Biology

Krishnapriya Tamma
Centre for Ecological Sciences, IISc

Ecology is defined as the study of the interactions between organisms and their environment that determine their abundance and distribution (Krebs 2000). Ecology can be studied at different spatial scales - starting from an individual animal and its habitat to whole ecosystems and their relationship to the environment. Much of my work has focused on understanding emergent ecological properties of ecosystems at large spatial scales. In this talk I will present my work in two parts.

Spatial patterns of distribution of biodiversity
The question of why there are so many species of plants and animals in the world has been central to the fields of ecology, biogeography and macroecology for many decades (Gaston 2000). It is widely known now that environmental gradients play an important role in determining diversity distribution patterns. My PHD thesis focused on the patterns and processes that have given rise to high mammalian diversity in Asia, and in the Himalayas. Specifically, I investigated the role of environment and other factors in driving the observed species richness patterns in South Asia and the Himalayas. In the first part of my work, I will present some of the key findings of my thesis briefly - especially in understanding the relative importance of environment and evolutionary history in determining spatial diversity patterns across South Asia and the Himalayas.  

Inferring critical points of ecosystem transitions from spatial data
While the environment is an important driver of the large scale diversity patterns, it does not mean that ecosystems are always stable across environmental values. Many ecosystems, for example tropical forests and coral reefs, remain stable across a range of environmental conditions. However, beyond a certain threshold driver value, they may undergo sudden shifts from their current state to an alternative state (Scheffer et al 2001). Such sudden shifts, called catastrophic regime shifts or critical transitions, are difficult to predict and can result in loss of ecosystem services. For instance, woodlands can turn into grasslands beyond threshold conditions of rainfall and fire (Staver et al 2011). Such transitions are not easily reversible, and a return to previous state requires a greater change in drive values, a phenomenon termed hysteresis. The point at which the transition occurs is called ‘critical point’, and so far methods to estimate critical points have been lacking. In the second part of my talk I will present work that I am currently involved in. I will demonstrate how we estimate critical points for forest-savanna ecosystems, using theoretical models and real-world data from Africa and Australia.