Lizards love deserts and snakes heart rainforests
The harsher the environment, the less rivalry between species. This is the main conclusion of a new study published in Nature Communications by a team of biologists from Germany and Spain. The researchers analyzed a dataset of more than 900 species of lizards and snakes across Africa to determine to what extent species living in the same communities in, e.g. savannas, deserts or rainforests are ecologically different from each other.
In theory, ecologically similar species, which are those that share the same lifestyle such as living on trees and eating the same prey, cannot successfully coexist as they would compete for the same space and resources (if the resources are limited). As a result, in areas where competition is high, communities are expected to consist of species with very different lifestyles. So far, however, this idea had never been compared across different types of environments, such as rainforests or deserts, or across an entire continent. In addition, the researchers analyzed in which areas the reptiles were most closely related and which areas comprised the most species, to gain ecological insights.
The conclusions of the study support a prominent theory, the so-called stress dominance hypothesis, which states that the relative importance of competition between species increases in environments with a high amount of resources. “In wet, climatically stable environments, like Africa´s tropical rainforests, species of lizards and snakes were closely related to each other, but ecologically very different, as it would be predicted by the stress dominance hypothesis. In contrast, species inhabiting the most extreme environments, Africa´s arid deserts like the Sahara or the Namib, were ecologically very similar to one another, despite being from very different evolutionary groups”, explains Till Ramm, researcher at the Museum für Naturkunde Berlin, Germany.
“The harsh environmental conditions in African deserts probably act as a filter that only species with certain types of specific lifestyles are able to pass”, says Johannes Müller, also researcher at the Museum für Naturkunde Berlin. “Or in other words: the environmental conditions in these regions are so harsh that the ability to cope with climate becomes more important than the ability to compete against other species”, explains Philipp Wagner from Allwetterzoo Münster. Nevertheless, deserts comprise the highest number of lizard species compared to all other African biomes, another interesting result of the study. “It is very surprising, that so many lizard species live in these harsh environments, while snakes are more abundant in the tropical rainforests, like the majority of other vertebrate groups”, adds Johannes Müller.