Over the years various plants and fruits have adapted to attract certain animals to eat them and ensure their survival by spreading their seeds. A recent study investigated how this phenomenon occurs by studying lemurs and plants in Madagascar and plants and apes in Uganda, ascertaining why fruits from closely-related plants can have such different appearances. By adapting their smell and colour the fruit is able to talk to specific animals and basically say “choose me”. Without this symbiotic communication and connection with their target animals, these plants would be at risk of going extinct.
The burning question in this experiment, led by Dr Valenta from Duke University and Dr Nevo from Ulm University was ‘How can you pin a fruit’s particular traits to an animal when many different animals, with their own evolutionary adaptations, interact with the same fruits?” Two national parks in Uganda and Madagascar provided an excellent case study for the experiment, Ranomafana National Park in Madagascar and Budongo Forest in Uganda. Sharing similar landscapes and related plants that, however, bear fruit that do not resemble each other and feeding animals with quite different sensibilities, the researchers were able to discover how the senses (sight, smell etc.) of the animals could have influenced the colours and smells of the fruits.
In Uganda, the monkeys and apes have tricolour vision (like humans) but in Madagascar, most lemurs can only see the blue-yellow spectrum which means they are red-green colourblind. The researchers set about collecting the ripe and unripe fruits that the animals feed on and analysed their colours with a spectrometer. They then discovered that each fruit’s colour was optimized against its natural backdrop to be suitable to the visual requirements of its primary seed disperser. In Uganda birds and apes can easily see red berries against a green background but in Madagascar, the berries are yellow in order to be spotted by the red-green colourblind lemurs.
Lemurs are known to use their sense of smell to communicate and even select mates so it makes sense that the olfactory senses play an important role in finding food, this presents another opportunity for plants to attract them, by using their scent. In Madagascar specifically, the researchers collected hundreds of ripe and unripe fruit and extracted their odours and tested which ones were most successful in attracting the lemurs. As suspected, the fruits that are dispersed solely by lemurs were the ones that had the strongest scent.
Dr Valenta said, “We’re only just beginning to understand how much plants and animals mean to one another, which to me is just a signal that it’s more important to conserve the entire thing intact.”