Emerging infectious diseases are reducing biodiversity on a global scale. Recently, the emergence of the chytrid fungus Batrachochytrium salamandrivorans resulted in rapid declines in populations of European fire salamanders. Here, we screened more than 5000 amphibians from across four continents and combined experimental assessment of pathogenicity with phylogenetic methods to estimate the threat that this infection poses to amphibian diversity. Results show that B. salamandrivorans is restricted to, but highly pathogenic for, salamanders and newts (Urodela). The pathogen likely originated and remained in coexistence with a clade of salamander hosts for millions of years in Asia. As a result of globalization and lack of biosecurity, it has recently been introduced into naïve European amphibian populations, where it is currently causing biodiversity loss.
Recent studies have identified range expansion as a potential driver of speciation. Yet it remains poorly understood how, under identical extrinsic settings, differential tendencies for geographic movement of taxa originate and subsequently affect diversification. We identified multiple traits that predict large distributional ranges in extant species of toads (Bufonidae) and used statistical methods to define and phylogenetically reconstruct an optimal range-expansion phenotype. Our results indicate that lineage-specific range-shifting abilities increased through an accumulation of adaptive traits that culminated in such a phenotype. This initiated the episode of global colonization and triggered the major radiation of toads. Evolution toward a range-expansion phenotype might be crucial to understanding both ancient widespread radiations and the evolutionary background of contemporary invasive species such as the cane toad.
Overseas dispersals are often invoked when Southern Hemisphere terrestrial and freshwater organism phylogenies do not fit the sequence or timing of Gondwana fragmentation. We used dispersal-vicariance analyses and molecular timetrees to show that two species-rich frog groups, Microhylidae and Natatanura, display congruent patterns of spatial and temporal diversification among Gondwanan plates in the Late Cretaceous, long after the presumed major tectonic break-up events. Because amphibians are notoriously salt-intolerant, these analogies are best explained by simultaneous vicariance, rather than by oceanic dispersal. Hence our results imply Late Cretaceous connections between most adjacent Gondwanan landmasses, an essential concept for biogeographic and palaeomap reconstructions.
Background: High taxonomic level endemism in the Western Ghats-Sri Lanka biodiversity hotspot has been typically attributed to the subcontinent's geological history of long-term isolation. Subsequent out of -and into India dispersal of species after accretion to the Eurasian mainland is therefore often seen as a biogeographic factor that 'diluted' the composition of previously isolated Indian biota. However, few molecular studies have focussed on into-India dispersal as a possible source of endemism on the subcontinent. Using c. 6000 base pairs of mitochondrial and nuclear DNA, we investigated the evolutionary history and biogeography of true toads (Bufonidae), a group that colonized the Indian Subcontinent after the Indo-Asia collision.
A taxonomic revision of the genus Nyctibatrachus is presented. As a result, we recognize 27 species, 12 of which are new to science and described herein. Three ‘lost’ species—Nyctibatrachus sanctipalustris, Nyctibatrachus sylvaticus and Nannobatrachus kempholeyensis are rediscovered after their original descriptions and the latter two species are neotypified. Four species are lectotypified (Nannobatrachus beddomii, Nyctibatrachus deccanensis, Nyctibatrachus major and Nyctibatrachus sanctipalustris). The taxonomic revision and description of new species is based on new morphological, behavioural, ecological and molecular data from available type specimens and/or recent collections from throughout the distribution range of Nyctibatrachus. Specimens from the type localities of all previously described species were collected and discussed along with the type specimens. Nyctibatrachus sholai is considered a junior subjective synonym of N. deccanensis. Nyctibatrachus sanctipalustris modestus is resurrected from synonymy, but allocated to the genus Fejervarya. A new gland, the subocular gland is introduced to anuran morphological terminology. Both the courtship behaviour and ovipositional sites of four species are described for the first time. The process of fertilisation was carried out in the absence of physical contact between males and females in all four species. Furthermore, previously unreported parental care behaviour is documented for the genus, including biparental egg attendance (probably clutch hydration) and egg guarding (active predator defense). A brief outline of tadpole development from egg to metamorph is provided for Nyctibatrachus aliciae, with figures of the major developmental stages.
The limbless, primarily soil-dwelling and tropical caecilian amphibians (Gymnophiona) comprise the least known order of tetrapods. On the basis of unprecedented extensive fieldwork, we report the discovery of a previously overlooked, ancient lineage and radiation of caecilians from threatened habitats in the underexplored states of northeast India. Molecular phylogenetic analyses of mitogenomic and nuclear DNA sequences, and comparative cranial anatomy indicate an unexpected sister-group relationship with the exclusively African family Herpelidae. Relaxed molecular clock analyses indicate that these lineages diverged in the Early Cretaceous, about 140 Ma. The discovery adds a major branch to the amphibian tree of life and sheds light on both the evolution and biogeography of caecilians and the biotic history of northeast India-an area generally interpreted as a gateway between biodiversity hotspots rather than a distinct biogeographic unit with its own ancient endemics. Because of its distinctive morphology, inferred age and phylogenetic relationships, we recognize the newly discovered caecilian radiation as a new family of modern amphibians.
What can we learn from the microbial communities on cheese? Very little is known about how microbes behave in the context of a community. Since studies have recently demonstrated that microbial communities living in and on the human body greatly impact our health, the importance of understanding how microbial communities function and how we can manipulate them is now widely recognized. By studying microbial communities that we already know how to manipulate, like those on cheese, we may readily find answers to questions about which forces are most important in determining succession of species within a microbial community, how species cooperate or compete within a community, and how whole communities respond to perturbations, like invasion by pathogenic species. The adaptation of cheese communities into a laboratory model system can help to delineate the principles that govern microbial communities. Why will cheese be such a good model system for studying microbial communities? A good model system must be simple, easily cultivated in the lab, and reproducible. The rind communities that form a biofilm on the surface of an aged cheese exhibit all of these properties. Because cheese communities have relatively few members, linking species to function will be experimentally practical. Since these communities grow on cheese, a defined substrate, their natural habitat is easily reproduced, and member species may be isolated in the lab. This will make it possible to reconstruct whole communities and observe their development. The simplicity, culturability, and reproducibility of cheese microbial communities will provide a unique, experimentally practical system that will help us understand how microbes live together. Where can I find out more?
Sex pheromones form an important facet of reproductive strategies in many organisms throughout the Animal Kingdom. One of the oldest known sex pheromones in vertebrates are proteins of the Sodefrin Precursor-like Factor (SPF) system, which already had a courtship function in early salamanders. The subsequent evolution of salamanders is characterized by a diversification in courtship and reproduction, but little is known on how the SPF pheromone system diversified in relation to changing courtship strategies. Here, we combined transcriptomic, genomic, and phylogenetic analyses to investigate the evolution of the SPF pheromone system in nine salamandrid species with distinct courtship displays. First, we show that SPF originated from vertebrate three-finger proteins and diversified through multiple gene duplications in salamanders, while remaining a single copy in frogs. Next, we demonstrate that tail-fanning newts have retained a high phylogenetic diversity of SPFs, whereas loss of tail-fanning has been associated with a reduced importance or loss of SPF expression in the cloacal region. Finally, we show that the attractant decapeptide sodefrin is cleaved from larger SPF precursors that originated by a 62 bp insertion and consequent frameshift in an ancestral Cynops lineage. This led to the birth of a new decapeptide that rapidly evolved a pheromone function independently from uncleaved proteins.
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