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Gulf of Guinea Expeditions 

July 11, 2008

The Race Continues: We Find Jita!

We are still on Principe and down to the hard corps: me, Wes and Josef. The mushroom and plant folks, Dennis, Brian, Tom and Rebecca are home in San Francisco by now. So it is time to tell you a little about my own research interests. Cobra Jita is a snake and we have been looking for it all week; in order to explain why, I need to tell you a frog story.
Josef and a big tree

Josef Uyeda. Bombom, Principe.  GG III (Weckerphoto)

As I have said, the fact that there are amphibians here at all is astounding; amphibians, along with primary freshwater fish, are among the poorest dispersers across saltwater barriers known. They are the last kinds of critters one would expect to find on an oceanic island…. Think of the Hawaiian Islands and the Galapagos, perhaps the two most intensely studied oceanic archipelagos in the world… no frogs or other amphibians, right? But here on Sao Tome and Principe we have seven amphibian species, one of which is the famous caecilian, Schistometopum thomense. How can this be? How did they get here? More on this later, but one of the keys is time: remember that Sao Tome is at least 15 million years old, and Principe is more than double that, perhaps 31 million years. Hawaii and the Galapagos are but 5 million years max.

During GG I, we collected series of little brown frogs of the genus Phrynobatrachus from various locations on both islands; at the time all of them were considered the same species, P. dispar, originally described from Principe over 100 years ago. In 2005, a bright young intern from Willamette University named Josef Uyeda, spent the summer in my lab studying these preserved specimens and concluded that the frogs were quite different. Josef joined GG II and did a lot of collecting on both islands, recorded calls, did dissections and comparisons of DNA from the critters on both islands. The results are that the two island frogs are VERY different; in fact, there is nearly 21% DNA sequence difference between the two; indicating that they have not interbred in many millions of years, possibly predating the existence of Sao Tome (yet they still look virtually identical!). Moreover the two together appear to be more closely related to East African species than to more nearby West African species, but more on that later. In 2007, Josef, I and Breda Zimkus of Harvard described the Sao Tome brown frogs as a new species, Phrynobatrachus leveleve.
Phrynobatrachus leveleve, Sao Tome

Phrynobatrachus leveleve, a new species from Sao Tome. Moquinque. GG III (Weckerphoto)
P. dispar, Principe

Phrynobatrachus dispar. Principe.  GG III (J. Uyeda photo)
Uyeda et al. 2007 Proc.C.A.S.

From Uyeda, et al. 2007. Proc. Calif. Acad. Sci. 58

This brings me to cobra jita (pronounced “zheetah” – it means snake slow, as opposed to the other Principe snake, cobra sua sua, which means snake fast!). Here we have the same situation as we had with the small brown frogs, Phrynobatrachus. Jita (more properly known as Lamprophis lineatus bedriagae, or lined house snake) has always been considered to be the same species on both islands. After our frog studies, I am not so sure! They look different – regrettably I will have to post a picture of the Sao Tome form later… didn’t bring one in my zip drive—the Principe form is much more obviously patterned than the Sao Tome snake. During GG I and GG II we got very good samples of the Sao Tome population, but for some reason, only one specimen from Principe.
Our first Jita- Lamprophis lineatus

Lamprophis “Jita” from Principe. GG III (Weckerphoto)
Jita's head

Jita from Sao Tome. GG II (D. Lin phot)

Josef is now a PhD candidate at Oregon State University and joined us a couple of weeks ago in our search for Jita (among other things I will describe later). Snakes, as you probably know, are where you find them… as primary predators, they are never very common but always around, and such has been the case here on Principe. It has taken us six days of trekking around in the forest, turning over logs, etc. to find six snakes. But I am delighted. This is certainly enough now to estimate the genetic distance between the two populations, and given the age of these islands, I will not be surprised at all to learn that they are distinct at the species level.
Josef and me

Josef and me hunting for the snake on Bom Bom Island. GG III (Weckerphoto)

We have learned a lot about this critter. On Sao Tome, Jita is primarily nocturnal while the daylight hours on that island seem to be dominated by the endemic Sao Tome green bush snake, Philothamnus thomensis. This is the situation we would predict using island biogeographic theory—no niche overlap – they both seem to eat frogs and skinks, but at different times. But here on Principe, all of the jitas we have caught have been during the daylight hours, as was the single individual caught during GG II in 2006. Moreover, the green snake of Principe (yes there is a green sua sua here as well, but not related to the Sao Tome species) also seems to be diurnal! They are incredibly fast; we have seen two of them and missed both. So until we can look at stomach contents, we seem to have an ecological mystery.
me, Josef and Ramos

