Saturday, 12 July 2014

Forest Buffalo in the Republic of Congo. What Species Is That?

As a detached but interested outsider looking in on the world of taxonomy and systematics, I have been kept entertained by the arguments and battles between parties and concepts that have raged over the decades. When looking over Lango Bai in the Republic of Congo in May, all these arguments coalesced into one thought: what species are these, referring of course to the Forest Elephant and the Forest Buffalo? I considered the Forest Elephant in my earlier post (16 June with video showing these two species). More recently, I have been looking up what the current thoughts are on the status of Forest Buffalo, a very different looking animal from its savanna counterpart.

From our all too brief observations in the Congo, the name Forest Buffalo seems inappropriate. They were all in the patches of savanna that characterise this region or in the bai. Indeed, work in the Central African Republic on their local distribution found them to be ‘highly dependent on clearings, as well as on the more open forest stands, characterised by large trees and open canopy’.

I always start to twitch when I read that the Forest Buffalo is a subspecies of Syncerus caffer. I hate the use of subspecies as a concept and regard it as an example of the past muddleheadedness of people who cannot bear uncertainty. However, that is not to say that geographical variation is not important nor that conservation measures based on geographical populations are not worthwhile.

The standard treatment of African buffalo is to treat the Forest form as a subspecies of S. caffer, S.c. nanus. In early years, the mammalian morphologists had it split as a separate species whereas mammalian taxonomists of the last century tended to be lumpers. Across Africa, the view was taken that these populations were freely inbreeding and, therefore, the same species.

The late Peter Grubb and his co-author Colin Groves took a different approach. They adopted the phylogenetic species concept to examine African ungulates. This species concept can be summed up informally as: if it looks markedly different then it is different. Applying this species concept and using quantitative morphometric data, they found a clear grounds for separating Syncerus nanus, now a full species, from Syncerus caffer. Such revisions brought howls of protest from some quarters on the grounds that conservation measures would be more difficult to apply with so many more species split on similar grounds. That argument, to me, is worthless: conservation policies must be informed by the science however uncomfortable that may be for practitioners and fundraisers of the former; scientific hypotheses guided by conservation politics are not science at all. They published their results in a book, Ungulate Taxonomy, published in 2011, nearly five years after Peter Grubb’s death.

I greatly enjoyed reading Groves and Grubb’s chapter, Theory of Ungulate Taxonomy since it neatly speared many of the trendy pursuits such as gathering DNA data, explained simply the problems in applying the biological species concept and discussed whether phenotypic plasticity can explain morphometric differences. In their criticism of using only mitochondrial DNA to provide “molecular evidence” they relate the story of sika and wapiti deer. I had not heard it and so I repeat it here:

The third reason is, of course, introgression. Hybridization between two species is frequently asymmetrical. This idea was put forth more than half a century ago by Flerov, who described hybrids between sika and wapiti in N China and the Russian Far East: “These hybrids are encountered comparatively frequently in the wild state and have been long known to the Chinese. The male wapiti during rutting drives away the weaker spotted deer male and covers his females. If this superiority of wapiti stags also applied in F1 and subsequent generations—as it well might since the size of the hinds would increase in consecutive backcross generations, and they would become accessible only to wapiti stags—then the proportion of sika DNA would halve in each successive generation, until we would end up with populations that were effectively wapiti but with sika mtDNA. This effect, known as nuclear swamping, seems widespread along ruminants…”.

So what is the available “molecular evidence” on the Forest Buffalo? Well there is some but as far as I can see it is all on mtDNA. I have read it but until nDNA results are reported I shall not consider it further here.

My guess at the moment is that Groves and Grubb are right and that it will be shown that the Forest Buffalo, S. nanus, is a ‘good’ species with a hybrid zone around it.

However, the physiologist then takes over. How many genes are responsible for the morphological differences between the two species and how—and when—do the products of those genes exert their effects?

Groves C, Grubb P. 2011. Ungulate Taxonomy. Baltimore: Johns Hopkins University Press.
Melletti M, Penteriani V, Boitani L. 2007. Habitat preferences of the secretive forest buffalo (Syncerus caffer nanus) in Central Africa. Journal of Zoology 271 178-186.