Societal Impact Statement
Research and publication of the planet's remaining plant and fungal species as yet unknown to science is essential if we are to address the United Nations Sustainable Development Goal (SDG) 15 “Life on Land” which includes the protection of terrestrial ecosystems and halting of biodiversity loss. If species are not known to science, they cannot be assessed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and so the possibility to protect them from extinction is reduced. Furthermore, until species are known to science they cannot be fully scientifically evaluated for their potential as new foods, medicines, and products which would help address SDGs 1,2,3, and 8.
Summary
Scientific discovery, including naming new taxa, is important because without a scientific name, a species is invisible to science and the possibilities of researching its ecology, applications and threats, and conserving it, are greatly reduced. We review new scientific discoveries in the plant and fungal kingdoms, based largely on new names of taxa published in 2019 and indexed in the International Plant Names Index and Index Fungorum. Numbers of new species in both kingdoms were similar with 1942 new species of plant published and 1882 species of fungi. However, while >50% of plant species have likely been discovered, >90% of fungi remain unknown. This gulf likely explains the greater number of higher order taxa for fungi published in 2019: three classes, 18 orders, 48 families and 214 genera versus one new family and 87 new genera for plants. We compare the kingdoms in terms of rates of scientific discovery, globally and in different taxonomic groups and geographic areas, and with regard to the use of DNA in discovery. We review species new to science, especially those of interest to humanity as new products, and also by life-form. We consider where future such discoveries can be expected. We recommend an urgent increase in investment in scientific discovery of plant and fungal species, while they still survive. Priorities include more investment in training taxonomists, in building and equipping collections-based research centers for them, especially in species-rich, income-poor countries where the bulk of species as yet unknown to science are thought to occur.
INTRODUCTION
While some species unknown to science are already known to local communities and may have local names, scientific discovery, including scientific naming of new taxa is important because without a scientific name, a species is invisible to the world of science and the possibility of researching its ecology, applications, phylogenetic placement, and threats is greatly reduced. Above all, scientific discovery and naming (henceforth “discovery”) is increasingly important for species conservation because the species which remain to be discovered are often those most likely to be at risk of extinction and giving them a name facilitates synthesis and dissemination of the available information about them, a vital first step in evaluating their extinction risk.
New discoveries in the plant kingdom have been published at rates of c. 2,100 to 2,600 species per year for the past 15 years (Figure 1a, IPNI, 2020, Willis 2017). For 2019, 1942 new species of vascular plants were registered on the International Plant Names Index (IPNI) by 28 February 2020 (Dataset S1). The number of new fungal species catalogued for 2019 by 1 March 2020 on Index Fungorum was 1882 (Index Fungorum, Dataset S2). As indexing of 2019 names from the scientific literature continues, totals for both plant and fungal species are likely to rise by at least tens if not hundreds of species before all 2019 publications have been indexed. The rate of species discovery for fungi has increased from 1,000 to 1,500 per year about 10 years ago, to around 2000 with a peak of over 2,500 species in 2016 (Figure 1b).
The fungal kingdom is significantly less well studied than the plant kingdom. Currently 148,000 species of fungi are recognized (Species Fungorum, 2020), the majority in the phyla Ascomycota and Basidiomycota (BOX 1), but it is estimated that the vast majority, over 90%, of fungal species are currently unknown to science and that the total number is somewhere between 2.2 and 3.8 million (Hawksworth & Lücking, 2017).
In contrast, known land plant species have been estimated to number c. 400,000 of which c. 380,000 are vascular plants, with 370,000 belong to the largest phylum, flowering plants (Angiospermae), although these numbers are debated (Nic Lughadha et al., 2016; Nic Lughadha, Bachman, & Govaerts, 2017) and the recently completed World Checklist of Vascular Plants lists 347,298 accepted species (WCVP, 2020). A decade ago, many plant scientists considered that the vast majority of flowering plants had already been discovered, with just 10%–20% remaining to be described (Joppa, Roberts, Myers, & Pimm, 2011 ). However, the fairly steady rates of publication of new plant species in the interim suggest otherwise (Figure 1a), as do the experiences of many botanists undertaking fieldwork in the tropics. For example, Corlett (2020) suggests as many as 100,000 more plant species remain to be discovered. Giam et al. (2012) consider that least disturbed tropical forests are centers of undescribed species diversity.
