Scientists estimates there are 8.7 million living species worldwide, from which some 86% have yet to be fully described. Many of the unknown animal species are believed to be small invertebrates, like some spiders and insects. Otherwise, big mammals species – we might think – are very well described and studied… There would not be much left to know, right? Well, nature always keeps its surprises to make us look again on what we think we know. Recently, Julian Fennessy and his group found that the only recognized species of giraffe is, in reality, four different species.
Giraffes are the tallest known mammal and they were described by the Swedish taxonomist Carl Linnaeus, in 1758. Nevertheless, Linnaeus had never seen a giraffe and he referred to 200-year-old descriptions. Later, new descriptions of other giraffe subspecies were based on variable and taxonomically unreliable morphological traits, such as coat markings, ossicones (the horn-like protuberance on giraffe’s head), and geographic distribution. One giraffe species and nine subspecies are commonly accepted. Even after a century of research, the distinctness of each giraffe subspecies was still unclear and some scientists believed there were up to eleven subspecies.
But what is a species at first? For years, all kind of taxonomic classifications, species definition included, were based on morphological characteristics and geographic distribution. You can imagine that this method could bring a great number of doubts and discussions, for instance: how marked differences should be to differentiate two or more species?. Genetic analysis aims to make this work less complicated – which doesn’t mean it’s easy and clear now. In the new study, Fennessy and his team examined DNA evidence taken from skin biopsies of 190 giraffes. They found that genetic differences suggest there are at least 4 distinct groups of giraffe, which apparently do not mate with each other in the wild, what would characterize 4 distinct species.
The four species they suggest to be recognized are: (1) southern giraffe (Giraffa giraffa), comprising two distinct subspecies: Angolan giraffe (G. g. angolensis) and South African giraffe (G. g. giraffa); (2) Masai giraffe (G. tippelskirchi); (3) reticulated giraffe (G. reticulata); and (4) northern giraffe (G. camelopardalis), which includes Nubian giraffe (G. c. camelopardalis), Kordofan giraffe (G. c. antiquorum) and West African giraffe (G. c. peralta) as distinct subspecies.
Figure 1. Four giraffe species. (Fennessy et al. Current Biology (2016))
Research authors highlight that the lack of gene flow between groups is unexpected, because wild giraffes are highly mobile and can interbreed in captivity. However, the genetic differentiation between the four giraffe groups is strong. For comparison, differences among giraffe species are as great as those between polar and brown bear
Figure 2. Species distribution and Sampling Locations (Fennessy et al. Current Biology (2016))
This new information has important implications for conservation, since giraffes’ populations are in dramatic decline across their range in Africa. Giraffe population numbers are threatened due to human population’s activities, like increasing land for agricultural needs. Also, in some regions of Namibia, there is illegal hunting or poaching collaborating to the decline. Over the last three decades, the number of giraffe individuals has dropped from 150,000 to fewer than 100,000. Now that we know they are not a single species, the conservation status of each of the 4 species can be better defined – and we can predict that at least some (if not all) of them are in serious trouble. Authors of the research said: “northern giraffe number less than 4,750 individuals in the wild, and reticulated giraffe number less than 8,700 individuals — as distinct species, it makes them some of the most endangered large mammals in the world and require doubling of protection efforts to secure these populations”.
Bruna de Oliveira Cassettari