Changes to Gulf of Guinea endemics (1 Viewer)

[Xenospiza]

One of the generally very interesting talks at the African Bird Club meeting yesterday was by Martim Melo and dealt with the birds of São Tomé and Príncipe.
Not only are they the home to a lot of endemics for such a small place, they also host a number of birds with up till now uncertain relationships. However, much of these have been unravelled, with some huge surprises!

(1) The small kingfishers should both be treated as subspecies of Alcedo cristata, Malachite Kingfisher, with nais (Príncipe) the most distinct.
(2) Amaurocichla bocagii, Bocage’s Longbill or São Tomé Short-tail: this is a pipit! Will have to be renamed to Anthus bocagii (and São Tomé Pipit?)
(3) Horizorhinus dohrni, Dohrn's Thrush-babbler: closely related to the hill-babblers (Pseudoalcippe) of the African mountains. The genus may not be retained.
(4) The genus Speirops (melanocephalus, Cameroon, brunneus, Fernando Po, leucophoeus, Príncipe and lugubris, Black-capped Speirops) is polyphyletic and should be lumped with Zosterops.
melanocephalus and brunneus belong to a “mainland clade” related to Z. stenocricotus (split from senegalensis?). The other two are in an “oceanic clade” related to the “normal-looking white-eyes” of São Tomé, Príncipe and Annobón. Moreover, Zosterops feae, São Tomé White-eye should be split from Z. ficedulinus, Príncipe White-eye. This leaves the latter, which is dependent on primary forest, as a highly threatened taxon (feae is common).
(5) The three sunbirds are not related to each other, but to three different mainland lineages. The present treatment of sunbirds with many genera is nonsense anyway according to genetics... but there will be no endemic genus left once all has been resolved.
(6) Turdus olivaceofuscus, Gulf of Guinea Thrush should be split into two island endemics, which means the primary forest dwelling T. xanthorhynchus, Príncipe Thrush is highly endangered. The form on São Tomé should be called São Tomé Thrush of course.
(7) The weavers should all stay in Ploceus. Genetics have shown that the curious São Tomé Weaver (sometimes called Thomasophantes sanctithomae) is related to Anaplectes rubriceps, Red-headed Weaver: this genus should be lumped into Ploceus.
(8) Last, but not least the seedeaters. The enigmatic Neospiza concolor, São Tomé Grosbeak (now easier to find since its favourite food plant is known) turned out to be the largest canary in the world (in good company with the largest sunbird, oriole and weaver). It is more closely related to Serinus rufobrunneus thomensis, “São Tomé Seedeater” than this “subspecies” is to the nominate Serinus r. rufobrunneus, Príncipe Seedeater. Obviously, this requires another split! S. rufobrunneus fradei living on Boné do Jóquei (a rock off Príncipe’s coast) is already genetically distinct (although very moderately), with no evidence of mixing with its neighbours across the water.
More interesting perhaps is that these relationships seem to indicate that the São Tomé Grosbeak and São Tomé Seedeater evolved sympatrically from a common ancestor (good news for people who study crossbills).

 

[jurek]

Wow, amazing. By any chance, some obscure warbler turns to be overlooked mokele-mbembe?

 

[Xenospiza]

Wow, amazing. By any chance, some obscure warbler turns to be overlooked mokele-mbembe?

Despite São Tomé being the only oceanic island with a caecilian, that's still a far cry from a mokele-mbembe... not enough swamps anyway!

But talking about mythical creatures:
There is an undiscovered scops owl on Príncipe (according to parrot collectors and sound recordings (frog not excluded)).
A rather large-bodied “Madeiran” Storm-Petrel population must breed somewhere in the Gulf of Guinea area.

 

[jurek]

Interesting!

I was surprised how many taxonomic changes there were. There must be quite a few unrecognized and mis-assigned species all over Africa!