The huge difference in level of knowledge between plant and fungal kingdoms is reflected in descriptions of new phyla. Twelve plant phyla are recognized, depending on taxonomic concepts, and no new phyla have been discovered for decades. In contrast, four new phyla of fungi were named in 2018, taking the total to 18 (Tedersoo et al., 2018). While new higher taxa of fungi are now commonly published each year—3 classes, 18 orders, 48 families, and 214 genera in 2019—this is not the case in plants. In 2019 for plants, no new classes or orders, and only one new family (Wightiaceae Liu et al., 2019) and 87 new genera were validly published.
There are several reasons why fungi are less well known than plants: They are challenging to study and many of them have cryptic lifestyles spending most of their time as hyphae, or more rarely as cells, e.g. in soil. Characters suitable for morphological classification are fewer than in plants and moreover the characters often overlap and are therefore challenging to use in classification. Also, convergent evolution is common in fungi (Willis, 2018). Finally, the diversity of the Kingdom Fungi is high while the number of mycologists compared to botanists is relatively small.
The increasing rate of fungal discovery in the past two decades is attributed to the advent of DNA studies which have become standard practice, in addition to the traditionally used morphological data, in describing new taxa. This has accelerated the discovery of new species and greatly facilitated the study of relationships. For species-level studies a single DNA marker, ITS (including two spacers ITS1 and ITS2 and the highly conserved 5.8S gene), is in many cases effective across the fungal kingdom for taxonomic purposes although in some groups other markers are needed as well. In contrast, for plants, no single marker is sufficient to distinguish species from each other across the kingdom, or indeed across flowering plants, and most species discoveries today are based solely on morphological data (E. Lucas pers. comm., D.Goyder pers. comm., I. Larridon pers. comm.). Most plant species have not been subjected to DNA studies. In fact, comprehensive sampling at generic level is still a target (PAFTOL, 2020). If it were possible to sample and analyse the DNA of plants in the same way as fungi, would species discovery be accelerated as it is for fungi, and would there be the same multiplier effect?
The time from the first collection of a putative new species to its formal description varies greatly. Barleria deserticola (Figure 2a), from the Namib coastal desert was first collected 160 years ago, by the explorer Friedrich Welwitsch, but was only re-found in 2009 by US botanist Erin Tripp and named in 2019 (Darbyshire, Tripp, & Chase, 2019). In contrast, the description and publication of Inversodicraea koukoutamba (Podostemaceae) collected from a waterfall in Guinea in 2018 took only one year from the first collection (Cheek, Molmou, Jennings, Magassouba, & van der Burgt, 2019). Delays in publication can reflect a lack of availability of specialist taxonomists with the capacity or time to write and publish a formal paper describing new species. They can also result from a former convention, in which naming a species from only a single specimen, showing a single phase of the species’ life cycle, was considered poor science (Cheek & Bridson, 2019). This convention contributed to the delay in publishing Vepris bali, a cloud forest tree of Cameroon collected 70 years ago. Although taxonomic capacity remains a constraint, aversion to describing species based on a single collection has now been largely overcome, with good reason: new collections may never become available. Vepris bali, for example, is presumed extinct (Cheek, Gosline, & Onana, 2018). Publication attracts interest and encourages others to seek new material in the field, sometimes resulting in rediscovery of species hitherto considered extinct (Humphreys, Govaerts, Ficinski, Nic Lughadha, & Vorontsova, 2019).
In fungi, confusion about the identity of the already published species hinders progress. In many groups, the type specimens of all published species need to be studied first, or neo- or epitypes designated for old names, before new names can be published for species. In addition, many new species are discovered from environmental specimens (usually soil samples) but, according to the current rules of nomenclature for fungi they cannot be named because of a lack of a physical voucher specimen which needs to be deposited in a fungarium (Lücking & Hawksworth, 2018; See BOX 2 for more on naming conventions). The debate is also still ongoing as to whether a short DNA sequence is sufficiently robust evidence to justify the publication of a new species name (Zamora et al., 2018), especially as thousands of well-known names still lack DNA barcodes (Schoch et al., 2014). Currently, two Special-purpose committees are exploring the use of DNA sequences as types, and this topic is due to be further discussed during the next International Mycological Congress in 2022 (May, 2018) and in the International Botanical Congress in 2023 (Turland, Wiersema, Monro, Deng, & Zhang, 2017).
