103 research outputs found
The Phylogenetic Position of the Enigmatic, Polypodium hydriforme (Cnidaria, Polypodiozoa): Insights from Mitochondrial Genomes
Polypodium hydriforme is an enigmatic parasite that belongs to the phylum Cnidaria. Its taxonomic position has been debated: whereas it was previously suggested to be part of Medusozoa, recent phylogenomic analyses based on nuclear genes support the view that P. hydriforme and Myxozoa form a clade called Endocnidozoa. Medusozoans have linear mitochondrial (mt) chromosomes, whereas myxozoans, as most metazoan species, have circular chromosomes. In this work, we determined the structure of the mt genome of P. hydriforme, using Illumina and Oxford Nanopore Technologies reads, and showed that it is circular. This suggests that P. hydriforme is not nested within Medusozoa, as this would entail linearization followed by recirculation. Instead, our results support the view that P. hydriforme is a sister clade to Myxozoa, and mt linearization in the lineage leading to medusozoans occurred after the divergence of Myxozoa + P. hydriforme. Detailed analyses of the assembled P. hydriforme mt genome show that: (1) it is encoded on a single circular chromosome with an estimated size of ∼93,000 base pairs, making it one of the largest metazoan mt genomes; (2) around 78% of the genome encompasses a noncoding region composed of several repeat types; (3) similar to Myxozoa, no mt tRNAs were identified; (4) the codon TGA is a stop codon and does not encode for tryptophan as in other cnidarians; (5) similar to myxozoan mt genomes, it is extremely fast evolving
Author Correction: The global distribution of tetrapods reveals a need for targeted reptile conservation
The global biogeography of lizard functional groups
Aim: Understanding the mechanisms determining species richness is a primary goal of biogeography. Richness patterns of sub-groups within a taxon are usually assumed to be driven by similar processes. However, if richness of distinct ecological strategies respond differently to the same processes, inferences made for an entire taxon may be misleading. We deconstruct the global lizard assemblage into functional groups and examine the congruence among richness patterns between them. We further examine the species richness – functional richness relationship to elucidate the way functional diversity contributes to the overall species richness patterns.
Location: Global.
Methods: Using comprehensive biological trait databases we classified the global lizard assemblage into ecological strategies based on body size, diet, activity times and microhabitat preferences, using Archetypal Analysis. We then examined spatial gradients in the richness of each strategy at the one-degree grid cell, biomes and realm scales.
Results: We found that lizards can best be characterized by seven 'ecological strategies': scansorial, terrestrial, nocturnal, herbivorous, fossorial, large and semiaquatic. There are large differences among the global richness patterns of these strategies. While the major richness hotspot for lizards in general is in Australia, several strategies exhibit highest richness in the Amazon Basin. Importantly, the global maximum in lizard species richness is achieved at intermediate values of functional diversity and increasing functional diversity further result in a shallow decline of species richness.
Main conclusions: The deconstruction of the global lizard assemblage along multiple ecological axes offers a new way to conceive lizard diversity patterns. It suggests that local lizard richness mostly increases when species belonging to particular ecological strategies become hyper-diverse there, and not because more ecological types are present in the most species rich localities. Thus maximum richness and maximum ecological diversity do not overlap. These results shed light on the global richness pattern of lizards, and highlight previously unidentified spatial patterns in understudied functional groups
100 ancient genomes show repeated population turnovers in Neolithic Denmark.
