Expansion of elevational range in a forest pest: Can parasitoids track their hosts?

• Published in: Ecosphere
• Main Authors: Hodar Correa, José Antonio, Cayuela, Luis, Heras, Daniel, Pérez Luque, Antonio Jesús, Torres Muros, Lucía
• Format: Article in Journal/Newspaper
• Language: English
• Published: Ecological Society of America 2021
• Subjects: Biological control; Elevational gradient; Host-parasitoid interactions; North Atlantic Oscillation Index; Pest dynamic; Pine processionary moth; Giles; North Atlantic; North Atlantic oscillation
• Online Access: http://hdl.handle.net/10481/69134; https://doi.org/10.1002/ecs2.3476

We are thankful to Karim Senhadji and Ramon Ruiz-Puche for their help during the field work, and to Sara Garcia Morato for her contribution to quantifying rates of parasitism in PPM clutches at the laboratory. Two anonymous referees contributed to improve the manuscript. This study was supported by projects PROPINOL (PN22/2008), GESBOME (P06-RNM-1890) from Junta de Andalucia, REMEDINAL TE-CM (S2018/EMT-4338) from Comunidad de Madrid, ADAPTAMED (LIFE14 CCA/ES/000612) from LIFE program, and GILES (PCIN-2016-150) from the ERANET-LAC H2020 Programme. Gradients in elevation impose changes in environmental conditions, which in turn modulate species distribution and abundance as well as the interactions they maintain. Along the gradient, interacting species (e.g., predators, parasitoids) can respond to changes in different ways. This study aims to investigate how egg parasitism of a forest pest, the pine processionary moth (PPM), Thaumetopoea pityocampa, vary along an elevational gradient (190-2000 m.a.s.l.) in a mountain range of SE Spain, including areas of recent elevational expansion, for a seven years period (2008-2014). We used generalized linear mixed models to ascertain the effect of both elevation and the winter North Atlantic Oscillation (NAO) index (a proxy of interannual climatic conditions) on the rate of parasitism, and the occurrence probabilities of two parasitoid species: a PPM specialist and a generalist species. Since four pine species are stratified along the elevational gradient, we repeated all the analyses separately for lowlands (190-1300 m. a.s.l.) and uplands (1350-2000 m. a.s.l.). Results showed a decrease in both parasitism rate and probability of occurrence of the two main parasitoid species with elevation, although decline was more severe for the specialist species. The effect of elevation was more conspicuous and intense in uplands than in lowlands. Positive NAO winter values, associated with cold and dry winters, reduced the rate of parasitism and the probability of occurrence of the two main parasitoid species-but particularly for the generalist species-as elevation increases. In a context of climate warming, it is crucial to mitigate PPM elevational and latitudinal expansion. Increasing tree diversity at the PPM expansion areas may favor the establishment of parasitoids, which could contribute to synchronizing host- parasitoid interactions and minimize the risk of PPM outbreaks. Junta de Andalucia PN22/2008 REMEDINAL TE-CM from Comunidad de Madrid S2018/EMT-4338 ADAPTAMED from LIFE program LIFE14 CCA/ES/000612 GILES from the ERANET-LAC H2020 Programme PCIN-2016-150 Junta de Andalucia P06-RNM-1890