Authors: Cheek et al
Societal Impact Statement Research and publication of the planet's remaining plant and fungal species as yet unknown to science is essential if we are to address the United Nations Sustainable Development Goal (SDG) 15 “Life on Land” which includes the protection of terrestrial ecosystems and halting of biodiversity loss. If species are not known to science, they cannot be assessed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and so the possibility to protect them from extinction is reduced. Furthermore, until species are known to science they cannot be fully scientifically evaluated for their potential as new foods, medicines, and products which would help address SDGs 1,2,3, and 8.
Summary Scientific discovery, including naming new taxa, is important because without a scientific name, a species is invisible to science and the possibilities of researching its ecology, applications and threats, and conserving it, are greatly reduced. We review new scientific discoveries in the plant and fungal kingdoms, based largely on new names of taxa published in 2019 and indexed in the International Plant Names Index and Index Fungorum. Numbers of new species in both kingdoms were similar with 1942 new species of plant published and 1882 species of fungi. However, while >50% of plant species have likely been discovered, >90% of fungi remain unknown. This gulf likely explains the greater number of higher order taxa for fungi published in 2019: three classes, 18 orders, 48 families and 214 genera versus one new family and 87 new genera for plants. We compare the kingdoms in terms of rates of scientific discovery, globally and in different taxonomic groups and geographic areas, and with regard to the use of DNA in discovery. We review species new to science, especially those of interest to humanity as new products, and also by life-form. We consider where future such discoveries can be expected. We recommend an urgent increase in investment in scientific discovery of plant and fungal species, while they still survive. Priorities include more investment in training taxonomists, in building and equipping collections-based research centers for them, especially in species-rich, income-poor countries where the bulk of species as yet unknown to science are thought to occur.
INTRODUCTION While some species unknown to science are already known to local communities and may have local names, scientific discovery, including scientific naming of new taxa is important because without a scientific name, a species is invisible to the world of science and the possibility of researching its ecology, applications, phylogenetic placement, and threats is greatly reduced. Above all, scientific discovery and naming (henceforth “discovery”) is increasingly important for species conservation because the species which remain to be discovered are often those most likely to be at risk of extinction and giving them a name facilitates synthesis and dissemination of the available information about them, a vital first step in evaluating their extinction risk. New discoveries in the plant kingdom have been published at rates of c. 2,100 to 2,600 species per year for the past 15 years (Figure 1a, IPNI, 2020, Willis 2017). For 2019, 1942 new species of vascular plants were registered on the International Plant Names Index (IPNI) by 28 February 2020 (Dataset S1). The number of new fungal species catalogued for 2019 by 1 March 2020 on Index Fungorum was 1882 (Index Fungorum, Dataset S2). As indexing of 2019 names from the scientific literature continues, totals for both plant and fungal species are likely to rise by at least tens if not hundreds of species before all 2019 publications have been indexed. The rate of species discovery for fungi has increased from 1,000 to 1,500 per year about 10 years ago, to around 2000 with a peak of over 2,500 species in 2016 (Figure 1b). The fungal kingdom is significantly less well studied than the plant kingdom. Currently 148,000 species of fungi are recognized (Species Fungorum, 2020), the majority in the phyla Ascomycota and Basidiomycota (BOX 1), but it is estimated that the vast majority, over 90%, of fungal species are currently unknown to science and that the total number is somewhere between 2.2 and 3.8 million (Hawksworth & Lücking, 2017). In contrast, known land plant species have been estimated to number c. 400,000 of which c. 380,000 are vascular plants, with 370,000 belong to the largest phylum, flowering plants (Angiospermae), although these numbers are debated (Nic Lughadha et al., 2016; Nic Lughadha, Bachman, & Govaerts, 2017) and the recently completed World Checklist of Vascular Plants lists 347,298 accepted species (WCVP, 2020). A decade ago, many plant scientists considered that the vast majority of flowering plants had already been discovered, with just 10%–20% remaining to be described (Joppa, Roberts, Myers, & Pimm, 2011 ). However, the fairly steady rates of publication of new plant species in the interim suggest otherwise (Figure 1a), as do the experiences of many botanists undertaking fieldwork in the tropics. For example, Corlett (2020) suggests as many as 100,000 more plant species remain to be discovered. Giam et al. (2012) consider that least disturbed tropical forests are centers of undescribed species diversity.
