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Amphibians are well known as osmotically sensitive organisms due to their highly permeable skin and eggs and, as such, biologists have mostly discounted their presence in saline environments. Yet, from the 1800s to the present day, scientists have repeatedly found amphibians living and breeding in a variety of saline coastal and inland habitats. Despite this plethora of observations, their presence in these habitats is still mostly ignored, and the last (and only) complete literature review documenting amphibians in brackish and saline habitats was completed over 50 yr ago. Here we provide a review of the literature of amphibians in saline waters and present data on 144 species, in 28 families, on every continent except Antarctica. In doing so, we make the case that salt tolerance in amphibians may not be as rare as generally assumed. Through classifying habitats and studies, we conclude that the abilities of dozens of species to locally adapt to coastal and inland saline habitats have been extensively studied, although more work on most observed species is still needed. Our understanding of the evolutionary processes leading to this adaptation is also in its infancy. We summarize the existing knowledge on this subject and present a possible framework toward the development of an evolutionary model of amphibian adaptation to salt, based on genetic variation for salt tolerance in populations and the nature of selection events in osmotically stressful environments. Finally, we discuss some possible limitations on the ability of amphibians to tolerate salt water. Understanding the abilities and constraints of amphibian populations to adapt to salt will become more critical as humans continue to impact the world’s freshwater resources through climate change, landscape modification, and pollution, and these habitats thus become increasingly stressful for amphibians.
The successful spread of invasive Cane Toads (Rhinella marina) across tropical Australia has been attributed to a lack of biotic resistance, based upon the inability of most anuran-eating vertebrate predators to tolerate the powerful chemical defenses of the toads. However, despite their high species richness, invertebrates have been much less studied than vertebrates as predators of Cane Toads. Our field and laboratory studies show that toads are killed and consumed by a phylogenetically diverse array of arthropod taxa. No arthropod predators consumed toad eggs in our laboratory experiments, but fishing spiders, water beetles, water scorpions, and dragonfly nymphs killed toad tadpoles, and ants and fishing spiders killed metamorph toads. Published accounts report predation on toads by crustaceans and hemipterans also. In our experiments, no predators showed any overt ill effects from consuming toad tissue. Dragonfly nymphs (Pantala flavescens) and fishing spiders (Dolomedes facetus) selectively took Cane Toad tadpoles at higher rates than some simultaneously offered native frog tadpoles. In combination with published data, our experiments suggest that the tadpoles and metamorphs of Cane Toads face high predation rates from the diverse and abundant invertebrate fauna of aquatic and riparian habitats in tropical Australia. The invasion of Cane Toads can potentially have positive effects on populations of many native animal species.
We reassessed the taxonomic status of the xenodontine snake Erythrolamprus bizona Jan (1863) based on a comprehensive review of literature records and comparative material. Our data demonstrate that the original diagnosis does not allow the unambiguous attribution of the name E. bizona to any population of the genus. After a thorough investigation in European institutions, we recovered two syntypes of the E. bizona type-series, confirming its composite nature. To circumvent the problem, we herein designate a lectotype for the species, providing a reformulated diagnosis and a detailed redescription. The lectotype represents one of the rare remaining specimens used in Giorgio Jan’s original descriptions during the second half of 19th century, and is housed in the Museo Civico di Storia Naturale di Milano, Milan, Italy. For more than seven decades, herpetologists have assumed that such material had been lost forever due to bombings of World War II. Nonetheless, our finding corroborates recent studies demonstrating that at least some of Jan’s snake types still exist for taxonomic research. Finally, we discuss the geographic congruence of the frequency distributions of segmental counts under an integrative approach aiming to maintain nomenclatural stability without ignoring preliminary evidence of taxonomic diversity.
Patagonia is a biodiverse area of high conservation priority, and Liolaemus lizards comprise a large component of the endemic fauna. Recent molecular and morphological studies have revealed cryptic species in several Liolaemus groups, including the Liolaemus lineomaculatus section (22 species recognized to date), which is endemic to Patagonia. Despite being a conspicuous component of this area, little is known about the morphological, ecological, and genetic variation of lizards of the L. lineomaculatus section; moreover species limits and past demographic scenarios are still uncertain for many of these species. In this paper, we characterize the morphological, ecological (niche envelope), and genetic variability of the four southernmost species of the L. kingii group (L. lineomaculatus section). Our main goal is to clarify species boundaries (using integrative taxonomy) as well as to infer evolutionary and demographic histories. For this paper we used a total of 241 specimens, 195 of which were used for morphological analyses (10 morphometric, 10 meristic, and 7 qualitative characters) and 226 were sequenced for cytochrome b. We summarized ecological variation by using environmental data from 62 localities of occurrence in a geospatial modeling analysis to estimate current and past species niche envelopes and to test for niche similarity. We identified genetic lineages and evaluated differentiation among them at molecular, morphological, and niche envelope levels. Overall, we found support for the specific status of L. baguali, L. escarchadosi, and L. sarmientoi based on differentiation along each of these three levels. Liolaemus tari is also differentiated from the other species, even though we could not evaluate its niche envelope due to small sample size. We also show the first evidence of possible hybridization among some of these species and recognize a new candidate species.
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