In choosing sites to target for protection, conservationists typically look for healthy ecosystems with high biodiversity — places with a great number and variety of species. Inventorying all the species living in a given locale is usually impossible, so instead, scientists often turn to what they call "bioindicators," species, or small groups of species, that when present suggest that a place has high biodiversity. A recent study in mongabay.com’s open-access journal Tropical Conservation Science tested several potential bioindicators in Malaysia, and found that butterflies came out on top.
A bioindicator might be chosen for a variety of reasons: perhaps it is especially sensitive to environmental factors or it occupies a unique niche. Determining the most reliable bioindicator is a difficult task and there is no standardized method for doing so. Instead, researchers largely rely on their intuition and experience to select the most suitable indicator species.
And in regions like Asia, where habitat and species loss is extreme due to a doubling of the human population in the past 40 years, determining appropriate bioindicators quickly and confidently is of great importance. “In order to conserve the most species, sites with the highest total biodiversity should be selected to receive the toughest protection,” the authors of the new study write.
To develop a reliable, standardized method for selecting a bioindicator, as well as to determine the best bioindicator for Malaysian forest ecosystems, the researchers studied three candidate taxa: bats, beetles, and butterflies. They chose those taxa because each has distinct characteristics and relationships with other species. Bats are top predators that feed on diverse prey; butterflies have close relationships with plants; and dung beetles have close relationships with mammals.
The researchers sampled each taxa at two separate sites over the course of three days and nights. The first sampling location was a botanical garden in Kuala Lumpur that is home to 1,600 species of tropical plants and once served as a rubber plantation. The second location was the selectively logged Ulu Gombak Forest Reserve not far outside the city.
To sample beetles, the researchers used simple baited pitfall traps that they left out overnight. To sample bats they used mist nets and traps, which they checked hourly to ensure no bat was injured or escaped. Butterflies they captured with hand-held nets. They collected genetic samples from each specimen.
The researchers then subjected the three taxa to four criteria to determine their utility as bioindicators. Desirable characteristics included ease of recognition by non-experts via DNA barcoding, practicality of collection, broad distribution as a group with distinct species present locally, and the ability to reflect the diversity of other species.
“We found that butterflies had the most potential as a bioindicator group,” the authors write. They showed that butterflies are easily identified by DNA barcoding; require little labor to collect; are common as a group in systems filled with plant life yet have species that live only in particular ecosystems; and reliably represent the diversity of other species.
The project also demonstrates a model conservationists might use to determine the best bioindicator among a group of potential candidates.
Syaripuddin, K., Sing, K., & Wilson, J. (2015). Comparison of butterflies, bats and beetles as bioindicators based on four key criteria and DNA barcodes. Tropical Conservation Science, 8(1), 138-149.