Ongoing declines for the world's amphibians in the face of emerging threats.

Systematic assessments of species extinction risk at regular intervals are necessary for informing conservation action1,2. Ongoing developments in taxonomy, threatening processes and research further underscore the need for reassessment3,4. Here we report the findings of the second Global Amphibian Assessment, evaluating 8,011 species for the International Union for Conservation of Nature Red List of Threatened Species. We find that amphibians are the most threatened vertebrate class (40.7% of species are globally threatened). The updated Red List Index shows that the status of amphibians is deteriorating globally, particularly for salamanders and in the Neotropics. Disease and habitat loss drove 91% of status deteriorations between 1980 and 2004. Ongoing and projected climate change effects are now of increasing concern, driving 39% of status deteriorations since 2004, followed by habitat loss (37%). Although signs of species recoveries incentivize immediate conservation action, scaled-up investment is urgently needed to reverse the current trends.

A new species of Lepidodactylus (Squamata: Gekkonidae) from Umboi Island, Papua New Guinea.

We describe a new species of Lepidodactylus from Umboi Island, just to the west of New Britain. It is a member of the Lepidodactylus guppyi Group and can be distinguished from all other Melanesian Lepidodactylus by aspects of digital scalation, digital webbing, enlarged femoral/precloacal scales, and color pattern. It is genetically distinct from its closest congeners, and genetic and morphological data indicate that the new species is most similar among named species to Lepidodactylus guppyi from the Solomon Islands, but it diverged from this species and other close relatives approximately 8 MYA or longer at a time prior to the existence of the island that it now occupies. The new species is known from only three individuals collected on a single tree, and efforts to find more animals in what seemed good habitat nearby were unsuccessful. This duplicates the pattern of apparent rarity seen for many Lepidodactylus species. Sufficient habitat exists on Umboi Island for arboreal geckos, suggesting that the species is not actually endangered but is ecologically cryptic. However, lack of needed information leads us to assess this species' conservation status as Data Deficient.

A revision of Gerrhopilus inornatus (Squamata: Gerrhopilidae) reveals a multi-species complex.

Melanesian blindsnakes of the genus Gerrhopilus have been little collected or researched. I examined specimens assigned in museums to Gerrhopilus inornatus and found considerable morphological diversity among them that indicates the presence of multiple species. I redescribe G. inornatus (Boulenger) based on the holotype and one additional specimen, and I describe six new species among specimens currently subsumed under that name from Papua New Guinea: Gerrhopilus flavinotatus sp. nov., Gerrhopilus lorealis sp. nov., Gerrhopilus papuanorum sp. nov., Gerrhopilus polyadenus sp. nov., Gerrhopilus slapcinskyi sp. nov., and Gerrhopilus wallachi sp. nov. Each species is currently known from only 1-3 specimens, and all but two are known only from single localities. In addition to traditional information on scale counts, habitus, and color patterns, I found the numbers and distributions of epidermal glands among the head shields to be especially useful for discriminating among species. The number of recognized Melanesian Gerrhopilus has increased tremendously in recent years, but the region has been poorly sampled for these snakes, and it is to be expected that additional species will be identified at such time as surveys can more effectively target these cryptic snakes.

Redescription of Lepidodactylus flaviocularis (Squamata: Gekkonidae), with the description of a new species from Makira Island, Solomon Islands.

Several species of geckos of the genus Lepidodactylus are endemic to the Solomon Islands and very poorly known. I redescribe one of these, L. flaviocularis, from Guadalcanal, based on examination of a second, newly obtained specimen and quantification of diagnostically useful features of the digits. I also describe a closely related new species from nearby Makira Island in the southern Solomon Islands. Both species are distinguished by their large number of undivided subdigital lamellae, extensive toe webbing, and a continuous row of enlarged precloacal/femoral scales. The new species is distinguished from L. flaviocularis by a number of scalational features and the color of the circumorbial scales. Both species are inhabitants of interior forest, and it remains uncertain whether they are naturally rare, rare due to interactions with invasive species, or simply have cryptic ecological habits, though the last seems most likely. Current evidence for both species is consistent with the taxon-cycle hypothesis, which posits ecological displacement to inland habitats of ancient island inhabitants by newer colonizers, but this remains to be critically tested. The limited pool of specimens available for both species necessitates assessing the IUCN conservation status of each as Data Deficient.

