Bookkeeping of insect herbivory trends in herbarium specimens of purple loosestrife ( Lythrum salicaria )

Abstract

The potential use of herbarium specimens to detect herbivory trends is enormous but largely untapped. The objective of this study was to reconstruct the long-term herbivory pressure on the Eurasian invasive plant, purple loosestrife ( Lythrum salicaria ), by evaluating leaf damage over 1323 specimens from southern Québec (Canada). The hypothesis tested is that that the prevalence of herbivory damage on purple loosestrife is low during the invasion phase and increases throughout the saturation phase. Historical trends suggest a gradual increase in hole feeding and margin feeding damage from 1883 to around 1940, followed by a period of relative stability. The percentage of specimens with window feeding damage did not begin to increase until the end of the twentieth century, from 3% (2–6%) in 1990 to 45% (14–81%) in 2015. Temporal changes in the frequency of window feeding damage support the hypothesis of an increasing herbivory pressure by recently introduced insects. This study shows that leaf damage made by insects introduced for the biocontrol of purple loosestrife, such as coleopterans of the Neogalerucella genus, can be assessed from voucher specimens. Herbaria are a rich source in information that can be used to answer questions related to plant-insect interactions in the context of biological invasions and biodiversity changes. This article is part of the theme issue ‘Biological collections for understanding biodiversity in the Anthropocene’.

Herbarium specimens provide historical evidence of Cardiaspina jerramungae (Hemiptera: Psylloidea, Aphalaridae) outbreaks on Eucalyptus occidentalis in the Lower Great Southern of Western Australia

“…; Beaulieu et al . ; Meineke et al . ) might exclude evidence of psyllid presence during periods of low population levels.…”

“…3). Collection bias favouring clean undamaged specimens (Abbott et al 1999;Beaulieu et al 2019;Meineke et al 2019) might exclude evidence of psyllid presence during periods of low population levels. However, it would be expected that the frequency of psyllid evidence on herbarium specimens would diminish with decreasing populations, particularly during non-outbreak periods, and be reflected in collected material.…”

“…The use of herbarium specimens to examine spatio‐temporal trends in herbivory which have consequences for ecosystem structure and function is being used increasingly as online metadata resources become more available (Beaulieu et al . ). Such studies are mostly used to trace changes in plant phenology (Meineke et al .…”

“…However, with the exception of E. wandoo, its development on these species has not been observed, and its presence may be a result of spillover from the original preferred host trees during periods with high population when the preferred host plant's foliage is depleted (Steinbauer & Nahrung 2016). The use of herbarium specimens to examine spatio-temporal trends in herbivory which have consequences for ecosystem structure and function is being used increasingly as online metadata resources become more available (Beaulieu et al 2019). Such studies are mostly used to trace changes in plant phenology (Meineke et al 2018).…”

Applying Machine Learning to Investigate Long Term Insect-Plant Interactions Preserved on Digitized Herbarium Specimens

“…Herbarium specimens preserve signatures of insect damage ("herbivory") through time on their leaves (Beaulieu et al, 2018;Meineke et al, 2018a). Herbivory encompasses diverse types of damage triggered by a wide range of insect taxa (for examples, see Fig.…”