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The highs and lows of dispersal: how connectivity and initial population size jointly shape establishment dynamics in discrete landscapes
Author(s) -
MorelJournel Thibaut,
Girod Pierre,
Mailleret Ludovic,
Auguste Alexandra,
Blin Aurélie,
Vercken Elodie
Publication year - 2016
Publication title -
oikos
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.672
H-Index - 179
eISSN - 1600-0706
pISSN - 0030-1299
DOI - 10.1111/oik.02718
Subject(s) - allee effect , metapopulation , biological dispersal , ecology , population , extinction (optical mineralogy) , biology , population size , spatial ecology , landscape connectivity , geography , demography , paleontology , sociology
Identifying the main factors driving introduced populations to establishment is a major challenge of invasion biology. Due to their small initial size, introduced populations are most vulnerable to extinction because of demographic stochasticity or Allee effects. While an increase in initial population size is known to increase establishment success, much remains to be understood regarding its interplay with connectivity in spatially structured environments. In order to better understand how demographic mechanisms interact at such spatial scale, we developed a stochastic model of population dynamics in discrete space to investigate the effect of connectivity and initial population size on establishment. The predictions derived from the model were then tested using experimental introductions of an insect parasitoid ( Trichogramma chilonis ) in spatially structured laboratory microcosms. Both theoretical and experimental results demonstrated that the connectivity of the introduction site had 1) a deleterious effect in the first generation when the introduced population was small and 2) a beneficial impact brought about by metapopulation effects in the subsequent generations. Interestingly, populations displayed a weakly pushed invasion pattern promoting early establishment, which was mainly underpinned by dispersal stochasticity and the discrete nature of the landscape. These results shed light on the critical influence of landscape connectivity on establishment dynamics.