Category Archives: Isabelle Heilman

Rising Temperature Effects on Small Mammal Populations in North-Central Chile

Posted on by
Reply

Although temperature increase is often the most discussed factor in the conversation about global climate change, precipitation is another important factor. In arid and semi-arid areas, such as western South America, changes in rainfall affect the flora and fauna in different ways. This area of the world is also particularly affected by the El Niño Southern Oscillation (ENSO), which causes periods of increased precipitation and flooding. Meserve et al. (2011) studied the effects of precipitation changes as a result of ENSO and climate change on small mammal populations in north-central Chile. They found that permanent resident small mammals went through large population changes during and after times of heavy rainfall, while temporary resident small mammal species abandoned the thorn scrub habitat for some periods of time. All small mammal species were able to survive in nearby mesic habitats. Species which had inhabited the area for a long time were also found to be more plentiful than more recent species. The authors predict that in the future, ENSO and precipitation affected by global climate change will contribute to changes in species distribution and richness in this area. —Isabelle Heilman
            Meserve, P.L., Kelt, D.A., Previtali, M.A., Milstead, B., Gutierrez, J.R. 2011. Global climate change and small mammal populations in north-central Chile. Journal of Mammology, 93 1223–1235.

            Precipitation is a major factor in the survival of flora and fauna in arid and semi-arid habitats. In areas such as western South America, changes in precipitation are seen due to the El Niño Southern Oscillation (ENSO). The ENSO causes periods of elevated rainfall and flooding, which can have positive or negative effects on the wildlife in these habitats. Meserve et al. (2011) studied the effects of increased rainfall due to ENSO on small mammal populations in north-central Chile. The results of their study show that abiotic factors linked with ENSO periods are significantly contributing to changes in species richness and distribution in these semiarid habitats. In the future, the researchers expect the populations of small mammals with long life spans to increase and outnumber the small mammals with shorter life spans, which will contribute to changes in species composition in these areas.
            Meserve et al. conducted their research in the Bosque Fray Jorge National Park in north-central Chile. The park is described as containing semiarid thorn scrub vegetation and fog forests with a Mediterranean semiarid climate, producing 90% of precipitation from May to September and its warm and dry period from December to March. Research for this study began in 1989, when the authors created a complex of 75 x 75 m small mammal live-trapping grids to assess the minimum number of small mammals living in each area. Small mammals were trapped for four days per month per grid. Perennial shrub cover, annual cover, geophyte cover, soil seed densities, and predator diet and activity were monitored in addition to the mammals. For each year of study, the rainfall was categorized as either less than the long term annual mean of 131 mm, or in the first, second, or third year of a rainy cycle. The precipitation and small mammal trapping data were analyzed using a mixed-model analysis of variance. Rainfall data between the first and second decades of experimentation were different, so the researchers also performed a Shannon-Weiner diversity index test to see if the difference in rainfall had an effect on species diversity.
            Both the responses of small mammals and plants to increased rainfall were variable with individual species responses influenced by residency status and life-history traits. Annual shrub cover in the area oscillated between a low of 0% during drought-ridden years of La Niña and a high of 86% during wet El Niño years. Changes in small mammal population were categorized by either permanent resident species or temporary resident species. The permanent resident species Octodon degus showed small reactions to heavy rainfall, while the populations of another permanent resident, Phyllotis darwani, appeared to fluctuate independent of rainfall. These differences could be explained by differences in life-history characteristics. Life-history of O. degus shows that variation is usually produced by long term patterns, while in P. darwani variation is quicker, possibly due to larger litters and more movement during times of heavy precipitation. Temporary residents Abrothrix longipilis and Oligoryzomys longicaudataus also acted differently from each other. A. longipilis had erratic population increases and decreases, usually during the wet periods, including some time of complete absence. O. longicaudataus had slow population increases during times of heavy precipitation and delayed decreases in dryer times.
            Despite the differences within the permanent resident species and the temporary resident species, there was a general pattern. Permanent resident species with high variability in population established long-term residence and temporary residents showed less variability but still were prone to absence from some areas completely. As global climate change continues, these semiarid areas are subject to increased ENSO events, which could intensify the current patterns and change the current species composition. 

