “Yearly data”** Yr = year N.P.mean  = estimated mean number of *L. equestris* individuals in early summer N.P.sd = standard deviation of early summer estimated mean N.P.shape = shape parameter for estimated gamma distribution N.P.rate = rate parameter for estimated gamma distribution N.FV.mean = estimated mean number of *L. equestris* individuals in late summer N.FV.sd = standard deviation of late summer estimated mean N.FV.shape = shape parameter for estimated gamma distribution N.FV.rate = rate parameter for estimated gamma distribution winter.temp = minimum temperature (°C) during the winter year (t) – year (t+1) snowdays = number of days with snow-covered ground during the winter year (t) – year (t+1) sun.JJA = total number of sunshine hours during June, July, and August sun.JJ = total number of sunshine hours during June and July healthy.fruit = number of fruit not attacked by *Euphranta connexa* fruit = the number of all fruits