Is Colobus guereza gallarum a valid endemic Ethiopian taxon?

Abstract

Abstract. Black-and-white colobus (Colobus guereza Rüppell, 1835) are arboreal Old World monkeys inhabiting large parts of the deciduous and evergreen forests of sub-Saharan Africa. Two of the eight subspecies of Colobus guereza are endemic to Ethiopia: C. g. gallarum and C. g. guereza. However, the validity of the Ethiopian taxa is debated and observed morphological differences were attributed to clinal variation within C. g. guereza. To date, no molecular phylogeny of the Ethiopian guerezas is available to facilitate their taxonomic classification. We used mitochondrial DNA markers from 94 samples collected across Ethiopia to reconstruct a phylogeny of respective mitochondrial lineages. In our phylogenetic reconstruction, augmented by orthologous sequence information of non-Ethiopian black-and-white colobus from GenBank, we found two major Ethiopian mitochondrial clades, with one being largely congruent with the distribution of C. g. guereza. The second clade was found only at two locations in the eastern part of the putative range of C. g. gallarum. This second lineage clustered with the lowland form, C. g. occidentalis, from central Africa, whereas the C. g. guereza lineages clustered with C. g. caudatus and C. g. kikuyuensis from Kenya and northern Tanzania. These two guereza lineages diverged around 0.7 million years ago. In addition, mitochondrial sequence information does not support unequivocally a distinction of C. g. caudatus and C. g. kikuyuensis. Our findings indicate a previous biogeographic connection between the ranges of C. g. occidentalis and C. g. gallarum and a possible secondary invasion of Ethiopia by members of the C. g. guereza–C. g. caudatus–C. g. kikuyuensis clade. Given these phylogenetic relationships, our study supports the two-taxa hypothesis, making C. g. gallarum an Ethiopian endemic, and, in combination with the taxon's very restricted range, makes it one of the most endangered subspecies of black-and-white colobus.

Skull variation in Afro-Eurasian monkeys results from both adaptive and non-adaptive evolutionary processes

“…The potential importance of drift in African colobine skull evolution is consistent with their evolutionary history occupying forest patches that probably decreased in size with climatic cooling, reducing gene flow between groups and promoting stochastic evolutionary processes in allopatry 29 , 30 . In particular, the complexity of red colobus ( Piliocolobus ) taxonomy (reviewed in 55 ), the probable presence of a “hybrid swarm” of some taxa 56 , and the difficulties of assigning clear morphological boundaries between taxa 57 suggests an evolutionary history that is far from straightforward.…”

“…It has been hypothesised (e.g., 29 , 30 ) that climatic fluctuations in the Plio-Pleistocene shaped some of the taxonomic diversity of Afro-Eurasian monkeys, through expansion and contraction of suitable habitats. These habitat pockets may be equivalent to isolates, with little gene flow with other populations 31 .…”

Records of Ethiopian and Eritrean mammals in Italian literature and museums, with some taxonomic notes

“…do not share the tail characters of C. guereza gallarum (Carpaneto & Gippoliti 1994), so distribution of C. guereza gallarum appears limited to the Eastern Arusi and Chercher region (Groves 2007). A genetic study (Zinner et al 2019) has recently confirmed the validity of C. guereza gallarum and its restricted geographic range. This case offers another example of the practical importance of taxonomic knowledge for both basic research and conservation (Gippoliti 2019).…”

Population Status, Diurnal Activity Pattern, Feeding Ecology, and Habitat Association of Colobus Monkey (Colobus guereza) in Saja Forest, Kaffa Zone, Southwest Ethiopia

“…e number of plant species consumed by guerezas in our study was much higher than that in Mekonnen and Hailemariam [17] (19 species), Hussen and Ejigu [18] (15 species), and Petros et al [47] (8 species). A higher number of different plant species consumed is expected in the dry season, as plants are of lower nutritional quality and so colobus monkeys would have to forage from a greater variety to meet their nutritional needs [48].…”