The Delay Between Species Composition Change in Response to Climate Change in Lowland Forests in France

Posted on by
Reply

In response to climate change, species redistribute themselves to find more suitable habitats. However, some species exhibit a gap between climate change and their redistribution response. Bertrand et al. (2011) studied this lag in species response to climate change in lowland and highland forests in France between 1965 and 2008. The researchers tested to see if the delay was greatest in the lowland species where climate change is most rapid. By comparing the temperature increases over time and the species composition, they found that the lowland species responded to only 0.02ºC of the 1.11ºC increase, while highland species responded to 0.54ºC of the 1.07ºC increase. Possible explanations for this variation include: higher proportion of resilient species in lowland areas, the availability of short distance escapes for highland species, and increased habitat fragmentation for lowland species. The authors conclude that although highland species are greatly threatened by climate change, the gap in response by lowland species is important and needs to be researched further to avoid a decrease in species in the lowland area.—Isabelle Heilman
Bertrand, R., Lenoir, J., Piedallu, C., Riofrío-Dillon, G., de Ruffray, P., Vidal, C., Pierrat, J.C., Gégout, J.C., 2011. Change in plant community composition lag behind climate warming in lowland forests. Nature, 479 517–520.

           
            Global climate change has caused species to change their distribution patterns, usually resulting in a shift toward higher altitudes and latitudes. In some cases however, there is a delay between the changes in climate and the species redistribution response. Theoretically the gap between climate change and species response should be larger at lowland forest levels than at the highland forest levels because climate change is faster at lower levels. Bertrand et al. (2011) studied this gap with respect to both lowland and highland forests in France, where the effects of climate change have been seen at a greater scale than the world average. To measure the gap, the authors compared “floristically reconstructed” temperatures and “climatically reconstructed” temperatures over the years 1965 to 2008. This method demonstrated a larger gap between the floristically reconstructed temperatures and climatically reconstructed temperatures in the lowland species than in the highland species.
 The climatically reconstructed temperatures were found using instrumental records and climate models. The floristically reconstructed temperatures were found using surveys of flora composition. Surveys from 1975 to 1985 (before the recent warming began) provided the data to create a transfer function using both weighted averaging partial least squares and Breiman’s random forest to estimate temperature from the plant compositions. These two temperature values were paired according to year and location and then compared to find the gap in response.
            The 44 year time period was then divided into two sections, 1965–1985 (before recent climate change) and 1987–2008 (after recent climate change). No significant difference between the temperatures was found for either highland or lowland species during the first time period. During the second time period, both lowland and highland species showed a significant difference between the two temperatures, however, the magnitude of difference was greatest in lowland species. This difference between highland and lowland species responses demonstrated that lowland species did have a greater gap between climate change and their redistribution response than highland species. The authors cited other surveys in different French mountains and a Mediterranean forest where lowland forests were also a relatively unreactive ecosystem with respect to climate change.
            To explain the different reactions of highland and lowland species to climate change, the authors turned to three distinctions between the two ecosystems. First, they considered that lowland areas contain more warmth seeking species, which could explain why species found in this area are more resistant to rising temperatures. Second, species in highland areas have to migrate shorter distances to find suitable climate, while species in lowland areas must migrate longer distances to find suitable temperatures for survival. The researchers called this a short distance escape opportunity in highland areas. Third, lowland species are subject to much more habitat fragmentation than highland species. This fragmentation affects the plants dispersal and migration abilities. These three factors probably act together to make lowland forests less reactive to climate change.
            Although the qualities of the lowland forest have lessened the effects of climate change on species distribution, this habitat will not experience stability forever. As temperatures continue to rise in the lowland forest, its inability to provide suitable climates for its species will change the species composition in the habitat. In the absence of short distance escapes, many plants that currently inhabit the lowland forest will die from being unable to find new suitable habitats once temperatures are too high. The authors recommend more research on the effects of climate change on lowland forests to better protect these valuable ecosystems.

