Ecological inheritance

Examples

There can be examples of ecological inheritance within one species to impact just that one species. In the book, On the Origin of Species, Charles Darwin described ways that organisms alter selection pressures by modifying local environments (i.e., habitats in which they live) that affect their fitness. For example, the effect of ecological inheritance on long-term evolutionary dynamics are performed by subsequent generations of earthworm that burrow through soil. As earthworms burrow, they modify soil structure and enrich the nutrient content by mixing decomposing organic matter with inorganic soil content. The burrowing makes water easily available and absorbed by earthworms in the soil, and consequently, worms have kept their ancestral freshwater kidneys rather than evolve terrestrial anatomy.

Ecological inheritance can also involve the chemicals produced by organisms of different species such as the sea urchin Holopneustes purpurascens and the red alga Delisea pulchra. The sea urchin metamorphoses on the red alga during its early stages of life but then moves to the brown algae Ecklonia radiate because of the chemicals produced on the red algae that deter the sea urchin after a certain period of time. The secondary metabolites produced by the algae modify the environment that the sea urchin inhabits, thus resulting in changes for the following generations making this an example of ecological inheritance as well as chemical ecology.

Also, ecological inheritance can occur within a species that affects the entire biosphere, and thus ecological inheritance has significant implications for macroevolution. Ancestral species may modify environments through their niche construction that may have consequences for other species, sometimes millions of years later. For instance, cyanobacteria produced oxygen as a waste product of photosynthesis (see great oxygenation event), which dramatically changed the composition of the Earth's atmosphere and oceans, with vast macroevolutionary consequences.

Additionally, as organisms adapt to climate change, the alterations they make to the environment will become a part of the future of ecological inheritance.

Ecological inheritance, ecosystem engineering, and niche construction

Almost all species engage in ecosystem engineering, which occurs when the availability of a resource is altered by organisms that create, alter, or destroy habitats. Niche construction occurs when the interactions and relationship between a species and its environment alters the niche and selective pressure of the species. Organisms modify their local environment, or habitat, by relocating to a different location or physically altering the selective environment; when these modifications alter the selection of subsequent generations, ecological inheritance occurs. Therefore, niche construction focuses on the evolutionary impact of species and their local environment. Ecosystem engineering has been described as a consequence of niche construction but it is not clear whether ecosystem engineering activities always influence selection. Ecological inheritance has been termed a 'persistor' that may influence evolution when the persistence of ecological inheritance is longer than the timing of the 'replicator' – a term Richard Dawkins used for gene.

Genetic inheritance vs. ecological inheritance

Genetic inheritance depends on the processes of reproduction that transmit genes between generations, from parents to offspring. Ecological inheritance takes the form of biotically modified selection pressure that can be passed on by organisms in one generation at any time in their lifetime to organisms of subsequent generations which therefore are essentially inheriting a type of territory or property. Ecological inheritance does not depend on replication of environmental factors, but rather on the persistence of environmental factors that affect the selective pressures of subsequent generations. For example, the trait of web construction by orb-web spiders has been shaped by natural selection and is passed onto subsequent generations through genetic inheritance; spider webs are not a form of ecological inheritance because they are too transient and do not affect the evolution of multi-generational populations of spiders via niche construction. If, however, the physical characteristics of a modified environment created by one generation continues to exist for the descendants, then niche construction is affecting more than one generation and ecological inheritance has occurred, as in the example of earthworms described above.

In genetic inheritance, descendants inherit genes (acted upon by natural selection) from their parents that contain information in the nucleotide sequences of DNA used to express phenotypes; in ecological inheritance, information is not transmitted in the same way, but instead, characteristics of a modified environment affect the phenotypic expression of descendants. The mechanisms of genetic and ecological inheritance are also different; whereas genetic inheritance depends on reproduction (e.g., sexual and asexual) where genes are transmitted in one direction from parent to offspring in the same species, the modified environment and its selective pressures caused by ecological inheritance can be handed down from one species to any other species within and between generations.

The modern synthesis

Ecological inheritance is considered a form of habitat construction, which has been considered a new way to expand upon natural selection as a way organisms influence their own evolution. Two assumptions under the Modern Synthesis are the following: (1) only genes are inherited from one generation to the next and (2) micro-evolutionary processes that include selection, drift, mutation, and gene flow affect patterns of macro-evolution. Since the early twentieth century, however, evolutionary biologists have modified the Modern Synthesis to include ways organisms modify the environment and inhabited by their subsequent generations. This new interpretation of the Modern Synthesis is called the extended evolutionary synthesis and describes how ecological inheritance affects evolution on micro- and macro-evolutionary scales because organisms modify their environments in non-random ways to generate selective pressures on subsequent generations.