 

[Jacana]

Despite São Tomé being the only oceanic island with a caecilian

just to split hairs... there are several around 10 i think species of caecilian in the Seychelles one of which is the smallest in the world. the Sao Tome species is rather spectactular, bright orange!

anyway back to the birds

 

[Xenospiza]

Just shows you how much I know about caecilians!

 

[l_raty]

More interesting perhaps is that these relationships seem to indicate that the São Tomé Grosbeak and São Tomé Seedeater evolved sympatrically from a common ancestor (good news for people who study crossbills).

Surely interesting, but knowing it happened is not going to solve the problems associated to sympatric speciation (and the taxonomy of crossbills ). These problems lie, partly at least, at a completely different level. A.o.:

- Sympatric speciation is logically incompatible with the taxonomic system.
Taxonomy works with a system of increasingly inclusive grouping levels, in which populations are by definition less inclusive than species. In a sympatric speciation process, a population (less inclusive) splits into two species (more inclusive). This simply cannot work.

- Sympatric speciation is logically incompatible with the Biological Species Concept.
In a classic allopatric speciation process, the progressive accumulation of differences in two allopatric populations finally results in two reproductively isolated species. A sympatric speciation process is the exact opposite: a population evolves into two distinct morphotypes, typically in answer to disruptive selection (selection against the "average" phenotype); these morphotypes must cease to interbreed - this is a sine qua non condition: if not, they will never evolve into more distinct entities; at this stage, in models at least, these morphotypes do not need to show any sort of genetic divergence other than quantitative; at this stage, reproductive isolation will typically still be under the control of extrinsic (environmental) factors - change these factors, the barriers could break down very easily. From this point on, the morphotypes will start following divergent evolutionary paths, and accumulate qualitative differences. Effective reproductive isolation is the final outcome of an allopatric speciation process, but it is only the starting point of a sympatric speciation process. The BSC assumes "speciation = reproductive isolation". This concept is intrinsically rooted in the assumption that speciation must be allopatric, and becomes completely flawed if applied to sympatric speciation.

(In fact, I've long been wondering to which extent the "classic" rejection of the sympatric speciation hypothesis had not always been a consequence of it being hardly compatible with widely accepted taxonomic concepts...)

 

[njlarsen]

- Sympatric speciation is logically incompatible with the taxonomic system.
Taxonomy works with a system of increasingly inclusive grouping levels, in which populations are by definition less inclusive than species. In a sympatric speciation process, a population (less inclusive) splits into two species (more inclusive). This simply cannot work.

I am not a scholar on this, but it seems to me your presentation omits a step:
In a sympatric speciation process, a population (less inclusive) splits into two populations which then becomes two species (more inclusive).

This may seem like splitting hairs, but elevation or use of different foods in a species which only mate on the food plant could be two ways of making the splitting of population into two take place, before the actual specieation takes place; on the other hand this makes the species effectively allopatric even if it only happens on a micro scale.

Niels

 

[ntbirdman]

Xenospiza - I'm only marginally familiar with Sao Tome endemics (and the African avifauna in general) but those results sound pretty cool! I'll need to look up some of those species. Is this work published or in progress?

l_raty, I'm very confused by your objections to sympatric speciation.

- Sympatric speciation is logically incompatible with the taxonomic system.
Taxonomy works with a system of increasingly inclusive grouping levels, in which populations are by definition less inclusive than species. In a sympatric speciation process, a population (less inclusive) splits into two species (more inclusive). This simply cannot work.

If I follow this correctly, then by logic no new species can arise by any process? Because new species arise when populations change - whether they are sympatric or allopatric.