The Effects of Climate Induced Advanced Flowering on Plant-Pollinator Exchanges

Posted on by
Reply

Rising temperatures due to global climate change can alter the phenology of plants, affecting their mutualistic partners, pollinators. These changes affect plant flowering time, which affects the amount and types of pollinators which will visit them. Rafferty and Ives (2011) examined how changes in flowering onset affected visitation by pollinators in fourteen perennial plants native to Wisconsin. Six of the 14 species demonstrated a change to sooner flowering in the past 70 years, the other eight did not exhibit any changes in flowering. The researchers experimentally advanced and delayed flowering of these species. The results showed that when flowering was artificially advanced, five of the six species with historically advanced flowering received more pollinator visits, while seven of the eight species with historically unchanged flowering received fewer visits from pollinators. Rafferty and Ives concluded that in their study species, phenological shifts to earlier flowering were not disrupting mutualistic relationships with pollinators. — Isabelle Heilman
Rafferty, N., Ives, A.R., 2011. Effects of experimental shifts in flowering phenology on plant-pollinator interactions. Ecology Letters 14, 69-74.

 When two organisms have a mutualistic relationship, changes in the life events of one organism directly affect the other. Life events are dependent on environmental cues, and changes in temperature could signal an organism to begin a life event earlier in the year than is historically expected. For plants, temperature is a cue to begin flowering and attract pollinators. In the mutualistic relationship between plants and pollinators shift in the flowering time of the plant may lead to changes in pollinator visitation. Rafferty and Ives (2011) investigated how shifts in flowering related to climate change affect pollinator visitation. The researchers used 14 perennial plant species native to Wisconsin and experimentally advanced or delayed their flowering time. Six of the plants had advanced flowering time already, and eight had historically unchanged flowering time.
To test the relationship between flowering time and pollinator visitation, the authors first raised plants of 14 species controlling for factors such as fertilizer and pot size. In order to experimentally advance flowering, plants were put into a greenhouse between 24ºC and 27ºC. Delayed flowering was achieved by putting the plants into greenhouses between 18ºC and 21ºC. To measure changes in plant composition which could affect pollinator attraction, the nectar and sucrose content were sampled one day before putting the plants into the field to observe pollinator interactions. This could only be performed for eight of the 14 plants. Once plants were put into the field, pollinator visitations were recorded. A visitation was defined as touching anthers, stigma and/or nectar of the flower.  Daily weather variables and the number of flowers present on each plant were also recorded.
To analyze the number of pollinators visiting, and visits received the authors used a general linear mixed model. Species of plant, time of day, maximum daily temperature, and precipitation were accounted for as fixed effects. A general linear mixed model was also used to assess the difference in composition of pollinators during the different weeks of experimentation.  Analysis of the differences between historically advanced flowering species and historically unchanged flowering species in pollinator visitation was done using a chi square analysis. To account for the phylogenetic relationships between the fourteen species, a parallel analysis was used. Nectar and sucrose content were examined using linear mixed models.
            These statistical tests showed that there was a significant change in number of pollinator visits in 12 of the 14 species. The historically advanced flowering species showed a trend of fewer pollinator visitations over time, compared to the historically unchanged flowering species. However, historically advanced flowering species were visited by more pollinators when their flowering was artificially advanced. The historically unchanged flowering species saw more pollinator visitations when flowering was artificially delayed. Nectar volume and sucrose concentration significantly changed for some plant species throughout the experiment, but there was no constant relationship when all of the species were considered.
            The two categories of perennial plants that Rafferty and Ives examined showed different interactions with pollinators under manipulated flowering time. These results show that changes in flowering phenology can affect visitation from pollinators. However, the authors did not find an expansion of mismatch between flowering onset and visits by pollinators. They explain that despite the earlier flowering caused by climate change, these plants still have a variety of pollinators available to visit them. The coordination of this phenological reaction between plants and pollinators is optimistic for the future of their mutualistic relationship under the rising temperatures of climate change. 

