The purpose of this study was to determine whether limited occurrence data for highly threatened species can provide useful spatial information to inform conservation. The study was conducted across central and southern China. We developed a habitat suitability model for the Critically Endangered Chinese giant salamander (Andrias davidianus) based on one biotic and three abiotic parameters from single‐site locality records, which represent the only relevant environmental data available for this species. We then validated model quality by testing whether increased percentage of predicted suitable habitat at the county level correlated with independent data on giant salamander presence. We randomly selected 48 counties containing historical records which were distinct from, and independent of, the single‐site records used to develop the model, and 47 additional counties containing >50% predicted suitable habitat. We interviewed 2,812 respondents near potential giant salamander habitat across these counties and tested for differences in respondent giant salamander reports between counties selected using each method. Our model predicts that suitable giant salamander habitat is found widely across central and southern China, with counties containing ≥50% predicted suitable habitat distributed in 13 provinces. Counties with historical records contain significantly more predicted suitable habitat than counties without historical records. There are no statistical differences in any patterns of respondent giant salamander reports in surveyed counties selected from our model compared with the areas of known historical giant salamander distribution. A Chinese giant salamander habitat suitability model with strong predictive power can be derived from the restricted range of environmental variables associated with limited available presence‐only occurrence records, constituting a cost‐effective strategy to guide spatial allocation of conservation planning. Few reported sightings were recent, however, with most being over 20 years old, so that identification of areas of suitable habitat does not necessarily indicate continued survival of the species at these locations.

Transposable elements (TEs) are a major determinant of eukaryotic genome size. The collective properties of a genomic TE community reveal the history of TE/host evolutionary dynamics and impact present-day host structure and function, from genome to organism levels. In rare cases, TE community/genome size has greatly expanded in animals, associated with increased cell size and changes to anatomy and physiology. Here, we characterize the TE landscape of the genome and transcriptome in an amphibian with a giant genome — the caecilianIchthyophis bannanicus, which we show has a genome size of 12.2 Gb. Amphibians are an important model system because the clade includes independent cases of genomic gigantism. The I. bannanicus genome differs compositionally from other giant amphibian genomes, but shares a low rate of ectopic recombination-mediated deletion. We examine TE activity using expression and divergence plots; TEs account for 15% of somatic transcription, and most superfamilies appear active. We quantify TE diversity in the caecilian, as well as other vertebrates with a range of genome sizes, using diversity indices commonly applied in community ecology. We synthesize previous models that integrate TE abundance, diversity, and activity, and test whether the caecilian meets model predictions for genomes with high TE abundance. We propose thorough, consistent characterization of TEs to strengthen future comparative analyses. Such analyses will ultimately be required to reveal whether the divergent TE assemblages found across convergent gigantic genomes reflect fundamental shared features of TE/host genome evolutionary dynamics.

Determining the dynamics and sustainability of human interactions with threatened species is essential to inform evidence‐based conservation, but data can be challenging to collect across large areas and multiple user groups. Chinese giant salamanders Andrias spp. are critically depleted across China. Wild populations were exploited during the 20th century, and more recently to support a large‐scale farming industry. However, robust data remain largely unavailable on the timing of population declines in relation to changing human pressures, on primary drivers of exploitation, or on the effectiveness of conservation legislation. We conducted a series of large‐scale interview surveys across the range of giant salamanders in China, targeting potential rural and urban user groups, and stakeholders involved with giant salamander exploitation and policy management (comprising 2,932 rural households, 66 salamander farms, 115 county government officials and 835 urban consumers). Giant salamander populations were probably declining from at least the 1980s due to exploitation for food, and negative cultural values associated with these animals have not prevented rural consumption. There has been a major escalation in exploitation following the establishment of a large‐scale giant salamander farming industry in the 2000s. Our results demonstrate wide‐scale and largely unregulated illegal hunting to stock farms at a country‐wide scale in order to support demand by urban consumers for high‐prestige rare meat. We estimate there were at least 42,000 wild‐caught breeding adult giant salamanders and 164,000 wild‐caught subadults in farms across China at the time of our survey. Salamander farming probably poses unsustainable pressure on giant salamander populations. Existing legislation has clearly proved ineffective at preventing the stocking of farms with wild‐caught animals, and our findings highlight an important gap in the effectiveness of China's conservation protection for some of its highest‐priority threatened species. Tackling this problem will likely require multiple coordinated approaches, including enforcement of legislation, increased penalties for removing giant salamanders from the wild, permanent identification of captive‐bred giant salamanders, and consumer‐focused interventions to reduce urban demand. A free Plain Language Summary can be found within the Supporting Information of this article.

