General Research Objective
In my M.Sc research I studied the evolution of longevity of different groups of Tetrapoda (amphibians, reptiles, birds and mammals). Together with my colleagues I published four papers examining how life-history and ecological factors relate to mortality rates, and how they affect the longevity of 4,100 Tetrapoda species.
Long lived reptilians: What causes reptiles to have longer lifespans?
Most recent studies on the variation of longevity focused on mammals and birds. My colleagues and I examined how extrinsic mortality factors, such as predation and environmental temperatures, are related to the variation in longevity among and within lizards, snakes, turtles and crocodiles. We found that species living on islands and in colder and more seasonal environments live longer.
Does nocturnal activity prolong gecko lifespan?
Most gecko species are nocturnal, as opposed to other lizard families. Because of the lower exposure to harmful UV radiation during the night, nocturnal species are expected to have lower intrinsic mortality rates, as they accumulate less harmful mutations and metabolic waste compared with diurnal species. My colleagues (one of them is my wife) and I compared diurnal and nocturnal geckos, and geckos to other lizards, to test whether nocturnality promotes longer lifespans. We found that although geckos live relatively long for lizards of their size, their activity time is unrelated to longevity, contradicting our predictions. Perhaps mortality through extrinsic causes (e.g., predation) may impose much stronger selective pressures than intrinsic causes.
Living in cold and dark captivity: What drives the variation in amphibian lifespans?
Surprisingly (or not), amphibians are the only tetrapod group in which longevity variation was never explored before. With my colleague, I explored the patterns and drivers of 527 amphibian species, spanning all orders- anurans, caudatans and caecilians.
We found that large amphibians living in colder environments probably experience slower growth and metabolic rates, reducing intrinsic drivers of mortality and increasing their lifespans. Species that reduce extrinsic mortality pressures via chemical protection and nocturnality have also increased their lifespans.
Higher metabolism does not necessarily mean a shorter lifespan
It has long been thought that animals that have slow metabolism live longer than those that have high metabolic rates. The notion is based on the assumption that animals with fast metabolic rates are more active, more exposed to predators, have higher rates of potentially harmful somatic mutations and produce more harmful metabolic by products such as free radicals. This trade-off between metabolism and lifespan is commonly referred to as the ‘rate-of-living’ theory.
In our recent publication , my colleagues and I showed that the assumption under the “rate of living” theory which has been around for almost a century is unsupported by the results of our large scale study (4,100 land vertebrate species: 2,214 endotherms & 1,886 ectotherms). We could not find any connection between animal metabolic rate and longevity, either when we tested all land vertebrates together (i.e. Mammals, Birds, Reptiles and Amphibians) or when we tested each group separately. We did find, however, that the ambient temperature affects the lifespan of ectotherms (Reptiles and Amphibians) in a way that reptile and amphibian species in colder regions live longer than their counterparts that live in warmer environments. If increasing ambient temperatures reduces longevity in these groups, ectothermic vertebrates may be more prone to extinction as temperatures rises in an unprecedented way due to global warming.
Check out our paper in the media: link