Me, Josef and Ramos on Bom Bom Island. GG III (Weckerphoto)

Our search has been greatly aided by an amazingly bright local naturalist; Jose Ramos Maria Vital Pires, or Ramos for short. Ramos has led us around this island searching for the elusive jita we have been blown away by his keen perception and observations of the local flora and fauna, and his delightful smile and sense of humor. The thing is everyone knows about this snake, most of the locals are to say the least, not exactly fond of snakes and one referred to as a “house snake” frequently comes a little too close for comfort, as you might imagine. But finding a snake when you are looking for it is entirely different matter. Our first success occurred on Bom Bom Island (not really and island, but sort of). I had just commented that the area Ramos was leading us through was too steep to find a snake, when he began excitedly shouting “snake!” only meters away. Within moments we had bagged our first jita.

There have been some rather ignominious moments for me personally. My two young compadres, Wes and Josef are willing to give me credit for catching but one jita, a dead one. The specimen had, in fact, been killed two hours earlier by a local woman who was delighted to have us remove it from along the road. This morning was the last straw. We had been combing Bom Bom Island again; Josef and Wes had taken a lower route than I and about an hour in, I heard Josef yell that they had caught a snake in the act of ripping a tail off a skink. Well and good, I thought, but where’s mine? So I am walking along, seeing snake food like skinks all over the place, when Wes and Josef come down the trail towards me. We stopped, admired the snake Josef had already bagged and the photos Wes took of it eating its skink tail, all three of us turned around…Josef stooped over and grabbed our largest jita of the expedition, about a foot behind me. I must have stepped right over it a moment beforehand. Perhaps it is not necessary to tell you that there has been much snickering among the younger members of this outfit ever since… Argh.
Josef catching Jita number five

Josef secures a jita. Bombom, Principe. GG III (Weckerphoto)
A local boy at Puerto Real

Parting shot.

More anon.

PARTNERS

 

We gratefully acknowledge the support of the Research Investment Fund of the California Academy of Sciences, the Société de Conservation et Développement  (SCD) for logistics, ground transportation and lodging, STePUP of Sao Tome http://www.stepup.st/ and especially the generosity of three private individuals, George F. Breed, Gerry F. Ohrstrom and Timothy M. Muller, for making GG III possible.

 


Filed under: Gulf of Guinea — bob @ 10:19 am

The Race: Glorious Ghost in the Forest

Scientists love islands because the processes of evolution on islands are simpler than they are on more complex, much larger continents and thus more easily studied. I have made the point that the islands of Sao Tome and Principe are very poorly known, but what we do know is very exciting. One evolutionary pattern that seems to consistently appear on islands is the phenomenon of gigantism; for some reason certain successful colonizers become very large on islands: for instance, think of the tortoises on the Galapagos Ids. or on Aladabra. There are a number of hypotheses that attempt to explain this phenomenon, but none is particularly compelling; nevertheless, the pattern exists and is very evident on the oceanic Gulf of Guinea Islands. The composite image below illustrates just a few of the giants on Sao Tome and Principe.

Some Island Giants

Think of potted plants for a moment… how large is a begonia? The central plant in this composite image is the largest species in the world, Begonia baccata. It is found only on the island of Sao Tome and reaches 10 meters in height! This particular specimen graces the southern shore of Lagoa Amelia at about 1480 m elevation – my head comes up to about flower level on this old friend (I am 6′ tall); these enormous plants are common at higher levels. The two birds figured are also giants: the yellow one on the right is the world’s largest weaver. Ploceus grandis,. and the one on the left is the world’s largest sunbird, Dreptes thomensis; both endemic to the larger island of Sao Tome. This is a good point at which to mention that island dwarfism is also an observable phenomenon  here as well, and the world’s smallest ibis, the Sao Tome Dwarf Ibis, Bostrychia bocagei is also an endemic.  The other critters in the collage, the frogs and the lizards, are all endemic giants but I will deal with them later. It is important to bear in mind that when we call a species a “giant”, we are describing its size compared to all of its other relatives only; such a species may not appear to be a giant at all, in our eyes.

The Sao Tome Giant Treefrog, Hyperolius thomensis, and I go back a long way; back to when I was writing my doctoral dissertation many years ago. This sapo (as all frogs are called on the islands) is endemic to Sao Tome only and is easily the largest member of its genus (Hyperolius)- females reach lengths of nearly 50 mm.from snout to vent!

