Ecological interactions are evolutionarily conserved across the entire tree of life.

Departamento de Ecología, Universidad de Granada, E-18071 Granada, Spain.
Nature (Impact Factor: 38.6). 06/2010; 465(7300):918-21. DOI: 10.1038/nature09113
Source: PubMed

ABSTRACT Ecological interactions are crucial to understanding both the ecology and the evolution of organisms. Because the phenotypic traits regulating species interactions are largely a legacy of their ancestors, it is widely assumed that ecological interactions are phylogenetically conserved, with closely related species interacting with similar partners. However, the existing empirical evidence is inadequate to appropriately evaluate the hypothesis of phylogenetic conservatism in ecological interactions, because it is both ecologically and taxonomically biased. In fact, most studies on the evolution of ecological interactions have focused on specialized organisms, such as some parasites or insect herbivores, belonging to a limited subset of the overall tree of life. Here we study the evolution of host use in a large and diverse group of interactions comprising both specialist and generalist acellular, unicellular and multicellular organisms. We show that, as previously found for specialized interactions, generalized interactions can be evolutionarily conserved. Significant phylogenetic conservatism of interaction patterns was equally likely to occur in symbiotic and non-symbiotic interactions, as well as in mutualistic and antagonistic interactions. Host-use differentiation among species was higher in phylogenetically conserved clades, irrespective of their generalization degree and taxonomic position within the tree of life. Our findings strongly suggest a shared pattern in the organization of biological systems through evolutionary time, mediated by marked conservatism of ecological interactions among taxa.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Mutualistic symbioses shape the evolution of species and ecosystems and catalyze the emergence of biological complexity, yet how such symbioses first form is unclear. We show that an obligate mutualism between the yeast Saccharomyces cerevisiae and the alga Chlamydomonas reinhardtii--two model eukaryotes with very different life histories--can arise spontaneously in an environment requiring reciprocal carbon and nitrogen exchange. This capacity for mutualism is phylogenetically broad, extending to other Chlamydomonas and fungal species. Furthermore, we witnessed the spontaneous association of Chlamydomonas algal cells physically interacting with filamentous fungi. These observations demonstrate that under specific conditions, environmental change induces free-living species to become obligate mutualists and establishes a set of experimentally tractable, phylogenetically related, synthetic systems for studying the evolution of symbiosis.
    Science (New York, N.Y.). 07/2014; 345(6192):94-8.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Most evidence of climate change impacts on food webs comes from modern studies and little is known about how ancient food webs have responded to climate changes in the past. Here, we integrate fossil evidence from 71 fossil sites, body-size relationships and actualism to reconstruct food webs for six large mammal communities that inhabited the Iberian Peninsula at different times during the Quaternary. We quantify the long-term dynamics of these food webs and study how their structure changed across the Quaternary, a period for which fossil data and climate changes are well known. Extinction, immigration and turnover rates were correlated with climate changes in the last 850 kyr. Yet, we find differences in the dynamics and structural properties of Pleistocene versus Holocene mammal communities that are not associated with glacial-interglacial cycles. Although all Quaternary mammal food webs were highly nested and robust to secondary extinctions, general food web properties changed in the Holocene. These results highlight the ability of communities to re-organize with the arrival of phylogenetically similar species without major structural changes, and the impact of climate change and super-generalist species (humans) on Iberian Holocene mammal communities.
    PLoS ONE 09/2014; 9(9):e106651. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The ecological effects of consumer guilds are strongly driven by the relative resource use of included species. Here we use stable isotopes in faecal samples from 6 co-occurring mammalian herbivores in an African savanna to identify species-specific trophic niches and detect patterns of interactions between herbivores and their feeding resources. Species-specific foraging strategies were reflected in the faecal δ13C values, with species aligning along both a browser-grazer gradient and a niche breadth gradient. Within the broad foraging strategies outlined by δ13C, δ15N indicated a seasonal shift in resource use for some herbivores. We expected that 13C isotope niches would overlap in a nested fashion, with the niches of grazers and browsers being included in those of mixed feeders, and that 15N niches would separate into discrete modules reflecting leguminous and protein content of respective diets. However, the observed structure was more complex, with combined modular and nested patterns of interactions between herbivores and 13C isotopes. We identified an isolated module comprising eland and its exclusive δ13C values, and a series of nested structures with a set of specialist herbivores (hartebeest and sable) which δ13C values were nested within those of more generalist herbivores (impala, waterbuck and zebra). Networks based on δ15N, however, reflected a higher level of overlap in resource use with random patterns in herbivore interactions with resources, and only a significant modular interaction pattern during the dry season. We suggest that the combined modular and nested pattern of δ13C interactions reflect the simultaneous mutualistic and antagonistic characteristics of plant–herbivore interactions. We argue that such interaction patterns could stabilize ecosystems by constraining effects of perturbations to specific modules and by increasing functional redundancy through nested interactions.
    Ecological Complexity 01/2014; 20:51–60. · 2.34 Impact Factor

Full-text (2 Sources)

Available from
May 23, 2014