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The Santa Cruz black salamander Aneides niger is a priority 3 California species of special concern with a restricted geographic range confined to the Santa Cruz Mountains. Anecdotal observations suggest that the species was relatively abundant in the early 1900s, but it has become more difficult to find in the past few decades. To better understand if the species has undergone population size fluctuations, we analyzed mitochondrial and nuclear sequence data to examine levels of genetic variation and phylogeographic structure, and test for signatures of population size change. We then reconstructed the climatic suitability for the species to 1) determine if past climate fluctuations could have influenced range size and genetic diversity, and 2) estimate the effects of future climate change on geographic range suitability as a proxy for possible future population size change. Genetic analyses detected low levels of genetic variation and a general lack of genetic structuring, suggesting a recent genetic bottleneck. While neutrality tests of individual loci were nonsignificant, skyline plot and isolation-with-migration analyses detected a relatively recent reduction in population size. Interpretation of these genetic results should consider the limited number of localities and individuals sampled for this species. Climatic suitability for Santa Cruz black salamanders was much lower during the last glacial maximum, which could be the cause of the detected historical change in population size. Future projections of climatic suitability under a high-emission scenario suggest a dramatic geographic range restriction to coastal areas. These projections highlight the need for the protection of coastal habitat patches to preserve existing coastal populations, and to maintain connectivity between coastal and inland habitats to allow the westward movement of populations and genes in response to climate change. [ABSTRACT FROM AUTHOR]

Organisms within freshwater and marine environments are subject to a diverse range of often co‐occurring abiotic and biotic stressors. Despite growing awareness of the complex multistress systems at play in aquatic ecosystems, many questions remain regarding how simultaneous stressors interact with one another and jointly impact aquatic species. We looked at multistress interactions in a protected stream ecosystem in Mendocino County, California. Specifically, we examined how diurnal temperature variation, turbidity, and predator cues altered the movement speed of larval Pacific giant salamanders (Dicamptodon tenebrosus). In a second experiment, we looked at how simulated low‐flow summer conditions impact the expression of heat‐shock proteins (HSPs) in the same species. Larvae moved almost one and a half times faster in the presence of chemical cues from trout and suspended sediment, and almost two times faster when both sediment and trout cues were present but were only marginally affected by temperature and visual cues from conspecifics. Interestingly, the order of stressor exposure also appeared to influence larval speed, where exposure to sediment and trout in earlier trials tended to lead to faster speeds in later trials. Additionally, larvae exposed to low‐flow conditions had more variable, but not statistically significantly higher, expression of HSPs. Our findings highlight the potential interactive effects of an abiotic stressor, sedimentation, and a biotic stressor, and predator chemical cues on an ecologically important trait: movement speed. Our findings also demonstrate the likely role of HSPs in larval salamander survival in challenging summer conditions. Taken together, these findings show that larval D. tenebrosus responds behaviorally to biotic and abiotic stressors and suggests a possible pathway for physiological tolerance of environmental stress. Consideration of multistress systems and their effects is important for understanding the full effects of co‐occurring stressors on aquatic organisms to guide appropriate conservation and management efforts based on ecologically relevant responses of organisms within an environment. [ABSTRACT FROM AUTHOR]

When invasive and endangered native taxa hybridize, the resulting admixture introduces novel conservation challenges. Across a large region of central California, a hybrid swarm consisting of admixed endangered California tiger salamanders (CTS) (Ambystoma californiense) and introduced barred tiger salamanders (BTS) (Ambystoma mavortium) has replaced native populations, threatening the genetic integrity of CTS and the vernal pool systems they inhabit. We employed a large‐scale, genomically informed field experiment to test whether shortening breeding pond hydroperiod would favor native CTS genotypes. We constructed 14 large, seminatural ponds to evaluate the effect of hydroperiod duration on larval survival and mass at metamorphosis. We tracked changes in non‐native allele frequencies with a 5237‐gene exon capture array and employed a combination of custom Bayesian and generalized linear models to quantify the effect of pond duration on salamander fitness. Earlier work on this system showed hybrid superiority under many conditions and suggested that hybrids are favored in human‐modified ponds with artificially long hydroperiods. Consistent with these earlier studies, we found overwhelming evidence for hybrid superiority. Very short hydroperiods substantially reduced the mass (1.1–1.5 fold) and survival probability (10–13 fold) of both native and hybrid larvae, confirming that hydroperiod likely exerts a strong selective pressure in the wild. We identified 86 genes, representing 1.8% of 4723 screened loci, that significantly responded to this hydroperiod‐driven selection. In contrast to earlier work, under our more natural experimental conditions, native CTS survival and size at metamorphosis were always less than hybrids, suggesting that hydroperiod management alone will not shift selection to favor native larval genotypes. However, shortening pond hydroperiod may limit productivity of hybrid ponds, complementing other strategies to remove hybrids while maintaining vernal pool ecosystems. This study confirms and expands on previous work that highlights the importance of hydroperiod management to control invasive aquatic species. [ABSTRACT FROM AUTHOR]

