identifier: traitmech:000047 label: habitat association definition: An ecological classification of the primary environment or niche an organism inhabits (e.g. free-living vs host-associated; soil, rhizosphere, gut). Microbial taxa show biogeographic structure across such habitats. definition_source: DOI:10.1038/nrmicro1341 trait_category: ECOLOGY term_kind: CLASS mapping_status: REVIEWED parent_traits: - METPO:1000059 synonyms: - synonym_text: niche association synonym_type: RELATED_SYNONYM source: DOI:10.1038/nrmicro1341 evidence: - reference: DOI:10.1038/nrmicro1341 notes: Martiny et al., "Microbial biogeography", support habitat/niche as a structuring axis of microbial distribution; parent of the habitat sub-variants. - reference: DOI:10.1038/nrmicro.2017.87 notes: Fierer, "Embracing the unknown", supports environment-specific microbial community membership (e.g. the soil microbiome) underpinning habitat association. causal_graphs: - graph_id: habitat_association_biogeographic_structure title: Habitat association structures microbial biogeography description: Evidence-backed causal sketch linking environmental habitat to the biogeographic patterning of microbial taxa. nodes: - node_id: habitat_association_trait label: habitat association node_type: TRAIT grounding: traitmech:000047 description: Ecological classification of the organism's primary environment. - node_id: habitat label: habitat node_type: ENVIRONMENTAL_FACTOR description: Free-living, host-associated, soil, rhizosphere, or gut habitat. grounding: ENVO:01000739 - node_id: biogeographic_structure label: biogeographic community structure node_type: QUALITY description: Habitat-specific microbial community membership. - node_id: community_composition label: microbial community composition node_type: QUALITY description: Taxonomic membership and structure of a microbial community in a habitat. - node_id: environmental_stress label: environmental stress node_type: ENVIRONMENTAL_FACTOR description: Abiotic stress (e.g. pH, salinity, contaminant load) imposed by a habitat. - node_id: selection_assembly label: deterministic selection in community assembly node_type: BIOLOGICAL_PROCESS description: Deterministic assembly process favoring environmentally adapted taxa. - node_id: ecological_drift label: ecological drift in community assembly node_type: BIOLOGICAL_PROCESS description: Stochastic demographic process contributing to community turnover. - node_id: dispersal_limitation label: dispersal limitation in community assembly node_type: BIOLOGICAL_PROCESS description: Spatial/historical process limiting taxon movement between habitats. - node_id: salinity label: salinity node_type: ENVIRONMENTAL_FACTOR description: Salt concentration; major abiotic filter structuring aquatic communities. - node_id: osmolyte_genes label: osmolyte transport and synthesis genes node_type: GENE_OR_PROTEIN description: Gene repertoire for compatible-solute transport/synthesis enabling salt tolerance. edges: - subject: habitat predicate: causes object: habitat_association_trait description: The organism's primary habitat sets its habitat-association classification. evidence: - reference: DOI:10.1038/nrmicro1341 notes: Martiny et al. show habitat as a structuring axis of microbial biogeography. predicate_id: biolink:causes - subject: habitat_association_trait predicate: associated with object: biogeographic_structure description: Habitat-associated taxa display environment-specific community membership. evidence: - reference: DOI:10.1038/nrmicro.2017.87 notes: Fierer documents environment-specific community membership (e.g. the soil microbiome). predicate_id: biolink:associated_with - subject: habitat predicate: structures object: community_composition description: The habitat/environment selects for spatial variation in community composition. evidence: - reference: DOI:10.1038/nrmicro1341 notes: Free-living taxa exhibit biogeographic patterns; the environment selects for spatial variation in diversity (Martiny et al. review). - subject: environmental_stress predicate: increases object: selection_assembly description: Higher environmental stress increases the contribution of deterministic selection to assembly. evidence: - reference: DOI:10.1038/s41564-023-01573-x notes: Selection producing more dissimilar communities increased with stress (groundwater assembly study). predicate_id: RO:0002213 - subject: environmental_stress predicate: decreases object: ecological_drift description: Higher environmental stress decreases the contribution of stochastic drift to assembly. evidence: - reference: DOI:10.1038/s41564-023-01573-x notes: Drift showed negative correlation with stress; stochastic importance decreased with increasing environmental stress. predicate_id: RO:0002212 - subject: environmental_stress predicate: decreases object: dispersal_limitation description: Higher environmental stress decreases the contribution of dispersal limitation to assembly. evidence: - reference: DOI:10.1038/s41564-023-01573-x notes: Dispersal limitation showed negative correlations with stress. predicate_id: RO:0002212 - subject: salinity predicate: structures object: community_composition description: Salinity is a primary abiotic regulator of aquatic community composition. evidence: - reference: DOI:10.1186/s40168-024-01979-7 notes: Lake microbiomes primarily regulated by salinity; saline vs freshwater lakes show distinct taxonomic profiles. - subject: salinity predicate: enriches object: osmolyte_genes description: Saline habitats enrich for osmolyte transport and synthesis genes. evidence: - reference: DOI:10.1186/s40168-024-01979-7 notes: Saline-lake microbiomes possess more genes encoding osmolyte transport and synthesis. curation_history: - timestamp: '2026-06-02T00:00:00Z' curator: claude action: PROPOSED_FROM_RESEARCH changes: Proposed candidate ECOLOGY axis class (habitat association) to parent the free-living/host-associated/soil/rhizosphere/gut habitat sub-variants. llm_assisted: true - timestamp: '2026-06-09T14:00:00Z' curator: claude action: CURATED_CAUSAL_GRAPH changes: Added evidence-backed causal graph (habitat / biogeographic structure) with biolink predicate groundings; promoted PROPOSED to REVIEWED. llm_assisted: true - timestamp: '2026-06-14T06:55:37Z' curator: claude action: GROUND_CAUSAL_NODES changes: Grounded 1 causal-node grounding field(s) via mappings/node_grounding.tsv (ENVO:01000739×1). llm_assisted: true - timestamp: '2026-06-23T00:00:00Z' curator: claude action: ENRICH_CAUSAL_GRAPH changes: Added 6 evidence-backed generic edges (7 new nodes) from the deep-research report. llm_assisted: true - timestamp: '2026-06-24T17:21:09Z' curator: claude action: GROUND_CAUSAL_PREDICATES changes: Grounded 3 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002212×2, RO:0002213×1). llm_assisted: true