Samir Suweis - Università di Padova #
Emerging patterns in Ecology:
the species persistence-time distributions #
Natural ecosystems are characterized by striking diversity of form
and functions and yet exhibit deep symmetries emerging across
scales of space, time and organizational complexity. Species-area
relationships and species-abundance distributions are examples
of emerging patterns irrespective of the details of the underlying
ecosystem functions. We present empirical and theoretical evidence
for a new macro-ecological pattern related to the distributions of
local species persistence times, defined as the timespans between
local colonization and extinctions in a given geographic region, and
empirically estimated from local observations of species' presence-
absence time series. Empirical distributions exhibit power-law scaling
limited by a cut-off determined by the rate of emergence of new
species. The scaling exponents depend solely on the structure of the
spatial interaction network, regardless of the details of the ecological
interactions, suggesting similarities between ecosystem dynamics
and critical systems in physics. We also present generalize and solve
analytically a related sampling problem. The framework developed
here also allows to link the cut-off timescale with the spatial scale
of analysis, and the persistence-time distribution to the species-area
relationship. We conclude that the inherent coherence obtained
between spatial and temporal macro-ecological patterns points at a
seemingly general feature of the dynamical evolution of ecosystems.