Hybridization between species affects biodiversity and population sustainability in numerous ways, many of which depend on the fitness of the hybrid relative to the parental species. Hybrids can exhibit fitter phenotypes compared to the parental lineages, and this 'hybrid vigour' can then lead to the extinction of one or both parental lines.In this study, we analysed the relationship between water loss and gas exchange to compare physiological performance among three tiger salamander genotypes—the native California tiger salamander (CTS), the invasive barred tiger salamanders (BTS) and CTS × BTS hybrids across multiple temperatures (13.5°C, 20.5°C and 23.5°C). We developed a new index of performance, the water‐gas exchange ratio (WGER), which we define as the ratio of gas exchange to evaporative water loss (μL VO2/μL H2O). The ratio describes the ability of an organism to support energetically costly activities with high levels of gas exchange while simultaneously limiting water loss to lower desiccation risk. We used flow through respirometry to measure the thermal sensitivity of metabolic rate and resistance to water loss of each salamander genotype to compare indices of physiological performance.We found that temperature had a significant effect on metabolic rate and resistance to water loss, with both traits increasing as temperatures warmed. Across genotypes, we found that hybrids have a higher WGER than the native CTS, owing to a higher metabolic rate despite having a lower resistance to water loss.These results provide a greater insight into the physiological mechanisms driving hybrid vigour and offer a potential explanation for the rapid spread of salamander hybrids. More broadly, our introduction of the WGER may allow for species‐ or lineage‐wide comparisons of physiological performance across changing environmental conditions, highlighting the insight that can be gleaned from multitrait analysis of organism performance. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The endangered Sonoma County population of the California Tiger Salamander, Ambystoma californiense, undergoes migrations between breeding pools and upland dry-season refugia. Orientation in this species during breeding migrations has been addressed minimally in previous studies, and literature is particularly sparse concerning newly metamorphosed juveniles. Previous works have not addressed the ability of metamorphs to orient or the way in which they search for upland refugia. The initial migration from natal pools to uplands following metamorphosis has been identified as a crucial life-history juncture for the persistence of this species. We evaluated fine-scale movements of newly metamorphosed California Tiger Salamanders as they moved away from breeding pools by capturing salamanders with a drift fence and then tracking individuals with fluorescent powder. Here we show that newly metamorphosed juveniles do not move randomly, and that they can re-orient to their upland migration after being interrupted and disoriented. Further, we demonstrate that while searching for burrow refugia, metamorph movement can be characterized as a correlated random walk. [ABSTRACT FROM AUTHOR]

Environmental change can disturb natural associations between wildlife and microbial symbionts, in many cases to the detriment of host health. We used a North American terrestrial salamander system to assess how the skin microbiota of amphibians responds to wildfires. In northern California's redwood/oak forests, we assessed how recent wildfires affected the skin microbiota of three different salamander species (Taricha sp., Batrachoseps attenuatus, and Ensatina eschscholtzii) over two different sampling seasons in 2018 and 2021. We found species‐specific responses to wildfire disturbance on the alpha diversity of the skin microbiota of terrestrial salamanders, although burning in general altered the composition of the skin microbiota. The effect of burning on alpha diversities and body condition indices varied by sampling season, suggesting an additional effect of annual climatic conditions on body condition and skin microbiota response. We tested all salamanders for Batrachochytrium dendrobatidis and found four infected individuals in 2018 and none in 2021. Our study documents correlations in the skin microbiota response to an increasing source of disturbance in western North American ecosystems. In addition, our results highlight the need to consider the effects of increased wildfire regimes/intensities and longitudinal effects on wildlife‐associated microbiota and animal health. [ABSTRACT FROM AUTHOR]

Several aquatic sampling techniques are commonly used to detect and quantify amphibian larvae. Although many techniques have been standardized, comparisons among methods have been poorly studied. We employed a removal design to investigate the detection rate of amphibian larvae using box enclosures and evaluated the reliability of timed dipnet sampling relative to the more quantitative box enclosure sampling across 13 vernal pools. For these comparisons, we studied larvae of the endangered California Tiger Salamander (Ambystoma californiense; CTS) and the smaller and more abundant tadpoles of the Pacific Treefrog (Pseudacris regilla; PTF). Based on N-mixture model estimates, box enclosure sampling captured only 5% more of the CTS larvae present than PTF tadpoles, despite disparities in their sizes and estimated abundances. Dipnet sampling was slightly more effective at detecting CTS larvae than was enclosure sampling, while both methods equally detected PTF tadpoles. We found a strong relationship (R2 = 0.92) between the densities of CTS larvae estimated from dipnet sampling and those calculated from the more quantitative enclosure sampling, indicating that dipnet sampling is a reliable measurement of relative abundance. We conclude that timed dipnet surveys can be an important tool for monitoring populations of CTS, and possibly other lenticbreeding amphibians, especially given its relative efficiency that can be replicated across both time and space. [ABSTRACT FROM AUTHOR]

Habitat creation is a common element of efforts to recover populations threatened by altered habitat. Unfortunately, human‐created habitats do not necessarily support re‐establishment of target species. We investigated the value of constructed vernal pools as breeding habitat for the endangered Sonoma County population of California tiger salamanders (Ambystoma californiense) by conducting 19 years of larval surveys in 118 pools that were natural (n = 40), constructed (n = 70), or natural with substantial human alterations (human‐altered, n = 8). California tiger salamander larval densities in human‐altered and natural pools declined over the study period, while larval densities in constructed pools showed non‐negative trends. Larval declines in natural pools may be attributed to long‐term degradation of the surrounding terrestrial habitat. Mean larval densities over the course of the study were equivalent between constructed and natural pools, when corrected for pool morphometry. In contrast, human‐altered pools had lower larval densities. To assure consistent California tiger salamander breeding, pools needed to be ≥30 cm deep and 240 m2 in area, with deeper (50–70 cm) and larger (1,600–1,800 m2) pools providing increased larval productivity. Over the study, there was no evidence of decrease in the rate of colonization of new pools. We conclude that constructed pools can be important tools in the recovery of imperiled pool‐breeding amphibians if proper design elements for the target species are considered. [ABSTRACT FROM AUTHOR]

