The Race: The Blog Returns with a Science Update

“The Race” has been silent for a while; a sabbatical accompanied by computer glitches at both sites (Wildlifedirect.org; calacademy.org) led to it, but this was not meant to signal a pause in our island work by any means! We will be returning to the islands for two more expeditions later this year.

During the past nine months or so, some important scientific papers have been published by expedition members; these continue to illustrate the unique nature of the island fauna and flora.

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Ricka Stoelting (D. Lin phot, GGI)

Ricka Stoelting was on the islands for a solid two months during GG I in 2001. The research she did on the unique Sâo Tomé caecilian was the basis for her MSc degree, and this has just been published; this paper is the first on the population genetics of a caecilian species,  and she has shed light on a number of issues involving this strange Sâo Tomé endemic.

Schisto

(left) Cobra bobo, Schistometopum thomense (A. Stanbridge phot. GG VII); (right) from Stoelting, et al., 2014, PLoS One.

Ricka discovered that there are four distinct populations of the cobra bobo that are genetically different from each other – not different enough to be considered separate species, but different enough to suggest that these populations were isolated from each other in the distant past (recall that evolution is genetic change accumulated in isolation over time). She also found that these different populations were probably separated from each other through major geological changes in the environment. Note (above right) that the western populations (green) and northern populations (red) are associated with volcanic landscapes less than 1 million years old, while the southern populations (blue) are associated with older volcanic soils of about 2.5 million years in age. This suggests that the formerly widespread caecilian species was wiped out to the north by volcanism about 1 million years ago, then later repopulated from the surviving southern population. The yellow population is very young, perhaps only about 36 thousand years. Currently Ricka is pursuing a PhD at the University of Wisconsin.

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Dr. Ricardo Lima with caecilian, Schistometopum thomense. (R. Ayres phot. GG. IV)

While on the subject of the endemic Sâo Tomé caecilian, I can report that our colleague, Dr. Ricardo Lima (above), just found three  caecilians while climbing the Pico de Sâo Tomé, and one of these establishes an altitude record for this strange worm-like amphibian species at 1504 meters (4,600+ feet).

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Dr. Rayna Bell on Sao Tome.  (A. Stanbridge phot, GG VI)

Last September, Rayna Bell, a participant on both GG VI and GG VII expeditions, completed her PhD degree at Cornell University; her doctorate was based on her work on the Hyperolius tree frogs of the islands, and the first part of it has just been published.

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(left) after Bell, R.C. et al. 2014. Journal of Biogeography. (right). Nearest mainland relative of island Hyperolius tree frogs. (RDC phot)

We knew from earlier work that the two tree frogs of Sâo Tomé were each other’s nearest relatives.  But where did they come from originally?  Dr. Bell’s research indicates that the nearest relative of both the endemic oceanic treefrog and the Sâo Tomé Giant treefrog is a member of a large group of species in West Africa, Hyperolius cinnamomeoventris (above right); in particular, a subset of this group she terms “clade A,” (indicated by green stars above left) appears to share joint ancestry with the island species.

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Hypothesized large “riverbank” raft.  (artwork by R.E.Cook)

Her research suggests that the common ancestor of the island treefrogs reached Sâo Tomé first, in a single colonization event, probably by rafting (above). This event likely occurred between 9 and 3.5 million years ago, and the original colonists probably originated from the Ogooué or Congo Rivers. On Sâo Tomé, these original “pioneers” differentiated into a giant highland form (now H. thomensis) and a smaller lowland species. Then, between 1.1 million and 270 thousand years ago, members of the lower elevation species, the oceanic treefrog, Hyperolius molleri dispersed to the much older island of Príncipe, where they again became isolated from the parent population on Sâo Tomé and began to accumulate genetic change (“speciation”). A second scientific paper by Dr. Bell on these species and their evolution on the Gulf of Guinea Islands is due out soon.

The status of the Sâo Tomé shrew (Crocidura thomensis) has been somewhat problematic, for scientists at least. Shrews are very poor overwater dispersers, and since it is possible for the shrew to have been transported from the mainland by man fairly recently, there have been questions about its validity as a true endemic species. Did it reach Sâo Tomé by natural means?  This strange insectivore was recorded only nine times after its original description in 1887 and until recently, it has also been considered quite rare. (Someone should have asked the locals!)

