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Unravelling the relative roles of top‐down and bottom‐up forces driving population change in an oceanic predator
Author(s) -
Horswill C.,
Ratcliffe N.,
Green J. A.,
Phillips R. A.,
Trathan P. N.,
Matthiopoulos J.
Publication year - 2016
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.1452
Subject(s) - apex predator , pelagic zone , population , ecology , predator , predation , climate change , ecosystem , top down and bottom up design , productivity , covariate , biology , environmental science , statistics , mathematics , demography , computer science , software engineering , macroeconomics , sociology , economics
In the open ocean ecosystem, climate and anthropogenic changes have driven biological change at both ends of the food chain. Understanding how the population dynamics of pelagic predators are simultaneously influenced by nutrient‐driven processes acting from the “bottom‐up” and predator‐driven processes acting from the “top‐down” is therefore considered an urgent task. Using a state‐space demographic model, we evaluated the population trajectory of an oceanic predator, the Macaroni Penguin ( Eudyptes chrysolophus ), and numerically assessed the relative importance of bottom‐up and top‐down drivers acting through different demographic rates. The population trajectory was considerably more sensitive to changes in top‐down control of survival compared to bottom‐up control of survival or productivity. This study integrates a unique set of demographic and covariate data and highlights the benefits of using a single estimation framework to examine the links between covariates, demographic rates and population dynamics.