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<p>Arthropod natural enemies such as <i>Tetrastichus planipennisi</i> Yang (Hymenoptera: Eulophidae) face novel environments when introduced to non-native ranges for classical biocontrol. Their ability to adapt to novel thermal regimes may determine their success in establishment. <i>T. planipennisi</i> was introduced to the USA in 2007 for classical biological control of the invasive emerald ash borer <i>Agrilus planipennis</i> Fairmaire (Coleoptera: Buprestidae). Previous studies found that <i>T. planipennisi</i> is chill-susceptible and its establishment is affected by winter mortality at higher latitudes. We conducted a field experiment during winter of 2021–2022 in Jericho Research Forest, Vermont, USA, to determine if the temperature at which spontaneous freezing occurs, known as the supercooling point (SCP), of <i>T. planipennisi</i> larvae changes in response to microhabitat manipulations of ambient temperature, and we measured eclosion. Larvae were placed under control conditions or artificial shelters that reduced temperature extremes. Larvae in control groups had significantly lower SCP values in January, February, and March compared to those in artificial shelters, with mean SCP values in control-group larvae 2.52&#xa0;°C lower in January, 1.70&#xa0;°C lower in February, 1.98&#xa0;°C lower in March, and higher eclosion success (median 18% in controls). SCP values were negatively correlated with monthly cooling rate and higher in shelter treatments, and degree-hours ≤  − 2&#xa0;°C best predicted eclosion. These findings demonstrate significant inter-individual variation in SCP in response to shifts in local habitat temperatures. Microclimatic variation may play a role in determining insect SCP capacity and emergence, particularly in northern regions with extreme winter conditions.</p>

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Effects of microhabitats and seasonal conditions on the supercooling points of Tetrastichus planipennisi (Hymenoptera: Eulophidae) in Vermont, USA

  • 期刊论文

  • 发表日期：

    2026年2月2日

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  • George Ni,
  • Nicholas J. Gotelli,
  • Jian J. Duan

摘要

Arthropod natural enemies such as Tetrastichus planipennisi Yang (Hymenoptera: Eulophidae) face novel environments when introduced to non-native ranges for classical biocontrol. Their ability to adapt to novel thermal regimes may determine their success in establishment. T. planipennisi was introduced to the USA in 2007 for classical biological control of the invasive emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae). Previous studies found that T. planipennisi is chill-susceptible and its establishment is affected by winter mortality at higher latitudes. We conducted a field experiment during winter of 2021–2022 in Jericho Research Forest, Vermont, USA, to determine if the temperature at which spontaneous freezing occurs, known as the supercooling point (SCP), of T. planipennisi larvae changes in response to microhabitat manipulations of ambient temperature, and we measured eclosion. Larvae were placed under control conditions or artificial shelters that reduced temperature extremes. Larvae in control groups had significantly lower SCP values in January, February, and March compared to those in artificial shelters, with mean SCP values in control-group larvae 2.52 °C lower in January, 1.70 °C lower in February, 1.98 °C lower in March, and higher eclosion success (median 18% in controls). SCP values were negatively correlated with monthly cooling rate and higher in shelter treatments, and degree-hours ≤  − 2 °C best predicted eclosion. These findings demonstrate significant inter-individual variation in SCP in response to shifts in local habitat temperatures. Microclimatic variation may play a role in determining insect SCP capacity and emergence, particularly in northern regions with extreme winter conditions.