Transposable elements (TEs) and the silencing machinery of their hosts are engaged in a germline arms-race dynamic that shapes TE accumulation and, therefore, genome size. In animal species with extremely large genomes (>10 Gb), TE accumulation has been pushed to the extreme, prompting the question of whether TE silencing also deviates from typical conditions. To address this question, we characterize TE silencing via two pathways—the piRNA pathway and KRAB-ZFP transcriptional repression—in the male and female gonads of Ranodon sibiricus, a salamander species with a ∼21 Gb genome. We quantify 1) genomic TE diversity, 2) TE expression, and 3) small RNA expression and find a significant relationship between the expression of piRNAs and TEs they target for silencing in both ovaries and testes. We also quantified TE silencing pathway gene expression in R. sibiricus and 14 other vertebrates with genome sizes ranging from 1 to 130 Gb and find no association between pathway expression and genome size. Taken together, our results reveal that the gigantic R. sibiricus genome includes at least 19 putatively active TE superfamilies, all of which are targeted by the piRNA pathway in proportion to their expression levels, suggesting comprehensive piRNA-mediated silencing. Testes have higher TE expression than ovaries, suggesting that they may contribute more to the species’ high genomic TE load. We posit that apparently conflicting interpretations of TE silencing and genomic gigantism in the literature, as well as the absence of a correlation between TE silencing pathway gene expression and genome size, can be reconciled by considering whether the TE community or the host is currently “on the attack” in the arms race dynamic.

Genetically-defined biodiversity units must align with practical conservation frameworks, and most conservation is conducted at the species level. Chinese giant salamanders have traditionally been interpreted as the single widespread species Andrias davidianus, but molecular studies have reinterpreted this taxon as representing multiple allopatric clades, and competing taxonomic hypotheses support different numbers of candidate species. We conducted species delimitation analyses using tree-based models (General Mixed Yule Coalescent, Poisson Tree Processes) and alignment-based models (Bayesian Phylogenetics and Phylogeography) to interpret diversification across Andrias within a comparative systematic framework, using 30 mitogenomes representing all recognised Chinese clades. Nearly all tested models provide support for at least seven statistically-resolved Chinese species-level lineages, and most provide support for nine species. Only four species have available names. Chinese Andrias populations are Critically Endangered, but unnamed species cannot be incorporated into national or international conservation frameworks and risk being excluded from recovery efforts. We urge taxonomists and conservation practitioners to focus more attention on the world’s largest amphibians, and non-standard taxonomic approaches may be required to name these species before they disappear.

Due to the overexploitation of farming, as well as habitat destruction, the wild population of Chinese giant salamander (CGS) Andrias davidianus, a species with seven genetically distinct lineages, has decreased by over 80% in the past 70 years. Traditional survey methods have proven to be unsuitable for finding this rare and elusive species. We evaluated the efficacy of environmental DNA (eDNA) sampling to detect CGS indirectly from its aquatic environment. We developed several species-specific primer sets; validated their specificity and sensitivity; and assessed their utility in silico, in the laboratory, and at two field sites harboring released farm-bred CGS. We detected the presence of CGS DNA by using polymerase chain reaction and Sanger sequencing. We also sequenced an amplicon mixture of seven haplotype-represented samples using high-throughput sequencing. Our eDNA methods could detect the presence of CGS at moderate densities reported across its range, proving them as a cost-effective way to establish broad-scale patterns of occupancy for CGS. In addition, our primers enabled the detection of mitochondrial lineage mixture or introduced individuals from geographically isolated populations of CGS.