One of the most difficult aspects of studying intact amphibian communities is that they tend to occupy isolated areas within inaccessible terrain—factors that both protect watersheds from development and disturbance while also making them difficult to study. We conducted an extensive survey of the freshwater herpetofauna of the remote King Range National Conservation Area in Northern California using a combination of visual encounter surveys and environmental DNA (eDNA) sampling. We found twelve species of native aquatic amphibians and the western pond turtle (Actinemys marmorata), and no introduced amphibians. Detection probabilities for the four most commonly encountered species, giant salamanders (Dicamptodon sp), foothill yellow-legged frogs (Rana boylii), western toads (Anaxyrus boreas), and black salamanders (Aneides flavipunctatus), were affected by substrate and canopy cover, but the effects of these habitat characteristics on detection probability were species specific. Neither survey method, visual encounter surveys nor eDNA sampling, was more effective than the other, and our study suggests that the use of visual encounter surveys in conjunction with eDNA sampling may counteract the shortcomings of either when done individually. Five species were found using both methods, seven were only encountered during visual encounter surveys, and one recorded only from eDNA sampling. DNA samples from two taxa, toads and giant salamanders, could not be resolved to species. Toad species identity was assigned to the only member of the candidate species with a species range known to overlap the study area; the other three candidate species occupy restricted ranges far from the study area. Neither of the two giant salamander candidate species have known species ranges overlapping the study area. One, the California giant salamander (D. ensata), is known to occur within 100 km. However, there is a paucity of genetic material in GenBank DNA library for both the California giant salamander and the coastal giant salamander (D. tenebrosus), a widely distributed species with a range overlapping the study area, which could lead to inaccurate assignment of eDNA fragments. [ABSTRACT FROM AUTHOR]

Among western North American amphibian lineages, the plethodontid salamander genus Batrachoseps has undergone the most extensive radiation. Here we describe a new species in the genus from the vicinity of Point Arguello, central California. This lineage falls within the B. pacificus group, but it is differentiated from other species in the group by both molecular sequence data and morphology. It is geographically disjunct from its close relatives, with a tiny range in unlikely habitat along a narrow strip of the Pacific Coast, where it is entirely surrounded by B. nigriventris, a distant relative. Although intraspecific molecular variation is almost entirely absent, some population structure was detected across the 4 km extent of its range. Because of its tiny range and limited genetic variation, the impacts of any potential modifications to its known habitat should be evaluated to ensure the species' continued conservation. [ABSTRACT FROM AUTHOR]

Individuals within animal societies are expected to mitigate the costs and enhance the benefits associated with group living. For example, sociality can facilitate the sharing of beneficial microbes among individuals, but can also increase transmission of pathogens, representing a major cost of group living. We examined the costs of sociality in the California slender salamander (Batrachoseps attenuatus), a terrestrial salamander which naturally forms close social aggregations. We investigated whether innate sociality (e.g., skin-to-skin contact) increases an individual's transmission risk of Batrachochytrium dendrobatidis (Bd), a fungal pathogen that emerged throughout the salamander's range over the last 50 years and has decimated hundreds of amphibian species globally. We found that in captivity, B. attenuatus exhibit random mixing within social groups, resulting in high contact rates and high potential for Bd transmission. Our experimental infection trials resulted in 50% mortality after 1 month in moist conditions. In order to test how group size affects pathogen transmission, we manipulated social group size and found a marked effect on the spread Bd among individuals; a single, uninfected individual contracted Bd much more rapidly in larger groups of infected individuals. Surprisingly, this did not translate into a more rapid death rate or higher pathogen infection loads. Our results show that the innate behavior of group formation represents a per-individual risk of socially acquired pathogens, with direct transmission being magnified in larger social groups. This study highlights one important cost of sociality in terrestrial salamanders and underscores the general susceptibility of social animals to novel invasive pathogens. Significance statement: Social behaviors typically evolve due to the benefits of associating with others, but they can also present risks such as disease transmission. The California slender salamander is highly social, with individuals forming close aggregations underneath cover items. Populations of this species have recently been discovered to suffer from the widespread and deadly fungal pathogen Batrachochytrium dendrobatidis (Bd) which is transmitted through aquatic zoospores. Because this salamander host species is fully terrestrial, we set out to determine if close aggregations (leading to skin-to-skin contact) provide opportunities for direct transmission of Bd. Infection trials in larger social groups revealed a more rapid spread of Bd; however, we did not witness more rapid death rates or ultimately higher pathogen infection loads. Our results show that the social behavior of these salamanders leads to a higher probability of acquiring Bd, highlighting the complex effects that emergent pathogens may have on social species. [ABSTRACT FROM AUTHOR]

Those waves were the language the forest studied when the forest was alone and those snakes salamanders, red-bellied newts those hemlock heads - those were the forest's dictionary. This forest wore a lace hem of wet ferns, and this beach was the wide bench this forest rested on. I Bonny Doon 2020 i Remember July my arms full of asters and you called me up to the porch where we ate from a basket of peaches with bread and butter and wine, and our daughters climbed down from the branches to dance and sing on the steps - how the trees all around smelled like sugar, and stars jangled like buttons of brass, how darkness came in like a child dressed up in the cape of a king. [Extracted from the article]

The phylogeny of California Slender Salamanders (Batrachoseps attenuatus), which inhabits Northern California's Coast Ranges and Sierra Nevada foothills, was previously investigated by Martínez-Solano et al. (2007), who recovered a monophyletic species that contained five geographically cohesive major clades. However, a population isolate of B. attenuatus found in the Sutter Buttes, a geographically isolated volcanic mountain range within the Sacramento Valley, was not available in their phylogenetic analysis. We sequenced the ∼780-base pair segment of the mitochondrial DNA cytochrome b (cytb) gene used in Martínez-Solano et al. (2007) to examine the phylogenetic placement of this isolated population within the B. attenuatus complex. Our results, based on a single mitochondrial marker, indicate that the Sutter Buttes population of B. attenuatus is genetically distinct and falls within the Martínez-Solano et al. (2007) "East Bay/Sierra subclade" that, in turn, is nested within their "Eastern" major clade. Although we cannot accurately estimate how long the Sutter Buttes population has been isolated, B. attenuatus was likely able to colonize the Sutter Buttes during pluvial Pleistocene interglacials when more contiguous woodlands may have opened dispersal corridors across the Great Central Valley. [ABSTRACT FROM AUTHOR]

