LM Key ecological concepts

This section of the course outlines essential ecological concepts that are important to fully understand SDM and species interactions with the environment. Some of these terms will recur throughout the course, so it is highly recommended that you familiarize yourself with them now.

Ecological niche and niche breadth

First, let’s examine the concept of niche breadth. Species Distribution Modeling (SDM) is also known as Environmental Niche Modeling, but what exactly is a species’ niche? The ecological niche encompasses not only the environmental conditions a species requires but also its role within the ecosystem, including interactions with other species. It can be divided into two main components (Hutchinson 1957):

Niche breadth refers to the range of environmental conditions and resources that a species can utilize. Species with a broad niche, also known as generalists, can thrive in a variety of conditions and make use of diverse resources. In contrast, species with a narrow niche (specialists) are limited to specific environmental conditions and resources. This distinction is important because it affects how species respond to environmental changes and interact with other species in their habitat.

Abiotic and Biotic Factors

The realized niche of a species can be influenced by biotic and abiotic factors:

  • Abiotic Factors: These are non-living environmental conditions, such as temperature, precipitation, soil type, and elevation, which can significantly influence where a species can survive.
  • Biotic Factors: Interactions between species—such as competition, predation, mutualism, and disease—play a crucial role in determining species distributions.

Often, abiotic and biotic factors interact, as in the case of how temperature can influence competitive interactions between species. Thus, it is essential to consider both factors when modeling species distributions to ensure accurate predictions.

Fitness

Fitness is the ability of an organism to survive and reproduce in a given environment (Orr 2009). Environmental conditions invluence a species fitness, as optimal conditions enhance an organism’s survival and reproductive success. Genetic adaptation also contributes, with species evolving traits suited to their specific habitats, which in turn affects their distribution. Additionally, resource availability, including access to food, mates, and shelter, directly impacts fitness.

Dispersal

Dispersal is the movement of individuals from their birthplace to new locations, influencing species distribution patterns. Dispersal mechanisms include:

  • Passive Dispersal: Transport via wind, water, or other organisms (e.g., seeds carried by wind or animals).
  • Active Dispersal: Organisms move by their own means (e.g., birds flying, mammals migrating).
  • Human-mediated Dispersal: Anthropogenic activities, such as trade and habitat fragmentation, alter natural dispersal patterns. Dispersal ability affects colonization success, genetic diversity, and responses to environmental change.

Environmental and geographic space: connecting ecological variables to species locations

SDM utilizes the relationship between environmental space and geographic space. Environmental space is defined by ecological variables such as climate and resource availability, representing the conditions that determine whether a species can survive in a given area. In contrast, geographic space refers to the actual physical locations where species are found.

Species distribution models bridge these two concepts by linking a species’ ecological tolerances to its geographic distribution, predicting where it is likely to occur.

Further reading

Hutchinson, G. E. (1957). Concluding remarks. Cold Spring Harbor Symposia on Quantitative Biology, 22, 415–427. https://doi.org/10.1101/SQB.1957.022.01.039

Orr, H. Fitness and its role in evolutionary genetics. Nat Rev Genet 10, 531–539 (2009). https://doi.org/10.1038/nrg2603

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