The huge difference in level of knowledge between plant and fungal kingdoms is reflected in descriptions of new phyla. Twelve plant phyla are recognized, depending on taxonomic concepts, and no new phyla have been discovered for decades. In contrast, four new phyla of fungi were named in 2018, taking the total to 18 (Tedersoo et al., 2018). While new higher taxa of fungi are now commonly published each year—3 classes, 18 orders, 48 families, and 214 genera in 2019—this is not the case in plants. In 2019 for plants, no new classes or orders, and only one new family (Wightiaceae Liu et al., 2019) and 87 new genera were validly published.
There are several reasons why fungi are less well known than plants: They are challenging to study and many of them have cryptic lifestyles spending most of their time as hyphae, or more rarely as cells, e.g. in soil. Characters suitable for morphological classification are fewer than in plants and moreover the characters often overlap and are therefore challenging to use in classification. Also, convergent evolution is common in fungi (Willis, 2018). Finally, the diversity of the Kingdom Fungi is high while the number of mycologists compared to botanists is relatively small.
The increasing rate of fungal discovery in the past two decades is attributed to the advent of DNA studies which have become standard practice, in addition to the traditionally used morphological data, in describing new taxa. This has accelerated the discovery of new species and greatly facilitated the study of relationships. For species-level studies a single DNA marker, ITS (including two spacers ITS1 and ITS2 and the highly conserved 5.8S gene), is in many cases effective across the fungal kingdom for taxonomic purposes although in some groups other markers are needed as well. In contrast, for plants, no single marker is sufficient to distinguish species from each other across the kingdom, or indeed across flowering plants, and most species discoveries today are based solely on morphological data (E. Lucas pers. comm., D.Goyder pers. comm., I. Larridon pers. comm.). Most plant species have not been subjected to DNA studies. In fact, comprehensive sampling at generic level is still a target (PAFTOL, 2020). If it were possible to sample and analyse the DNA of plants in the same way as fungi, would species discovery be accelerated as it is for fungi, and would there be the same multiplier effect?
The time from the first collection of a putative new species to its formal description varies greatly. Barleria deserticola (Figure 2a), from the Namib coastal desert was first collected 160 years ago, by the explorer Friedrich Welwitsch, but was only re-found in 2009 by US botanist Erin Tripp and named in 2019 (Darbyshire, Tripp, & Chase, 2019). In contrast, the description and publication of Inversodicraea koukoutamba (Podostemaceae) collected from a waterfall in Guinea in 2018 took only one year from the first collection (Cheek, Molmou, Jennings, Magassouba, & van der Burgt, 2019). Delays in publication can reflect a lack of availability of specialist taxonomists with the capacity or time to write and publish a formal paper describing new species. They can also result from a former convention, in which naming a species from only a single specimen, showing a single phase of the species’ life cycle, was considered poor science (Cheek & Bridson, 2019). This convention contributed to the delay in publishing Vepris bali, a cloud forest tree of Cameroon collected 70 years ago. Although taxonomic capacity remains a constraint, aversion to describing species based on a single collection has now been largely overcome, with good reason: new collections may never become available. Vepris bali, for example, is presumed extinct (Cheek, Gosline, & Onana, 2018). Publication attracts interest and encourages others to seek new material in the field, sometimes resulting in rediscovery of species hitherto considered extinct (Humphreys, Govaerts, Ficinski, Nic Lughadha, & Vorontsova, 2019). In fungi, confusion about the identity of the already published species hinders progress. In many groups, the type specimens of all published species need to be studied first, or neo- or epitypes designated for old names, before new names can be published for species. In addition, many new species are discovered from environmental specimens (usually soil samples) but, according to the current rules of nomenclature for fungi they cannot be named because of a lack of a physical voucher specimen which needs to be deposited in a fungarium (Lücking & Hawksworth, 2018; See BOX 2 for more on naming conventions). The debate is also still ongoing as to whether a short DNA sequence is sufficiently robust evidence to justify the publication of a new species name (Zamora et al., 2018), especially as thousands of well-known names still lack DNA barcodes (Schoch et al., 2014). Currently, two Special-purpose committees are exploring the use of DNA sequences as types, and this topic is due to be further discussed during the next International Mycological Congress in 2022 (May, 2018) and in the International Botanical Congress in 2023 (Turland, Wiersema, Monro, Deng, & Zhang, 2017).