Monitoring terrestrial invertebrates in a Scalesia forest in Galapagos

May 7, 2019

By Jacqueline Rodríguez, Entomologist with the Charles Darwin Foundation

Scalesia forest, Los Gemelos, Santa Cruz Island

Scalesia forest, Los Gemelos, Santa Cruz Island (© Heinke Jäger)

I first came to Galapagos in 2013 to work as an entomologist with the Galapagos Biosecurity Agency (ABG). I soon became interested in introduced invertebrates, particularly invasive invertebrates and their impacts on the local ecosystems. Some of the species that especially caught my attention were the very aggressive tropical fire ant (Solenopsis geminata), the Mediterranean fruit fly (Ceratitis capitata) and the yellow paper wasp (Polistes versicolor). I wanted to be part of the group of scientists that contributes to finding solutions to challenges caused by invasive species.

In 2014, I joined the research team at the Charles Darwin Research Station (CDRS), which is the operational arm of the Charles Darwin Foundation (CDF) in Galapagos. I now work on several terrestrial invertebrate projects, including the ecological restoration of the Scalesia forest at Los Gemelos, in the highlands of Santa Cruz Island.

The Los Gemelos project team, from left: Author Jacqueline Rodríguez, Project leader Heinke Jäger, Diego Nieto and Patricio Picón

The Los Gemelos project team, from left: Author Jacqueline Rodríguez, Project leader Heinke Jäger, Diego Nieto and Patricio Picón (© Francisco Martínez)

This unique forest, dominated by the endemic Scalesia pedunculata tree, is one of the more magnificent ecosystems in Galapagos. Unfortunately, it has been reduced to a mere 1% of its original range — primarily due to agricultural activities before the establishment of the Galapagos National Park in 1959, but also afterwards. More recently, the forest remnants have been invaded by introduced plant species like blackberry (Rubus niveus), which was first recorded in the Santa Cruz highlands in 1968.

The rate that these plant species displaced the threatened Scalesia trees was alarming, prompting the Galapagos National Park Directorate (GNPD) to start a campaign to manually and chemically control blackberry and other invasive plant species in the area. In 2014, with the support of Galapagos Conservancy, the CDF initiated an ongoing project to evaluate the impacts of the control measures on plant and invertebrate species at Los Gemelos in collaboration with the GNPD.

The author working in the Scalesia forest

The author working in the Scalesia forest (© Diego Nieto)

Monitoring the terrestrial invertebrates in the Scalesia forest (like spiders, ants, beetles, moths, butterflies, wasps, etc.) gave me the opportunity to do what I had always dreamed of: applied science in support of conservation! Working with invertebrates, providing scientific advice, generating information that can be used to inform management decisions by the GNPD, and providing a service to the community are all goals that I’m now able to realize. As an entomologist, I have always faced the challenge of explaining what my work consists of and why it is important. Luckily, in Galapagos — where science is the basis for management decisions and conservation priorities — it is much easier, so here I go!

Placing a Malaise trap

Author and field assistant Marcelo Loyola placing a Malaise trap (© Samantha Renda)

To monitor invertebrates, I go into the forest with a volunteer and my local Galapagos field assistant, Marcelo Loyola. Our challenge is to place several traps to collect the invertebrate specimens, while trying to minimize our impact on the site and struggling to make our way through the dense blackberry thickets. Once we emerge from the forest, we head back to the laboratory at the CDRS to classify and identify our samples. This final phase is the most complicated part of the process, but it provides valuable information on the invertebrate diversity of this ecosystem.

But why are the invertebrates and their identification so important? Terrestrial invertebrates are excellent biological indicators for ecosystem health. This means that changes in their species diversity and richness are reliable signs for more profound changes in the ecosystem. If an invasive plant species displaces native and endemic plants that invertebrates feed on, this causes a limited food supply, which in turn generates a change in the numbers of the existing invertebrates. Insect-eating birds are also affected by this lack of food needed for reproduction and chick rearing.

Our initial results indicated fluctuations in the diversity and abundance of spiders, butterflies and moths, which serve as ‘energy bars’ for finches and their nestlings due to a high protein content. Some invertebrate species feed exclusively on Scalesia trees and in return, Scalesia depends on these critters for pollination.

Analyzing the changing diversity of invertebrates over time will help in our understanding of the Scalesia forest ecosystem. This in-depth understanding of how the system works is essential to effectively evaluate and improve management actions carried out by the GNPD to protect and restore the unique Scalesia forest on Santa Cruz Island.

 

Jacqueline Rodriguez CDFJacqueline Rodríguez has been working at the Charles Darwin Research Station as an entomologist since 2014. She is involved in several entomology projects and collaborated in the management of the Invertebrates Collection at Charles Darwin Foundation for three years. Currently, her focus is on ecological restoration projects, like monitoring invertebrates in the unique Scalesia forest in the Santa Cruz highlands to evaluate the effects of chemical control of invasive plant species. Jacqueline is also working on other terrestrial invasive species projects, including the search of how best to control the invasive yellow paper wasp Polistes versicolor.

Author bio photo © Nicolás Moity.

 

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