Hybridization between native and non‐native species is an ongoing global conservation threat. Hybrids that exhibit traits and tolerances that surpass parental values are of particular concern, given their potential to outperform native species. Effective management of hybrid populations requires an understanding of both physiological performance and the underlying mechanisms that drive transgressive hybrid traits. Here, we explore several aspects of the hybridization between the endangered California tiger salamander (Ambystoma californiense; CTS) and the introduced barred tiger salamander (Ambystoma mavortium; BTS). We assayed critical thermal maximum (CTMax) to compare the ability of CTS, BTS and F1 hybrids to tolerate acute thermal stress, and found that hybrids exhibit a wide range of CTMax values, with 33% (4/12) able to tolerate temperatures greater than either parent. We then quantified the genomic response, measured at the RNA transcript level, of each salamander, to explore the mechanisms underlying thermal tolerance strategies. We found that CTS and BTS have strikingly different values and tissue‐specific patterns of overall gene expression, with hybrids expressing intermediate values. F1 hybrids display abundant and variable degrees of allele‐specific expression (ASE), likely arising from extensive compensatory evolution in gene regulatory mechanisms between CTS and BTS. We found evidence that the proportion of genes with allelic imbalance in individual hybrids correlates with their CTMax, suggesting a link between ASE and expanded thermal tolerance that may contribute to the success of hybrid salamanders in California. Future climate change may further complicate management of CTS if hybrid salamanders are better equipped to deal with rising temperatures. [ABSTRACT FROM AUTHOR]

Stream-obligate amphibians are important indicators of ecosystem health in the Pacific Northwest, but distributional information to improve forest management is lacking in many regions. We analyzed archived DNA extracted from water samples in 60 pools in streams on private timberlands in Mendocino County, California, for 3 California Species of Special Concern—Coastal Tailed Frogs (Ascaphus truei), Foothill Yellow-legged Frogs (Rana boylii), and Southern Torrent Salamanders (Rhyacotriton variegatus)—to better understand their distributions in the region. Detection probabilities for eDNA of Foothill Yellow-legged Frogs and Coastal Tailed Frogs were positively influenced by water temperature. eDNA occurrence for both frogs was affected by whether silt or organic matter was a dominant substrate in the sampled pool, and Foothill Yellow-legged Frog eDNA occurrence was also affected by water temperature. Foothill Yellow-legged Frog eDNA occurrence had a strong, positive association with water temperature, with occurrence unlikely below 14°C and very likely above 16°C, and a positive association with silt or organic substrates in pools, which was likely an indicator of higher-order stream reaches. In contrast, Coastal Tailed Frogs had a negative association with silt or organic substrates. Historical visual detections were generally congruent with findings using eDNA, but differences highlight important areas for further study. We did not detect Southern Torrent Salamanders using eDNA at any sites. Our study reinforces that ecological relationships of these species are varied, and shows the importance of maintaining the integrity of streams with diverse characteristics for conserving stream amphibians. [ABSTRACT FROM AUTHOR]

Global efforts to conserve declining amphibian populations have necessitated the development of rapid, reliable, and targeted survey methods. Environmental DNA surveys offer alternative or complementary methods to traditional amphibian survey techniques. The California tiger salamander Ambystoma californiense (CTS) is endemic to California, where it breeds in vernal pools. In the past 25 y, CTS has faced a 21% loss of known occurrences, largely through habitat loss, and it is threatened by hybridization with an introduced congener. Protecting and managing remaining CTS populations rely on accurately monitoring changes in their spatial distribution. Current monitoring practices typically use dip-net surveys that are time-consuming and prone to false negative errors. To provide a new resource for monitoring and surveying larval CTS, we designed an assay and tested it on water samples collected from 29 vernal pools at two locations in California. We compared environmental DNA results to contemporaneous dip-net surveying results and found the assay agreed with positive dip-net results in 100% of cases. In several instances, we also detected the presence of CTS genetic material in the early spring before larvae hatched, potentially offering a new, earlier detection option for this imperiled species. This assay provides a valuable, noninvasive molecular tool for monitoring the spatial distribution of the CTS in vernal pools. [ABSTRACT FROM AUTHOR]

The fungal pathogen, Batrachochytrium dendrobatidis (Bd), has devastated biodiversity and ecosystem health and is implicated as a driver of mass amphibian extinctions. This 100-year study investigates which environmental factors contribute to Bd prevalence in a fully terrestrial species, and determines whether infection patterns differ between a fully terrestrial amphibian and more aquatic host species. We performed a historical survey to quantify Bd prevalence in 1127 Batrachoseps gregarius museum specimens collected from 1920 to 2000, and recent data from 16 contemporary (live-caught) B. gregarius populations from the southwestern slopes of the Sierra Nevada mountains in California, USA. We compared these results to Bd detection rates in 1395 historical and 1033 contemporary specimens from 10 species of anurans and 427 historical Taricha salamander specimens collected throughout the Sierra Nevada mountains. Our results indicate that Bd dynamics in the entirely terrestrial species, B. gregarius, differ from aquatic species in the same region in terms of both seasonal patterns of Bd abundance and in the possible timing of Bd epizootics. [ABSTRACT FROM AUTHOR]

Background. The southern California biodiversity hotspot has had a complex geological history, with both plate tectonic forces and sea level changes repeatedly reconfiguring the region, and likely driving both lineage splittings and extinctions. Here we investigate patterns of genetic divergence in two species of slender salamanders (Plethodontidae: Batrachoseps) in this region. The complex geological history in combination with several organismal traits led us to predict that these species harbor multiple ancient mitochondrial lineages endemic to southern California. These species belong to a clade characterized by fine-scale mitochondrial structure, which has been shown to track ancient splits. Both focal species, Batrachoseps major and B. nigriventris, are relatively widely distributed in southern California, and estimated to have persisted there across millions of years. Recently several extralimital populations of Batrachoseps were found in the San Joaquin Valley of California, a former desert area that has been extensively modified for agriculture. The origins of these populations are unknown, but based on morphology, they are hypothesized to result from human-mediated introductions of B. major. Methods. We sequenced the mitochondrial gene cytochrome b from a geographically comprehensive sampling of the mitochondrial lineages of B. major and B. nigriventris that are endemic to southern California. We used phylogenetic analyses to characterize phylogeographic structure and identify mitochondrial contact zones. We also included the San Joaquin Valley samples to test whether they resulted from introductions. We used a bootstrap resampling approach to compare the strength of isolation-by-distance in both Batrachoseps species and four other salamander species with which they co-occur in southern California. Results. The northern lineage of B. major harbors at least eight deeply differentiated, geographically cohesive mitochondrial subclades. We identify geographic contact between many of these mtDNA lineages and some biogeographic features that are concordant with lineage boundaries. Batrachoseps nigriventris also has multiple deeply differentiated clades within the region. Comparative analyses highlight the smaller spatial scales over which mitochondrial divergence accumulates in Batrachoseps relative to most other salamander species in southern California. The extralimital populations of Batrachoseps from the San Joaquin Valley are assigned to B. major and are shown to result from at least two independent introductions from different source populations. We also suggest that B. major on Catalina Island, where it is considered native, may be the result of an introduction. Some of the same traits that facilitate the build-up of deep phylogeographic structure in Batrachoseps likely also contribute to its propensity for introductions, and we anticipate that additional introduced populations will be discovered. [ABSTRACT FROM AUTHOR]

