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.].

The systematics of the Galaxias olidus hyper-species complex from freshwater habitats in south-eastern, mainland Australia is revised. Galaxias olidus Günther 1866 is redescribed, Galaxias fuscus Mack 1936 and Galaxias ornatus Castelnau 1873, previously synonymised with G. olidus (sensu lato), are reinstated as valid taxa and redescribed, and 12 taxa are described as new: Galaxias aequipinnis sp. nov., Galaxias arcanus sp. nov., Galaxias brevissimus sp. nov., Galaxias gunaikurnai sp. nov., Galaxias lanceolatus sp. nov., Galaxias longifundus sp. nov., Galaxias mcdowalli sp. nov., Galaxias mungadhan sp. nov., Galaxias oliros sp. nov., Galaxias supremus sp. nov., Galaxias tantangara sp. nov., and Galaxias terenasus sp. nov. These species are morphologically similar and, whilst there is extensive overlap in meristic counts and morphometric characters, each can be diagnosed by unique combinations of characters, including allozyme loci and colour pattern; morphological diagnosis is improved greatly if based on freshly formalin-fixed material. Galaxias schomburgkii Peters 1868, Galaxias bongbong Macleay 1881, Galaxias kayi Ramsay & Ogilby 1886 and Galaxias oconnori Ogilby 1912 are retained as junior synonyms of G. olidus (sensu stricto). The types for Galaxias findlayi Macleay 1882 are lost and no specimens matching its description were collected or examined from the Mt. Kosciuszko region; it is also currently retained as a junior synonym of Galaxias olidus s.s. The species G. terenasus sp. nov. and G. arcanus sp. nov. are the most morphologically specialised in the complex and G. olidus s.s remains the most morphologically variable species. It also remains the most widespread taxon, though its previously known distribution is reduced, particularly in the south-west of its range. Nine species are narrow-range endemics, known from one, or only a few, locations, and these restricted distributions most probably reflect the fragmentation and reduction of former ranges caused by the effects of alien salmonids. Eleven species are of conservation concern, most are considered critically endangered.

Globally, freshwater fishes are declining at an alarming rate. Despite much evidence of catastrophic declines, few Australian species are listed as threatened under national legislation. We aim to help redress this by identifying the Australian freshwater fishes that are in the most immediate risk of extinction. For 22 freshwater fishes (identified as highly threatened by experts), we used structured expert elicitation to estimate the probability of extinction in the next ~20 years, and to identify key threats and priority management needs. All but one of the 22 species are small (<150mm total length), 12 have been formally described only in the last decade, with seven awaiting description. Over 90% of these species were assessed to have a >50% probability of extinction in the next ~20 years. Collectively, the biggest factor contributing to the likelihood of extinction of the freshwater fishes considered is that they occur in small (distributions ≤44km2), geographically isolated populations, and are threatened by a mix of processes (particularly alien fishes and climate change). Nineteen of these species are unlisted on national legislation, so legislative drivers for recovery actions are largely absent. Research has provided strong direction on how to manage ~35% of known threats to the species considered, and, of these, ~36% of threats have some management underway (although virtually none are at the stage where intervention is no longer required). Increased resourcing, management intervention and social attitudinal change is urgently needed to avert the impending extinction of Australia’s most imperilled freshwater fishes.

Aim The incidence of major fires is increasing globally, creating extraordinary challenges for governments, managers and conservation scientists. In 2019–2020, Australia experienced precedent‐setting fires that burned over several months, affecting seven states and territories and causing massive biodiversity loss. Whilst the fires were still burning, the Australian Government convened a biodiversity Expert Panel to guide its bushfire response. A pressing need was to target emergency investment and management to reduce the chance of extinctions and maximise the chances of longer‐term recovery. We describe the approach taken to rapidly prioritise fire‐affected animal species. We use the experience to consider the organisational and data requirements for evidence‐based responses to future ecological disasters. Location Forested biomes of subtropical and temperate Australia, with lessons for other regions. Methods We developed assessment frameworks to screen fire‐affected species based on their pre‐fire conservation status, the proportion of their distribution overlapping with fires, and their behavioural/ecological traits relating to fire vulnerability. Using formal and informal networks of scientists, government and non‐government staff and managers, we collated expert input and data from multiple sources, undertook the analyses, and completed the assessments in 3 weeks for vertebrates and 8 weeks for invertebrates. Results The assessments prioritised 92 vertebrate and 213 invertebrate species for urgent management response; another 147 invertebrate species were placed on a watchlist requiring further information. Conclusions The priority species lists helped focus government and non‐government investment, management and research effort, and communication to the public. Using multiple expert networks allowed the assessments to be completed rapidly using the best information available. However, the assessments highlighted substantial gaps in data availability and access, deficiencies in statutory threatened species listings, and the need for capacity‐building across the conservation science and management sectors. We outline a flexible template for using evidence effectively in emergency responses for future ecological disasters.