Melanesia holds the world's most diverse and intact insular amphibian fauna.

Identifying hotspots of biological diversity is a key step in conservation prioritisation. Melanesia-centred on the vast island of New Guinea-is increasingly recognised for its exceptionally species-rich and endemic biota. Here we show that Melanesia has the world's most diverse insular amphibian fauna, with over 7% of recognised global frog species in less than 0.7% of the world's land area, and over 97% of species endemic. We further estimate that nearly 200 additional candidate species have been discovered but remain unnamed, pointing to a total fauna in excess of 700 species. Nearly 60% of the Melanesian frog fauna is in a lineage of direct-developing microhylids characterised by smaller distributions than co-occurring frog families, suggesting lineage-specific high beta diversity is a key driver of Melanesian anuran megadiversity. A comprehensive conservation status assessment further highlights geographic concentrations of recently described range-restricted threatened taxa that warrant urgent conservation actions. Nonetheless, by world standards, the Melanesian frog fauna is relatively intact, with 6% of assessed species listed as threatened and no documented extinctions; and thus it provides an unparalleled opportunity to understand and conserve a megadiverse and relatively intact insular biota.

Cryptic extinction risk in a western Pacific lizard radiation.

Cryptic ecologies, the Wallacean Shortfall of undocumented species' geographical ranges and the Linnaean Shortfall of undescribed diversity, are all major barriers to conservation assessment. When these factors overlap with drivers of extinction risk, such as insular distributions, the number of threatened species in a region or clade may be underestimated, a situation we term 'cryptic extinction risk'. The genus Lepidodactylus is a diverse radiation of insular and arboreal geckos that occurs across the western Pacific. Previous work on Lepidodactylus showed evidence of evolutionary displacement around continental fringes, suggesting an inherent vulnerability to extinction from factors such as competition and predation. We sought to (1) comprehensively review status and threats, (2) estimate the number of undescribed species, and (3) estimate extinction risk in data deficient and candidate species, in Lepidodactylus. From our updated IUCN Red List assessment, 60% of the 58 recognized species are threatened (n = 15) or Data Deficient (n = 21), which is higher than reported for most other lizard groups. Species from the smaller and isolated Pacific islands are of greatest conservation concern, with most either threatened or Data Deficient, and all particularly vulnerable to invasive species. We estimated 32 undescribed candidate species and linear modelling predicted that an additional 18 species, among these and the data deficient species, are threatened with extinction. Focusing efforts to resolve the taxonomy and conservation status of key taxa, especially on small islands in the Pacific, is a high priority for conserving this remarkably diverse, yet poorly understood, lizard fauna. Our data highlight how cryptic ecologies and cryptic diversity combine and lead to significant underestimation of extinction risk. Supplementary Information: The online version contains supplementary material available at 10.1007/s10531-022-02412-x.

Collapse of the endemic lizard Podarcis pityusensis on the island of Ibiza mediated by an invasive snake.

The invasive snake Hemorrhois hippocrepis colonized the island of Ibiza (Balearic Islands) in 2003 as stowaways inside trunks of olive trees imported for gardening. It has quickly spread since 2010, posing a threat to the island's only remaining endemic vertebrate, the Ibiza wall lizard Podarcis pityusensis. We map the yearly expansion rate of the snake and estimate via transect surveys how severely it affects the distribution and abundance of the endemic lizard. As well, we surveyed 9 of 30 small lizard populations on islets surrounding Ibiza that have been isolated since the Last Glacial Maximum. Snakes had invaded 49% of Ibiza's land area by 2018, and censuses show a critical contrast in lizard abundance between areas with and without snakes; almost all censuses in areas without snakes show lizard presence whereas nearly all censuses in areas with H. hippocrepis lack lizard sightings. Moreover, at least one subspecies previously thriving on one of the offshore islets has become extinct, and there have been several snakes recorded swimming between Ibiza and the surrounding islets. Therefore, lizard populations have been dramatically reduced or have vanished within the range of the snake, and our results quantitatively support upgrading this species' threat level for extinction. This study can inform to programs to manage invasive snake populations and to conservation actions to recover the endemic lizard.

