Invasive Blackberry Outcompetes the Endemic Galapagos Tree Daisy Scalesia pedunculata

Authors

Bernhard Riegl, Nova Southeastern UniversityFollow
Anna Walentowitz, University of Bayreuth
Christian Sevilla, Galapagos National Park Directorate
Rafael Chango, Galapagos National Park Directorate
Heinke Jäger, Charles Darwin Foundation

ORCID

https://orcid.org/0000-0002-6003-9324

Document Type

Article

Publication Title

Ecological Applications

ISSN

1939-5582

Publication Date

6-2023

Keywords

biological invasion, extinction, Galapagos, invasive species control, island endemic, restoration, Rubus, Scalesia

Abstract

Island florae are under threat from habitat loss and competition with introduced species worldwide. In the Galapagos Islands, the endemic tree daisy Scalesia pedunculata (Asteraceae) is the dominant tree in the cloud forest of Santa Cruz Island but suffers from competition with the invasive blackberry Rubus niveus. At the site Los Gemelos, a S. pedunculata population was monitored from 2014 to 2021 following mechanical and chemical removal of R. niveus from 17 plots and compared with 17 additional plots where R. niveus remained. The aim of this study was to evaluate the impacts of the R. niveus invasion on S. pedunculata by characterizing the effects of R. niveus removal. Parameters measured in S. pedunculata were diameter at breast height (DBH, from which annual growth rates were determined), total height, survival of individual plants, and recruitment. In the presence of R. niveus, S. pedunculata trees had smaller DBH stems and shorter asymptotic maximum heights, growth rates declined for thin trees, the mortality of larger trees was elevated, and S. pedunculata recruitment was absent. R. niveus removal resulted in DBH-ratios of S. pedunculata more frequently meeting our threshold for fast growth (1.2), trees growing significantly thicker and taller, annual mortality being lower (12.5% vs. 16.2% per year), and recruitment being successful. In the presence of R. niveus, lower survival, growth, and absent recruitment suggested that S. pedunculata could reach quasi-extinction in ~20 years. Swift and decisive management action is needed to prevent the Scalesia forest on Santa Cruz Island from disappearing in less than two decades.

DOI

https://doi.org/10.1002/eap.2846

Volume

33

Issue

4

First Page

e2846

Comments

© 2023 The Ecological Society of America.

NSUWorks Citation

Bernhard Riegl, Anna Walentowitz, Christian Sevilla, Rafael Chango, and Heinke Jäger. 2023. Invasive Blackberry Outcompetes the Endemic Galapagos Tree Daisy Scalesia pedunculata .Ecological Applications , (4) : e2846 . https://nsuworks.nova.edu/occ_facarticles/1355.