The role of a species in its ecosystem can be described as its ecological niche—the organism’s pattern of living, including how it obtains resources, its habitat preferences, interactions with other species, and the conditions it tolerates. Species fulfill multiple roles that together shape ecosystem structure, function, and resilience. Key roles a species can play

• Native vs nonnative: Native species have evolved in a region and are adapted to local conditions; nonnative (or invasive) species can disrupt ecosystems by outcompeting natives, altering habitats, or changing resource availability. These roles influence community composition and ecosystem processes.

• Indicator species: Some species reflect the health of an environment. Their presence, abundance, or absence can signal changes in environmental conditions such as pollution, habitat loss, or climate shifts.

• Keystone species: A keystone species has a disproportionately large effect on ecosystem structure relative to its abundance. Removing a keystone species can trigger cascading changes that alter the numbers and types of other species and overall ecosystem function.

• Foundation species (often not always labeled the same as keystones): These species create or modify habitats that support many other organisms, such as corals building reefs or trees forming forests. Their activities shape the physical environment and access to resources for others.

Common ecosystem functions mediated by species

• Energy flow and trophic interactions: Predators, herbivores, and decomposers regulate food webs, affecting population dynamics and energy transfer through the system.

• Nutrient cycling and soil processes: Dung beetles, fungi, bacteria, and other organisms recycle nutrients, influence soil structure, and impact plant productivity.

• Pollination and seed dispersal: Many plants rely on animals for reproduction and distribution, impacting plant community composition and regeneration.

• Habitat modification and ecosystem engineering: Some species physically alter the environment (e.g., beavers building dams; certain trees shaping canopy structure), thereby creating new niches for other organisms.

How roles relate to ecosystem services

• Species contribute to services such as food production, water regulation, climate buffering, disease control, and aesthetic/cultural values. This arises from their interactions, abundances, and functional traits within the ecosystem.

Nuances and perspectives

• Species traits determine their role: Life-history traits, feeding strategies, metabolism, and dispersal capacities influence how a species interacts with others and the environment, thereby defining its niche and functional impact.

• Context-dependence: The role of a given species can vary by ecosystem context (e.g., a predator may be keystone in one system but not in another) and can change with environmental conditions and community composition.

• Diversity vs function: While species richness matters, recent work emphasizes the functional contributions of individual species (their specific roles) in mediating ecosystem processes, sometimes more directly than overall diversity alone.

If you’d like, I can tailor a concise overview for a specific ecosystem (e.g., coral reefs, tropical forests, or grasslands) or focus on particular species and their known roles.