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Munguia M.,CSIC - National Museum of Natural Sciences
PloS one | Year: 2012

A common assumption in bioclimatic envelope modeling is that species distributions are in equilibrium with contemporary climate. A number of studies have measured departures from equilibrium in species distributions in particular regions, but such investigations were never carried out for a complete lineage across its entire distribution. We measure departures of equilibrium with contemporary climate for the distributions of the world amphibian species. Specifically, we fitted bioclimatic envelopes for 5544 species using three presence-only models. We then measured the proportion of the modeled envelope that is currently occupied by the species, as a metric of equilibrium of species distributions with climate. The assumption was that the greater the difference between modeled bioclimatic envelope and the occupied distribution, the greater the likelihood that species distribution would not be at equilibrium with contemporary climate. On average, amphibians occupied 30% to 57% of their potential distributions. Although patterns differed across regions, there were no significant differences among lineages. Species in the Neotropic, Afrotropics, Indo-Malay, and Palaearctic occupied a smaller proportion of their potential distributions than species in the Nearctic, Madagascar, and Australasia. We acknowledge that our models underestimate non equilibrium, and discuss potential reasons for the observed patterns. From a modeling perspective our results support the view that at global scale bioclimatic envelope models might perform similarly across lineages but differently across regions.


Lobon-Cervia J.,CSIC - National Museum of Natural Sciences
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2014

Recently, Minto et al. (2008), based on a fishery data set including marine, estuarine, and freshwater fishes, described higher variability in the survival rates of juveniles at low rather than at high parental density in an inversely density-dependent fashion and suggested density-dependent mechanisms underpinning those patterns. This study, based on a long-term study of brown trout (Salmo trutta; a species and habitat not included in the Minto et al. (2008) analysis), documents that survival rates in these stream-living populations exhibit a pattern that matches exactly those reported by Minto et al. (2008). Nevertheless, hypothesis testing rejected the occurrence of stock-recruitment relationships and the operation of density-dependent recruitment regulation. The patterns elucidated for these brown trout populations can be entirely explained by the operation of two single environmental factors, namely, stream discharge in March determining annual survival rates across streams and sites and site-specific depth determining site-specific survival rates. It is open to question that exactly the same patterns can be generated by two sets of opposing factors, density-dependent (i.e., Minto et al. 2008) and environmental factors (i.e., this study). The consistency of this pattern suggests that survival rates and recruitment are probably determined by environmental factors across fish populations and habitats.


Boto L.,CSIC - National Museum of Natural Sciences
Proceedings. Biological sciences / The Royal Society | Year: 2014

Horizontal gene transfer is accepted as an important evolutionary force modulating the evolution of prokaryote genomes. However, it is thought that horizontal gene transfer plays only a minor role in metazoan evolution. In this paper, I critically review the rising evidence on horizontally transferred genes and on the acquisition of novel traits in metazoans. In particular, I discuss suspected examples in sponges, cnidarians, rotifers, nematodes, molluscs and arthropods which suggest that horizontal gene transfer in metazoans is not simply a curiosity. In addition, I stress the scarcity of studies in vertebrates and other animal groups and the importance of forthcoming studies to understand the importance and extent of horizontal gene transfer in animals.


Lobon-Cervia J.,CSIC - National Museum of Natural Sciences
Freshwater Biology | Year: 2012

