QLS Guest seminar - Friday, 16 February

[Sarnataro Erica]

QUANTITATIVE LIFE SCIENCES  GUEST SEMINAR

Friday, 16 February 2018 at 11:00,
ICTP, Central Area, 2nd floor, old SISSA building


Speaker: Silvia Zaoli - École polytechnique fédérale de Lausanne (EPFL)

Title: A Finite-size Scaling Framework Uncovers the Covariations of 
Ecological Scaling Laws

Abstract:
Scaling laws in ecology are recurrent and pervasive patterns observed in 
ecosystems, intended both as functional relationships among 
ecologically-relevant quantities and the probability distributions that 
characterize their occurrence. Well-known examples include the 
Species-Area relationship (SAR), quantifying the increase of 
biodiversity with ecosystem area, and Kleiber’s law, the allometric 
relation between organismic size and metabolic rate. The interest in 
these laws lies in their intrinsic predictive power: how many species 
would go extinct if the ecosystem shrinks to half its size? What is the 
mass of the largest organisms inhabiting ecosystems of different extent? 
Are there more large-sized or small-sized organisms and species? Scaling 
laws observed empirically often conform to power-laws, /A=B^a /, where 
/a/ is the scaling exponent. Although their functional form appears to 
be ubiquitous, empirical scaling exponents may vary with ecosystem type 
and resource supply rate.
While ecological laws have been often studied independently, simple 
heuristic reasonings show that they are linked. Such reasonings, 
however, do not allow accounting for finite-size effects, restricting 
the range for power-law behavior in finite ecosystem due to ecological 
or biological constraints on organismic size, or for other deviations 
from pure power-laws. These limits demand for a different approach.  The 
ubiquity of power-laws and the presence of finite-size constraints 
suggest finite-size scaling theory as a useful tool in this context. A 
scaling hypothesis for the joint probability distribution of abundance 
and body mass of species inhabiting an ecosystem of finite size is 
proposed and used to derive macroecological patterns. The hypothesis is 
supported by a broad class of resource-limited community dynamics 
stochastic models. Precise linkages among ecological laws were derived 
from the proposed scaling hypothesis, in the form of algebraic 
relationships among scaling exponents. Such relationships rationalize 
the observed variability of ecological exponents across ecosystems, 
clarifying how changes in one ecological pattern affect the remaining 
ones. Predicted covariations were verified on empirical data. This 
model-free approach allows investigating the effects of different 
ecological or biological assumptions on the covariation of scaling 
exponents.


Indico web page: http://indico.ictp.it/event/8521/


Everyone interested is most welcome to attend!

-- 
Erica Sarnataro
Group Secretary
Quantitative Life Sciences
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Trieste,  Italy
Tel. +39-040-2240623
www.ictp.it/research/qls.aspx
e-mail:qls at ictp.it