Invasive Plants and Insects

Invasive Plants and Insects

PROJECT:

Conservation of Vulnerable Species in Galapagos through Effective Management of Invasive Plants and Invertebrates

INSTITUTION:

Charles Darwin Foundation

LEADS:

Dr. Heinke Jäger, Restoration Ecologist (Invasive Plants)

Dr. Charlotte Causton, Project Coordinator (Invasive Invertebrates)

 

Controlling quinine at Media Luna on Santa Cruz. (© Lorea Cardas)

Scientists monitor a plot of controlled quinine in the Santa Cruz highlands. (Photo © Lorea Cardas)

 

Milestones

  • The invasive blackberry found in Galapagos was determined, in 2016, to have originated from China; this knowledge is vital in the search for a biological control agent.
  • Rust fungi has been shown to be promising as a viable biological control for blackberry in Galapagos; with the knowledge that the blackberry in Galapagos originates from China, a search for the precise fungus is planned.
  • Research determined that blackberry may not need to be completely eradicated if a method for sufficient control is discovered.
  • A natural die-back of invasive quinine in Galapagos that began around 2008-2010 has continued. Current studies to determine the cause and whether that can be used in a long-term control program have begun.

Background

The unique animals and plants of the Galapagos Archipelago have experienced few extinctions, mainly due to late colonization by humans and the high level of protection provided by the Government of Ecuador. Nevertheless, native species have been seriously affected by land use change and invasive species, particularly on the five human-inhabited islands of Santa Cruz, San Cristóbal, Floreana, Isabela, and Baltra.

As of 2017, scientists had confirmed that 810 introduced plant species were established in Galapagos. Over 80% were brought to the Islands deliberately for agricultural or domestic use by individuals unaware of their potential to cause harm. Many of the plants introduced for cultivation have spread and threaten native species and habitats.

There are 70 species of introduced insects established in Galapagos. Currently, the Charles Darwin Foundation (CDF), with support from Galapagos Conservancy, is involved in a series of research projects to combat the most aggressive invasive species.

Blackberry

Introduced blackberry

Introduced blackberry (© H. Jäger)

Blackberry (Rubus niveus), a spiny shrub from Asia, was introduced to Santa Cruz and San Cristóbal Islands in the 1970s. It has since spread to Santiago Island and was brought to Isabela and Floreana Islands by residents. Blackberry invades the wetter parts of the islands, forming dense thickets up to 13 feet tall. It grows rapidly and has a massive seed bank. The dense blackberry thickets prevent recruitment of native seedlings and impact native plant communities such as the unique Scalesia forest, along with the native animal species that inhabit them.

Quinine

A scientist monitors quinine in the Santa Cruz highlands

Project leader Heinke Jäger monitors quinine. (© L. Cardas)

Quinine (Cinchona pubescens) was introduced to Santa Cruz Island in the 1940s. It is one of the most invasive woody species in Galapagos, adversely impacting native vegetation. Considered a “transformer” species, quinine has changed the species composition and community structure of the Santa Cruz highlands. Ongoing efforts by the Galapagos National Park Directorate (GNPD), using both manual and chemical control, are not feasible on a broad scale. In addition, research has revealed that these control methods may result in more harm than good. Current research focuses on improving the effectiveness of these techniques, while exploring other control options.

The potential of using biological control for both blackberry and quinine is being explored. This would involve the release of natural enemies (most likely a disease or insect species) of the target species. Biological control is one of the best permanent and self-sustaining management solutions for widespread plant invasions over large areas. However, biological control agents must be specific to the target species. Pre-release testing, which often requires several years, is vital to ensuring that the agent will not negatively impact the native ecosystem.

Introduced Ants

Island ecosystems, where there are few endemic ant species, are especially sensitive to invasive ants, which have no natural competitors or predators. Introduced ant species often undergo exponential population growth and immediate establishment. They have the potential to seriously impact native and endemic flora and fauna. They can also affect agricultural activities, domestic animals, and can produce allergic reactions in humans.

Currently of concern in Galapagos are the little fire ant (Wasmannia auropunctata), the tropical fire ant (Solenopsis geminata), the Singapore ant (Monomorim destructor), and the big-headed ant (Pheidole megacephala). The Galapagos National Park Directorate (GNPD), the Charles Darwin Foundation (CDF), and the Galapagos Biosecurity Agency (ABG) have all been involved in efforts to study, control, and/or eradicate these species.

Introduced Wasps

Introduced in 1988, the invasive wasp Polistes versicolor is now found throughout the Archipelago. The wasps prey on large numbers of native insects (especially moth and butterfly larvae), compete for food with insectivorous species, and indirectly affect other ecosystem processes, such as pollination. Polistes can cause severe allergic reactions in humans. They are commonly found in large numbers at visitor sites, local vegetable markets, and on farms.

Although there has been sporadic research to understand this species, there is not yet an effective control method. In 2015, during research on Philornis downsi, it was discovered that high numbers of Polistes were attracted to traps with yeast. The CDF and their international colleagues are currently working to develop a yeast-based bait laced with insecticide that could be used in a ‘lure and kill’ approach to target wasp nests.

Further Reading

Galapagos Report 2015-16: Biodiversity & Ecosystem Restoration section, see:

  • Restoration of the blackberry-invaded Scalesia forest: Impacts on the vegetation, invertebrates, and birds – Jäger et al. – pages 142-148.
  • Total number and current status of species introduced and intercepted in the Galapagos Islands – Causton et al. – pages 181-183.
     

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