They are hunters, farmers, harvesters, gliders, herders, weavers and carpenters. They are ants and they make up a large part of our world, including more 10 000 species and a large part of the animal biomass in most terrestrial ecosystems. Like other invertebrates, ants are important for the functioning of ecosystems. They play vital roles from aerating the soil and dispersing seeds and nutrients, to scavenging and preying on other species. However, a global vision of their diversity is lacking. Now, researchers from the Biodiversity and Biocomplexity Unit of the Okinawa Institute of Science and Systems (OIST), in collaboration with several institutes around the world, have developed a high-resolution map that merges existing knowledge with learning. automatic to estimate and visualize ant diversity. The maps and dataset were published in a Science Improvements post.
“This study helps add ants, and invertebrates in general, to the discussion on biodiversity conservation,” said Professor Evan Economo, who leads the Biodiversity and Biocomplexity Unit. “We need to know the locations of the centers of high diversity of invertebrates in order to know the areas that can be the subject of future research and environmental protection.”
Professor Economo added that the resource will also be used to answer a number of biological and evolutionary questions, such as how life has diversified and how patterns of diversity have arisen.
This decade-long project began when the study’s co-leading author and former OIST submit-doctoral fellow, Dr. Benoit Guénard (now at the University of Hong Kong), worked with Professor Economo to create a database of occurrence records for different ant species from online repositories, museum collections and approximately 10 000 scientific publications. Researchers around the world contributed and helped identify the errors. More than 10 000 species were examined, which varied considerably in the amount of data available .
However, the vast majority of these records, while containing a description of the sampled location, lacked the precise coordinates necessary for mapping. To solve this problem, co-author Kenneth Dudley of the Environmental Informatics Section of OIST built a computer workflow for estimating coordinates from available data, which also checked all data for errors.
Next, JSPS postdoctoral researcher and co-first author Dr. Jamie Kass, along with Dudley and research technician Fumika Azuma, made different range estimates for each ant species depending on the amount of data available. For species with less data, they built shapes around the data details. For species with more data, the researchers predicted the distribution of each species using statistical models that they tuned for optimal complexity.
The researchers collated these estimates to form an overall map, divided into a grid of 20 km by 20 square km, which showed an estimate of the number of ant species per square (called species richness). They also created a map showing the number of ant species with very small ranges per square (called species rarity). In general, species with small ranges are particularly vulnerable to environmental changes.
However , there was another problem to overcome – sampling bias. “Some areas of the world that we thought were centers of diversity weren’t showing up on our map, but the ants in those areas weren’t well studied,” Dr. Kass explained. “Other regions were extremely well sampled, for example some get-togethers of the United States and Europe, and this sampling difference may affect our estimates of global diversity.”
So the researchers used machine learning to predict how their diversity would change if they sampled all regions of the world equally, and in doing so, they identified areas where they estimate that there are many unknown and unsampled species. Prof Economo said: “It gives us a kind of ‘treasure map’, which can guide us to where we should explore next and look for new species with restricted ranges.”
Okinawa, in southern Japan, has been identified as a center of rarity, as many of the endemic species of these islands have very small ranges, approximately 1000 times smaller than species distributed in North America and Europe. Thus, places like Okinawa are essential for environmental security to conserve biodiversity.
When researchers compared the rarity and richness of ant distributions to amphibians , birds, mammals and reptiles relatively well studied, they found that ants were about as different from these vertebrate groups as the vertebrate groups were from each other, which was unexpected. since ants are evolutionarily far removed from vertebrates. This is vital because it suggests that priority areas for vertebrate diversity may also have high diversity of invertebrate species. But, at the same time, it is necessary to recognize that the biodiversity patterns of ants have unique characteristics. For example, the Mediterranean and East Asia appear to be centers of diversity for ants more than for vertebrates.
Finally, the researchers looked at the defense of these areas of great diversity of ants. They found it to be a small percentage – only 15% of 10 % of richest antarity centers had some kind of legal protection, such as a nationwide park or reserve, that is less than existing protection for vertebrates.
“Obviously, we have a lot of work to do to protect these critical areas,” concluded Professor Economo.