Whos your daddy? On the identity and distribution of the paternal hybrid ancestor of the parthenogenetic gecko Lepidodactylus lugubris (Reptilia: Squamata: Gekkonidae).

The widespread parthenogenetic gecko Lepidodactylus lugubris is comprised of several clonal lineages, at least one of which has been known for some time to have originated from hybridization between its maternal ancestor, Lepidodactylus moestus, and a putatively undescribed paternal ancestor previously known only from remote islands in the Central Pacific. By integrating new genetic sequences from multiple studies on Lepidodactylus and incorporating new genetic sequences from previously sampled populations, we recovered a phylogenetic tree that shows a close genetic similarity between the generally hypothesized paternal hybrid ancestor and a recently described species from Maluku (Indonesia), Lepidodactylus pantai. Our results suggest that the paternal hybrid ancestor of at least one parthenogenetic clone of L. lugubris is conspecific with L. pantai and that the range of this species extends to Palau, the Caroline Islands, the Kei Islands, Wagabu, and potentially other small islands near New Guinea. Deeper genetic structure in the western (Palau, Maluku) versus eastern (eastern Melanesia, Micronesia, Polynesia) part of this species range suggests that the western populations likely dispersed via natural colonization, whereas the eastern populations may be the result of human-mediated dispersal. The potential taxonomic affinities and biogeographic history should be confirmed with further morphological and genetic analyses, including research on L. woodfordi from its type locality, which would have nomenclatural priority if found to be conspecific with L. pantai. We recommend referring to the wide-ranging sexual species as Lepidodactylus pantai until such a comparison can be made.

A new species of Lobulia (Squamata: Scincidae) from Papua New Guinea.

I describe a new skink of the genus Lobulia from Mt. Simpson in southeasternmost New Guinea. This species differs from all other members of the genus in having only three pairs of enlarged chin shields and only the first pair in medial contact. It is most similar in scalation to L. elegans but is readily distinguished from that species by its color pattern, body size and shape, and numbers of lamellae. Morphological data on L. elegans have not been reported since the description of the holotype in 1897, so I provide a redescription of that species based on six specimens-including the holotype-of certain conspecificity and from within approximately 100 km of the type locality at Mt. Victoria. I also elevate Lygosoma elegantoides lobulus from synonymy with Lobulia elegans, from which it is readily distinguished on the basis of scalational and color-pattern features. The resurrected L. lobulus and the new species from Mt. Simpson represent the seventh and eighth recognized species of Lobulia, and the Mt. Simpson species is the fifth member of the Papuan herpetofauna that is apparently endemic to Mt. Simpson. Mt. Simpson appears to be a moderate center of local endemism within southeastern New Guinea.

A new species of Toxicocalamus (Squamata: Elapidae) from Papua New Guinea.

I describe a new species of the fossorial elapid snake genus Toxicocalamus from Mt. Simpson, Milne Bay Province, in southeastern New Guinea. The new species is similar to the poorly diagnosed T. loriae but differs from that species (and all other Toxicocalamus with the preocular distinct from the prefrontal) in having the preocular not in contact with the nasal and in having a pale-gray or yellow venter with gray bands across each ventral scale. The new species came from elevations of 1300-1490 m a.s.l. on the north slope of Mt. Simpson, and it seems likely to be confined to the mid-elevations of that mountain, judging from its morphological differences with specimens obtained from similar elevations on nearby Mt. Dayman. If true, this would make it the sixth species of herpetofauna apparently endemic to Mt. Simpson. This snake was common and found in both village gardens and adjacent primary rainforest, and I estimate its area of extent to be approximately 50,000 ha, so its IUCN conservation status would appear to be Least Concern.

