title: Global biodiversity assessment and hyper-cryptic species complexes: more than one species of elephant in the room?
abstract: Several recent estimates of global biodiversity have concluded that the total number of species on Earth lies near the lower end of the wide range touted in previous decades. However, none of these recent estimates formally explore the real "elephant in the room", namely, what proportion of species are taxonomically invisible to conventional assessments, and thus, as undiagnosed cryptic species, remain uncountable until revealed by multi-gene molecular assessments. Here we explore the significance and extent of so-called "hyper-cryptic" species complexes, using the Australian freshwater fish Galaxias olidus as a proxy for any organism whose taxonomy ought to be largely finalized when compared to those in little-studied or morphologically undifferentiated groups. Our comprehensive allozyme (838 fish for 54 putative loci), mtDNA (557 fish for 605 bp of cytb), and morphological (1963-3389 vouchers for 17-58 characters) assessment of this species across its broad geographic range revealed a 1500% increase in species-level biodiversity, and suggested that additional taxa may remain undiscovered. Importantly, while all 15 candidate species were morphologically diagnosable a posteriori from one another, single-gene DNA barcoding proved largely unsuccessful as an a priori method for species identification. These results lead us to draw two strong inferences of relevance to estimates of global biodiversity. First, hyper-cryptic complexes are likely to be common in many organismal groups. Second, no assessment of species numbers can be considered "best practice" in the molecular age unless it explicitly includes estimates of the extent of cryptic and hyper-cryptic biodiversity. [Galaxiidae; global estimates; hyper-diverse; mountain galaxias; species counts; species richness.].
authors.affiliation: Evolutionary Biology Unit, South Australian Museum, North Terrace, SA 5000, Australia;School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia; mark.adams@samuseum.sa.gov.au.
authors.forename: Mark
authors.initials: M
authors.lastname: Adams
authors.affiliation: Aquatic Ecology Section, Arthur Rylah Institute for Environmental Research, Department of Environment and Primary Industries, 123 Brown Street, Heidelberg, VIC 3084, Australia;Institute for Applied Ecology and Collaborative Research Network for Murray-Darling Futures, University of Canberra, ACT 2601, Australia and.
authors.forename: Tarmo A
authors.initials: TA
authors.lastname: Raadik
authors.affiliation: School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Burridge
authors.affiliation: Institute for Applied Ecology and Collaborative Research Network for Murray-Darling Futures, University of Canberra, ACT 2601, Australia and.
authors.forename: Arthur
authors.initials: A
authors.lastname: Georges
mesh_terms: D000818:Animals; D044822:Biodiversity; D058893:DNA Barcoding, Taxonomic / Q000592:standards; D050259:Genes, Mitochondrial / Q000235:genetics; D007527:Isoenzymes / Q000378:metabolism; D008969:Molecular Sequence Data; D036441:Osmeriformes / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics; D010802:Phylogeny; D013045:Species Specificity
chemical_list: D007527:Isoenzymes