Sao Tome Giant Treefrog, Hyperolius thomensis. GG I and GG II – D. Lin

Nearly all of the original material from which this species was described in 1886 was destroyed in the fire in Lisbon.  But I managed to find four remaining specimens, two in Vienna and two at the Natural History Museum in Vienna, allowing me to treat them in my dissertation.  In 1988 and again 1990 more specimens were reported by a Swiss worker, but her published locality data are very general, if not vague, and it turns out that most of the material she worked on was collected by locals at her request prior to her arrival.  During GG I, we visited most of her reported localities, finding nothing until we finally got lucky. Now, I can state that this most flamboyant of treefrogs is currently known for certain from only a single locality!  Our work in GG I, II and III has confirmed that this marvelous critter is known only from higher elevations (above 1000 m), inhabiting the canopy of old secondary or primary growth trees on steep slopes.  And it appears to breed only in the water-filled holes in trees with fluted bark or buttresses.  This is a rarity – in Africa, only 9 other frog species are known to breed in phytotelmata (scientific word for treehole). But it makes sense.  Most frogs lay eggs, which develop into free-swimming, gilled tadpoles, which then metamorphose.  Although there are many fast moving rivers on the steep slopes of Sao Tome, these are far to swift for breeding; still bodies of water simply do not exist. So, H. thomensis has adapted to breeding in ephemeral, rain-filled holes in the trunks of very large trees! All of the other frogs native to the islands utilize slow moving or still water for reproduction.

The tree -  GG III (J. Clara  phot)

This is the only tree in which we have collected the Sao Tome Giant treefrog.  It is at about 1100 m on a high ridge, and we return each expedition to check its status. Adults are usually present but there are always eggs and tadpoles at different stages of development in the holes.  Tom and Rebecca, our botanists, could not identify this tree – it is simply too tall its see its canopy, and moreover it is festooned with epiphytes.

Frogs and eggs in treeholes -   GG III (Weckerphoto)

Wes Eckerman, our photographer tried to climb it, and then tried to climb an adjacent tree to see if there were more holes, but the tree is just too big in girth to handle; with our friend Jose Clara, we tried to erect a crude ladder to examine a hole farther up the trunk but to no avail.

GG III (RCD photo)

I do not mean to imply that this species is restricted to this tree.  We have heard the species calling at night from high up in the canopy and reasonably certain that it is pretty widespread, at least in the high elevation forests we have visited – I suspect it is present on Sao Tome anywhere the trees are large enough and that. of course.  means upslope above the former Portuguese plantations.  What is different about this single documented tree is that it is the only one whose rain-filled holes are within our reach – there are undoubtedly more holes in many more trees that are too high for us to access.  I am left with the notion that given its restricted range and peculiar breeding biology, the Sao Tome Giant Treefrog is a classic indicator species; its presence means healthy mature forest.  If I were to choose an icon to symbolize the dogged persistence of pockets of nature in the face of man’s depredations and at the same time the attitude, beauty and whimsy of the citizens of Sao Tome and Principe, it would be this gorgeous island giant. Josef, my former student, informs me that he has already seen the name of this species on a price list in the pet trade in Europe.  If you  wonder why I have not described the location of this tree is in more detail, now you know. 

In the last posting, I promised you a picture of the cobra jita of Sao Tome. Here are shots of both island forms, which are currently considered to be the same species.

Sao Tome Jita – RCD, GG I

Principe Jita – GG III (Weckerphoto)

Not only do these critters look different from those on Sao Tome (stripes vs. patterned blotches), theyact differently as well. On Sao Tome, cobra jita appears to be strictly nocturnal; during GG I and GG II we easily found them at night by first listening for the loud choruses of oceanic treefrogs (more aboutthem later). So far as we know, the Sao Tome jita largely feeds on these frogs while they are breeding and is strictly nocturnal; to see at least ten of these snakes in a single night under the right conditions is not uncommon.

 

R. Stoelting, my grad student, with her first Jita - GG I  ( RCD phot)  

After our week on Principe, however, I am prepared to say that that jita is diurnal and although we will not know until we check stomachs, I think it feeds on lizards and small rodents. We even located a chorus of treefrogs behind Bombom but failed find a jita, nor did we ever find one during our night hunts. Only time and careful study of morphology nd DNA will tell us how closely related these two island snakes really are.

Thanks to Caitlin D. for her generous donation. We are doing what we can!

