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Aim: To test two prominent, alternate hypotheses that provide explanations for the great accumulation of endemic species in the Kimberley bioregion in north-western Australia, using an extensively sampled, region wide phylogeny of northern Australia’s most speciose freshwater fish family, Terapontidae. Specifically, we test whether the Kimberley may act as (1) a “museum” accumulating taxa and endemic species over time or (2) a “cradle” of more recent diversification and neoendemism. Location: The Australian monsoonal tropics Taxon: Grunters (Terapontidae) Methods: We obtained a robust and well supported Bayesian phylogeny for the family using DNA sequences from mtDNA and nuclear gene regions. We performed molecular phylogenetic analyses using species tree methods including molecular dating analysis, ancestral range reconstruction, and diversification analysis. Results: Based on our phylogeny, the combined molecular clock estimates and likelihood-based historical biogeographic reconstructions suggest that terapontids recently transitioned into the Kimberley from the east during the late-Miocene. We found that 80% of Kimberley terapontids diversified within the Kimberley in the last 3 Ma. Further, diversification analyses identified a single significant shift in diversification rates ~1.4 Ma that corresponds with a change in global climate midway through the Pleistocene that was predominantly driven by speciation in the Kimberley. Main Conclusions: The weight of evidence suggests that the Kimberley has been a “cradle” of evolution for Terapontidae, rather than a “museum”. Our analysis provides strong evidence for a geologically recent transition of terapontids into the Kimberley from regions to the east during the late Miocene followed by a significant increase in speciation rates during the Pleistocene, driven by speciation in the Kimberley. The results provide important insight into the evolutionary and biogeographical processes that have shaped the regions unique biota, which will inform land managers working to protect and conserve both species and the processes responsible for generating and sustaining them.
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A major focus of ecology is to understand and predict ecosystem function across scales. Many ecosystem functions are only measured at local scales, while their effects occur at a landscape level. Here, we investigate how landscape-scale predictions of ecosystem function depend on intraspecific competition, a fine-scale process, by manipulating intraspecific density of shredding macroinvertebrates and examining effects on leaf litter decomposition, a key function in freshwater ecosystems. For two species, we found that per-capita leaf processing rates declined with increasing density following power functions with negative exponents, likely due to interference competition. To demonstrate consequences of this nonlinearity, we scaled up estimates of leaf litter processing from shredder abundance surveys in 10 replicated headwater streams. In accordance with Jensen’s inequality, applying density-dependent consumption rates reduced estimates of catchment-scale leaf consumption by an order of magnitude relative to density-independent rates. Density-dependent consumption estimates aligned closely with metabolic requirements in catchments with large, but not small, shredder populations. Importantly, shredder abundance was not limited by leaf litter availability and catchment-level leaf litter supply was much higher than estimated consumption. Thus leaf litter processing was not limited by resource supply. Our work highlights the need for scaling-up which accounts for intraspecific interactions.
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1. Among plant traits, plant secondary metabolites such as tannins mediate plant herbivore interactions but also have after-life effects on litter decomposition and nutrient cycling. We propose that niche construction mechanisms based on positive plant-soil feedbacks (PSF) could influence the evolution of tannin production. 2. By modeling the flow of nitrogen (N) and carbon (C) through plants and soil in a spatially explicit context, we explored the relative contribution of herbivory and positive PSF as drivers of tannin evolution. We assumed soil N to be contained in labile and recalcitrant compartments, the latter made of tannin-protein complexes from which plants can absorb nutrients via associations with mycorrhizal fungi. 3. In infertile environments and for plants with low biomass turnover rates, we show that when tannins modify soil properties locally, positive PSF alone can drive their evolution. We further predict the existence of positive coevolutionary feedbacks between associations with mycorrhizal fungi with a decaying ability and tannins, possibly triggered by the evolution of the latter as protection against herbivores. In line with our theoretical results, empirical evidence suggest that tannins are mostly present in plants with low tissue turnover, associated with mycorrhizal fungi able to decay organic matter and inhabiting infertile environments. 4. Synthesis. Our model proposes that the evolution of tannin production can be triggered by positive PSF, provided that tannins promote the local N retention and that mycorrhizal fungi associated with plants are able to absorb N from tannin-protein complexes. In our model, tannin production evolves only in infertile ecosystems, in agreement with field observations. Our findings highlight that the strength of niche construction depends on the ecological context, hence that global ecological properties constrain local eco-evolutionary dynamics.
