Completing Linnaeus’s inventory of the Swedish insect fauna: Only 5,000 species left?

Abstract

Despite more than 250 years of taxonomic research, we still have only a vague idea about the true size and composition of the faunas and floras of the planet. Many biodiversity inventories provide limited insight because they focus on a small taxonomic subsample or a tiny geographic area. Here, we report on the size and composition of the Swedish insect fauna, thought to represent roughly half of the diversity of multicellular life in one of the largest European countries. Our results are based on more than a decade of data from the Swedish Taxonomy Initiative and its massive inventory of the country's insect fauna, the Swedish Malaise Trap Project The fauna is considered one of the best known in the world, but the initiative has nevertheless revealed a surprising amount of hidden diversity: more than 3,000 new species (301 new to science) have been documented so far. Here, we use three independent methods to analyze the true size and composition of the fauna at the family or subfamily level: (1) assessments by experts who have been working on the most poorly known groups in the fauna; (2) estimates based on the proportion of new species discovered in the Malaise trap inventory; and (3) extrapolations based on species abundance and incidence data from the inventory. For the last method, we develop a new estimator, the combined non-parametric estimator, which we show is less sensitive to poor coverage of the species pool than other popular estimators. The three methods converge on similar estimates of the size and composition of the fauna, suggesting that it comprises around 33,000 species. Of

Mangroves are an overlooked hotspot of insect diversity despite low plant diversity

“…We also attempted to estimate species richness using extrapolation via frequency ratio [ 62 ] and combined non-parametric estimators (CNE) [ 63 ], with the former being widely used to estimate microbial diversity [ 64 , 65 ]. Both estimators suggest that mangroves are even more species-rich than rainforest and swamp forest habitats (Additional file 2 : Figure S4) with coastal- and urban forests yielding even higher estimates.…”

“…The habitat type “mangrove” was treated both as a single habitat as well as separate sites (PU, SB, SMN, SMO, others) in separate analyses. We also obtained species richness extrapolations for each habitat using a frequency ratio estimator [ 62 ] and a combined non-parametric estimator (CNE) [ 63 ] based on combined Chao1 and Chao2 extrapolations. Both were performed in R, with the former using the breakaway package and the latter using R code published with the original manuscript.…”

Revision of the Swedish species of Neoxorides Clément, 1938 (Ichneumonidae: Poemeniinae) with the description of a new species and an illustrated key to species

“…Our knowledge of species diversity in insects is still embarrassingly incomplete, even in relatively well-known regions such as Europe. A large inventory based on millions of insect specimens from the Swedish Malaise Trap Project (SMPT) recently concluded that the largest gaps in our knowledge are among dipteran decomposers and hymenopteran parasitoids (Ronquist et al 2020), such as Ichneumonidae Latreille, 1802 (also called "Darwin wasps" since recently: Klopfstein et al 2019). Even small and easily recognized genera still hold undetected diversity, if examined carefully.…”

Detecting flying insects using car nets and DNA metabarcoding

“…Although our results are based on one month's sampling in 2018, it is strikingly similar in overall taxonomic composition to the multiyear national assessment for Sweden based on Malaise traps. Similar to SMTP, we also find most of the new species detected belong to Diptera and Hymenoptera [39]. However, our approach is much quicker and covers a much larger geographical area.…”