PARTNERS

 

We gratefully acknowledge the support of the Research Investment Fund of the California Academy of Sciences, the Société de Conservation et Développement  (SCD) for logistics, ground transportation and lodging, STePUP of Sao Tome http://www.stepup.st/ and especially the generosity of three private individuals, George F. Breed, Gerry F. Ohrstrom and Timothy M. Muller, for making GG III possible.

 


Filed under: Gulf of Guinea — bob @ 10:19 am

The Race: Matters of Currency

 Yes, the title is a play on words, and given the great threat posed to the unexplored natural environments of these two little unique islands by future oil revenues, I suppose a more appropriate title would be “Matters of Urgency,” but I couldn’t help myself.  In this posting I want to talk about the work of Dr. Richard Mooi, who was with us on GG II.

  

Rich stalks an unsuspecting sea urchin on São Tomé. D. Lin phot. GG II. 

Dr.Rich Mooi is a Curator in our Department of Invertebrate Zoology, but more importantly to us (and to the blog title!), he is one of the world’s authorities on echinoids, a large phylum that includes sea urchins, seas stars and what we Americans call “sand dollars,” the flat, disk-like tests (exoskeletons) of which we find commonly on our beaches.  One of the most fascinating, yet poorest known sand dollars in the world is Rotula deciesdigitata, known only from the Gulf of Guinea.  This species is probably not really rare but the places it occurs are remote and not frequently visited by scientists.  Hence, they are super-scarce in the world’s natural history collections; even more so in North America.

 

Technical photo.  Rotula deciesdigitata. 

The unit of currency in the Republic of São Tomé and Prìncipe is the Dobra; there are about 15,000 of ‘em to the US dollar.  Here is a photo of a bunch of dobras drying on my bed at Bom Bom Island on Principe.  Why? Well, the wonderful folks at Bombom Island and SCD allowed us to attempt to survey by boat the otherwise inaccessible southwest shore of Prìncipe; at a critical point, too many of us climbed into a small red dinghy and flipped in the surf.  Along with the dobras went a lot of equipment including cameras, my cell phone, ipod, etc.—more on this in another posting.

  

Drying dobras  RCD GGIII

 

The offending boat, post-flipping.  Weckerphoto GG III 

Anyway, once we finally found specimens of Rich’s Rotula, it was only natural that they become “sand dobras,” and the only beach we have found them on the west side of Sao Tome became Sand Dobra Beach– its real name is Praia Morrão.

 

Rotula deciesdigitata on Sand Dobra Beach.  D. Lin phot. GG II 

During GG II, Rich and I swam out beyond the surf line to try to secure a live specimen for DNA analysis (remember, the test you find on the beach is not the living animal, but rather its exoskeleton).  The undertow was so powerful that we both nearly drowned, but we did find one specimen that retained a greenish color, suggesting that there might be some remaining tissue to analyze; the jury is still out on this. The sand dobras present a rather interesting mystery, in that they appear to be wholly unrelated to those of the New World, while such might not be the case with other echinoderms. In his own words, Rich says “this strange pattern is further underscored by the fact that as I looked at all the other echinoderms around Sao Tome, the faunas were nearly perfectly Caribbean in nature.  There were times that I felt as though I was snorkeling around in Florida or Belize — at least as far as the sea urchins were concerned.  The rotulids were a glaring exception to that.”

Rich working.  D. Lin phot. GG II.   

Interestingly, there are many species with holes and notches in them throughout the Caribbean.  These are almost all members of a sand dollar family known as the Mellitidae. However, there are absolutely no mellitids on the west coast of Africa.  In fact, there are no “true” sand dollars at all.  The truth is that the Gulf of Guinea sand dobras are not even closely related to the Caribbean sand dollars, but belong not only to a different family (Rotulidae), but to a completely different major clade (suborder). This is perplexing. 

 

Rotula deciesdigitata on Sand Dobra Beach. Weckerphoto  GG III 

Dr. Rich Mooi is still working on the many fascinating echinoderms he collected on the beaches and tidepools of  São Tomé and Prìncipe in 2006, and I will report his discoveries as they appear.     

PARTNERS

 

We gratefully acknowledge the support of the Research Investment Fund of the California Academy of Sciences, the Société de Conservation et Développement  (SCD) for logistics, ground transportation and lodging, STePUP of Sao Tome http://www.stepup.st/ and especially the generosity of three private individuals, George F. Breed, Gerry F. Ohrstrom and Timothy M. Muller, for making GG III possible.

 


Filed under: Gulf of Guinea — bob @ 10:18 am
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