1.This study investigates when and where density dependence operates on the mortality rates of stream-resident brown trout Salmo trutta. To this aim, I explored populations in habitats of different quality containing high, low or intermediate densities over broad scales of space and time. The study is based on census data of 170 cohorts quantified from recruitment to the total disappearance at 12 sites in four contrasting tributaries of the Rio Esva drainage (north-western Spain), over the years 1986-2007. 2.Log 10-transformed survivor density over time highlighted a consistent pattern for the 170 cohorts characterised by the occurrence of only two life stages. An early stage starts at recruitment, lasts about half the lifetime and shows no or negligible mortality. A threshold time at 425-620days after emergence preceded a second stage of continuous and constant mortality until the final disappearance of the cohorts. Consequently, in all scenarios, mortality only occurred in the adult component and no effect of season, year, age-class and/or reproductive stage was detected. 3.Substantial spatial and temporal variations typified both recruitment (range R=0.01-1.62indm -2) and adults' mortality rates (range Z=0.03-0.38day -1). Nested anovas revealed strong effects of site and year on both recruitment and mortality with sites interspersed along the stream gradients where recruitment and mortality were typically high relative to other sites located either nearby in the same stream or distant in another stream, where both recruitment and mortality rates were typically low or intermediate. 4.Adult mortality rates plotted against recruitment for the 170 cohorts pooled revealed a continuous, positive power relationship that explained 45.3% of variation in mortality rates over the whole range of recruitment values. Similarly, highly significant power relationships were elucidated for site-specific mortality rates averaged across years and for annual-specific mortality rates averaged across sites against the corresponding mean recruitment averaged across years and sites, respectively. These relationships support the hypothesis that the operation of density dependence is scale independent and context independent but operates in a continuous manner across all scenarios examined. 5.A chronic effect of density dependence on adult losses induces temporally persistent populations maintained by a low number of spawners. Apparently, the operation of density dependence adjusts the number of spawners to the availability of rearing and spawning habitat. This dynamic process may also help to explain the small effective population size (Ne) recently documented by genetic studies of stream-living brown trout and other salmonids. © 2012 Blackwell Publishing Ltd.


Boto L.,CSIC - National Museum of Natural Sciences
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

The contribution of horizontal gene transfer to evolution has been controversial since it was suggested to be a force driving evolution in the microbial world. In this paper, I review die current standpoint on horizontal gene transfer in evolutionary thinking and discuss how important horizontal gene transfer is in evolution in the broad sense, and particularly in prokaryotic evolution. I review recent literature, asking, first, which processes are involved in the evolutionary success of transferred genes and, secondly, about the extent of horizontal gene transfer towards different evolutionary times. Moreover, I discuss the feasibility of reconstructing ancient phylogenetic relationships in the face of horizontal gene transfer. Finally, I discuss how horizontal gene transfer fits in the current neo-Darwinian evolutionary paradigm and conclude there is a need for a new evolutionary paradigm that includes horizontal gene transfer as well as other mechanisms in the explanation of evolution. © 2009 The Royal Society.


Abascal F.,CSIC - National Museum of Natural Sciences | Zardoya R.,CSIC - National Museum of Natural Sciences
BioEssays | Year: 2012

Leucine-rich repeat-containing 8 (LRRC8) proteins are composed of four transmembrane helices and 17 leucine-rich repeats (LRR). Although LRRC8 proteins have been associated with important processes, like maturation of B cells or adipocyte differentiation, their biology and molecular function are largely unknown. We found that LRRC8 proteins originated from the combination of a pannexin and an LRR domain (most likely related to the SHOC2, LAP, RSU1 and LRRIQ4 protein families) before the diversification of chordates. We propose that, like pannexins, LRRC8 proteins form hexameric channels, which participate in cell-cell communication processes. According to the inferred topological model, and contrary to what was previously assumed, the six LRR domains are located in the cytoplasm, and could participate in the organisation of signalling cascades. By compiling available proteomics and gene expression data, and on the basis of the LRRC8 proposed hexameric channel structure, we present clues to the function of this family. © 2012 WILEY Periodicals, Inc.


Van der Made J.,CSIC - National Museum of Natural Sciences
Quaternary Science Reviews | Year: 2011