Southern Torrent Salamanders (Rhyacotriton variegatus) are a cold, headwater-inhabiting amphibian native to the Pacific Northwest. This genus of salamanders is considered highly aquatic, even in postmetamorphic stages, although instances of terrestrial movement have been observed. This note reports our opportunistic field observations for terrestrial movement in R. variegatus, which primarily occurred in the vicinity of Marys Peak, Benton County, Oregon. [ABSTRACT FROM AUTHOR]

For many taxa, new records of non-native introductions globally occur at a near exponential rate. We undertook a systematic review of peer-reviewed publications on non-native herpetofauna, to assess the information base available for assessing risks of future invasions, resulting in 836 relevant papers. The taxonomic and geographic scope of the literature was also compared to a published database of all known invasions globally. We found 1,116 species of herpetofauna, 95% of which were present in fewer than 12 studies. Nearly all literature on the invasion ecology of herpetofauna has appeared since 2000, with a strong focus on frogs (58%), particularly cane toads (Rhinella marina) and their impacts in Australia. While fewer papers have been published on turtles and snakes, proportionately more species from both these groups have been studied than for frogs. Within each herpetofaunal group, there are a handful of well-studied species: R. marina, Lithobates catesbeianus, Xenopus laevis, Trachemys scripta, Boiga irregularis and Anolis sagrei. Most research (416 papers; 50%) has addressed impacts, with far fewer studies on aspects like trade (2%). Besides Australia (213 studies), most countries have little location-specific peer-reviewed literature on non-native herpetofauna (on average 1.1 papers per established species). Other exceptions were Guam, the UK, China, California and France, but even their publication coverage across established species was not even. New methods for assessing and prioritizing invasive species such as the Environmental Impact Classification for Alien Taxa provide useful frameworks for risk assessment, but require robust species-level studies. Global initiatives, similar to the Global Amphibian Assessment, using the species and taxonomic groups identified here, are needed to derive the level of information across broad geographic ranges required to apply these frameworks. Expansive studies on model species can be used to indicate productive research foci for understudied taxa. [ABSTRACT FROM AUTHOR]

Emerging infectious disease is a growing threat to global biodiversity. The infectious disease chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) has led to the decline and extinction of hundreds of amphibian species. Severe Bd-caused epizootics have been documented in North, Central and South America—with many of the research focused on anurans. California, where Bd-related epizootics and amphibian declines have been reported, has some of the highest diversity of salamanders. After more than a decade since the first known epizootic in California, little is known about Bd disease dynamics in salamanders. Pacific newts (Genus: Taricha) are ideal study species because of their abundance, wide geographic range, occurrence in both aquatic and terrestrial habitats, and how little is known about Bd infection dynamics for this group. We conducted a retrospective study to determine the relationship between Pacific newts and the fungal pathogen. We tested 1895 specimens collected between 1889–2009 and found no evidence of Bd-infected Pacific newts until the late 1940’s. Although we estimate that Bd emerged in this genus and rapidly spread geographically throughout California, we did not find evidence for epizootic dynamics. Bd infection prevalence and intensity, two measures commonly used to estimate dynamics, remained consistently low over time; suggesting Pacific newts may not be highly susceptible. Also, we found the timing of first Bd emergence in Pacific newts predate Bd emergence in other California salamander species. In addition, we found several environmental and anthropogenic factors correlated with Bd prevalence which may help explain Bd disease dynamics in the genus Taricha. Pacific newts may be a reservoir species that signal pathogen invasion into California salamanders, though further studies are needed. [ABSTRACT FROM AUTHOR]

We examined seasonal reproductive patterns of the Del Norte Salamander, Plethodon elongatus, in mixed conifer and hardwood forests of northwestern California and southwestern Oregon. Seasonal size differences in reproductive structures suggested that maximum spermatogenic activity occurred during the late summer, with spermatozoa transfer to the vasa deferentia occurring in the fall through spring. Maximum development of mature follicles occurred during the winter; however, follicular growth occurred year-round and was asynchronous among individuals. Courtship and mating probably occurred in late fall through early spring, with egg deposition from spring into early summer. Reproduction for females was not annual, and patterns suggested that the reproductive cycle was biennial or less frequent. In contrast, evidence indicated annual reproduction in males. Gravid females contained an average of 10 mature follicles. [ABSTRACT FROM AUTHOR]