Taxonomy of Micronesian monitors (Reptilia: Squamata: Varanus): endemic status of new species argues for caution in pursuing eradication plans.

In the light of recent phylogenetic studies, we re-assess the taxonomy and biogeography of the Varanus populations distributed in the Micronesian islands of Palau, the Western Carolines and the Marianas. Whether these populations are of natural origin or human introductions has long been contentious, but no study has fully resolved that question. Here, we present molecular and morphological evidence that monitor lizards of the Varanus indicus Group reached both Palau and the Mariana Islands sometime in the late Pleistocene and subsequently differentiated into two separate species endemic to each geographical region. One species is confined to the Mariana Islands, and for these populations, we revalidate the name V. tsukamotoi Kishida, 1929. The other species has a disjunct distribution in Palau, the Western Carolines and Sarigan Island in the Northern Marianas and is herein described as V. bennetti sp. nov. Both species are most closely allied to each other, V. lirungensis and V. rainerguentheri, suggesting that colonization of Micronesia took place from the Moluccas. We discuss the biogeographic distributions of both species in the light of the likely colonization mechanism and previous arguments for human introduction, and we argue that bounties for Palauan populations are ill-advised and plans for eradication of some other populations must first demonstrate that they are, in fact, introduced and not native.

A new species of Lepidodactylus (Squamata: Gekkonidae) from the mountains of northeastern Papua New Guinea: older than the hills.

We describe a new species of Lepidodactylus with an unusual distribution across scattered localities in three isolated mountain ranges of northeastern New Guinea. It is a member of the Lepidodactylus pumilus group and can be distinguished from all other Melanesian Lepidodactylus by aspects of size, scalation, digital webbing, and coloration. Previously published genetic and morphological data indicate that the new species is most similar to Lepidodactylus magnus, but it diverged from this species and other close relatives in the mid-Miocene or earlier, potentially on islands of the former South Caroline Arc. Estimated divergence dates between the new species and its sister taxon suggest that cladogenesis occurred before the uplift of the mountains that they currently inhabit. Recent systematic work also emphasizes an apparent pattern of increasing body size with elevation in species from the Lepidodactylus pumilus group from northeastern New Guinea, with the largest species occurring in montane habitats where few or no other gecko species are known. Both lines of evidence are consistent with an existing hypothesis that the Lepidodactylus pumilus group is an old insular lineage within which contemporary species diversity and distributions have been strongly shaped by low ability to effectively compete against other aggressive geckos in species-rich lowland rainforests. The role that biotic interactions may have played in shaping tropical gecko communities along elevational gradients warrants further investigation.

Cryptic diversity and non-adaptive radiation of montane New Guinea skinks (Papuascincus; Scincidae).

New Guinea, the world's largest and highest tropical island, has a rich but poorly known biota. Papuascincus is a genus of skinks endemic to New Guinea's mountain regions, comprising two wide-ranging species and two species known only from their type series. The phylogeny of the genus has never been examined and the relationships among its species - as well as between it and closely related taxa - are hitherto unknown. We performed the first large-scale molecular-phylogenetic study of Papuascincus, including sampling across the genus' range in Papua New Guinea. We sequenced three mitochondrial and two nuclear markers from 65 specimens of Papuascincus and reconstructed their phylogenetic relationships. We also performed species-delimitation analyses, estimated divergence times and ancestral biogeography, and examined body-size evolution within the genus. Papuascincus was strongly supported as monophyletic. It began radiating during the mid-Miocene in the area now comprising the Central Cordillera of New Guinea, then dispersed eastward colonising the Papuan Peninsula. We found evidence of extensive cryptic diversity within the genus, with between nine and 20 supported genetic lineages. These were estimated using three methods of species delimitation and predominantly occur in allopatry. Distribution and body-size divergence patterns indicated that character displacement in size took place during the evolutionary history of Papuascincus. We conclude that the genus requires comprehensive taxonomic revision and likely represents a species-rich lineage of montane skinks.

