In our recent publication in the Journal of Biogeography, we assembled a comprehensive distribution map of all reptiles in Africa in order to quantify their geographical overlap with the other vertebrate groups, and to assess the environmental correlates underlying these patterns.

The latitudinal gradient of increasing biological diversity towards the equator is one of the best recognized patterns in biogeography, and has been acknowledged for some time. The naturalist, Alexander von Humboldt wrote of his travels over 200 hundred years ago, that as we approach the tropics, "the greater the variety of structure, form, colour, youth and vigor of organic life." A number of well-known hypotheses explaining this pervasive pattern of the increasing number of different species towards the equator have since proliferated. These include elevated ambient energy and precipitation, the number of different habitats or niches, higher plant productivity, and many more.

To create our geographic distribution map of reptiles in Africa, we obtained data from a variety of field-guides and atlases, museum databases, the primary literature, IUCN assessments, and maps based on expert knowledge of reptile species and the habitats they occupy. A challenging aspect of the project was to ensure that our maps remained current with respect to new species discoveries and taxonomic name changes (which are constantly being revised), and we also had to confirm the validity of type specimen identifications and localities, especially those referenced from obscure sources and archaic museum specimens. We used GIS software to digitize and overlay the maps of each individual African reptile species (1,601 species in total!) one on top of the other, which allowed us to count the number of species present in a given area - which we call “species richness”.

When we looked at which environmental predictors best explained these species richness maps we found that net primary productivity (the amount of photosynthetic activity by plants) and precipitation explain most of the variation in reptile and other vertebrates. This explains the clear latitudinal pattern seen in their respective maps, which reflects a strong correlation with plant productivity and rainfall as you move closer to the equator. But again, lizards are unique in that none of these environmental correlates explain their distributions. This is because lizards are well adapted to a wide range of habitats including the tropics as well as the harsh conditions of the desert where plant productivity and rainfall are low. We also showed that individual lizard species on average occupy smaller geographic distributions, reflecting their ability to occupy diverse niches.

Our findings that the distribution of lizard species in Africa is unique when compared to the other vertebrate groups now confirms a pattern that has been seen elsewhere in previous studies (i.e. Australia) and most recently by our paper on the global distribution of reptiles. This shows the importance of studying the diverse reptile groups distinctly instead of lumping them all together, and will have bearing on large-scale conservation efforts that do not represent all reptile groups.

Author: Amir Lewin

In an article published in Biological Conservation we tallied the number of page-views each reptile species’ page in all of Wikipedia language editions had during 2014. We further correlated these numbers with various other attributes of the reptiles.

There is a debate in conservation as to whether the fact that we as humans like a particular species justifies conserving it, regardless of its importance from an ecological point of view. But although this idea of some species being "culturally valuable" has been around for some time, it has been difficult to measure and define. Whether or not we want to take these cultural variables into account when shaping conservation policy, we need data to support those decisions. In our study we looked at 55.5 million page views in the year 2014 for all of the 10,002 species of reptile accessed in Wikipedia.

Among more traditional conservationists there may be the view that we shouldn't incorporate cultural values into decisions about policy or funding. However, the fact is that whether we like it or not, we already do – how much funding do lions get compared with, for example, a species of small snail that doesn't even have an English name, even if the snail is more at risk of going extinct? The biases are already there. There's also an argument that the traditional thinking around conservation hasn't quite worked, so we need to reframe our approach. Regardless of the point of view you take, having this sort of quantitative data is critical.

The findings of this article have been picked up by several news outlets such as The Guardian, Haaretz Daily Newspaper, as well as Mongabay, Oxford University news and many others.

Authors: John C. Mittermeier and Uri Roll