Biological invasions and habitat alteration are often detrimental to native species, but their interactions are difficult to predict. Interbreeding between native and introduced species generates novel genotypes and phenotypes, and human land use alters habitat structure and chemistry. Both invasions and habitat alteration create new biological challenges and opportunities. In the intensively farmed Salinas Valley, California (U.S.A.), threatened California tiger salamanders ( Ambystoma californiense ) have been replaced by hybrids between California tiger salamander and introduced barred tiger salamanders ( Ambystoma tigrinum mavortium ). We conducted an enclosure experiment to examine the effects habitat modification and relative frequency of hybrid and native California tiger salamanders have on recruitment of salamanders and their prey, Pacific chorus frogs ( Pseudacris regilla ). We tested whether recruitment differed among genetic classes of tiger salamanders (hybrid or native) and pond hydroperiod (seasonal or perennial). Roughly 6 weeks into the experiment, 70% (of 378 total) of salamander larvae died in 4 out of 6 ponds. Native salamanders survived ( n = 12) in these ponds only if they had metamorphosed prior to the die-offs. During die-offs, all larvae of native salamanders died, whereas 56% of hybrid larvae died. We necropsied native and hybrid salamanders, tested water quality, and queried the California Department of Pesticide Regulation database to investigate possible causes of the die-offs. Salamander die-offs, changes in the abundance of other community members (invertebrates, algae, and cyanobacteria), shifts in salamander sex ratio, and patterns of pesticide application in adjacent fields suggest that pesticide use may have contributed to die-offs. That all survivors were hybrids suggests that environmental stress may promote rapid displacement of native genotypes. Efectos Letales de la Calidad del Agua sobre Salamandras de California Amenazadas pero no sobre Salamandras Híbridas Concurrentes [ABSTRACT FROM AUTHOR]

Growth, age at maturity, and survival are life-history parameters that provide important information for understanding population dynamics. We modeled growth and age at maturity for an island population of Arboreal Salamanders, Aneides lugubris, using snout--vent length (SVL) growth intervals from a 4-yr capture--mark--recapture study fit to the von Bertalanffy growth interval model. We estimated annual survival as a function of SVL using a multistate open robust design model, and computed age-specific survival using results from the von Bertalanffy growth model. Arboreal Salamanders have indeterminate growth that slows with age from hatchling size (24.4-mm SVL) to the mean adult (asymptotic) size of 66.0-mm SVL. Age at maturity is 2.69 yr, and average adult age is 8-11 yr. Annual survival increased with age from 0.363 in age 0 to 0.783 in ages >4 yr. Our results provide the first estimates of life-history parameters for this species and indicate similarities to other terrestrial salamanders from low-elevation Mediterranean climates. [ABSTRACT FROM AUTHOR]

California tiger salamander distribution extends well into more xeric habitats than the three genera investigated by Cohen(1952), and California tiger salamanders have been known to survive substantial losses in body mass (Searcy et al. 2014). California tiger salamander, dehydration, desiccation, entrapment, monitoring, rehydration, rescued, Ambystoma californiense, trench Keywords: Ambystoma californiense; California tiger salamander; dehydration; desiccation; entrapment; monitoring; rehydration; rescued; trench EN Ambystoma californiense California tiger salamander dehydration desiccation entrapment monitoring rehydration rescued trench Citation: Cava, Z. A., K. M Garten, S. M. Foster, and J. A. Alvarez. [Extracted from the article]

The article discusses a study that quantifies the kinematics of level walking of California newt, Taricha torosa using a treadmill for its terrestrial locomotion and a trackway submerged in shallow water for its underwater movement. It mentions that Taricha torosa was chosen to be the subject of the study because it is acknowledged to be the closest postural model of early tetrapods and are capable of walking both in a terrestrial and underwater environment. Further, this study also offers a comparison of California newt to that of other sprawling tetrapods with respect to their motor patterns that control their ability to walk in different environments.

Background: Island populations are excellent model systems for studies of phenotypic, ecological and molecular evolution. In this study, molecular markers of mitochondrial and nuclear derivation were used to investigate the evolution, structure and origin of populations of the California slender salamander (Batrachoseps attenuatus) inhabiting the six major islands of San Francisco Bay, formed following the rising of sea level around 9,000 years ago. Results: There was a high degree of congruence in the results of analyses of nucleotide and allozyme data, both of which strongly support the hypothesis that, for the majority of the islands, salamanders are descended from hilltop populations that became isolated with the formation of the Bay ca. 9,000 years ago. There are two exceptions (Alcatraz and Yerba Buena) where the evidence suggests that salamander populations are wholly or in part, the result of anthropogenic introductions. Comparison of the molecular data and the interpretations drawn therefrom with an earlier morphological study of many of the same salamander populations show some of the same evolutionary trends. Conclusion: In spite of marked differences between the evolutionary rates of the two kinds of molecular markers, both indicate distinctive and similar patterns of population structure for B. attenuatus in the San Francisco Bay Area and its islands. With the two noted exceptions, it is clear that most island populations were established prior to the 9,000 years since the formation of the Bay. Results of coalescence-based analyses suggest that for most island populations the mtDNA lineages from which they were derived date from the Pleistocene. It can be said that, based on observed values of genetic diversity, the last 9,000 years of evolution on these islands have been characterized by relative stability, with the occasional extinction of some haplotypes or alleles that were formerly shared between island and mainland populations but overall maintaining high levels of variation (with the exception of Alcatraz). In contrast, there is some evidence for rapid morphological changes between populations in some islands and their closest mainland counterparts. This pattern of rapid morphological divergence (e. g., resulting from founder effects) is similar to that observed in other studies about recent colonization of island habitats. [ABSTRACT FROM AUTHOR]

To advance the development of conservation planning for rare species with small geographic ranges, we determined habitat associations of Siskiyou Mountains salamanders (Plethodon stormi) and developed habitat suitability models at fine (10 ha), medium (40 ha), and broad (202 ha) spatial scales using available Geographic Information Systems data and logistic regression analysis with an information theoretic approach. Across spatial scales, there was very little support for models with structural habitat features, such as tree canopy cover and conifer diameter. Model-averaged 95% confidence intervals for regression coefficients and associated odds ratios indicated that the occurrence of Siskiyou Mountains salamanders was positively associated with rocky soils and Pacific madrone (Abutus menziesii) and negatively associated with elevation and white fir (Abies concolor); these associations were consistent across 3 spatial scales. The occurrence of this species also was positively associated with hardwood density at the medium spatial scale. Odds ratios projected that a 10% decrease in white fir abundance would increase the odds of salamander occurrence 3.02-4.47 times, depending on spatial scale. We selected the model with rocky soils, white fir, and Oregon white oak (Quercus garryana) as the best model across 3 spatial scales and created habitat suitability maps for Siskiyou Mountains salamanders by projecting habitat suitability scores across the landscape. Our habitat suitability models and maps are applicable to selection of priority conservation areas for Siskiyou Mountains salamanders, and our approach can be easily adapted to conservation of other rare species in any geographical location. [ABSTRACT FROM AUTHOR]