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The Sâo Tomé  shrew (phot. Dr. Mariana Carvalho).  (left) Dr. Ricardo F. de Lima.

In a recent publication, (below) our colleague, Dr. Ricardo Lima has added twenty-three new locality records for this fascinating creature, indicating that it is not rare. It has just been overlooked. An excellent ecologist, de Lima has assessed the conservation status of this important species.  Moreover, he and his colleagues have provided tissue so that we have been able to examine its DNA to determine whether or not it arrived on the island by natural means or was more recently brought by man. It appears to be a true endemic species (to be reported in a future publication), and as such it is the only non-flying endemic mammal species on the island of Sâo Tomé.

de Lima et al
From de Lima, R.F., et al]. 2015 Fauna & Flora International. Oryx. Grey dots denote localities known in 1996. Black dots are new localities.

During GG II (2006), we collected two shrew new-borns on the island of Príncipe which at the time we assumed were a mainland species, Crocidura poensis. Dr. Luis Ceriaco, who is now an adjunct member of our CAS faculty, subsequently obtained many more adult individuals on the island (it is much more common than C. thomensis) and surprisingly this species is also new and endemic.

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From Ceriaco, et al. 2015. Mammalia

Dr. Ceriaco has just formally described it as Crocidura fingui, its name in the local Creole. So the only non-flying endemic mammals in the Republic of Sâo Tomé and Príncipe are shrews! I do not think any biogeographer would have predicted this (see August 2010 blog: the “Magic of Molecules).

Here’s the parting shot:

sand dollar
Rotula deciesdigitatus, one of the rarest sand dollars in the world; in the islands, known principally from Praia Morrao, west coast of Sao Tome. (Weckerphoto, GG III)
PARTNERS

We are most grateful to Arlindo de Ceita Carvalho, Director General, Victor Bomfim, and Salvador Sousa Pontes of the Ministry of Environment, Republic of São Tomé and Príncipe for their continuing authorization to collect and export specimens for study, and to Ned Seligman, Roberta dos Santos and Quintino Quade of STePUP of Sao Tomehttp://www.stepup.st/, our “home away from home”. We gratefully acknowledge the support of the G. Lindsay Field Research Fund, Hagey Research Venture Fund of the California Academy of Sciences for largely funding our initial two expeditions (GG I, II). The Société de Conservation et Développement (SCD) and Africa’s Eden provided logistics, ground transportation and lodging (GG III-V), and special thanks for the generosity of private individuals who made the GG III-VII expeditions possible: George G. Breed, Gerry F. Ohrstrom, Timothy M. Muller, Mrs. W. H. V. Brooke, Mr. and Mrs. Michael Murakami, Hon. Richard C. Livermore, Prof. & Mrs. Evan C. Evans III, Mr. and Mrs. Robert M. Taylor, Velma and Michael Schnoll, and Sheila Farr Nielsen; GG VI supporters include Bom Bom Island and the Omali Lodge for logistics and lodging, The Herbst Foundation, The “Blackhawk Gang,” the Docent Council of the California Academy of Sciences in honor of Kathleen Lilienthal, Bernard S. Schulte, Corinne W. Abel, Prof. & Mrs. Evan C. Evans III, Mr. and Mrs. John Sears, John S. Livermore and Elton Welke. GG VIII was funded by a very generous grant from The William K. Bowes Jr. Foundation, and substantial donations from Mrs. W.H.V.“D.A.” Brooke, Thomas B. Livermore, Rod C. M. Hall, Timothy M. Muller, Prof. and Mrs. Evan C. Evans, Mr. and Mrs. John L. Sullivan Jr., Clarence G. Donahue, Mr. and Mrs. John Sears, and a heartening number of “Coolies”, “Blackhawk Gang” returnees and members of the Academy Docent Council. Once again we are deeply grateful for the support of the Omali Lodge (São Tomé) and Bom Bom Island (Príncipe) for both logistics and lodging and for partially sponsoring part our education efforts for GG VII and GG VIII.

Our expeditions can be supported by tax-deductable donations to “California Academy of Sciences Gulf of Guinea Fund”

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