1,721,201 research outputs found
Climbing on the La Canna Volcanic Sea Stack to Obtain First-Hand Data on the Tiniest Population of the Critically Endangered Aeolian Wall Lizard Podarcis raffonei
Full text linkAmong the extant populations of the critically endangered Aeolian wall lizard, the most vulnerable is the one surviving on La Canna, a columnar volcanic stack off the Filicudi Island. Here, I report the results of the first climbing expedition by a biologist on La Canna, that contributed direct observations and updated information on the size, morphology, and genetic variability of this population. Lizard density at the sampling site (a small terrace at 50 m of elevation) was 1.7 m−2, twice of a previous estimate. Standard methods for estimating population size are unsuitable for La Canna. An educated guess of about a hundred individuals can be drawn, considering the extent of habitat available on the stack and the number of observed lizards. Lizards on La Canna were not fearless, despite what was reported by alpinists, possibly because of aggressive intraspecific interactions or high environmental temperatures during sampling. Biometric data significantly extend the body size of La Canna’s lizards and indicate that it is not smaller than other P. raffonei populations. A complete lack of genetic diversity was found at the mitochondrial nd4 gene, in line with previous allozyme data and with estimates on other microinsular Podarcis populations. The small size of the La Canna population implies severe genetic drift and an extremely high level of inbreeding, as supported by low heterozygosity found across the genome. Detrimental effects of inbreeding depression are evident as cephalic malformations observed in all captured lizards of La Canna and might represent the more immediate threat to the persistence of this population
Revision shock in Pacific oysters taxonomy: The genus Magallana (formerly Crassostrea in part) is well-founded and necessary
No full textThe description of the genus Magallana provoked taxonomic 'revision shock' among Bayne and colleagues, who criticised: (1) the supporting evidence for this taxonomic change, (2) the procedure used and (3) its impact on the nomenclatural stability of oysters. Here, we demonstrate that the description of the genus Magallana fulfils the norms of taxonomic and indexing revisions, and is well-founded on a scientific basis. The clade named Magallana is supported by a robust phylogeny based on comprehensive taxon sampling, independent datasets and varied analytical methods. A new maximum likelihood phylogenetic analysis of oysters, based on mitochondrial gene order data (representing molecular phenotypes above the sequence level), has provided additional support for this classification. These results are fully consistent with all previously published phylogenetic studies, thus providing an unambiguous indication of the stability of the clade that meets all the currently accepted criteria for naming clades as taxa. We show that, while the criterion of 'morphological diagnosability' is not applicable at any level of oyster classification, several striking molecular phenotypes are diagnostic of Magallana, both at the nuclear and the mitochondrial genome level. The classification with three genera Magallana, Crassostrea and Talonostrea reflects the evolutionary diversity of Crassostreinae and is consistent with taxonomic ranking criteria adopted for other oyster subfamilies
Molecular phylogenetics in 2D: ITS2 rRNA evolution and sequence-structure barcode from Veneridae to Bivalvia
No full textIn this study, we analysed the nuclear ITS2 rRNA primary sequence and secondary structure in Veneridae and comparatively with 20 Bivalvia taxa to test the phylogenetic resolution of this marker and its suitability for molecular diagnosis at different taxonomic levels. Maximum-Likelihood and Bayesian trees based on primary sequences were congruent with (Profile-) Neighbor-Joining trees based on a combined model of sequence-structure evolution. ITS2 showed higher resolution below the subfamily level, up to the intraspecific level, providing a phylogenetic signal comparable to (mitochondrial and/or nuclear) gene fragments two-five times longer. Structural elements of the ITS2 folding, such as specific mismatch pairing and compensatory base changes, provided further support for the monophyly of some groups and for their phylogenetic relationships. Veneridae ITS2 folding is structured in six domains (DI-VI) and shows five striking sequence-structure features. Two of them, the Basal and Apical STEMs, are common to Bivalvia, while the presence of both the Branched STEM and the Y/R stretches occurs in five superfamilies of the two Heterodonta orders Myoida and Veneroida, thus questioning their reciprocal monophyly. Our results validated the ITS2 as a suitable marker tool for venerids phylogenetics and taxonomy, and underlined the significance of including secondary structure information for both applications at several systematic levels within bivalves
Cross-scale predictions allow the identification of local conservation priorities from atlas data.
