Variation in the diversity and richness of parasitoid wasps based on sampling effort

Abstract

Parasitoid wasps are a mega-diverse, ecologically dominant, but poorly studied component of global biodiversity. In order to maximise the efficiency and reduce the cost of their collection, the application of optimal sampling techniques is necessary. Two sites in Auckland, New Zealand were sampled intensively to determine the relationship between sampling effort and observed species richness of parasitoid wasps from the family Ichneumonidae. Twenty traps were deployed at each site at three different times over the austral summer period, resulting in a total sampling effort of 840 Malaise-trap-days. Rarefaction techniques and non-parametric estimators were used to predict species richness and to evaluate the variation and completeness of sampling. Despite an intensive Malaise-trapping regime over the summer period, no asymptote of species richness was reached. At best, sampling captured two-thirds of parasitoid wasp species present. The estimated total number of species present depended on the month of sampling and the statistical estimator used. Consequently, the use of fewer traps would have caught only a small proportion of all species (one trap 7–21%; two traps 13–32%), and many traps contributed little to the overall number of individuals caught. However, variation in the catch of individual Malaise traps was not explained by seasonal turnover of species, vegetation or environmental conditions surrounding the trap, or distance of traps to one another. Overall the results demonstrate that even with an intense sampling effort the community is incompletely sampled. The use of only a few traps and/or for very short periods severely limits the estimates of richness because (i) fewer individuals are caught leading to a greater number of singletons; and (ii) the considerable variation of individual traps means some traps will contribute few or no individuals. Understanding how sampling effort affects the richness and diversity of parasitoid wasps is a useful foundation for future studies.

Ecosystem type might mask the effect of ecosystem recovery on parasitoids’ biodiversity quality

“…The apparently low efficiency is a common issue when collecting Ichneumonidae, and it seems hard to improve even when increasing the sampling effort because of the high proportion of singletons that are usually found. For instance, Gómez et al (2018) had a 7710 Malaise trap days effort in Peruvian Amazonia and collected about 60% of potential Ichneumonidae richness, and Saunders and Ward (2018) in Australia, with a sampling effort of 840 Malaise trap days, reached about 66% of estimated richness. Considering that we had a sampling effort of c. 1620 Malaise trap days, a 65-70% of completeness might be assumed as respectable.…”

Hymenoptera functional groups’ shifts in disturbance gradients at Andean forests in Southern Ecuador

“…Although showed as highly effective for parasitoids (Mazón and Bordera 2008) and aculeates in general (Volpato et al 2020), with some reported bias either towards males (Aguiar and Santos 2010) or females (Mazón et al 2020), scent-baited traps or entomological nets seem to work better for bees (Santos Júnior et al 2014;Ferronato et al 2018;Alvarenga et al 2020). Other sampling methods should be used to complement Malaise traps, especially when time for field work is brief (McGravy et al 2016;Saunders and Ward 2018). Sampling should also include different weather seasons in order to have a better representation of all Hymenoptera families and to clarify if bees have reduced populations in these forests.…”

Using a Collection Heath Index to prioritise access and activities in the New Zealand Arthropod Collection

“…Of all the groups, Hymenoptera has the highest proportion of level 4 (integrate). This is due to several large surveys from university student projects (Frost et al 2015, Kendall and Ward 2016, Saunders and Ward 2018; and also a growing voucher collection associated with specimens for DNA barcoding and machine-learning imaging projects.…”

“…However, the resources available within taxonomic collections seldom match wider expectations from the scientific community, end users and funding agencies. Particularly relevant is the increased demands on collections staff for access and the use of specimens and their data (digitisation) and concern that collections are often being inundated with specimens from environmental surveys (McGinley 1993, Schilthuizen et al 2015.…”