Interrogating Genomic-Scale Data for Squamata (Lizards, Snakes, and Amphisbaenians) Shows no Support for Key Traditional Morphological Relationships.

Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups. For one of the most diverse and species-rich groups, the squamate reptiles (lizards, snakes, and amphisbaenians), an inverse correlation between the number of taxa and loci sampled still persists across all publications using DNA sequence data and reaching a consensus on the relationships among them has been highly problematic. In this study, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome-scale data. Importantly, we address genomic support for the traditional taxonomic groupings Scleroglossa and Macrostomata using novel machine-learning techniques. We interrogate genes using various metrics inherent to these loci, including parsimony-informative sites (PIS), phylogenetic informativeness, length, gaps, number of substitutions, and site concordance to understand why certain loci fail to find previously well-supported molecular clades and how they fail to support species-tree estimates. We show that both incomplete lineage sorting and poor gene-tree estimation (due to a few undesirable gene properties, such as an insufficient number of PIS), may account for most gene and species-tree discordance. We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata. We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; among the three toxicoferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).

New species of Cyrtodactylus (Squamata: Gekkonidae) from Karkar Island, Papua New Guinea.

We describe a new species of Cyrtodactylus from Karkar Island, an active volcano off the northern coast of New Guinea. It is a member of the C. sermowaiensis species group, which is defined by the absence of enlarged precloacal and femoral scales and the absence of precloacal/femoral pores in males. This species group includes two other species, one of which is widespread along the northern mountain ranges of New Guinea, and the other of which is restricted to Manus Island. The new species differs from each of these in its larger size; more-tuberculate dorsum; wide, even bands across the dorsum; and uniformly brown crown of the head. Distributional data suggest that the C. sermowaiensis species group originated on the former islands of the South Caroline Arc, although only C. sermowaiensis currently occupies terranes derived from that arc. The other two species are now restricted to volcanic islands that originated independent of that arc, but the current restriction of our new species to Karkar Island seems likely to be a relictual distribution of a formerly wider range. The status of Karkar as an active volcano, and the explosive sterilization or virtual disappearance of other islands in the Bismarck Volcanic Arc, suggest that the new species could be at threat of immediate extinction should a similar explosive eruption occur on Karkar.

New species of Lepidodactylus (Squamata: Gekkonidae) from New Guinea and adjacent islands.

I describe five new species of Lepidodactylus from New Guinea or adjacent islands that are members of Brown Parker's (1977) phenetic Groups I and II and belong to the clades identified as the L. orientalis, L. pumilus, and L. novaeguineae groups of Oliver et al. (2018a). One of the new species is restricted to an isolated mountain range on New Guinea; the remainder inhabit offshore islands ranging from 3-250 km from New Guinea. These species are distinguished from their congeners primarily by unique combinations of toe lamellar numbers and shape, numbers and distribution of enlarged precloacal/femoral scales and pores, toe webbing, toe width, and color pattern. These clades are ancient, and the ancestor of one of them has been on the East Papuan Composite Terrane for at least 28 MY, highlighting the long-term importance of that former large island in generating regional biodiversity. At least one, and probably three, of the new species are inhabitants of forest interiors; one occupies disturbed coastal areas; and the habitat of the last is currently unsurmisable. All of the new species likely have restricted geographic distributions, with four of them being limited to one or a few small islands. As a result of their small ranges, rapid habitat conversion in the ranges of some of these species, and the threat of further habitat loss in the others, most of these species are of conservation concern although it is uncertain if any of them is under immediate threat.

A revision of Callulops doriae (Anura: Microhylidae), with descriptions of four new species.