Being able to efficiently and accurately delimit species is one of the most basic and important aspects of systematics because species are the fundamental unit of analysis in biogeography, ecology, and conservation. We present a rationale and approach for combining ecological niche modeling, spatially explicit analyses of environmental data, and phylogenetics in species delimitation, and we use our methodology in an empirical example focusing on Aneides flavipunctatus, the black salamander (Caudata: Plethodontidae), in California. We assess the relationships between genetic, environmental, and geographic distance among populations. We use 11 climatic variables and point locality data from public databases to create ecological niche models. The suitability of potential contact zones between parapatric lineages is also assessed using the data from ecological niche modeling. Phylogenetic analyses of portions of the mitochondrial genome reveal morphologically cryptic mitochondrial lineages in this species. In addition, we find that patterns of genetic divergence are strongly associated with divergence in the ecological niche. Our work demonstrates the ease and utility of using spatial analyses of environmental data and phylogenetics in species delimitation, especially for groups displaying fine-scaled endemism and cryptic species. [ABSTRACT FROM AUTHOR]

Amphibian declines have been documented worldwide; however the vast majority are species associated with aquatic habitats. Information on the status and trends of terrestrial amphibians is almost entirely lacking. Here we use data collected across a 12-yr period (sampling from 1984-86 and from 1993-95) to address the question of whether evidence exists for declines among terrestrial amphibians in northwestern California forests. The majority of amphibians, both species and relative numbers, in these forests are direct-developing salamanders of the family Plethodontidae. We examined amphibian richness and evenness, and the relative abundances of the four most common species of plethodontid salamanders. We examined evidence of differences between years in two ecological provinces (coastal and interior) and across young, mature, and late seral forests and with reference to a moisture gradient from xeric to hydric within late seral forests. We found evidence of declines in species richness across years on late seral mesic stands and in the coastal ecological province, but these differences appeared to be caused by differences in the detection of rarer species, rather than evidence of an overall pattern. We also found differences among specific years in numbers of individuals of the most abundant species, Ensatina eschscholtzii, but these differences also failed to reflect a consistent pattern of declines between the two decadal sample periods. Results showing differences in richness, evenness, and relative abundances along both the seral and moisture continua were consistent with previous research. Overall, we found no compelling evidence of a downward trend in terrestrial plethodontid salamanders. We believe that continued monitoring of terrestrial salamander populations is important to understanding mechanisms of population declines in amphibian species. [ABSTRACT FROM AUTHOR]

We used mitochondrial cytochrome b sequences (up to 778 bp) and starch gel electrophoresis (45 loci) to examine the phylogeographical history of 39 populations of the California newt, Taricha torosa. Phylogenetic and population genetic methods were integrated to infer history at deep and shallow time depths. Using a molecular clock, the subspecies T. t. torosa and T. t. sierrae were estimated to have diverged 7–13 Mya. Within T. t. torosa, genetically differentiated groups were identified along coastal California, in southern California, and in the southern Sierra Nevada. The coastal group exhibited isolation by distance, but a lack of genetic variation north of present-day Monterey was indicative of a recent range expansion. In southern California, a disjunct population in central San Diego County was genetically diverged from coastal populations to the north (Nei’s genetic distance of 0.113). However, mtDNA and protein data were geographically discordant regarding the boundary between the coastal and southern Californian groups, and a biogeographical scenario was developed to account for this discordance. The southern Sierran clade of T. t. torosa was weakly diverged from coastal populations for mtDNA sequence variation, yet was strongly differentiated for allozyme variation (Nei’s genetic distance of 0.17–0.20). Populations of T. t. sierrae exhibited substantial population structure, and showed a steeper pattern of isolation by distance than did coastal populations of T. t. torosa. These results are interpreted in consideration of the known geomorphological history of California. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 213–239. [ABSTRACT FROM AUTHOR]

The Klamath-Siskiyou forests of northern California and southern Oregon are recognized as an area of globally outstanding biological distinctiveness. When evaluated at a national or global level, this region is often, necessarily, considered to be uniformly diverse. Due to large variation in biotic and abiotic variables throughout this region, however, it is unlikely that biological diversity is uniformly distributed. Furthermore, land management decisions nearly always occur at spatial scales smaller than this entire region. Therefore, we used field data from a random sampling design to map the distribution of local and regional richness of terrestrial molluscs and salamanders within northern California's portion of the Klamath-Siskiyou region. We also evaluated the protection afforded by reserves established for varying reasons (e.g. for inspiration and recreation for people vs. species conservation) to hotspots of species richness and species representation of these taxa. No existing reserves were created with these taxa in mind, yet it was assumed that reserves established largely around considerations for the northern spotted owl (Strix occidentalis caurina) would afford adequate protection for many lesser-known species. Species of terrestrial molluscs and salamanders share two general features: (1) they have extremely low vagility, and (2) they are often associated with moist, cool microclimates. Existing reserves disproportionately included areas of hotspots of species richness for both taxa, when hotspots included the richest c. 25% of the area, whereas non-reserved lands contained greater than expected areas with lower species richness. However, when a more strict definition of hotspot was used (i.e. the richest c.10% of areas), local hotspots for both taxa were not disproportionately found in reserves. Reserves set aside largely for human aesthetics and recreation and those set aside for biodiversity both contributed to the protection of areas with high (greatest 25%) species richness. Existing biodiversity reserves represented 68% of mollusc species and 73% of salamander species, corresponding to the 99th and 93rd percentiles, respectively, of species representation achieved by simulating a random distribution of the same total area of reservation. Cumulatively, however, reserves set aside for inspiration and biodiversity represented 83% of mollusc species and 91% of salamander species. The existing reserves provide conservation value for terrestrial molluscs and salamanders. This reserve network, however, should not be considered optimal for either taxa. [ABSTRACT FROM AUTHOR]

