Scientists have discovered only a tiny fraction of living insect species, but up to as many as 20 million insect species may exist

Amazing stuff!

"... according to a new study ... Using statistical methods borrowed from another field, a team of entomologists estimates there may be as many as 20 million insect species on our planet—more than three times the previous estimate. ...

Scientists have long debated exactly how many insect species there are, with the previous consensus being about 6 million. 

Over the past 3 centuries, entomologists have described about 1 million insect species, but finding and describing them all would be a daunting—if not impossible—task. ...

To obtain an improved estimate of insect diversity, Colwell and colleagues studied years of data from insect surveys in Costa Rica’s Guanacaste National Park and applied statistical methods borrowed from epidemiology. The researchers started by taking a closer look at a subfamily of parasitoid wasps known as Microgastrinae, which infamously lay their eggs inside living caterpillars. These wasps are extremely well-studied: Scientists have described about 3000 species of Microgastrinae, many of which are found in Costa Rica. So, the team decided to test how well insect surveys within the park have captured the diversity of the wasps living there.

Over the past several years, scientists conducting surveys of flying insects in the park have identified 388 species of Microgastrinae within a core set of traps and 578 within an additional set. Independently, when scientists looked at caterpillars that had been parasitized within the park, they identified 889 wasp species.

However, when Colwell and his colleagues examined these data sets, they were surprised to find little overlap in the species captured with traps and by examining caterpillars. That mismatch showed both methods must only be tallying a fraction of the total number of Microgastrinae species within the park. To estimate that total, the researchers used a statistical method developed by epidemiologists to estimate the size of a population affected by a disease based on incomplete tallies of the ill—as if the true number of wasp species was like the true number of sick people in an outbreak. The approach indicated the park is home to a whopping 2394 Microgastrinae species. ..."

From the significance and abstract:

"Significance

For more than 40 y, entomologists have attempted to estimate the number of insect species on Earth, with the current consensus—the figure most experts accept—at about six million. Using genetic information (DNA barcodes) for 1.6 million individual tropical insects, a deep census of a highly diverse group of parasitoid wasps, and powerful statistical strategies, we conservatively estimate that the true number of insect species is at least 14 to 20 million—two to three times higher than current estimates. Already known to be the most diverse group of animals, a doubling or tripling of estimated insect diversity has profound implications for our understanding of the scale, richness, and future of biodiversity on Earth.

Abstract

Estimating the number of insect species on Earth is a daunting challenge. The current consensus estimate—about six million species—is likely far too low, as we will show.

Our estimate of the global number of insect species rests on a sample of more than 1,600,000 DNA-barcoded insect specimens representing 53,945 species from 15 “core” Malaise traps deployed in dry forest, cloud forest, and rainforest ecosystems of the Área de Conservación Guanacaste (ACG) in Costa Rica. Even this massive sample fails to reveal the full extent of ACG insect species richness. To estimate total ACG insect richness, we adjust the observed count of insect species by an “undersampling ratio,” computed for a hyperdiverse subfamily of parasitoid wasps (Braconidae: Microgastrinae).

The ratio compares microgastrine richness from the core Malaise traps to a lower-bound estimate of true microgastrine richness—including undetected species—based on 21,669 specimens from three sources: the 15 core Malaise traps, 15 “peripheral” Malaise traps spanning all three ecosystems, and 11,373 DNA-barcoded specimens reared from some 1,500 species of microgastrine-parasitized caterpillars (Lepidoptera).

To estimate global insect richness, we apply Earth/ACG ratios for tree species and several animal taxa to upscale our estimate of ACG insect richness (nearly 333,000 species). Adopting conservative assumptions, we reach an estimate of 14 to 20 million insect species on Earth, depending on the upscaling group—two to three times the current consensus estimates. Upscaling instead from a point estimate of ACG richness with a wide CI, global estimates reach nearly 30 million species."

Scientists have discovered only a tiny fraction of living insect species | Science | AAAS "About 1 million insect species have been described, but a new analysis suggests tens of millions more may be out there"

Constructing a lower-bound estimate of the global number of insect species on a hyperdiverse empirical foundation (open access)

Fish, reconsidered: A major update of the ‘Tree of Life’ draws surprising connections

Amazing stuff!

"... drew many surprising connections while completely revising the Tree of Life branches concerning ray-finned fishes, which represent more than 35,000 species — tunas, clown fish, catfish, piranhas, etc. – accounting for nearly all vertebrate fish species and about half of living vertebrate species. ...

Prior to the new revisions, ray-finned fishes were sorted into taxonomic groups largely based on morphology — their physical forms and structures — and other observable traits, which doesn’t capture all relationships among lineages ... Molecular genetic analysis ... has clarified relationships among lineages but, until now, those discoveries have never been synthesized and incorporated into an updated Tree of Life.

“Our knowledge of the fish Tree of Life is dramatically different than it was 20 years ago,” ... “Genetics has upended our understanding of how major fish lineages relate to each other. ...
In all, the researchers defined 97 inclusive groups based on common ancestry, accounting for 830 lineages. Only one of the 97 groups is new. They focused on consolidation, extracting more than 20 group names that they deemed redundant. ..."

From the abstract:

"Classification of the tremendous diversity of ray-finned fishes (Actinopterygii) began with the designation of taxonomic groups based on morphological similarity. Starting in the late 1960s morphological phylogenetics became the basis for the classification of Actinopterygii but failed to resolve many relationships, particularly among lineages

within the hyperdiverse Percomorpha. The introduction of molecular phylogenetics led to a dramatic reconfiguration of actinopterygian phylogeny. Refined phylogenetic resolution afforded by molecular studies revealed an uneven diversity among actinopterygian lineages, resulting in a proliferation of redundant group names in Linnean ranked classifications. Here we provide an unranked phylogenetic classification for actinopterygian fishes based on a summary phylogeny of 830 lineages of ray-finned fishes that includes all currently recognized actinopterygian taxonomic families and 287 fossil taxa. We provide phylogenetic definitions for 90 clade names and review seven previously defined names. For each of the 97 clade names we review the etymology of the clade name, clade species diversity and constituent lineages, clade diagnostic morphological apomorphies, a review of synonyms, and discuss the clade's

nomenclatural and systematic history. The new classification is free of redundant group names and includes only one new name among the 97 clade names we review and describe, yielding a comprehensive classification that is based explicitly on the phylogeny of ray-finned fishes that has emerged in the 21st century and rests on the foundation of the previous 200 years of actinopterygian systematic research."

Fish, reconsidered: An updated ‘Tree of Life’ draws surprising connections | YaleNews In a major new work, ... ichthyologist ... revises branches of the Tree of Life concerning most fish species based on the latest scientific knowledge.

Phylogenetic classification of living and fossil ray-finned fishes (Actinopterygii) (open access)