Which species are most at risk, and how will that affect seed dispersal?
La Trobe University zoologist Dr Heloise Gibb has just returned from a scientific journey, exploring ant behaviour on three continents.
A community ecologist, Dr Gibb is interested in the interactions between species and how different species coexist in an ecosystem. She investigates generalities across the globe in how ants respond to changes in the complexity of their habitats.
Habitat complexity describes the amount of structure an animal encounters in its home range. For example, after a bushfire an area with thick bush becomes open and therefore changes from a complex habitat to a simple habitat. The increasing opening up of new farmland for food and biofuels in a world of dwindling oil supplies has similar impacts.
Dr Gibb’s study in Sweden, Australia and South Africa used natural and manipulated habitats to explore potential impacts of habitat disturbance and climate change on ants. She says human disturbance of habitats usually results in those habitats becoming more simple, so she wanted to find out how changes in ground level complexity caused by humans affect ant species in these areas.
Australia alone has more than 5,000 different species of ants, so it is too time consuming to study them all. Instead, Dr Gibb looks at the size and shape of ants in various habitats. She also investigates the speed at which they find food and whether they are able to defend it by recruiting other ants from their nest.
Wide-eyed and fast
She found that in more complex habitats, you get smaller ants, which can more easily manoeuvre through cramped areas, but are slow. In contrast, in more open habitats you get larger ants that can travel faster and further. Also, the eyes of ants differ according to habitat. In a complex habitat, ants had eyes on the side of their head. In an open habitat, eyes were on top of the head so the ants had a broader view of their surroundings.
Knowing differences between species of ants, where they are found and how they behave is a matter of interest to more than just zoologist and ants. For example, Dr Gibb says ants are important in the dispersal of plant seeds such as wattles.
Larger species in open habitats can travel greater distances and distribute seeds further. In an open habitat, species are also more likely to run into one another, so we expect more fighting between the species.
Dr Gibb found similar responses on all continents. This means that species with similar characteristics, eg size, are likely to respond in similar ways to human impacts on their habitats. Knowing this makes it easier to work out which species are at most risk and how that might affect important roles of those species, such as seed dispersal.
According to Dr Gibb ‘an understanding of habitat complexity will allow you to understand the effects of a broad range of human disturbances, including land clearing and climate change’.
‘Anything that humans do to simplify a habitat,’ she says, ‘will have an effect on the ant population. Urbanisation, agriculture and forestry leads to habitat changes. Climate change will also alter the composition of plants and thus habitat complexity, for example, by increasing the frequency of fires.
‘To protect ants and other species dependent on complex habitats, it is important that we ensure that at least some elements of farming and other production landscapes mimic the features that are available to ants and other organisms in their natural habitats.’
● This article was written by Sindre Hellkas, left, a Norwegian international Master of Global Communications student, who worked in La Trobe’s Media and Communications Unit.