European Spring Temperature Increases Effects on Brood Parasitism of Cuculus canorus

Posted on by
Reply

To avoid parental care of their young, brood parasite species lay their eggs in the nests of other bird species so that the owner of the nest nurtures their chicks. To effectively parasitize their hosts, brood parasites such as the common cuckoo, Cuculus canorus, coordinate with the annual cycle of their host. Temperature increases can change the biological processes of the host species, disrupting the synchronicity between the parasite and the host, limiting host options for the parasite.  To combat these disruptions, C. canorus choose different host species. Møller et al. (2011) predicted that C. canorus would prefer long-distance migratory hosts rather than resident or short term migratory hosts during periods of elevated spring temperatures. To test this prediction, the researchers analyzed the relative frequency of parasitism in long-distance migratory hosts and short-distance migratory or resident hosts in 23 European countries in the time periods: 1958 to 1989 and 1990 to 2009. They found that parasitism in resident and short term migratory species decreased as spring temperatures increased. This result shows that as global temperature continues to increase, brood parasites will have different and fewer options for hosts, which could affect their overall population. — Isabelle Heilman
Møller, A.P, Saino, N., Adamík, P., Ambrosini, R., Antonov, A., Campobello, D., Stokke, B.G., Fossøy, F., Lehikoinen, E., Martin-Vivaldi, A., Moksnes, A., Moskat, C., Røskaft, E., Rubolini, D., Shulze-Hagen, K., Soler, M., Shykoff, M., 2011. Rapid change in host use of the common cuckoo Cuculus canorus linked to climate change. Proceedings of the Royal Society 278, 733-738.

Brood parasites such as the common cuckoo, Cuculus canorus, try to harmonize their reproductive cycle with that of their host. By matching up their reproductive cycles, the parasitic species can lay their eggs in the nest of another species and leave that species to take care of the parasite’s young. Environmental effects such as temperature increases can change reproductive processes of the host species, disrupting the synchronicity between the parasite and the host, which can lead to reproductive limitations for the parasite and in extreme cases, extinction. European temperatures have been rising, which has affected migratory patterns of birds and in turn, the species and amount of hosts available for brood parasites. Møller et al.studied the brood parasite C. canorus to see if the relative frequency of resident or short-distance migratory species selected as hosts changed after 1990. Relative frequency was defined as the number of C. canoruseggs present in the nest of a host species relative to the number of total C. canorus eggs. They also studied the relationship between host selection and changes in spring temperature.
To test their predictions about host selection based on temperature, the researchers used a database containing 32,843 records of cuckoo parasitism in Europe. They grouped the host species into two groups: long-distance migrants who spent winter in Sub-Saharan Africa or the Indian Sub-continent, and short-distance migrants or residents. Mean daily temperature data from individual countries was taken from ECMWF ERA-Interim data for 1989 to 2009 and ERA-40 data was used for the time period before 1989. Countries that were directly bordering and had similar rates of temperature change were grouped. Population trends of the two migratory pattern classifications were also considered. The authors used general linear analyses to find the relationships between relative frequency of parasitism in the years 1990 to 2009 and temperature changes in the country groupings. The year 1990 was used as a cut-off because the rate of climate change has been the greatest after this year. Years 1958 to 1989 were used as covariates in the analyses.
The results showed that there was a significant decrease in the use of resident and short-distance migratory species as hosts. Also, there were a smaller proportion of C. canoruseggs in short-distance migratory or resident hosts’ nests in areas where spring temperatures had increased.  These findings support the researcher’s initial predictions that short-distance migratory and resident species where less-regularly selected as hosts for C. canorus during the time period 1990 to 2009 compared to host selection from earlier time periods. After 1990, spring temperatures increased at a greater rate, implying that climate change plays a part in host selection for C. canorus. This finding shows that as temperature increases, C. canorus will have fewer host species to choose from, which could have serious consequences on their population size in the future. 

