How many species of giraffe are there in Africa? David M. Brown 1 and Nicholas J. Georgiadis 2

1. Masai (tippelskirchi) Southern Africa capensis+angolensis Reticulated (reticulata) Western Africa peralta+rothschildi Population clusters of composite microsatellite genotypes How many species of giraffe are there in Africa? David M. Brown1 and Nicholas J. Georgiadis2 1. University of California, Los Angeles; 2. Mpala Research Centre • RATIONALE • The genus Giraffa in Africais comprised of phenotypically distinct groups, currently classified as nine ‘subspecies’. • • Are the different groups reproductively isolated, and perhaps different species? • • Or do the different groups interbreed, and will their distinctiveness disappear over time? • • Arguments have surrounded these questions for over 100 years. • • The different giraffe groups have hybridized in captivity. • • What does this variation mean in evolutionary terms? • What are the evolutionary dynamics of giraffes in the wild? Nuclear DNA: THE GENETIC HISTORY OF POPULATIONS AND SPECIES Masai (tippelskirchi) giraffes have a unique SNP (single nucleotide polymorphism) in the FES intron sequence, distinguishing them from all others. APPROACH We examined genetic variation in the mitochondrial and nuclear genomes of free-ranging individual giraffes from six taxonomic giraffe subspecies. We are tested whether the giraffe subspecies: • Are genetically isolated from each other: Is genetic isolation recent or deep in evolutionary time? • Are hybridizing with each other: Is hybridization rare or common? • Biopsy-dart samples were collected from 397 free-ranging individual giraffes representing six subspecies: * Giraffa camelopardalis peralta (W) from Niger * G.c. rothschildi (N) from Uganda and Western Kenya * G.c. reticulata (R) from Kenya * G.c. tippelskirchi (M) from Kenya and Tanzania * G.c. angolensis (S) from Namibia * G.c. capensis (S) from South Africa • Fig. 3. FES: cladogram of single-copy nuclear intron sequences, representing: • * peralta (W) N=5 • * rothschildi (N) N=10 • * reticulata (R) N=14 • * tippelskirchi (M) N=27 • * capensis (S) N=10 • * angolensis (S) N=11 • Microsatellites: hypervariable sections of DNA • *17 different microsatellite markers • *397 individual giraffes from six taxonomic groups: • * peralta (W) N=28 * tippelskirchi (M) N=142 • * rothschildi (N) N=81 * capensis (S) N=27 • * reticulata (R) N=80 *angolensis (S) N=38 • Mitochondrial DNA: MATERNAL HISTORY • Mitochondrial DNA is maternally inherited and does not capture the genetic history of males in a species. • 656 nucleotide fragment starting in cytochrome b extending through tRNAs to control region. • Okapi was used as the ‘outgroup’ for reconstruction of the phylogenetic tree. • There were 37 unique mtDNA sequences (haplotypes) found in 266 individuals. • CONCLUSIONS • Mitochondrial DNA • • Each of the sampled groups has a unique set of haplotypes (Reticulated, Rothschilds, Peralta, Masai, • Angolensis, Capensis). • • Exceptions to monophyly may be due to retention of ancestral polymorphism, or hybridization at range • boundaries, for example, between tippelskirchi females and reticulata males in the Athi Plains region. • Since there is no evidence for nuclear DNA hybridization between them, it is likely that recurrent backcrossing • of hybrid females to tippelskirchi males replaced the reticulata genome in hybrid individuals over many • generations. • Nuclear DNA: Microsatellites • • Microsatellite genotypes cluster into 4 major nuclear DNA pools: Reticulated, Rothschilds + Peralta, Masai, • Angolensis + Capensis • Each gene pool is equivalent of a monophyletic group (no interbreeding between them) • • Some evolutionary force has kept reticulata and tippleskirchi reproductively isolated from each other: • *Ecological selection for climate or some other factor? • *Sexual selection? • The population genetic structure of giraffes in the wild conflicts with the currently held classification of ‘9 • subspecies’. • There are at least four distinct groups of giraffes that, based on genetic evidence, appear to be reproductively • isolated from each other in the wild. • • These groups may correspond with different species of giraffe. • Table 1. Distribution of mtDNA haplotypes by sampling location • peralta (W) N=22; rothschildi (N) N=51; reticulata (R) N=63; • tippelskirchi (M) N=83; capensis (S) N=12, angolensis (S) N=35 • Each taxonomic subspecies has a unique set of mtDNA haplotypes • No haplotypes were shared between groups • Fig. 2. (right) Phylogenetic tree of mitochondrial haplotypes • Each group is monophyletic with exception of one Masai • haplotype grouping with reticulated giraffes. • In general, giraffes of different morphotypes are not • interbreeding in the wild.