Reduced Body Size is a Positive Response to Climate Change

by Anna Alquitela

Surveying 85 unique sites on the western borders of North Carolina and Virginia, biologist Nicholas Caruso and his team collected data on adult specimens of Appalachian woodland salamanders (genus Plethodon). The results showed a reduction in salamander body size in accordance with lower climate temperatures. Because woodland salamanders are lungless they breathe through their skin and require a moist environment for survival. The authors used historical and present-day data to model the changes in body size of 15 species of salamanders over the past 55 years. The dataset included 9,450 adult body size measurements from 102 populations of the 15 different species of salamanders. An 8% reduction in the average salamander size was found in all of the species over the 55-year study (Caruso et al, 2014). The reduction in body size reveals the plasticity of organisms to adapt to changes in climate. Because body size is directly linked to diet and foraging behavior, growth rates are also affected. Smaller body size means less surface area, and less loss of moisture through cutaneous responses. Also, the salamanders that were surveyed have demonstrated an increase in metabolism. Continue reading

Are species distribution models validated by field trials?

by Kyle Jensen

Invasive species, especially plant species, are one of the greatest current threats to the Earth’s biodiversity. It is feared that with the advent of global warming areas favorable to such species will increase, especially for those invasives from warmer climates that have naturalized near areas of marginal temperature. This could have negative impacts on the diversity of exposed populations, so species distribution models (SDMs) have been developed to estimate possible future distributions of organisms. These models make predictions by relating occurrence data to environmental conditions, giving a general idea of how the potential threat of an invasive species may change over time, and suggesting possible mitigation activities. Such models however have rarely been tested against experiments from the field. Sheppard et al. (2014) seek to validate SDMs through field trials at varying sites based on suitability as predicted by SDMs. If the predicted success of species in the models matches those of actual field trials, then we could be more confident in ability of models to assess the risk of invasive success. The experiment also addresses the validity of the enemy release hypothesis, which is often assumed to be the case in invasive studies. The hypothesis posits that invasive species leave behind any natural enemies when they are introduced to a new environment, which would contribute to their success. This experiment questions that assumption and its use in SDMs. Continue reading

The Endangered Species Act: Conservation-Reliant Species

by Alexander Birk

The United States Endangered Species Act (ESA) is responsible for the protection of species and their habitats. The ESA maintains a list of the species at risk; the ultimate goal is to get these species off of the list. In order to get an endangered species removed (delisted) the ESA must regard that species as self-sustaining. The definition of a self-sustaining species becomes difficult as the ESA looks at conservation-reliant species. A conservation-reliant species is defined as a species that has been delisted; however it requires management in order to prevent it from once again being at risk. Continue reading

Amazonian Bacterial Communities after Ecosystem Conversion

by Caroline Vurlumis

The Amazon rainforest is the most extensive tropical forest worldwide containing the largest amount of plant and animal diversity. For years there has been deforestation to create agriculture and cattle pasture which greatly harms biodiversity and causes homogenization in bacterial communities. Rodrigues et al. (2013) tested the impacts of soil microbial biodiversity when land is converted from forest to agriculture. Using transects from forest and pasture, the authors took soil samples of each to test local (alpha) diversity and differentiation (beta) diversity by concentrations of taxonomy and phylogeny. The results showed an increase in alpha diversity and decrease in beta diversity indicating a significant difference in bacterial communities when conversion occurs. There was significant loss in endemic species diversity and an increase of homogenization in the soil which poses a higher risk for net loss of biodiversity in the future. As a result of this study the authors argue that microbial biodiversity loss should be strongly considered when engaging in land conversion due to its important role in tropical ecosystems. Continue reading

Biodiversity Protects Plant-Pollinator Phenological Synchrony from Climate Change

by Lia Metzger

Biodiversity has been linked to the protection and sustenance of ecosystems against the loss of individual species. Studies have found that climate change, a contributor to the loss of species, has caused significant changes in phenology, mostly in species active in the spring. The biodiversity insurance hypothesis has never been expanded to include phenological synchrony as a possible buffer against the loss of individual species due to climate change. Bartomeus et al. (2013) investigated the phenological changes of wild bee species and of commercial apple crops over 46 years to find if bees and apples had phenological synchrony and if this was related to the richness of pollinator species. Using a contemporary data set, the authors picked pollinators that most frequently visited apple and tested for their phenological complimentarity. Bee and apple data were compared over time to find phenological mismatch and the rate of phenological change for different species with respect to apple bloom. Phenological synchrony was then tested against wild bee biodiversity. Phenological synchrony was found to increase with increasing biodiversity of the bee species and stabilize over time even though the rate of phenological shifting differed between species. Continue reading

Predicting Species Range Shifts Under Climate Change

by Cameron Lukos

Global climate change is causing long lasting effects on all of Earth’s natural systems. A consequence of these changes is species range shifting. Accurately predicting these shifts is very difficult and many methods have been criticized. The standard bioclimate envelope models (BEMS) have been criticized as too simple because they do not incorporate biotic interactions or evolutionary adaptation. BEMs are widely used though. Kubish et al. (2013) wanted to determine the evolutionary conditions of dispersal, because local adaptation or interspecific competition may be of minor importance for predicting future shifts. They used individual-based simulations at two different temperatures as well as competing simulations. Their results show that in single-species scenarios excluding adaptation, species follow optimal habitat conditions or go extinct if their connection to the environment becomes too weak. With competitors, their results were dependent on habitat fragmentation. If a species was highly connected to its habitat, the range shifted as predicted; if a species was only moderately connected to its environment, there was a lag time, and with low connectivity to the environment, the result was extinction. Based on this work, Kubisch et al. determined that the BEMs may work well as long as habitats are well connected and there is no difficulty dispersing. Continue reading

Partial Protection in Mexican MPA Only Marginally Effective in Restoring Reef Ecosystem

by Katie Huang

Loreto Bay National Park (LBNP) is a marine protected area (MPA) in the Gulf of California, Mexico, which bans fishing in some areas and allows limited amounts in others. However, since only a small region of the MPA is completely protected, it is possible that the benefits of a no-take area do not offset the effects of the permitted fishing. From 1998 to 2010, Rife et al. (2013) surveyed the biomasses of fish in sites within the LBNP and in open control areas and compared the data from before and after the MPA was established. They found that the biomasses of protected and open area fish were not significantly different. Although the biomasses of herbivorous and zooplanktivorous fish increased significantly within the MPA’s restricted area, the authors did not observe changes in apex predator and carnivore biomasses which suggests that the reef ecosystem is still unhealthy even after 13 years of protection. Possible explanations include poor enforcement of regulations as well as the small size of the restricted area, and management solutions should address these issues to make the LBNP more effective. Continue reading