I investigate the taxonomy of frogs currently assigned to the single species Callulops doriae, which is unique in the genus for its warty, dark-spotted dorsum and large yellow or orange blotches in the groin and on the hidden surfaces of the thighs. I show that many species are currently encompassed under this single name, I remove Manthophryne neuhaussi from synonymy, and I describe four new species, three of which have long been in museum collections, and one of which is newly collected by me. Each of these new species is most readily distinguished by their unique color patterns, but additional morphological features-primarily morphometric-also serve to distinguish among them. Despite this partition of C. doriae, additional museum specimens cannot be assigned to any of the species treated here and certainly represent unrecognized species. But the poor states of preservation of some of these and the absence of color-pattern information in life preclude describing them until new material of each is available. Three of the six species treated herein, which occur in the southern portion of the Papuan Peninsula, were previously included in a molecular phylogeny, and inferred dates of divergence for them accord well with the geological dynamism of this region created by opening of the Woodlark Rift. In two cases, pairs of species are reported in general sympatry, and elevational data suggest that these species are likely to segregate elevationally where their ranges approach each other. At least four of the species treated herein are known to produce viscous glandular secretions that presumably deter predators, and I describe the defensive display of one of these, which I presume is aposematic.

Taxonomy of Litoria graminea (Anura: Hylidae), with descriptions of two closely related new species.

I clarify the correct provenance and taxonomic identity of the poorly known canopy-dwelling frog, Litoria graminea, from New Guinea. I base my redescription upon analysis of relevant historical material as well as upon more recently obtained specimens from several localities in Papua New Guinea. Determining the correct identity of L. graminea makes clear that one recently named species (L. dux Richards Oliver) is a junior synonym of that taxon and that additional close relatives of that species remain undescribed, two of which I describe here. The first is known from a series of localities along the southern versant of the Central Dividing Range and the Owen Stanley Mountains. The second is known from a single site in the foothills of the Owen Stanley Mountains in Central Province, Papua New Guinea. Differences among the species are largely confined to pigmentation features and the shape of the male nuptial pads. Further, I show that several morphometric and color-pattern features earlier thought to distinguish among members of this complex are encompassed by natural variation within true L. graminea, making the characters taxonomically uninformative. The two newly described species share the unusual feature of having green oral mucosa, although their bones were white in life. This coloration is presumably due to sequestration of biliverdin, as seen in a few other tropical treefrogs, but the function of this sequestration remains unknown.

Neural basis of trigeminal chemo- and thermonociception in brown treesnakes, Boiga irregularis (Squamata: Colubridae).

To elucidate the nociceptive system of the brown treesnake, Boiga irregularis, we exposed isolated brown treesnake trigeminal neurons to thermal and chemical stimulation. We measured responses as changes in intracellular calcium using ratiometric fluorescent calcium imaging. Responses to aversive thermal and chemical identified several classes of putative nociceptors. Compounds that were aversive excited many trigeminal neurons, putative chemonociceptors. Identification as nociceptors was further supported by lack of activation by compounds that were not aversive. Brown treesnake neurons had thermal thresholds ranging from 32 to 49 °C. The distribution was discontinuous, with a population of thresholds from 32 to 45 °C and a population with thresholds > 48 °C. Thermal stimulation of 48 °C has been shown to be strongly aversive to brown treesnakes, is lethal, and suggests the presence of thermonociceptors. Thermal sensitivity of brown treesnake trigeminal neurons greatly overlaps with chemical sensitivity; only 1.1% of neurons were sensitive to only thermal stimulation. 50% of brown treesnake trigeminal neurons tested with both > 48 °C and cinnamaldehyde responded to both stimuli, identifying putative polymodal nociceptors. Although a previous study found brown treesnakes insensitive to capsicum extract containing capsaicin, brown treesnake trigeminal neurons responded to capsaicin. These findings are of evolutionary interest as well as providing potential insights into managing this significant pest species.