Residence Time, Biogeographical Origin, and Climate as Predictors for Range Size and Species Richness of Exotic Plants in Great Britain

Posted on by
Reply

The spread potential of exotic species depends on several factors in the new environment. De Albuquerque et al.(2011) researched some of these factors to see which most affected range size and species richness of exotic plants in Great Britain. The factors they observed on 1,406 exotic species were the amount of time since the plant had been introduced to the new habitat, the origin of the plant, climate of the new habitat, and the human footprint. De Albuquerque et al. grouped the plants into four residence time categories and three biogeographical origins. They found that range increased with residence time and region of origin did not have a strong effect. The results also showed that the human footprint played a small role in determining species richness, while climate was the predominant factor. —Isabelle Heilman
De Albuquerque, F.S., Castro-Díez, P., Rueda, M., Hawkins, B.A., Rodríguez, M.Á., 2011. Relationships of climate, residence time, and biogeographical origin with the range sizes and species richness patterns of exotic plants in Great Britain. Plant Ecology 212, 1901-1911.

In the study of invasive ecology there is a hypothesis which predicts that the more time an invasive species has been in a certain area, the greater the chance that the species will be widespread. De Albuquerque et al. tested this hypothesis in their study of exotic species in Great Britain. Using data from the New Atlas of British and Irish Flora, they explored the various factors that determine species richness and range size of exotic species. The goals of the study were to find the relationship between range size and biogeographical origins and mean residence time of the species, how climate and human footprint affect species richness, and whether species richness grouped by origin and mean residence time have overlapping distributional patterns.
To begin the study, the authors grouped the plant species into four categories determined by their residence time. The oldest species group was the archaeaphytes, which first inhabited Great Britain before 1500, then the older neophytes from 1550–1800, the intermediate neophytes from 1800–1900, and the recent neophytes from 1900–2011. All of the species were also categorized according to their biogeographical origin, either Northern Holarctic, Mediterranean, or Tropical/subtropical. Range sizes of the different categories of species were determined using the Atlas of British and Irish Flora divided into 10×10 km cells, excluding islands and coastal areas with less than 50% land in the cell. The researchers also considered species richness variables in the groups of energy, water, combined water-energy, topography, and human footprint. 
Analysis of the relationship between residence time and range expansion of the exotic species was performed using ANOVA tests and a Tukey’s unequal-N-HSD test to also compare the mean number of grid cells occupied by all groups and the mean residence time for the three neophyte groups, because the year of introduction of archaeaphytes is unknown. An ANCOVA test was used to find the relationship between the plant’s origin and its range expansion. To test the effects of climate and human footprint, OLS multiple regression and partial regressions were used. The effects of environmental factors, such as water and energy were determined by a Varimax-rotated principal component analysis, which showed that the mean annual temperature and annual precipitation were the strongest environmental factors, and were then used in the multiple regressions for climate and human footprint.
The results of the study showed that residence time was the greatest indicator of exotic species range size. Archaeaphytes were the species that had occupied the area the longest and had the largest species ranges, while the youngest group, the new neophytes, had the smallest species range size. Biogeographical origin was not significant; however species that came from the Northern Holarctic and the Mediterranean had larger species ranges than those from the Tropics/subtropics. The researchers also found that temperature had the greatest effect on exotic species richness patterns. Species richness increased in Great Britain going from north to south, and mean annual temperature was the largest correlate of environmental factors.
Although mean residence time was the strongest predictor variable, temperature also played a large role in the expansion of exotic species and their species richness across Great Britain. Exotic species can invade habitats and drain the resources from native plants, killing them. Even though the full effects of climate change are yet to be seen, temperature increases could play a large role in the future expansion of exotic species, causing the death of many native plants. 

The Interactions of Temperature Change and Contaminant Toxicity in Ambystoma barbouri

