Novel habitat, predictable responses: niche breadth evolution in geckos

At a time of immense ecological change (such as the Anthropocene), organisms have a few options. They can move, tolerate, adapt, or, in failing to do so, face extinction. One or most of those options may not be available to most species. For example, the question of whether most species can adapt rapidly enough to maintain populations in degrading habitats, rising temperatures and increasing environmental variability has (at least in part) motivated the study of rapid or contemporary evolution. Studying the probability of successful selection and adaptation over ecological timescales may be very important for understanding the options available to species.

de Amorim et al. (2017, PNAS) describe one such example, where the result of novel environmental change provides a unique opportunity to observe rapid evolution. Beginning in 1996, a reservoir in Central Brazil was created by flooding a huge area, creating nearly 300 islands and massively affecting local wildlife. Gymnodactylus amarali was the most common lizard (a termite-specialized gecko), and the authors sought to determine the impacts of rapid isolation on the species.

Isolation on islands created an new set of biotic conditions – other termite eating lizards went extinct on islands, increasing the available diet breadth, particularly increasing the availability of larger termites. Larger termites require geckos have the physical ability to catch and processes them. One possibility is that to take advantage of this new resource, G. amarali on islands would need larger heads. Because larger heads and bodies come with increased energy requirements, the authors predicted that the island geckos would have larger heads, but no change in overall body size.

Termite size increased on average on islands; for the same body size, head length tended to be larger on islands. 

Indeed, island geckos had higher diet breadths, driven by the availability of larger termites and an increased ability to catch them via larger head lengths. Increased diet breadth was accompanied by increased head size, but not body size.

Notably, this change in diet and associated characters occurred independently across multiple reservoir islands, beginning once they were isolated from the mainland. This is an interesting example of rapid evolution precisely because evolution took the same path in every case, and because it occurred so rapidly (less than 15 years). This is not always the expectation - in many cases, human activities (e.g. fragmentation) will increase decrease population sizes and genetic diversity, thereby increasing drift and decreasing the predictability (and speed) and adaptation. Contrasts between successful and unsuccessful adaptive responses will help us understand better how and when fragmentation threatens populations.

Mariana Eloy de Amorim, Thomas W. Schoener, Guilherme Ramalho Chagas Cataldi Santoro, Anna Carolina Ramalho Lins, Jonah Piovia-Scott, and Reuber Albuquerque Brandão. 2017. Lizards on newly created islands independently and rapidly adapt in morphology and diet. PNAS. 114 (33) 8812-8816.

The vanishing pangolin: How do you change the value of an endangered species?

Extinction is forever. Extinction reduces the biological heritage of the Earth and is something that we cannot undo.

While living in China, and traveling around Asia, I have said something to my children I have never said before: “I want you to take a really good look, these animals will go extinct in your lifetime”.  I said this as we were watching 8 of the 60 remaining Hong Kong pink dolphins.

Hong Kong pink dolphin (photo by Shirley Lo-Cadotte)

Species become rare and endangered for many reasons, like habitat destruction, pollution, human facilitated spread of problematic species (rats for example), and direct harvesting. While all of these factors are subject to laws and regulations that attempt to control them, it is the last one, harvesting, that relies most on altering peoples' wants and desires. I don’t know why, but to me it is also the saddest cause, the idea that a species dies out because we desire it and kill it or chop it down, just doesn’t seem right.  

Walking through the market alley near my apartment in Guangzhou, China, I saw something that both intrigued and horrified me: a dead and quartered pangolin. You may not be familiar with pangolins –also called scaly anteaters; they are mammals about the size of a large cat or medium-small dog (like a cocker spaniel), with a very long and thick prehensile tail that they use in trees. Their most unique feature is that they are covered in large flat scales that are made of keratin –the same as your fingernails. 

A Chinese pangolin, Manis pentadactyla (https://commons.wikimedia.org/wiki/File:Pangolin%27s_tail.jpgsted to Flickr by verdammelt cc-by-sa-2.0) 

Pangolins are critically endangered. They also have the distinction of being one of the most trafficked animals in the world. In China and Vietnam there is high demand for pangolins because they are considered a delicacy and more importantly their scales are used in traditional medicine. These scales are believed to provide a cure for a number of diseases, including cancer. The incidence of cancers in China is skyrocketing, which is not surprising given the level of pollution, and couple this with increasing affluence, the desire and ability to pay for pangolin parts has never been greater.

Obviously pangolin scales do not cure cancer. You might as well save your money and suck on your fingernails instead, but evidence and logic are not likely to sway mortal fear. There are groups in Asia dedicated to protecting endangered animals and educate citizens about wildlife. Such organizations have an opportunity to capitalize on recent attitude shifts in China and elsewhere, where animal wellbeing is increasingly seen as important. In China, pet ownership has increased dramatically over the past decade and pets are now seen as companions –which I suspect was partially a result of the one-child policy. But the demand for pangolins still exists. When we visited the Angkor Conservation Centre in Cambodia, which works tirelessly to rehabilitate animals and educate people, they were recovering from the theft of one of their pangolins from an enclosure, which they knew was transported to China.

