Abstract

In many fragmented habitats, the detectability of a population in a habitat patch closely depends on the local abundance of individuals. However, metapopulation studies rarely connect abundance and detectability. We propose a framework for using abundance-based estimates of detectability in the analysis of a spatially-explicit stochastic patch occupancy model (SPOM). We illustrate our approach with the example of Tenebrio opacus, a beetle inhabiting hollows in old trees, and have based it on a 6-year monitoring programme of adult beetles in an area harbouring a high density of old oaks. We validated our abundance-based methodology by showing that the estimates of detectability were positively and significantly correlated with those obtained from presence/absence data (Pearson r=0.54, p<2E-16) in our study system. We further showed that the height of the hollow on the tree and the area of its entrance hole, the living status and girth of the host tree, and the time of survey significantly affected the detectability of beetle populations. Median detectability was 51% for one survey. The SPOM analysis revealed a high but heterogeneous extinction risk among trees, suggesting a metapopulation dynamics between the classic and mainland-island paradigms. However, it also indicated unexplained beetle colonization of trees in our study, despite the fact that we included limited detectability in our estimation procedure. This may have been due to the cryptic larval stage of T. opacus and may thus invalidate the use of a classic SPOM in our study system.

Keywords

Occupancy; SPOM; Likelihood; Missing data; Colonization

Published in

Oecologia
2018, Volume: 188, number: 3, pages: 671-682
Publisher: SPRINGER

SLU Authors

• Laroche, Fabien

  • Department of Ecology, Swedish University of Agricultural Sciences
    
  • National research institute of science and technology for environment and agriculture (IRSTEA)

• Paltto, Heidi

  • Department of Ecology, Swedish University of Agricultural Sciences
    

• Ranius, Thomas

  • Department of Ecology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Ecology


Publication identifier

DOI: https://doi.org/10.1007/s00442-018-4220-5

Permanent link to this page (URI)

https://res.slu.se/id/publ/96996