One strategy to protect species from the dangers of climate change is to relocate them to more suitable habitats. In order to successfully relocate a species, many factors must be considered, including the physiology of the organism. Besson and Cree (2011) studied the suitability of the Orokonui Ecosanctuary as a relocation habitat for a lizard species in New Zealand, the tuatara Sphenodon punctatus. The tuatara’s native habitat in the Cook Strait of New Zealand is threatened by the rising temperatures of climate change. The researchers evaluated the potential of successful relocation of the tuatara to the cooler habitat in Orokonui by comparing its preferred body temperature, feeding behaviors in cooler temperatures, and critical thermal minimum to three lizards that currently inhabit the area. The results showed that the tuatara responded to the three tests similarly to the other three lizards, indicating that the tuatara may be able to successfully relocate to the Orokonui Ecosanctuary and escape the dangerous effects of climate change in their current habitat. — Isabelle Heilman
Rising global temperatures caused by climate change are making current habitats unsuitable for a variety of species. One lizard species in New Zealand, the tuatara Sphendon punctatus, is threatened by climate change. It has been proposed to move this species from its current habitat on the Cook Strait islands in northern New Zealand to the Orokonui Ecosanctuary in the southeast, which has a cooler climate by 3–4ºC. The researchers measured the suitability of this new habitat by comparing responses to colder temperature in feeding behaviors, the critical thermal minimum, and preferred body temperature of the tuatara to three lizard species, common geckos, jewelled geckos, and McCann’s skinks, which already inhabit Orokonui. The results demonstrated that the tuatara would likely be able to survive in the cooler temperatures of the new habitat.
The researchers used ten juvenile tuatara, thirteen common geckos, fourteen McCann’s skinks, and ten jewelled geckos in their experiment. Each species became accustomed to the laboratory habitat and schedule over a period of at least four months before the experiment began. To test the effect of cooler temperature on feeding behavior, the lizards were fed mealworms at 20º, 15º, and 5ºC to simulate autumn and winter temperatures. To prepare before each temperature session, the lizards were not fed during one week and given access to a heat lamp to accelerate digestion. Once the mealworm was given to the lizards, the authors observed the time between the introduction and apprehension of the worm (prey catching), first apprehension and swallowing of the worm (prey handling), and swallowing and appearance of the plastic tag inserted into the mealworm in the lizard’s feces (gut passage). After observing these behaviors at all three temperatures, the lizards were placed in an incubator and cooled at 1º C per hour. This continued until the lizards reached a temperature where they lost control of their muscles, which was the critical temperature minimum (CTM). The researchers then increased the temperature in the laboratory to simulate summer temperatures. The lizards were presented with a temperature gradient and their temperature selections were measured four times within every 24 hour period.
The effects of temperature on feeding behavior were measured using a linear mixed effect test, where the temperature and species were fixed factors and the three feeding activities were dependent variables. CTM of each species was analyzed using a Kruskal-Wallis test. Repeated measures ANOVA tests were used for the preferred temperature data. These analyses revealed that as the temperature decreased so did food consumption in the lizards. However, temperature affected each feeding behavior differently. Prey catching time increased with temperature across all species. Increases in prey handling time were most obvious between the 12º and 5ºC temperatures sets, but decreased over all the temperature sets. Gut passage time was affected by both temperature and species, although all species had slower gut passage times or a lack of feces as the temperature got cooler. CTM was significantly different for each species; however the CTM of tuatara was similar to that of the two gecko species. Preferred body temperature was similar among the four species, with all four preferring the 20º to 27ºC temperature range.
The results of the statistical tests demonstrate enough similarities between the tuatara and the three lizard species to signify that the tuatara could be able to live in the cooler Orokonui habitat. However, this experiment also demonstrated a possible limitation for their survival in colder temperatures. The tuataras were unable to digest the mealworms at 5ºC without the help of a heat lamp. In their natural habitat, tuatara bask in the sun to aid in digestion, yet the Orokonui habitat has limited basking space, which could be problematic for the tuatara to complete digestion. To combat this danger, the tuatara could increase basking time when the temperature is warm enough.