Major migration events in Holocene Eurasia have been characterized genetically at broad regional scales <sup>1-4</sup> . However, insights into the population dynamics in the contact zones are hampered by a lack of ancient genomic data sampled at high spatiotemporal resolution <sup>5-7</sup> . Here, to address this, we analysed shotgun-sequenced genomes from 100 skeletons spanning 7,300 years of the Mesolithic period, Neolithic period and Early Bronze Age in Denmark and integrated these with proxies for diet ( <sup>13</sup> C and <sup>15</sup> N content), mobility ( <sup>87</sup> Sr/ <sup>86</sup> Sr ratio) and vegetation cover (pollen). We observe that Danish Mesolithic individuals of the Maglemose, Kongemose and Ertebølle cultures form a distinct genetic cluster related to other Western European hunter-gatherers. Despite shifts in material culture they displayed genetic homogeneity from around 10,500 to 5,900 calibrated years before present, when Neolithic farmers with Anatolian-derived ancestry arrived. Although the Neolithic transition was delayed by more than a millennium relative to Central Europe, it was very abrupt and resulted in a population turnover with limited genetic contribution from local hunter-gatherers. The succeeding Neolithic population, associated with the Funnel Beaker culture, persisted for only about 1,000 years before immigrants with eastern Steppe-derived ancestry arrived. This second and equally rapid population replacement gave rise to the Single Grave culture with an ancestry profile more similar to present-day Danes. In our multiproxy dataset, these major demographic events are manifested as parallel shifts in genotype, phenotype, diet and land use
Sexes and species as rival units of niche saturation during community assembly
This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.Aim
Community assembly is traditionally assumed to result from speciation and colonization mediated by available niche space. This paradigm is expanded by the theory that niche space can also be saturated by intersexual adaptive divergence (ecological sexual dimorphism) when interspecific competition is relaxed. This theory (here termed ‘niche-packing equivalence’) predicts that the evolution of ecological sexual dimorphism constrains the ecological opportunity that would otherwise lead to ecological speciation or colonization, and that saturation of niches by different species constrains divergent selection for divergence between the sexes. Therefore, sexes and species are equivalent, yet antagonistic units of niche occupation. We present the most comprehensive test of the niche-packing equivalence theory at ecological time-scales (assemblage level) to date.
Location
South America
Major taxa studied
Liolaemus lizards.
Methods
We identified 23 Liolaemus assemblages varying in species richness and sexual size dimorphism (SSD), distributed across a wide environmental range. We used mixed effects models, permutation tests and Markov Chain Monte Carlo (MCMC) regressions to quantify the relationship between SSD and species richness. We then partitioned the body size niche dimension between the sexes and amongst species, and tested for non-overlapping body size distributions. We regressed SSD and species richness of each assemblage against environmental predictors, using multi-model inference and structural equation modelling.
Results
Sexual dimorphism declines with increasing species richness, and a strong signal of tension between the two remains following phylogenetic control. This pattern is accompanied by evidence of constraints on body-size partitioning amongst species and between the sexes: the two units of niche saturation tend not to overlap. However, across assemblages, species richness and SSD correlate with different environmental variables, suggesting that their tension is context-specific.
Main conclusions
Our evidence supports the prediction that sexual dimorphism and species richness are alternative outcomes of adaptive radiation. However, this antagonism is mediated by a suite of environmental predictors that influence dimorphism and species richness differentially.The authors thank David Hosken, Tim Barraclough, Trine Bilde, Lilly Harvey, Shai Meiri, Dave Shuker and Jonathan Chase for valuable insights on earlier versions of this manuscript. Alejandro Scolaro provided extensive data and expertise on Patagonian assemblages of lizards. Three referees and Adriana Ruggiero made excellent critical comments to improve this paper. This study was funded by the Leverhulme Trust, and received additional support from the University of Lincoln through a RIF Grant to D.P.-D. D.J.H. was supported by NERC standard grant NE/L007770/1 and by NERC International Opportunities Fund NE/N006798/1
Lateralization in escape behaviour at different hierarchical levels in a Gecko: Tarentola angustimentalis from eastern Canary Islands
