Earth & Sky

The following individual was interviewed for today’s show. Our thanks to:

Dr. S. Blair Hedges
Department of Biology
The Pennsylvania State University
University Park, PA

Interview with Dr. S. Blair Hedges 12–2–01:

ES: Please tell me a little about yourself.

BH: My name is Blair Hedges. I’m an evolutionary biologist at Penn State.

ES: I understand that there’s some excitement about a new discovery?

BH: We’ve recently discovered what is the smallest lizard in the world, actually the smallest amniote vertebrate, a group that includes birds, mammals, and reptiles.

ES: Where did you make this discovery?

BH: On the larger island of Hispaniola. It’s a small island called Isla Beata in the Dominican Republic. The lizard is about 16 mm from the snout to the base of the tail, so it can curl up on a dime or a nickel. It lives in leaf litter, the dead leaves in the tropical forest. There are only eight specimens that we’ve found. It’s probably a little more common then that, they weren’t easy to collect. First you have to get to the island, which takes a little bit of trouble. What’s interesting about this smallest lizard is that it’s not very far from the U.S., being in the Caribbean, people go to that region for vacation and travel. A lot of people wouldn’t realize that there’s a lot of biodiversity in the Caribbean region. But in fact there’s about 10,000 endemic plants [species] and 900 endemic vertebrates [species], that is lizards and frogs and mammals and birds. And much of them are really endangered because they almost always occur in forests, and 90% of the forests in the Caribbean have been removed by humans through agriculture and slash and burn methods. And so it’s going rapidly. And even though there are national parks, there’s a lot of deforestation going on in the national parks. So much of that wildlife, including the small lizards, really is endangered and probably will disappear within the next 5,10,15 years and probably sooner than the forests in the Amazon, the forests in the Amazon are even more extensive than the forests in the Caribbean.

ES: Can you tell me a little bit about the environmental conditions of the lizard?

BH: We don’t know a whole lot about this lizard in terms of ecology and behavior because there’s so few specimens, but it appears to live in the leaf litter, that is the dead leaves. It’s a brown lizard, and of course the dead leaves are brown, so it blends in very well. That’s a term called cryptic, it’s a cryptic lizard. To find them you really have to get down on your hands and knees and move your fingers around through the leaf litter and watch for sudden movement and try and grab it. We have to wear gloves, because we might damage the small lizard’s tail. So you have to use your fingers to pick them up gently. So we don’t know too much more about it except that it lives in the forest in the leaf litter and it probably eats very small invertebrates, that is tiny insects probably less than 1 mm in diameter. It probably gets eaten by snakes that occur on the island and birds that might be lucky enough to spot it moving in the leaf litter. And undoubtably it’s eaten also by tarantulas that occur on the island. In this case we have a lizard probably being preyed upon by a spider, whereas lizards normally eat spiders when the lizards are much larger.

ES: I understand that you also discovered the smallest frog in the world too.

BH: Just to clarify, a cuban herpatologist Alberto Estrada, collected the smallest frog in the world in eastern Cuba, and I described it in 1996. So it’s kind of funny that I’m associated with the smallest frog and the smallest lizard. People are probably thinking that I have a little box in my lab that shrinks animals. But I think the significance of these finds is that they’re such unique and unusual organisms that are being discovered still and they’re so close to the United States. They really illustrate how little we know about the present biodiversity of the earth, and they’re rapidly disappearing. Now the reason why these smallest and largest organisms are on islands is probably because of this concept of empty niches. And what that means is that different organisms occupy a particular niche, or environment. They eat certain food items and they do certain behaviors. And on islands much of the flora and fauna usually gets there by dispersing in the water. And if a group never reaches the island, but another one does, that other group that does reach the island can expand evolutionarily into that empty niche that’s there because it wasn’t filled. And it’s the exact same principle that occurred after the big dinosaur extinction, the big asteroid that collided with earth 65 million years ago, and the dinosaurs became extinct, opening up a lot of niches for mammals, which at that time were very small, like rodents, and just in the next few million years you had tremendous evolution and adaptation into these niches, leading to elephants and large carnivoirs like lions and so forth. So, same concept ? but on islands you have these empty niches and sometimes they’re the smallest and the largest. In the case of this lizard, the niche that it may be filling could be of an invertebrate, like a spider, normally on the mainland that just didn’t happen to get to that little island.

ES: Why is this island in the Carribean called a biodiversity hotspot?

BH: Oh yeah, the Caribbean region is considered to be a biodiversity hotspot because it has an unusually high proportion of endemic plants and animals, that is about 10,000 endemic plants and 900 endemic vertebrates. And, in addition the flora and fauna is under the threat of extinction because of deforestation. There’s only about 10% of the forest remaining in the Caribbean. So it’s in pretty bad shape compared to other parts of the world. For example in South America and many parts of the Amazon, they still have 30–40% of the forests left, so it’ll be decades before the last forest disapears there. But in the Caribbean, already the last forests are disappearing. Today, in countries like Haiti, there’s less than 1% of the forest left.

ES: Are these hotspots particularly important?

BH: The reason for conservationalists to point out these biodiversity hotspots is to say: Look, we recognize that there are a limited amount of resources in the worlds for conserving what’s left of biodiversity. So let’s find the areas where those limited resources will go the farthest in protecting what’s left. So they came up with these 25 hotspots around the world which make up only a little over 1% of the total land surface, but you have as much as 30–40% of the plants and animals concentrated on that tiny bit of land surface. And so they say let’s focus our efforts on these areas because we know that we can’t protect everything.