Overall, the authors found that the relocation of tuatara from the islands of Cook Strait to Orokonui Island could be possible. The feeding responses at cooler temperatures, CTM, and preferred body temperature of the tuatara were similar to that of the common gecko, jewelled gecko, and McCann’s skink which currently inhabit Orokonui. This experiment demonstrates the importance of considering physiological factors of species when finding an area for relocation to avoid the dangerous effects of climate change.
Throughout evolutionary history, species have had to adapt to changes in temperature in their habitats to be able to survive. However, the changes in temperature as a result of current climate change may be too fast for species to be able to adapt effectively. The loss of these species would cause large gaps in the “tree of life” diagram which illustrates the relationships of different species throughout history. Thullier et al. (2011) studied the effects of climate change on the diversity of plant, mammal, and bird species across Europe. A variety of models and forecasts were utilized to find that the vulnerability of species to the effects of climate change is not strongly linked by close relation or proximity on the tree of life diagram. Thullier et al. also found that in the future, species diversity will decrease in Southern Europe, but increase in Northern Europe. Despite the increases in diversity in the North, the decreases will be strong enough to move all of Europe toward species homogenization.—Isabelle Heilman
Certain groups of related species are more susceptible than others to harm by humans, raising the question of whether related species on the tree of life diagram will also be more susceptible to harm caused by climate change. Adaptability to change in climate differs among species; however, related species tend to have similar characteristics of adaptability. If related species are similarly vulnerable to the effects of climate change, the losses of related species would be more obvious in the tree of life diagram. To measure the effects of climate change on the tree of life of European species, Thullier et al. examined 1,280 plant, 340 bird, and 140 mammal species found across Europe. The researchers used species distribution models and climate prediction models to find that variances in suitable climate were alike in related species. Using the information from ranges in suitable climate as a stand-in for extinction risk, the researchers then saw that although there would be a decrease in diversity among related species, however, the calculated decrease was not greater than the decrease under a random extinction model. By mapping present and future species distribution, the authors found that the future spatial distribution of species in Europe will change, with Northern Europe increasing in diversity and Southern Europe decreasing in diversity.
To find the changes in suitable climate for the plant, bird, and mammal species, the researchers used several species distribution models, high resolution global climate models, and four emission scenarios in periods of 29 years from 1969 to 2080. Vulnerability of species to effects of climate change was found as a value between –100 and >100 calculated by the change in area with suitable climate for each species. This value, the change in suitable climate (CSC), was used to represent the probability of extinction and was compared with a random extinction model which was found by randomizing the probability of extinction and finding the new amount of species diversity. To measure the relatedness of plant and bird species, the authors ran searches at the family level on a compilation of smaller trees of life to find the highest likelihood tree. For the mammal trees, the researchers used 100 evolutionary trees based on the work of Fritz et al. (2009). To find the spatial distribution of the species, the authors estimated the area where the species where projected to exist by the amount pixels taken up on a map.
It was found that closely related species had similar suitable climate ranges, but some species’ suitable climate was reduced, while others increased. Birds in Tringa and Numenius species had decreased suitable climate ranges, while Ardeidae species increased. Plants were mostly found to contract their ranges. Mammals were found to be least vulnerable to harm as a result of climate change. Comparing the results of the constructed and random models showed that the predicted effects of climate change on species diversity did not vary greatly from randomized effects. The modeling showed that some areas of Europe will have positive changes in species diversity, while other areas will have negative ones. Southern Europe currently experiences high species diversity, however in the future it will experience low species diversity. Northern Europe currently has low species diversity, but in the future it will experience high species diversity.
Changes in climate across Europe are changing the amount of suitable climate habitats where plant, mammal, and bird species can live. According to this study, the overall amount of species diversity will not change dramatically, however the spatial distribution of species on the tree of life will. Spatial distribution of species across Europe will also change, with greater species diversity at the higher elevations and latitudes of Northern Europe. Measures to control the speed of global warming must be taken in an effort to allow these species to adapt and to avoid major damage to the tree of life diagram.
Other Works cited
Fritz, S., Bininda-Emonds, O., Purvis, A. Geographical variation in predictors of mammalian extinction risk: big is bad, but only in the tropics. Ecology Letters 6, 538–549 (2009)