At the individual level, to be behaviourally lateralized avoids costly duplication of neural circuitry and decreases possible contradictory order from the two brain hemispheres. However, being prey behaviour lateralized at higher hierarchical levels could generate different negative implications, especially if predators are able to make predictions after multiple encounters. These conflicting pressures, namely between the advantages for individuals and the disadvantages for populations could be concealed if higher-level lateralization would arise from the combination of lateralized behaviours of individuals which are mutually dependent. Here, we investigated the lateralization patterns in the escape behaviour of the gecko Tarentola angustimentalis undergoing a predatory attack simulation in a "T" maze experiment. Results showed that gecko populations displayed different degrees of lateralization, with an overall dominance of right-biased individuals. This trend is similar to that observed in the Podarcis wall lizards, which share predators with Tarentola. In addition, different morphological parameters plausible to affect refuge selection were explored in order to link directional asymmetries at morphological level with lateralization during refuge selection.Fieldwork was carried out with the support of the project PTDC/BIA-BEC/101256/2008 funded by Fundação para a Ciência e a Tecnologia (FCT, Portugal). E.G.-M. was supported by postdoc grant from FCT (SFRH/BPD/72806/2010). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Thanks are due to Herve Seligmann and an anonymous reviewer for comments and suggestions on an earlier draft of the manuscript.publishe
The global distribution of tetrapods reveals a need for targeted reptile conservation
The distributions of amphibians, birds and mammals have underpinned global and local conservation priorities, and have been
fundamental to our understanding of the determinants of global biodiversity. In contrast, the global distributions of reptiles,
representing a third of terrestrial vertebrate diversity, have been unavailable. This prevented the incorporation of reptiles into
conservation planning and biased our understanding of the underlying processes governing global vertebrate biodiversity. Here,
we present and analyse the global distribution of 10,064 reptile species (99% of extant terrestrial species). We show that richness
patterns of the other three tetrapod classes are good spatial surrogates for species richness of all reptiles combined and of
snakes, but characterize diversity patterns of lizards and turtles poorly. Hotspots of total and endemic lizard richness overlap
very little with those of other taxa. Moreover, existing protected areas, sites of biodiversity significance and global conservation
schemes represent birds and mammals better than reptiles. We show that additional conservation actions are needed to
effectively protect reptiles, particularly lizards and turtles. Adding reptile knowledge to a global complementarity conservation
priority scheme identifies many locations that consequently become important. Notably, investing resources in some of the
world’s arid, grassland and savannah habitats might be necessary to represent all terrestrial vertebrates efficiently
A roadmap for island biology: 50 fundamental questions after 50 years of The Theory of Island Biogeography
Aims The 50th anniversary of the publication of the seminal book, The Theory
of Island Biogeography, by Robert H. MacArthur and Edward O. Wilson, is a
timely moment to review and identify key research foci that could advance
island biology. Here, we take a collaborative horizon-scanning approach to
identify 50 fundamental questions for the continued development of the field.
Location Worldwide.
Methods We adapted a well-established methodology of horizon scanning to
identify priority research questions in island biology, and initiated it during the
Island Biology 2016 conference held in the Azores. A multidisciplinary working
group prepared an initial pool of 187 questions. A series of online surveys was
then used to refine a list of the 50 top priority questions. The final shortlist
was restricted to questions with a broad conceptual scope, and which should
be answerable through achievable research approaches.
Results Questions were structured around four broad and partially overlapping
island topics, including: (Macro)Ecology and Biogeography, (Macro)Evolution,
Community Ecology, and Conservation and Management. These topics were
then subdivided according to the following subject areas: global diversity patterns
(five questions in total); island ontogeny and past climate change (4); island rules
and syndromes (3); island biogeography theory (4); immigration–speciation–extinction
dynamics (5); speciation and diversification (4); dispersal and colonization
(3); community assembly (6); biotic interactions (2); global change (5);
conservation and management policies (5); and invasive alien species (4).
Main conclusions Collectively, this cross-disciplinary set of topics covering
the 50 fundamental questions has the potential to stimulate and guide future
research in island biology. By covering fields ranging from biogeography, community
ecology and evolution to global change, this horizon scan may help to
foster the formation of interdisciplinary research networks, enhancing joint
efforts to better understand the past, present and future of island biotas
THE ROLE OF SPACE AGENCIES IN THE FORMATION OF AN EFFECTIVE STATE POLICY FOR THE DEVELOPMENT OF THE SPACE INDUSTRY
Given the global trends in the space goods and services market, as well as the strategic importance of the space industry as a multiplier for the development of high-tech innovation economy, it is important to review and optimize the role of space agencies in shaping and prioritizing state space policy.
The global space industry is changing rapidly, moving to the fourth stage of development - the construction of the ecosystem of the "New Space", which is characterized by rapid commercialization of the space sector, expanding the range of industry participants and increasing innovation.
Today, the domestic space industry needs quick and effective solutions to reform the national space policy, balanced approaches to state regulation and management of the industry, taking into account global trends in the global space sector.
Keywords: space industry, space agency, international cooperation, public policy, "New Space".</jats:p
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