- Sympatric speciation is logically incompatible with the Biological Species Concept.
In a classic allopatric speciation process, the progressive accumulation of differences in two allopatric populations finally results in two reproductively isolated species. A sympatric speciation process is the exact opposite: a population evolves into two distinct morphotypes, typically in answer to disruptive selection (selection against the "average" phenotype); these morphotypes must cease to interbreed - this is a sine qua non condition: if not, they will never evolve into more distinct entities; at this stage, in models at least, these morphotypes do not need to show any sort of genetic divergence other than quantitative; at this stage, reproductive isolation will typically still be under the control of extrinsic (environmental) factors - change these factors, the barriers could break down very easily. From this point on, the morphotypes will start following divergent evolutionary paths, and accumulate qualitative differences. Effective reproductive isolation is the final outcome of an allopatric speciation process, but it is only the starting point of a sympatric speciation process. The BSC assumes "speciation = reproductive isolation". This concept is intrinsically rooted in the assumption that speciation must be allopatric, and becomes completely flawed if applied to sympatric speciation.

This is incredibly perplexing to me. I've never heard of sympatric speciation being against the BSC. The BSC assumes "speciation = reproductive isolation", yes, but does not assume the timing of the various barriers to gene flow. Populations can diverge in the face of gene flow and then evolve barriers to gene flow. I simply don't see how this scenario invalidates the BSC.

I'm not really arguing for sympatric speciation, I think there is little evidence for it except for a few limited cases, but I think your rejections of it are quite confused. Feel free to elaborate.

Cheers,
Nick

 

[Xenospiza]

Xenospiza - I'm only marginally familiar with Sao Tome endemics (and the African avifauna in general) but those results sound pretty cool! I'll need to look up some of those species. Is this work published or in progress?

Some of it has been published (like the work on ‘Speirops’), but a lot is in progress.

 

[l_raty]

I'm not really arguing for sympatric speciation, I think there is little evidence for it except for a few limited cases, but I think your rejections of it are quite confused. Feel free to elaborate.

No rejection on my side - at least, not of the involved processes. (I'm not rejecting ring speciation either, yet this also cannot be handled correctly by taxonomy, and whether it represents speciation or not is also open to discussion.)

One problem with sympatric speciation is that it has the potential to be local with respect to the mother species - it could happen within a subpart of this species only, and if there are other populations of the mother species elsewhere that remain untouched, their classification will unavoidably become problematic. (Creating, for example, situations in which we could be "forced" to elevate two subspecies to species level, just because of something that happened to a third one...) This is quite different from a global process that splits a whole species in two (or more) units, that will then make their way up the whole hierarchy of differentiation. But of course this doesn't make the process impossible - just difficult to represent in the taxonomic system.

About the BSC and to take things from another angle: The ultimate test of speciation under the BSC is persistence in sympatry. But if the entire process of differentiation can happen in sympatry, then we cannot continue to assume that this is an unambiguous indication of a deep divergence. Instead, we must expect that among the organisms that persist in sympatry, some will be at a very early stage of differentiation - potentially less differentiated than allopatric taxa we would at best treat as subspecies; potentially not far enough in the process to make its irreversibility even remotely certain.

For an example of a model of ecological sympatric speciation, you can see: http://www.iiasa.ac.at/~dieckman/reprints/DieckmannDoebeli1999.pdf
The individuals in this model (and the resulting sympatric "species") differ only by a quantitative character, that must have a potential of heritable variation, and must determine and limit the part of the resources each individual will be able to use efficiently ("as for example when beak size in birds determines the size of seeds consumed"). The available resources must also present a range of variation broad enough that individuals using the opposite extremes will not be in competition anymore. Under these conditions, frequency-dependent competition is expected to induce an evolutionary branching - the expected outcome is two distinct morphs exploiting the opposite ends of the resources. The transition from one to two morphs can be fast if mating probabilities are directly linked to the ecological character (see Fig 3a). Nothing qualitatively "new" arises during this process - it's all just a game of allele frequencies; the potential of giving rise to a population similar to each of the morphs was already entirely present in the mother population.
Of course it's only a model. But if this type of thing can happen, I would not really feel comfortable calling the two resulting morphs "species" at this point of their evolution. Even if they don't interbreed.
--
Best,
Laurent -

 

[jurek]

Well, in case of Gulf of Guinea - you can never say these birds appeared in historic times, when e.g. lower sea levels created two isolated habitats, or come from two colonizations of one extinct mainland species...