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Species’ geographic range limits often result from maladaptation to the novel environments beyond the range margin. However, we rarely know which aspects of the n-dimensional environment are driving this maladaptation. Especially of interest is the influence of abiotic versus biotic factors in delimiting species’ distributions. We conducted a two-year reciprocal transplant experiment involving manipulations of the biotic environment to explore how spatio-temporal gradients in precipitation, fatal mammalian herbivory, and pollination affected lifetime fitness within and beyond the range of the California annual plant, Clarkia xantiana ssp. xantiana. In the first, drier year of the experiment, fitness outside the range edge was limited mainly by low precipitation, and there was some evidence for local adaptation within the range. In the second, wetter year, we did not observe abiotic limitations to plant fitness outside the range; instead biotic interactions, especially herbivory, limited fitness outside the range. Together, protection from herbivory and supplementation of pollen resulted in 3-7 fold increases in lifetime fitness outside the range margin in the abiotically benign year. Overall, our work demonstrates the importance of biotic interactions, particularly as they interact with the abiotic environment, in determining fitness beyond geographic range boundaries.
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The origin of the mammalian order Eulipotyphla has been debated intensively with arguments around whether they began diversifying before or after the Cretaceous-Palaeogene (K-Pg) boundary at 66 Ma. Here, we used an in-solution nucleotide capture method and next generation DNA sequencing to determine the sequence of hundreds of ultra-conserved elements (UCEs), and conducted phylogenomic and molecular dating analyses for the four extant eulipotyphlan lineages—Erinaceidae, Solenodontidae, Soricidae, and Talpidae. Concatenated maximum-likelihood analyses with single or partitioned models and a coalescent species-tree analysis showed that divergences among the four major eulipotyphlan lineages occurred within a short period of evolutionary time, but did not resolve the interrelationships among them. Alternative suboptimal phylogenetic hypotheses received consistently the same amount of support from different UCE loci, and were not significantly different from the maximum likelihood tree topology, suggesting the prevalence of stochastic lineage sorting. Molecular dating analyses that incorporated among-lineage evolutionary rate differences supported a scenario where the four eulipotyphlan families diversified between 57.8 and 63.2 Ma. Given short branch lengths with low support values, traces of rampant genome-wide stochastic lineage sorting, and post K-Pg diversification, we concluded that the crown eulipotyphlan lineages arose through a rapid diversification after the K-Pg boundary when novel niches were created by the mass extinction of species.
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Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups. For one of the most diverse and species-rich groups, the squamate reptiles (lizards and snakes, amphisbaenians), an inverse correlation between the number of taxa and loci sampled still persists across all publications using DNA sequence data and reaching a consensus on the relationships among them has been highly problematic. Here, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome scale data. Importantly, we address genomic support for the traditional taxonomic groupings Scleroglossa and Macrostomata using novel machine-learning techniques. We interrogate genes using various metrics inherent to these loci, including parsimony-informative sites, phylogenetic informativeness, length, gaps, number of substitutions, and site concordance to understand why certain loci fail to find previously well-supported molecular clades and how they fail to support species-tree estimates. We show that both incomplete lineage sorting and poor gene-tree estimation (due to a few undesirable gene properties, such as an insufficient number of parsimony informative sites), may account for most gene and species-tree discordance. We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata. We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; and between the three toxiferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).
