Blog Archives

The Hot Eurasian nightlife - How do different environmental forces affect nocturnality in lizards?

10/10/2017

In a recent publication in Global Ecology and Biogeography we explored the prevalence of nocturnality amongst Eurasian lizard species and tried to understand what drives these patterns.

Most animals – at least those that live above ground – are active either during the day or during the night. Being active at either time of day carries with it unique benefits and challenges, and thus particular adaptations. Because of this being nocturnal or diurnal is a trait that is pretty rigid amongst closely related species.

Lizards as a group are thought to be ancestrally diurnal. Most of them remain so to this day. Furthermore, they are ectotherms and are predominantly small bodied tetrapods and could thus be particularly affected by the climatic differences between day and night. For this work we collected distribution range and activity time data for all 1,113 lizard species found throughout mainland Eurasia. We then looked at links between richness patterns of lizards with either temperature or productivity.

Cyrtodactylus trilatofasciatus (Photo: Lee Grismer)

We found that nocturnal lizards have the highest species richness in the tropics and in deserts, and their richness decreases when they get closer to the North Pole. Nocturnal lizards are precluded altogether from the coldest regions inhabited by lizards – in high mountains and the highest latitudes.

Stenodactylus sthenodactylus (Photo Uri Roll)

Ambient temperature has a strong influence on richness patterns of both diurnal and nocturnal lizards, where species numbers increase with an increase in temperature. Productivity was found to be more tightly related to the proportion of nocturnal species – again in a positive relationship.

We think that our results point towards the fact that low temperatures are a limiting factor for lizard activity period. It is possible that the year-round warm nights of tropic regions enabled lizards to move towards nocturnal activity. In hot deserts, perhaps the combination of hot days and aridity make diurnal activity less attractive, whereas nocturnal activity can provide shelter from these extreme conditions

Author: Enav Vidan

Stenodactylus doriae (Photo Uri Roll)

0 Comments

A short history of GARD and how it has been used to highlight gaps in global conservation priorities

9/10/2017

2 Comments

In a paper published in Nature Ecology and Evolution we present the first global maps of all reptiles - and thus complete the global distributions of all tetrapods. We further explore how the new reptile information changes how we think about global conservation priorities. As this is the first place where all of the GARD maps have been used and published, we use this opportunity to share some of the history of GARD itself, as well as the particular work that was carried out for this paper.

The beginnings of GARD
Planning for reptile conservation globally we first needed to map the distribution of all known species. About 8500 of them when we started in 2006, about 10,500 now recognized. This was a time when such global databases were being published for amphibians, birds, and mammals – some of us have been instrumental in assembling those databases, so we felt fairly confident we knew how it should be done.

What we were wondering, however, was whether the fact that reptile distributions were not collated at the time was not because it couldn’t be. A quick survey of available field guides and herpetology books revealed that maps of the sort used to assemble distribution data for birds and mammals were simply unavailable for huge parts of the world, including most of the crucial regions in tropical South America, Africa and Southern Asia.

GARD meeting, Oxford (photo: Uri Roll)

GARDians competing for that 'perfect' picture of a gecko

Thus the Global Assessment of Reptile Distribution working group (GARD) was formed. In the meantime we started recruiting the people who did much of the actual legwork – graduate students who digitized maps from existing sources, as well as the maps that started pouring in from the reptile experts among the GARD members. We had to keep track with constant taxonomic changes, species splits and new reptile species discoveries (many of them by GARD members themselves) – resulting in additional 200 species or reptiles nowadays being added annually.

We finally had at least some data for all the species or reptiles we thought one could map about two year ago. Then we met again to start the immensely important process of reviewing the distribution data to ensure errors were kept to the minimum (a process that is still ongoing).

Early on in compiling the data we got the feeling that lizard ‘hotspots’ were not in the tropics, where virtually all other groups studied so far have the most species. Once the maps were fully compiled this was very evident. The unique thermal requirements of reptiles enable them to thrive in drier habitats, allowing them to evolve and prosper in deserts.

Vipera bornmuelleri (photo: Uri Roll)

Do unique reptilian biologies and ecologies demand particular conservation needs?
Or in other words do the major global conservation priorities designations adequately represent reptiles or do their unique distributions make them less protected. It turns out that many reptiles – predominantly lizards and turtles are left out of global priority regions and protected areas.

Hypsilurus papuensis (photo: Alex Slavenko)

We therefore wanted to explore how the focus of future conservation efforts need to change to properly represent reptiles. To do this we run prioritization optimization procedures which enabled us to highlight various regions of the world predominantly in drylands, savannah, steppe, and also islands that increase in importance when reptile distribution data are added. More broadly this work highlights the need of getting better data for lesser known groups in order to compile truly inclusive conservation planning that encapsulates all of biodiversity.

Ecoregions that increase in importance for conservation, when reptile data are added (dark blue - top decile ecoregions, light blue - top quartile ecoregions)

Authors: Shai Meiri and Uri Roll

2 Comments

The Hot Eurasian nightlife - How do different environmental forces af﻿fect nocturnality in lizards?

A short history of GARD and how it has been used to highlight gaps in global conservation priorities

Author

Archives

Categories

The Hot Eurasian nightlife - How do different environmental forces affect nocturnality in lizards?