DOI: 10.5061/dryad.0k6djhb9b
title: Spring dispersal and reproductive potential Ips typographus

description: Diapause is a common strategy in insects to respond to reoccurring adverse
 events. The European spruce bark beetle Ips typographus is an important
 forest pest in Eurasia affecting spruce-dominated forests by eruptive
 outbreaks, which are likely to become more frequent and severe in a
 changing climate. It expresses a reproductive diapause to cope with harsh
 winter conditions. As diapause also affects the activity and voltinism of
 I. typographus, understanding its regulation by abiotic environmental
 factors can help to mitigate outbreak risks, e.g. by coordinating
 management measures or adapting silvicultural strategies. While diapause
 induction in late summer and autumn has been shown to be mainly triggered
 by photoperiod and modified by temperature, information on environmental
 cues affecting post-diapause swarming in spring is scarce. In late
 winter/early spring 2021 and 2023, we conducted a laboratory experiment
 assessing spring swarming and reproductive potential of I. typographus
 after diapause termination under various temperature and photoperiodic
 conditions. We applied mean temperatures between 13 and 23 °C with daily
 oscillations of ±5 °C and daylengths between 9 and 14 h (January to
 April). Post-diapause temperature sums had the strongest effect on spring
 swarming, modified by daily maximum temperatures, while photoperiods only
 had a small and ambiguous effect. In contrast, reproductive potential of
 dispersing beetles remained almost unaffected by temperature sum, daily
 temperature, and photoperiod. Our results show that spring swarming can
 potentially start right after cold temperatures in mid-winter have
 terminated diapause. Ongoing climate warming will consequently extend the
 reproductive season, likely increasing voltinism and population density of
 I. typographus. Our findings can be implemented in phenology- and risk
 assessment models to more accurately predict the temperature-dependent
 phenology and infestation risk in a future climate, to ultimately
 facilitate bark beetle management (e.g. sanitation and salvage logging)
 and guide long-term silvicultural adaptations.
description: In laboratory experiments performed in 2021 and 2023, emergence
 of Ips typographus von experimental logs and the reprodutive potential of
 female beetles was assessed under different controlled fluctuating
 temperatures and daylengths.
description: # Spring dispersal and reproductive potential Ips typographus
 [https://doi.org/10.5061/dryad.0k6djhb9b](https://doi.org/10.5061/dryad.0k6djhb9b) ## Description of the data and file structure In late winter/early spring 2021 and 2023, we conducted a laboratory experiment assessing spring swarming and reproductive potential of *I. typographus* after diapause termination under various temperature and photoperiodic conditions. We applied mean temperatures between 13 and 23 °C with daily oscillations of ±5 °C and daylengths between 9 and 14 h (January to April). Flight activity was assessed by counting emerging beetles from experimental logs, while reproductive potential was assessed by disecting female beetles to record the mean number of eggs per ovariole and the mean relative vitellarium length. ### Files and variables #### File: data21.csv **Description:** all data recorded in the experiment in 2021 ##### Variables * trial: trial of the respective observation * start: start of the respective trial (Date) * date: date of the respective observation (Date) * mean temperature: mean temperature of the scenario (°C) * amplitude: amplitude of the scenario (°C) * temperature curve: type of temperature curve of the scenario * daylength: daylength of the respective trial (hours) * emerged individuals: emerged individuals recorded at the respective observation (n) #### File: data23.csv **Description:** all data recorded in the experiment in 2023 ##### Variables * trial: trial of the respective observation * start: start of the respective trial (Date) * date: date of the respective observation (Date) * mean temperature: mean temperature of the scenario (°C) * amplitude: amplitude of the scenario (°C) * temperature curve: type of temperature curve of the scenario * daylength: daylength of the respective trial (hours) * total emerged individuals: (n); total individual in respective observation * individual: sampling number for dissected individual; NA indicates observations that are not applicable * sex: sex of the respective individual (f = female, m = male); NA indicates observations that are not available * eggs: number of eggs in the ovariol of the respective individual (n); NA indicates observations that are not applicable * vitellarium length: vitellarium length of the respective individual (µm); NA indicates observations that are not applicable * total length: total ovariole length of the respective individual (µm); NA indicates observations that are not applicable ## Code/software Data can be opend using R-Studio