The Chinese authorities are coming down hard on the illegal pangolin trade. They now routinely arrest individuals selling pangolins and seize large shipments. While such seizures and arrests show that the Chinese government is taking pangolin protection seriously, there is only so much they can do while demand is high.

Police confiscating a large illegal pangolin shipment bound for China (photo originally from news.163.com) 

My Mother-in-law, who is from southern China, said it best when I told her about the dead pangolin in the alley: “people just need to be educated”. That is really where the answer lies. Laws can only change peoples’ behaviour so much; education campaigns are desperately needed. Currently, there is an internationally funded billboard campaign in China to stop people from buying elephant ivory. Ivory demand is high in China. Despite the importance of reducing ivory purchases, I would argue that this type of education campaign needs to focus a little closer to home, and Pangolin conservation efforts are in desperate need of help. 

When we were visiting the conservation centre in Cambodia, I told my children that the Pangolin would go extinct in their lifetime. I really hope that I am wrong.

To fence or not to fence, that is the question*

The stereotypical view of African drylands is often of a parade of elephants marching steadily across endless expanse of savannah grassland –free to roam. Another staple image, especially of African savannah documentaries, is the massive wildebeest migration where thousands of individual animals moving as an aggregation navigating the hazards of the landscape.

Majestic African animal migrations. Main image: "Wildebeest-during-Great-Migration" by Bjørn Christian Tørrissen - Own work by uploader, http://bjornfree.com/galleries.html. Licensed under CC BY-SA 3.0 via Wikimedia Commons. Inset: By Amoghavarsha amoghavarsha.com (Own work) CC BY-SA 3.0 via Wikimedia Commons

In both of these examples, animals are moving with purpose for food and water, because this is how an animal survives in a place where rainfall and vegetation are seasonably variable. These migrations are vital to the survival of many dryland species. But even at smaller scales, and much less dramatically than a massive migration, animals need to move through a landscape to access food, water and mates.

Yet, as human populations spread their influence by altering ecosystems, they increasingly come in contact with wildlife, and often compete with them for space, water and agricultural crops. To reduce these human-wildlife conflicts, people often erect fences to exclude species and steer them elsewhere. Farmers and ranchers, concerned with their livelihood, need to exclude grazers from crops and predators from domesticated animal herds.

Example of a dryland fence barrier. From: Photo by William I. Boarman, USGS, From press release: USGS Report Finds Too Few Studies Assess the Success of Desert Tortoise Recovery Actions, Aug. 10, 2006. http://online.wr.usgs.gov/ocw/g_agassizii/barrier_fence.jpg

While fencing might offer some protection to human interests, fences can also have broad long-term consequences for animal populations. However, it is also increasingly appreciated that fencing can be used as a conservation measure to protect animals from these conflicts and from illegal hunting. In a thoughtful paper on dryland fencing policy, Durant and colleagues argue that current fencing policies are often based on limited information, with an under appreciation of the large-scale, long-term consequences of fencing nature.

Durant and colleagues argue that fencing can result in multiple costs and benefits. They cite an important example –fencing to protect lions. Fences constructed as a lion conservation tool may result in higher lion population sizes –which seems to valid fencing as a conservation tool; but yet analyses showed that when carrying capacities are accounted for, fences may not provide better protection, and further may not be worth the economic and ecological costs.

Lions of the Masai Mara –do they benefit from fences? Photo by Benh LIEU SONG (Own work) CC BY-SA 3.0 via Wikimedia Commons    

 The authors recommend that fencing policy needs to driven by evidence, and not a reaction to human-wildlife conflict alone. The critical factors that they suggest are: 1) Economic sustainability of erecting and maintaining fences, and that the benefits justify the costs; 2) The permeability of the barrier, because not all species will equally perceive the fence as a hard edge, and so a fence may not be a well justified as a universal management tool; 3) Using fencing within a landscape context –fences may complicate how animals deal with natural features, such as cutting off a natural river crossing; 4) Connectivity is critical for both the maintenance of genetic variability within populations and allowing animals to access variable and ephemeral resources; 5) Ensuring that fences do not interfere with or reduce the delivery of ecosystem services; and finally 6) Safeguarding the wellbeing of human communities, especially marginalized and vulnerable groups that might depend on resources from natural areas.

By creating international policy and regulations based on these six criteria, Durant and colleagues argue that sensible fencing policy can be developed, which ensures that fences are used to maximally benefit humans, animals and natural processes.

 *Note -this post was originally written for the Applied Ecologist's Blog.