Posted on by
Reply

Amphibians are especially vulnerable to the effects of climate change because they are ectothermic and because of their permeable skin allows for toxins to enter their body easily. Despite these characteristics, their mobility on land lets them escape from toxins in water for periods of time, but while in their embryonic and larval stages, amphibians have limited mobility and cannot escape from the contaminants in their water environments. To help prevent prolonged exposure to contaminants in these stages, development of amphibians can be accelerated by increasing temperature. Rohr et al. (2011) used embryonic and larval forms of the salamander Ambystoma barbouri to test the combined effects of the contaminant atrazine and temperature on hatching, metamorphosis, growth, and survival. They found that increases in concentration of atrazine impeded hatching and metamorphosis and decreased growth and survival. Increases in temperature resulted in more growth and faster development, but also lower survival rates in embryos. Instead of contributing to the negative effects of atrazine, temperature helped the salamanders combat the effects of atrazine by decreasing the time spent exposed to the contaminant. —Isabelle Heilman
Rohr, J., Sesterhenn, T., Stieha, C., 2011. Will climate change reduce the effects of a pesticide exposure of amphibians?: partitioning the effects on exposure and susceptibility to contaminants. Global Change Biology 17, 657–666.

           
            Usually only the negative effects of rising temperature are considered when talking about climate change. Rising temperatures can accelerate the growth rates of organisms, reducing the amount of time they spend in their vulnerable embryonic and larval stages. More developed organisms have a greater chance of survival because of their improved biological processes. For amphibians, this means that they have the ability to leave toxic environments and reduce their exposure to damaging chemicals. Using the embryonic and larval forms of the salamander Ambystoma barbouri, Rohr et al. observed the effects of temperature and the toxin atrazine. The researchers hypothesized that rises in temperature would raise both the toxicity of atrazine and the developmental speed of the salamanders, which would lower the total amount of time the salamanders were exposed to atrazine.
            The study measured the effects of temperature and atrazine on hatching, metamorphosis, growth, and survival separately for embryonic and larval stages. For each experiment, 12 randomly chosen A. barbouri were put into a glass bowl, for a total of 64 bowls. These bowls were controlled for light and water conditions. Four solutions of atrazine were prepared in 0, 4, 40 and 400 μg L-1 concentrations, to simulate the range of atrazine concentrations found in nature. Each bowl was treated with one solution; however after the first metamorphosis in the larval experiment, 8 bowls in each temperature were treated with an acetone control solution. For the embryonic experiment, the bowls were divided into two groups, one at 13ºC and another at 19ºC.  The larval experiment covered a greater range of temperatures, separating the bowls into four groups, at 16ºC, 19ºC, 22ºC, and 25ºC. The A. barbouri were observed until all of the embryos had hatched or died (49 days) and all of the larvae had metamorphosed or died (78 days). Those salamanders still alive at the end of the experiment were euthanized, preserved, and weighed.
            The data from the experiment were statistically analyzed after a log transformation, which allowed for a better statistical fit. Generalized linear model tests were used to analyze the effects of atrazine and temperature in the embryonic experiment, while regression-based tests were used for the larval experiment because of the lack of a duplication of each temperature and concentration treatment. Results from the embryonic statistical tests showed that although the embryos hatched sooner and were heavier at the 19ºC treatments, they were also more likely to die at this temperature than at 13ºC. Atrazine negatively affected hatching time and embryonic survival. All four concentrations increased embryonic mortality rates, but only the highest concentration of atrazine significantly affected hatching time.  In the larval experiment, atrazine concentration was found to negatively predict larval survival and also decrease larval mass. Temperature was positively correlated with developmental rate. Interestingly, the effect of atrazine on survival rate did not depend on temperature or amount of time exposed to the contaminant. Rising temperature was not found to increase the toxicity of atrazine.
            Although in this experiment temperature had a positive effect on development and lowered the amount of exposure to atrazine, the results of this experiment should not be interpreted to mean that rising temperatures provide an overall benefit for salamanders. The authors point out that global climate change not only affects temperature, but also precipitation, which is another factor to consider for the overall effects of atrazine and other contaminants. To most benefit the A. barbouriand other organisms, the focus should be placed on reducing the contaminants that end up in these habitats in the first place. 

Physiological Considerations for Reptile Relocation due to Climate Change

Posted on by
Reply

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

Besson, A.A., Cree, A., 2011. Integrating physiology into conservation: an approach to help guide translocations of a rare reptile in a warming environment. Animal Conservation 1, 28-37.

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.

