About Taxonomic Homogenisation Post-Mass Extinction

The Great Dying, occurring 252 million years ago, was Earth’s most extinction event. It eradicated around 80-90 per cent of marine species and about 70 per cent of land vertebrate families. Recent research has shed light on the phenomenon of taxonomic homogenisation that followed this event. This process describes how surviving species began to resemble each other across different ecological communities.

Taxonomic Homogenisation

Taxonomic homogenisation refers to the convergence of species composition across various ecosystems. After the Great Dying, fossil records indicate that surviving organisms exhibited striking similarities, regardless of their geographical locations. This phenomenon suggests loss of biodiversity.

Causes of Homogenisation

Researchers attribute taxonomic homogenisation to environmental changes rather than ecological factors. Two primary drivers were identified – ecological release and shifts in environmental conditions. Ecological release occurs when predator populations decline, allowing surviving species to thrive unchecked. Environmental shifts create new hospitable habitats for certain species.

The Research Model

To investigate these hypotheses, scientists developed a model using geochemical data on oceanic oxygen levels and temperatures. They also included physiological data from modern marine invertebrates, such as clams and snails, which are related to species that either survived or became extinct during the Great Dying. This approach allowed researchers to simulate how ancient species might have responded to environmental changes.

Findings on Species Distribution

The model revealed that hardy invertebrates, such as molluscs, became more prevalent in the fossil records not merely due to random survival but because their physiological traits suited the altered environmental conditions. This finding provides a straightforward environmental explanation for the success of certain survivors and the global scale of homogenisation.

Implications for Current Biodiversity

The study’s insights extend beyond historical analysis. Researchers warn that current anthropogenic climate change could lead to a similar taxonomic homogenisation in modern oceans. This marks the importance of understanding past extinction events to predict and mitigate future biodiversity loss.

Future Research Directions

The research team intends to apply their model to other mass extinction events, such as the end-Cretaceous extinction that eliminated the dinosaurs. This could deepen the understanding of how species adapt to extreme environmental changes over geological time scales.

Questions for UPSC:

1. Critically analyse the concept of ecological release and its impact on biodiversity in post-extinction scenarios.
2. Estimate the potential consequences of taxonomic homogenisation on modern marine ecosystems.
3. What is the significance of physiological adaptations in species survival during mass extinction events? Explain.
4. With suitable examples, point out the relationship between climate change and biodiversity loss in contemporary environments.

Answer Hints:

1. Critically analyse the concept of ecological release and its impact on biodiversity in post-extinction scenarios.

1. Ecological release occurs when predators decline, allowing prey species to expand unchecked.
2. This can lead to increased competition among surviving species, potentially reducing diversity.
3. Post-extinction scenarios often result in fewer ecological niches, promoting homogenisation.
4. Survivor species may dominate ecosystems, leading to a loss of unique adaptations.
5. Examples include rapid population growth of certain species after predator extinction, affecting ecosystem balance.

2. Estimate the potential consequences of taxonomic homogenisation on modern marine ecosystems.

1. Taxonomic homogenisation can lead to reduced biodiversity, making ecosystems less resilient to changes.
2. Homogenised ecosystems may become vulnerable to diseases and environmental stressors.
3. Loss of unique species can disrupt food webs and ecological interactions.
4. Increased similarity among species reduces the potential for adaptive responses to climate change.
5. Homogenisation may also affect fisheries and marine resource management, impacting human livelihoods.

3. What is the significance of physiological adaptations in species survival during mass extinction events? Explain.

1. Physiological adaptations enable species to cope with extreme environmental changes, such as temperature and oxygen fluctuations.
2. Survivors with favorable traits are more likely to thrive in altered habitats post-extinction.
3. Such adaptations can enhance reproductive success and colonisation of new areas.
4. Examples include molluscs that survived the Great Dying due to their tolerance to low oxygen levels.
5. About these adaptations aids in predicting future species’ responses to climate change.

4. With suitable examples, point out the relationship between climate change and biodiversity loss in contemporary environments.

1. Climate change alters habitats, leading to species migration and loss of specialized niches.
2. Examples include coral bleaching, which threatens marine biodiversity and ecosystem services.
3. Changes in temperature and precipitation patterns can disrupt breeding cycles and food availability.
4. Invasive species often thrive in changing climates, outcompeting native species and reducing diversity.
5. Overall, climate change accelerates the rate of extinction, as seen in amphibian populations worldwide.