Mammal Evolution in Africa: Vegetation Changes Drive Adaptation, Study Finds
A recent study challenges the widely accepted notion that the growth of grasslands was the main driver of mammal evolution in Africa during the late Cenozoic era. Instead, the study suggests that changes in vegetation played a crucial role in shaping the spatial ranges of mammal groups and influencing their adaptations. These findings have implications for understanding the evolution of modern humans and other mammal species.
A recent study challenges the widely accepted notion that the growth of grasslands was the main driver of mammal evolution in Africa during the late Cenozoic era. Instead, the study suggests that changes in vegetation played a crucial role in shaping the spatial ranges of mammal groups and influencing their adaptations. These findings have implications for understanding the evolution of modern humans and other mammal species.
Impact of Vegetation Changes on Mammal Spatial Ranges
To investigate the impact of vegetation changes on mammal evolution, a team of researchers led by Kathryn Sokolowski from the University of Utah conducted a study. They focused on understanding how much vegetation needed to change to trigger significant responses from mammal groups. The researchers examined 58 herbivorous species in 123 African parks and nature reserves, analyzing data on species presence and absence as well as vegetation cover using satellite imagery.
Dietary Preferences and Vegetation Cover
The study specifically looked at the dietary preferences of four different groups of mammals: grazers, browsers, frugivores, and mixed feeders. The researchers found that most species preferred environments with a mean fraction woody cover (fwc) of 0.5. This measure compares the area of trees and shrubs to grasses, herbaceous vegetation, and unvegetated areas. Closed settings (fwc > 0.7) were less favored than open settings (fwc 0.3).
However, it was observed that only four species clearly preferred open grassland environments, while 11 species showed a drop in occurrence with a change from woodland to grassland.
Impact on Different Species
The study revealed that some species were minimally sensitive to shifting vegetation cover, while others showed a significant decline or drop in occurrence. For example species like gemsbok, springbok, red-fronted gazelle, and mountain zebra expressed a clear preference for open environments, making them more vulnerable as woody cover increases. On the other hand, species like duikers and several antelope showed a decrease in occurrence when transitioning from confined woodland to open grassland.
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Some species, including warthogs and bush elephants, showed minimal sensitivity to vegetation changes, while others fell within the medium range of grassland and forest cover.
Savannah Ecosystem
The research team concluded that savannah ecosystems were the most likely to have proliferated during the late Cenozoic era. These ecosystems featured a carpet of grass with interspersed shrubs and trees, providing suitable habitats for grazers browsers, and mixed feeders.
The vegetation in such environments was likely influenced by annual precipitation, which could shift the ecosystem towards more arid or rainy conditions, impacting the availability of food for different mammal species.
Implications for Paleoecological Reconstructions
The study cautions against relying solely on fossil evidence to reconstruct historical landscape changes. Fossil evidence may represent only a snapshot of the community averaged across a vast area, making it less reliable for accurately understanding mosaic ecosystems. The researchers suggest that certain fossils should not be considered as “indicator species” in paleoecological reconstructions.
Conclusion
Contrary to the prevailing belief that grassland expansions drove mammal evolution in Africa this study highlights the importance of vegetation changes in shaping mammal spatial ranges and adaptations. By examining the preferences of different mammal species and their response to shifting vegetation cover, the researchers provide valuable insights into the evolution of mammalian communities in Africa during the late Cenozoic era. These findings have implications for understanding the evolution of modern humans and other mammal species in African ecosystems.