Effects of Climate Change on Fish Reproduction and Early Development

Posted on by
Reply

Fish use water temperature as a cue for reproduction through a series of hormonal stimulations. Some species reproduce in the warmer spring, while others in the cooler fall. The rising temperatures due to global climate change cause spring reproducing species to spawn earlier and fall species to spawn later. Pankhurst and Munday (2011) reviewed several different studies to find the range of effects climate change has on the reproduction and early developmental stages of fish. The authors found that in addition to affecting spawning timing, temperature also impacts the size of larvae when hatched, which influences their overall chance of survival. Another result of climate change—ocean acidification—also impacts the survival of fish by damaging fish’s sensory perceptions of their environment. If not mitigated, these effects of climate change will greatly reduce fish’s ability to reproduce and affect biodiversity in both marine and river ecosystems. —Isabelle Heilman
Pankhurst N.W., Munday P.L, 2011. Effects of Climate Change on Fish Reproduction and Early Life History Stages. Marine and Freshwater Research 62, 1015–1026.

            Environmental changes caused by global warming such as temperature increase and ocean acidification impact reproduction and developmental stages in fish. Using current research, Pankhurst and Munday review the known effects of climate change, in particular rising temperature, on fish throughout their lives. Temperature changes trigger hormone production, which then prompts reproduction or stress responses. Increased temperature also increases the development and nutritional requirements of young fish. Even though fish use an acid-base regulation system to limit the effects of lowered pH caused by ocean acidification, research indicates that prolonged exposure to elevated carbon dioxide can decrease aerobic activity in fish, which could then have an effect on reproduction. The effects of water temperature and pH changes vary by fish species, but especially affect species with limited suitable habitat ranges.
            Changes in the environment can elicit hormone production in fish. These hormones can trigger maturation, reproduction and anti-stress responses. Most hormone production processes occur within a limited range of temperatures. The production begins once the minimum temperature is reached, and then hormone synthesis increases as temperature increases. As temperature reaches the higher end of the range, hormone production decreases. Rising temperatures can affect fish hormonal systems by reaching the upper temperature range faster, inhibiting reproduction hormone synthesis.  Some research also indicates that higher temperatures elicit a hormonal stress response. Fish respond to stress by quickly increasing access to stored energy and sending more oxygen to their tissues. Although this response is beneficial in short term stressful situations, maintaining this behavior long term can have damaging effects on reproduction and growth for fish.
Egg and larval stages of fish are especially vulnerable to the negative effects of elevated temperatures and ocean acidification. Small changes in pH or temperature can dramatically reduce the chances of survival in fish eggs. However, because fish reproductive systems respond to environmental temperature cues, it is possible that fish will finish their reproduction process before the water is too warm for their eggs to survive. For the eggs that do survive, warmer temperature can lead to shorter incubation periods, earlier hatching and accelerated development. Increased temperatures also speed up rates of development for larvae, which could be an advantage for survival and later reproduction. These faster rates of development utilize faster metabolic rates which require more food ingestion, making larvae more vulnerable to starvation in habitats with fewer sources of food. 
Current research on ocean acidification demonstrates that lower pH levels may not have a significant effect on the development of fish in the larval stages, but that they could have a large effect on olfactory sensitivity. Fish use their sense of smell to gather information from their environment such as to distinguish between kin and non-kin fish. When exposed to a more acidic environment, fish begin to confuse olfactory signals and can become attracted to dangerous smells, such as those of their predators. The consequences of confusing safe and dangerous smells can have damaging effects on survivorship and decrease population overall.
The effects of climate change on fish are mostly seen in their reproduction processes and during their developmental stages. To prevent the loss of fish species diversity in our oceans and rivers we must combat water temperature increases and ocean acidification. The authors also call for more research into the biological pathways of fish because very little is known about their intricate hormonal systems, which could be the key in fully understanding the effects of climate change on fish. 

Effects of Climate Change on Plant, Mammal, and Bird Species Diversity on the Tree of Life in Europe

Posted on by
Reply

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

Thuiller, W., Lavergne, S., Roquet, C., Boulangeat, I., Lafourcade, B., Araujo, M., 2011. Consequences of climate change on the tree of life in Europe. Nature 470, 531–534.

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)