Endemic Galapagos Tree Daisy Scalesia pedunculata Threatened by Competition with Nonnative Blackberry Rubus niveus

Photo 1. (A) The distribution and population size of the Galapagos Tree Daisy Scalesia pedunculata (1) suffers from competition with nonnative trees such as Cedrela odorata (2), Cinchona pubescens (3) and (B) nonnative undergrowth bushes, most seriously from Rubus niveus (4). (C) A removal experiment and subsequent 8 years of monitoring showed that S. pedunculata can successfully recruit in areas with low undergrowth such as non-native Tradescantia fluminensis (5), but it fails completely to recruit in the presence of R. niveus. Photo credit: B. Riegl (A), H. Jäger (B), M. San José (C). Photo 2. (A) Scalesia pedunculata trees are true trees and follow an asymptotic growth function. Under competition with Rubus niveus, S. pedunculata produces thinner, shorter trees with a reduced life-span. (B) Scalesia pedunculata is a relatively short-lived species and shows strong, pulsed, recruitment dynamics in undisturbed habitat. The shown high density of recruits was only observed in the immediate aftermath of R. niveus removal, but later decreased. However, in the continued presence of R. niveus, no recruitment at all was observed over the 8-year study period. Photo credit: H. Jäger. Photo 3. The endemic Scalesia pedunculata forest is a unique ecosystem that provides an important habitat for many invertebrates and vertebrates, such as this (A) Monarch Butterfly Danaus plexippus megalippe and the (B) endangered Little Vermillion Flycatcher Pyrocephalus nanus. Past control of invasive Rubus niveus has had temporary negative effects on arthropod biomass and bird breeding success of Darwin's finches, but is outweighted by long-term habitat restoration benefits. Photo credit: M. San José. These photographs illustrate the article “Invasive blackberry outcompetes the endemic Galapagos tree daisy Scalesia pedunculata” by Bernhard Riegl, Anna Walentowitz, Christian Sevilla, Rafael Chango, and Heinke Jäger, published in Ecological Applications. https://doi.org/10.1002/eap.2846