Four new species of horseshoe bats have been discovered in East and Southern Africa, after scientists pieced together clues such as DNA data and the most intense frequency of sonar calls of each of these flying mammals. One of the species is found in a remote part of the the Kruger National Park, and another is only found in Mozambique.
It was previously thought that only one type of large horseshoe bat, Hildebrandt's Horseshoe Bat (Rhinolophus hildebrandtii), is found widespread throughout East Africa and the tropical habitats of Zimbabwe and the Mpumalanga province of South Africa.
"We now know that a total of five distinct species of large horseshoe bats occur in central and eastern Africa," says lead author Prof Peter Taylor of the University of Venda. "Now we also know that Hildebrandt's Horseshoe Bat, the species initially known to science, actually only occurs in East Africa."
Two of the new species have been named in honour of dedicated Southern African conservationists – Ms Lientjie Cohen, a scientist of the Mpumalanga Tourism and Parks Agency in South Africa, and the late Zimbabwean Dr. Reay Smithers, author of Southern Africa's most comprehensive mammal anthology. A third species is named after Mount Mabu in honour of the largest rainforest in southern Africa – an area under severe threat - in which it resided.
The investigation was led by bat experts and evolutionary geneticists Prof Peter Taylor of the University of Venda, Dr Samantha Stoffberg of Stellenbosch University, Prof Ara Monadjem of the University of Swaziland, Dr Corrie Schoeman of the University of KwaZulu-Natal, Dr Julian Bayliss of the Conservation Science Group at the University of Cambridge in the United Kingdom and the Mulanje Mountain Conservation Trust in Malawi, and Dr Woody Cotterill of Stellenbosch University and the Africa Earth Observatory Network (AEON). The new species are Cohen's Horseshoe Bat (Rhinolophus cohenae), Smithers' Horseshoe Bat (Rhinolophus smithersi), the Mozambican Horseshoe Bat (Rhinolophus mossambicus) and the Mount Mabu Horseshoe Bat (Rhinolophus mabuensis).
The researchers compared key characteristics of the bats, including sonar calls, their skull shape, genitalia, and crucially divergence in DNA sequences to diagnose and classify the new species.
The definitive DNA studies were conducted by Dr Samantha Stoffberg, a postdoctoral researcher in the Evolutionary Genomics Research Group of the Department of Botany and Zoology at Stellenbosch University.
"These bats are textbook examples of cryptic species, meaning that they are really very difficult to tell apart just based on their looks and morphology," explains Dr Stoffberg. "DNA comparisons have made it possible for us to clearly distinguish between these species."
Thanks to discoveries made in Zimbabwe in 1980 of so-called Hildebrandt's Horseshoe Bats that did not quite fit the bill, scientists were first alerted to the fact that further investigation was needed. More anomalous populations of Hildebrandt's Horseshoe Bats were discovered elsewhere a decade later, notably in Mpumulanga, and then more recently in Mozambique. "But solving the puzzle had only just begun," Dr Woody Cotterill of Stellenbosch University remembers their trail of discovery.
Typical of their family, these yet unnamed horseshoe bats exhibited species specific echolocation calls. "Their specific calls provided the fortunate first clues in our search," Dr Cotterill says. "We found these differ not only among bats from various parts of Africa, but critically of bats found in the same localities."
Species specific sonar calls are measured by differences in peak echolocation frequency. Frequency differences are diagnostic between species. Field workers can measure these frequencies with the help of bat detectors to identify these cryptic species in the wild.
"Once we started comparing museum specimens from these populations, we then noticed statistically significant differences in the body size and skull shapes of these bats across the region," says Prof Taylor. Interestingly, here the largest "giant" species turn out to be restricted to Afromontane habitat islands on mountaintops in Mpumulanga and Mozambique, while the smaller "dwarfs" occur at lower altitudes along major river valleys.
The DNA analyses, using a molecular clock, revealed yet more surprises. "These species are relatively old and evolved in the Pliocene Epoch over the past 5-2 million years," says Dr Cotterill. "We suggest that because of climatic extremes and geomorphological changes across eastern Africa, the ancestors of these species were isolated on either mountain tops or along river valleys."
Cohen's Horseshoe Bat
Cohen's Horseshoe Bat (Rhinolophus cohenae) was first discovered by Mpumalanga Tourism and Parks Agency scientist Lientjie Cohen in 2004 in the Barberton Mountainlands Nature Reserve near Barberton. Cohen is an active member of the Gauteng and Northern Regions Bat Interest Group.
"We are naming this bat species after Ms Cohen to acknowledge her significant contribution towards the conservation and discovery of new bat species in South Africa, and particularly in Mpumalanga," says Prof Peter Taylor of the University of Venda.
Cohen's Horseshoe Bat (Rhinolophus cohenae) has the lowest call peak frequency of the five Rhinolophus species under investigation. It has a very wide noseleaf.
It is believed to only be found in the Mpumalanga province of South Africa, for instance in the Sudwala area near Nelspruit.
"I am not aware of any other bat species being endemic to Mpumalanga Province, which would make this species one of great conservation importance," adds Prof Taylor.
The discoveries are described in the the open source journal PLOS ONE and can be downloaded freely from http://dx.plos.org/10.1371/journal.pone.0041744.