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Freshwater is one of the most critical elements for sustainable development of ecosystems and societies. River basins, concomitant with administrative zones, form a common unit for freshwater management. So far, no comprehensive, global analysis exists that would link the ecological challenges of the planet's river basins to the capacity of the societies to cope with them. We address this gap by performing a geospatial resilience analysis for a global set of 541 river basins. We use the social‐ecological systems (SES) approach by relating three ecological vulnerability factors (human footprint, natural hazards, water scarcity) with three adaptive capacity factors (governance, economy, human development), based on temporal trajectories from 1990 to 2015. Additionally, we examine resilience by subtracting ecological vulnerability from adaptive capacity. The most striking result is the fundamentally different patterns of controlling factors of the resilience in different developing regions, particularly those of Africa and Asia. Their root causes are particularly low adaptive capacity in Africa, and high ecological vulnerability in Asia. Alarmingly, the difference between those continents grew within the study period. Finally, this study highlights the rapid dynamics of adaptive capacity in comparison to ecological vulnerability, the latter having more inertia. Their fragile balance is of our interest; they can either support or counteract each other depending on the geographic location.
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Collective responses to threats occur throughout the animal kingdom but little is known about the cognitive processes underpinning them. Antipredator mobbing is one such response. Approaching a predator may be highly risky, but the individual risk declines and the likelihood of repelling the predator increases in larger mobbing groups. The ability to appraise the number of conspecifics involved in a mobbing event could therefore facilitate strategic decisions about whether to join. Mobs are commonly initiated by recruitment calls, which may provide valuable information to guide decision-making. We tested whether the number of wild jackdaws responding to recruitment calls was influenced by the number of callers. As predicted, playbacks simulating three or five callers tended to recruit more individuals than playbacks of one caller. Recruitment also substantially increased if recruits themselves produced calls. These results suggest that jackdaws use individual vocal discrimination to assess the number of conspecifics involved in initiating mobbing events, and use this information to guide their responses. Our results show support for the use of numerical assessment in antipredator mobbing responses and highlight the need for a greater understanding of the cognitive processes involved in collective behaviour.
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Social animals that live in domiciles constructed from biomaterials may facilitate microbial growth. Spider webs are one of the most conspicuous biomaterials in nature, yet almost nothing is known about the potential for webs to harbor microbes, even in social spiders that live in dense, long-term aggregations. Here, we tested whether the dominant bacteria present in social spider webs vary across sampling localities and whether the more permanent retreat web harbors compositionally distinct microbes from the more ephemeral capture webs in the desert social spider Stegodyphus dumicola. We also sampled spider cuticles and prey items in a subset of colonies. We found that spider colonies across large spatial scales harbored similar web-associated bacterial communities. We also found substantial overlap in bacterial community composition between spider cuticle, prey, and web samples. These data suggest that social spider webs can harbor characteristic microbial communities and potentially facilitate microbial transmission among individuals, and this study serves as the first step towards understanding the microbial ecology of these peculiar animal societies.
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Background. The Plasmodium vivax Reticulocyte Binding Protein (PvRBP) family is involved in red blood cell recognition and members of this family are potential targets for antibodies that may block P. vivax invasion. To date, the acquisition of immunity against PvRBPs in low malaria transmission settings and in a broad age group of exposed individuals has not been investigated. Methodology/Principal Findings. Total IgG antibody levels to six members of the PvRBP family (PvRBP1a, PvRBP1b, PvRBP2a, PvRBP2b, a non-binding fragment of PvRBP2c (PvRBP2cNB) and PvRBP2-P2) were measured in samples collected from individuals living in two regions of low P. vivax endemicity in Brazil and Thailand. In both settings, levels of total IgG to PvRBP1a, PvRBP2b, PvRBP2cNB, and PvRBP2P-2 increased statistically significantly with age as shown by the correlation coefficient, denoted as rho (rho=0.17-0.49; P<0.001), and those to PvRBP1a, PvRBP2b and PvRBP2cNB were significantly higher in infected individuals than those in uninfected individuals by using Wilcoxon's signed-rank test (P<0.001). Of the six PvRBPs examined, only antibodies to PvRBP2b were associated with protection against clinical malaria in both settings (Hazard Ratio=0.45-0.50, P≤0.032). Conclusion/Significance. Our results indicate that PvRBP2b warrants further preclinical development as a blood-stage vaccine candidate against P. vivax. Total IgG responses to PvRBPs were also shown to be promising immunological markers of exposure to P. vivax infection.
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