ES: What kind of impact are humans making on biodiversity in general, and particularly in Hispanola?

BH: The inpact of humans on biodiversity follows pretty diverse categories. If you focus on the forest, where much of the biodiversity on land occurs, we have logging efforts which are going on in places like the Amazon where companies are harvesting trees for building materials. But more frequently, I think that the primary reason in places like the Caribbean, in areas that already have a low amount of forest cover, is through peasant farming. That is, slash and burn, where a peasant family that’s occupying some land illegally, they don’t have a deed to that land, just to survive they clear a patch of forest, a patch of virgin rain forest, and burn the trees. And then after they’re cleared then crops like beans or casaba, a staple are planted. They work the land for two or three years, and then they move on, because by then the nutrients have already washed out and the land is no longer fertile. So they clear out another hectare of land. And so that’s a major cause of loss of biodiversity and deforestation in areas like the Caribbean. And another major cause, probably the second one, would be the production of charcoal for cooking fuel. And this is a really big problem in the Caribbean because you can make charcoal from even really small twigs and saplings, and quite often in places like Haiti even the saplings are harvested from an area. And the wood is buried in the ground, with rocks on top of it, ignited, and left to smolder, and that makes charcoal. And then they use that to cook their food with, since they don’t have electricity going out to these peasant huts in the countryside. And so those two reasons are probably major reasons for the loss of forest, and consequently biodiversity in the Caribbean I would say.

ES: What special hardships does the sphaero face because of it’s tiny size?

BH: The major hardship that this lizard would face, like any animal at the lower limit of its body size, is the relatively high surface to volume ratio, that is the proprotion of the skin to the proportion of the body. And the reason for that is, the more skin the higher the evaporation. So a small lizard like this will tend to dry up much more quickly than a larger lizard, and this can be a problem when the weather changes. The leaf litter, which is normally moist, might dry up, and it has to quickly find a place that has a higher humidity, and if it doesn’t it’ll die. So this can be a problem for animals this small. In fact I suspect that it’s probably the major problem.

ES: What motivates you to look for new species of life?

BH: The main reason that I’ve been involved in research in the Caribbean is to try and figure out how thw biota, the flora and fauna, got to the island, whether it was by rafting on vegetation or blowing in the wind, the flotsam and jetsom, or by literally moving with the islands through continental drift. And so there’s several different mechanisms for organisms to arrive at islands. And then there’s also the question of where they came from, if they did disperse. Whether it was from South America, North America, Central America. And we can get answers to those questions by sequencing their DNA and using phylogenetic methods to make family trees, evolutionary trees, of their history. And we also use molecular clocks to time when they made this voyage out to the island. So that’s my main reason for working out in the Caribbean. But as a consequence, going out there to collect samples we encounter new species quite often, at least 50 or more in the last 15 years. I’m sure that there are many more species remaining to be found and described down there. So it’s pretty exciting work! I enjoy it.

ES: One thing I forgot to ask you about is, how long have these geckos been on the island?

BH: The interesting thing about these geckos, the genus sphaerodactyls, and I just call them spheros, a common name for short, there’s an amber deposit in the Domincan Republic, one of the biggest in the world is in that country, and there are sphaerodactylus embedded in that amber 15–20 million years ago. So that tells us that we know the island was there 15–20 million years ago and there were these little geckos. And so they’ve definitely been here that long and probably even much earlier. And molecular clocks also agree that its been 20–30 milion years since they’ve been on the island.

ES: What was the island like, say a few hundred years ago?

BH: When Columbus first arrived, the island of Hispaniola was completely forested. In fact most parts of the world were forested, aside from the major deserts like the Sahara and so forth. So now it’s roughly 10%, depending on how you classify complete forest and incomplete forest. People might disagree about the details. There’s roughly 10% of the original Caribbean forest that’s left. So that’s a lot of forest that’s disappeared. Much of the lowland forest was cut a long time ago, hundreds of years ago, you know when the mahogany wood was being harvested out of the Caribbean. But that’s been exhausted for many years. And now they’re cutting the last remaining patches on the most remote pieces of land in the Caribbean, which is typical around the world. The last remaining forest is the area where humans have the most difficuty to reach. Not only scientists, but the local people, the local population.

ES: Is there anything else that you’s like to share with the listeners of Earth and Sky?

BH: Well, the ultimate thing that humans can do is to reduce the rate of population growth. But given that’s propbably not going to change in the near future, in the short term, to protect what’s left I would say: Enforce these national park boundaries. There are national parks that have been errected in these various countries that, if they were enforced, they would actually protect a lot of the biodiversity. But unfortunately they’re just not enforced, they don’t have enough resources. So maybe if agencies from the developed first–world countries could funnel resources to specifically , say hiring park rangers and enforcing these park boundaries, helping the countries enforce the park boundaries, and maybe – this sounds horrible ? relocating these locals that are occupying the land illegally, the sqatters. Because only a small number of the people in a country are really causing a major amount of the loss of biodiversity. It’s just these relatively small number of families that are doing the slash and burn agricuture. Most of the population of course lives in cities. And we all contribute to the loss of biodiversity, all of us in the world. But of you really want to put your finger on the immediate short term cause for this loss, it would be these people who cutting hecatares of forest up in the national parks and in sensitive areas. And so there has to be a sensitive way to somehow relocate those people so they can live their life in another part of the country, and not where they were removing this biodiversity. So that’s my thought on this biodiversity crisis from seing it in the field.