No full textFor planning practical measures aimed at biodiversity protection, conservation
priorities must be identified at a local scale. Unfortunately, identifying local
conservation priorities requires high-resolution data on species distribution, and
these are often unavailable. Atlases of species distribution provide data for several
groups of organisms in many different areas but are often too coarse in resolution
to provide valuable information. We explored the possibility of cross-scale modelling
species distributions and we clarified, for the first time, its effect on prioritization
exercises. We used different modelling techniques for scaling down atlas
data for Sardinian reptiles, validated the outcomes with detailed, field-sampled
data, and compared conservation priorities deriving from atlas maps and downscaled
models. Doing this, we obtained as a further result the identification of
priority species and areas for future conservation strategies. Our results encourage
us to experiment further with this approach. Through the downscaling procedure,
we obtain high-resolution models with strong variations in predictive performances,
although most of the models show satisfactory/excellent scores. This testifies
that low-resolution data can be downscaled maintaining low rates of omission
and commission errors. Increasing the resolution of distribution maps used for
prioritization influences the spatial patterns of priority but does not modify the
evaluation of species representation. Overall, we show that atlases can meet the
large demand for distribution data by decision makers if appropriate downscaling
procedures are adopted. In addition, we provide practical instruments for the
conservation of reptiles in Sardinia by identifying priority species and areas that
require strict management
Genetic Divergence Across Glacial Refugia Despite Interglacial Gene Flow in a Crested Newt
Full text linkMtDNA-based phylogeography has illuminated the impact of the Pleistocene Ice Age on species distribution dynamics and the build-up of genetic divergence. The well-known shortcomings of mtDNA in biogeographical inference can be compensated by integrating multilocus data and species distribution modelling into phylogeography. We re-visit the phylogeography of the Italian crested newt (Triturus carnifex), a species distributed in two of Europe’s main glacial refugia, the Balkan and Italian Peninsulas. While a new 51 nuclear DNA marker dataset supports the existence of three lineages previously suggested by mtDNA (Balkan, northern Italy and southern Italy), the nuclear DNA dataset also provides improved resolution where these lineages have obtained secondary contact. We observe geographically restricted admixture at the contact between the Balkan and northern Italy gene pools and identify a potential mtDNA ghost lineage here. At the contact between the northern and southern Italy gene pools we find admixture over a broader area, as well as asymmetric mtDNA introgression. Our species distribution model is in agreement with a distribution restricted to distinct refugia during Pleistocene glacial cycles and postglacial expansion with secondary contact. Our study supports: (1) the relevance of the north-western Balkan Peninsula as a discrete glacial refugium; (2) the importance of north-eastern Italy and the northern Apennine as suture zones; and (3) the applicability of a refugia-within-refugia scenario within the Italian Peninsula
Host plant associations in Western Palaearctic Longitarsus flea beetles (Chrysomelidae, Galerucinae, Alticini): a preliminary phylogenetic assessment
No full textExploring the Synthetic Speech Attribution Problem Through Data-Driven Detectors
No full textIn recent years, numerous techniques to manipulate multimedia data and generate hyper-realistic synthetic content have been presented. These inauthentic data are hazardous as they can lead to numerous threats and dangers when misused. This has led the forensic community to propose multiple approaches to tackle both detection and attribution problems. Solving the detection problem consists in determining whether some given data is genuine or false. Solving the attribution problem consists in determining which specific technique has been used to manipulate or generate the observed data. In this paper we address the attribution problem on synthetic speech. We consider a set of methods initially proposed for synthetic speech detection, and adapt them to identify which speech generation algorithm has been used to synthesize a speech track. Our goal is to sample the versatility of these systems and verify how far the detection and attribution tasks are from each other. We test the models in a closed-set scenario and compare their performance with that of a well-established baseline. Moreover, we propose different solutions to address the task in an open-set situation. The encouraging results show that the considered methods can provide a representation of the input signal that is meaningful for both detection and attribution
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