The dispersal of the genus Homo occurred against a background of continuous environmental change. Here, dispersals of large mammals through the Levantine Corridor and into Western Europe and Java are studied and compared to existing records of climatic change and dispersals of early humans and lithic industry. The first human dispersal (with Oldowan lithic industry) out of Africa, around or shortly before 1.8 Ma may have been triggered by biological evolution and increased social organisation, rather than environmental change. After that event, increasing aridity led to decreased faunal exchange between Africa and Eurasia and may have isolated the human populations of Africa and Africa. Southern (Java) and Eastern Asia (China) also seem to have been isolated. Human dispersal into Western Europe may have been limited by closed environments in Central Europe until about 1.2 Ma ago, when faunal dispersal into Europe suggests the cyclic spread of open environments to the west. Acheulean technology originated in Africa, some 1.6-1.5 Ma ago, but its dispersal into Eurasia may have been obstructed by an arid Southwest Asia, until broadly about 0.9 Ma ago, when faunal exchange suggests that the area became temporarily less dry. By 0.6-0.5 Ma ago it reached Europe. © 2010 Elsevier Ltd.


Lobon-Cervia J.,CSIC - National Museum of Natural Sciences
Oecologia | Year: 2010

The objective of this study was to elucidate the effects of density dependence on the individual size variation of brown trout (Salmo trutta) juveniles. Recruitment (the abundance of the youngest juveniles in May when they were 2 months old); the mean size attained by those individuals in September (6 months old) and the corresponding size variability around the mean size quantified with the coefficient of variation (CV) were examined in 22 year-classes at seven sites of two contrasting tributaries of the Rio Esva drainage (north-western Spain). Both mean size and CV tended to be site-specific but density dependence in the form of recruitment dependence affected both mean size and CV: the mean size depicted negative power relationships with increased recruitment whereas the CV increased positively with increased recruitment. However, this pattern differed among sites. At two out of seven sites, there was no obvious relationship between the mean size and recruitment. The CV increased positively with increased recruitment at all sites, although at several sites the CV described linear relationships and at others described power relationships. As a consequence, the stronger effects of density dependence on mean size occurred at low densities with minor effects at high densities, whereas density dependence operated on CV with continuous effects within the whole range of recruitment variation except at several sites where lower effects occurred at high densities. Thus, the occurrence, shape and intensity of competitive interactions underlying density dependence as a major cause of size variation differed across temporal and spatial scales. © 2010 Springer-Verlag.


Boto L.,CSIC - National Museum of Natural Sciences
Proceedings of the Royal Society B: Biological Sciences | Year: 2014

Horizontal gene transfer is accepted as an important evolutionary force modulating the evolution of prokaryote genomes. However, it is thought that horizontal gene transfer plays only a minor role in metazoan evolution. In this paper, I critically review the rising evidence on horizontally transferred genes and on the acquisition of novel traits in metazoans. In particular, I discuss suspected examples in sponges, cnidarians, rotifers, nematodes, molluscs and arthropods which suggest that horizontal gene transfer in metazoans is not simply a curiosity. In addition, I stress the scarcity of studies in vertebrates and other animal groups and the importance of forthcoming studies to understand the importance and extent of horizontal gene transfer in animals. © 2014 The Author(s) Published by the Royal Society. All rights reserved.


Grant
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 362.07K | Year: 2016

Many pathogens of global health and conservation concern infect multiple host species. Ebola is a classic example, circulating naturally within a reservoir host community, and with the potential to jump across to another host species with devastating effect. Clearly it is vital to understand how such pathogens are maintained in their host communities, and which species play a major role in spreading those pathogens. However, obtaining that understanding is notoriously hard. We have recently developed a mathematical approach to measure a host communitys ability to maintain a pathogen, and identify key hosts that drive pathogen spread. Importantly, unlike previous methods, this approach can be parameterised using relatively coarse-grained, easily-collected data (standard measures of host abundance and infection occurrence). We will provide the first rigorous test of this model, applying it to a natural multihost-pathogen system of major conservation concern: chytrid fungus (Bd) in amphibian communities. Bd is a major cause of amphibian declines worldwide, but we dont understand how it spreads through or is maintained by amphibian communities. We will apply our mathematical approach to historical and new data, and use it to identify those key hosts, and predict the effect of removing them. Crucially, we will then directly test those predictions by carrying out species removal experiments. Overall this will provide a rigorous test of our mathematical tool, show how host communities affect pathogen spread in general, and provide specific guidelines for the management of Bd in particular.

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