Afromontane small mammals do not follow the hump-shaped rule: altitudinal variation in the Soutpansberg Mountains, South Africa

Abstract

Abstract:Altitudinal transects of biodiversity are important to understanding macro-ecological patterns. Hump-shaped altitudinal profiles in species richness are a common pattern in terrestrial small-mammal communities studied previously mostly in New World mountain ranges. Based on capture–mark–recapture live-trapping conducted over four seasons (four nights per session) along an altitudinal transect from 1000 to 1747 m asl on the southern slopes of the Soutpansberg Mountains of northern South Africa, we recorded 12 species of small mammal, including nine rodents, two shrews and one elephant shrew (sengi). Three species of rodent and the sengi dominated the communities whilst six species were recorded with three or fewer captures. Although we found no effect of season, we found a significant linear increase in terrestrial small-mammal richness (but not Simpson's diversity, D) with altitude in the Soutpansberg Mountains located just north of the Tropic of Capricorn in South Africa. This trend could best be explained by an increase in the proportion of rocky cover and a change in vegetation from savanna to grassland. Peak densities of three common rodent species and one common insectivore varied from 10 ha−1 (Elephantulus myurus) to 54 ha−1 (Micaelamys namaquensis) and density showed no significant variation with season. However, density either declined (Aethomys ineptus) or increased (Rhabdomys dilectus and Elephantulus myurus) significantly with altitude; this variation was best explained by the proportion of rocky cover. Seasonal variation had a significant effect on body mass of two rodent species. A review of small-mammal studies from major mountain ranges in Africa and Madagascar found that the hump-shaped pattern is not common. Declines in richness with increasing altitude as well as cases of no significant altitudinal change were the most common patterns noted. Tropical African mountains (including the Soutpansberg with 27 species) have far higher small-mammal diversity than temperate African mountains.

Tapping into technology and the biodiversity informatics revolution: updated terrestrial mammal list of Angola, with new records from the Okavango Basin

“…This diversity compares favourably with studies reviewing the diversity of terrestrial small mammals (Taylor et al 2015) and bats (Schoeman et al 2013; Taylor et al 2013; Cooper-Bohannon 2016; Herkt et al 2016) in African highlands generally. However, the estimate of terrestrial small mammal richness is probably grossly under-estimated as a GBIF search of central Angola yielded 42 species, compared with our list of 13 species of shrews and rodents based on captures.…”

Changes of bat species composition over altitudinal gradients on northern and southern aspects of the Soutpansberg mountain range, South Africa

“…The model domain of each aspect was bound by the altitudinal range of each study area (McCain 2005). We applied simple linear regression to test the correlation between empirical and predicted values (Taylor et al 2015).…”

“…The study of Presley et al (2012) found that the metacommunity structure along an altitudinal gradient differs between bats, rodents and birds. While altitude seems to influence how the metacommunities are structured, bat communities are overlapping whereas groups of birds replace each other along the gradient, even more so do rodents (Taylor et al 2015). It is suggested that bird and rodent communities are structured according to the microhabitat they are specialized on, whereas bat community structure might be influenced more by the temperature, productivity and food, that particular species tolerate.…”

Taxonomic anarchy or an inconvenient truth for conservation? Accelerated species discovery reveals evolutionary patterns and heightened extinction threat in Afro-Malagasy small mammals

“…A revision of the Otomys irroratus species complex resolved two species restricted to the grassland (Otomys auratus) and fynbos (O. irroratus sensu stricto) biomes of South Africa (Taylor et al 2009, Engelbrecht et al 2011). Taylor et al 2009, 2011, Engelbrecht et al 2011, predicted range changes due to climate change under the A2 emission scenario (from Taylor et al 2015Taylor et al , 2016 and changes in the IUCN Red List status with different regional (Friedmann andDaly 2004, Child et al 2016) The two values listed for predicted % range changes refer to values calculated assuming (first value) and not assuming (second value) dispersal. Abbreviations as follow: N/A, not assessed; LC, least concern; DD, data deficient; VU, vulnerable; EN, endangered; CR, critically endangered.…”