 

[thyoloalethe]

The news that Amaurocichla is a pipit is a stunner - I presume it is embedded within Anthus?

On the other hand I was expecting Speirops to end up not being related to Zosterops, so the fact that they are (sort-of) where they are supposed to be is also a bit of a surprise. Now I'm hoping someone will do some work on some of the other oddball genera in the Zosteropidae from Indonesia (Madanga, Tephrozosterops, Heleia, etc.) - maybe they really are white-eyes after all?

 

[Richard Klim]

Príncipe Thrush

One of the generally very interesting talks at the African Bird Club meeting yesterday was by Martim Melo and dealt with the birds of São Tomé and Príncipe...
Turdus olivaceofuscus, Gulf of Guinea Thrush should be split into two island endemics, which means the primary forest dwelling T. xanthorhynchus, Príncipe Thrush is highly endangered. The form on São Tomé should be called São Tomé Thrush of course.

Melo, Bowie, Voelker, Dallimer, Collar & Jones 2010. Multiple lines of evidence support the recognition of a very rare bird species: the Príncipe thrush. J Zool: in press.
http://www3.interscience.wiley.com/journal/123533850/abstract

[Already recognised by IOC following Sinclair & Ryan 2003.]

Richard

 

[Richard Klim]

Príncipe Thrush

Dallimer, Melo, Collar & Jones 2010. The Príncipe Thrush Turdus xanthorhynchus: a newly split, 'Critically Endangered', forest flagship species. Bird Cons Int: in press.
http://journals.cambridge.org/actio...2429&fulltextType=RA&fileId=S0959270910000390

Richard

 

[Peter Kovalik]

Anaplectes

(7) The weavers should all stay in Ploceus. Genetics have shown that the curious São Tomé Weaver (sometimes called Thomasophantes sanctithomae) is related to Anaplectes rubriceps, Red-headed Weaver: this genus should be lumped into Ploceus.

See also Lahti's provisional molecular phylogeny of Ploceidae:
http://qcpages.qc.edu/Biology/Lahti/Research/Weavers.html

 

[Richard Klim]

Príncipe Thrush

Melo, Bowie, Voelker, Dallimer, Collar & Jones 2010. Multiple lines of evidence support the recognition of a very rare bird species: the Príncipe thrush. J Zool: in press.

J Zool 282(2): 120–129. [pdf]

Dallimer, Melo, Collar & Jones 2010. The Príncipe Thrush Turdus xanthorhynchus: a newly split, 'Critically Endangered', forest flagship species. Bird Cons Int: in press.

BCI 20: 375–381. [pdf]

 

[Mohamed Amezian]

Undiscovered scops owl on Príncipe?

There is an undiscovered scops owl on Príncipe (according to parrot collectors and sound recordings (frog not excluded)).

Martim Melo in Rapinas nocturnas (Sep, 2014): O mistério nocturno das remotas florestas da Ilha do Príncipe.

"The mysterious nocturnal in the remote forests of the Príncipe island".

 

[Richard Klim]

Annobón Scops Owl

Also relevant to this thread: www.birdforum.net/showpost.php?p=2989994&postcount=229.

 

[jurek]

Martim Melo in Rapinas nocturnas (Sep, 2014): O mistério nocturno das remotas florestas da Ilha do Príncipe.

"The mysterious nocturnal in the remote forests of the Príncipe island".

During my short visit in Principe in 2013 we heard similar sound at dusk in the forest along the road going to Bom Bom resort. It it turned to be the local Glossy Starling which makes varied calls. At sunset it made similar series of short hooting sounds, not connected to its typical babble.

BTW, at night on Sao Tome we heard several weird, high-pitched "kra-ka-kra-ka" sounds coming from the forest canopy, and wondered if it were frogs or maybe some birds (Madeiran Storm-Petrel?). I think frogs were more probable.