Climate change impacts depend in large part on land-management decisions; interactions between global changes and local resource management, however, rarely have been quantified. We used a combination of experimental manipulations and simulation modeling to investigate the effects of interactions between cattle grazing and regional climate change on vernal pool communities. Data from a grazing exclosure study indicated that 3 years after the removal of grazing, ungrazed vernal pools dried an average of 50 days per year earlier than grazed control pools. Modeling showed that regional climate change could also alter vernal pool hydrology. Increased temperatures and winter precipitation were predicted to increase periods of inundation. We evaluated the ecological implications of interactions between grazing and climate change for branchiopods and the California tiger salamander ( ) at four sites spanning a latitudinal climate gradient. Grazing played an important role in maintaining the suitability of vernal pool hydrological conditions for fairy shrimp and salamander reproduction. The ecological importance of the interaction varied nonlinearly across the region. Our results show that grazing can confound hydrologic changes driven by climate change and play a critical role in maintaining the hydrologic suitability of vernal pools for endangered aquatic invertebrates and amphibians. These observations suggest an important limitation of impact assessments of climate change based on experiments in unmanaged ecosystems. The biophysical impacts of land management may be critical for understanding the vulnerability of ecological systems to climate change. [ABSTRACT FROM AUTHOR]

Female salamanders in the suborder Salamandroidea store sperm in cloacal glands called spermathecae. Scanning electron microscopy was used to study these glands in females of the Southern Torrent Salamander, Rhyacotriton variegatus (Rhyacotritonidae), from northern California. Sperm initially enter the cloaca in a tangled mass from the spermatophore cap, but within the spermathecal tubules, small groups become aligned along their long axes. Sperm nuclei typically are embedded in apical microvilli of the secretory cells forming the distal acini of the spermathecae. Junctional complexes between apices of adjacent epithelial cells are occasionally broached or otherwise absent, and sperm can be found in the intercellular canaliculi between such cells. Spermathecae of R. variegatus are simple glands that branch off a tube extending dorsally into cloacal tissue. This spermathecal anatomy is in-between that of the Plethodontidae, which have a compound tubuloaveolar gland as the single spermatheca, and other saiamandroids, in which sperm storage occurs in numerous simple tubular glands, each one a spermatheca. Sperm associations in the simple spermathecae of R. variegatus, however, are most similar to those reported for plethodontids. [ABSTRACT FROM AUTHOR]

Plethodon elongatus and P. stormi (Caudata: Plethodontidae) are Pacific Northwest endemic species which occur in northwestern California and southwestern Oregon. Studies on these salamanders have resulted in differing taxonomic conclusions, but the underlying historical hypotheses, at both inter- and intraspecific levels, have never been examined in a molecular framework. Here, representatives of 81 populations from throughout the range of both taxa are sequenced. Portions of three mitochondrial protein-coding genes (cytochrome b, NADH dehydrogenase subunit 4, and ATPase 6) were sequenced. Four haplotype groups with nonoverlapping geographical ranges were recovered in separate and combined analyses of the data. One clade corresponds to the distribution of P. stormi, while the remaining three comprise P. elongatus. Phylogenetic relationships among haplotype groups differ in separate analyses of the genes but converge on a well-supported topology, with P. elongatus and P. stormi as monophyletic sister taxa, in combined Maximum Parsimony and Maximum Likelihood analyses. Population genetic analyses of mismatch distributions and Tajima's D-statistic are consistent with range expansion for the largest clade within P. elongatus, covering the northern two-thirds of the species range. In contrast, the P. stormi haplotype clade and the P. elongatus clade from the southern third of the species range may have been relatively stable. Morphological boundaries between P. elongatus and P. stormi are largely congruent with mitochondrial DNA breaks and continued treatment as sister taxa is supported. Although mitochondrial DNA haplotype groups may reflect historical separation within P. elongatus, genetic barriers are incongruent with intraspecific patterns of morphological variation. [ABSTRACT FROM AUTHOR]

Species conservation often focuses on preserving populations on remnant habitat patches, typically without evidence that this approach is sufficient for halting declines. We employed a 19-year dataset to examine the adequacy of this approach for recovering the Sonoma County distinct population segment of California tiger salamanders (SCTS; Ambystoma californiense), California, USA, which now exists almost entirely in remnant habitat patches designated as preserves across a rapidly urbanizing landscape. We estimated relative SCTS larval densities from standardized annual surveys from 2002 to 2020 across 118 vernal pools in eight preserves. We found that relative larval SCTS densities decreased by 48% over the study period, indicating that current efforts to conserve SCTS are inadequate for long-term viability. Increased densities were only observed at the single study preserve where SCTS were introduced. Temporal trends in larval density among preserves were best explained by the number of pools available to SCTS, and the ability of breeding pools to retain water throughout the larval period. Specifically, preserves with >1 breeding pool and ≥1 breeding pool that held water for at least two months following the breeding season (into late April) even in dry years had substantially lower rates of larval decline. Active conservation management of preserves, including provision of multiple breeding pools, at least some of which are resilient to variable future precipitation regimes, will be required to effectively conserve SCTS. We expect these findings to apply broadly to the conservation of many species of pool-breeding amphibians. [ABSTRACT FROM AUTHOR]

The article offers information of BATRACHOSEPS ATTENUATUS (California Slender Salamander). LEUCISM. Albinism, and report an observation of an adult leucistic B. attenuatus, a widespread and abundant species that occurs north of about 36° latitude.

The article offers information on Dicamptodon ensatus (California giant salamander), a large ambystomatid salamander of coastal northern California known to prey on a variety of vertebrates.