@article {99939, title = {Large herbivores suppress liana infestation in an African savanna.}, journal = {Proc Natl Acad Sci U S A}, volume = {118}, year = {2021}, month = {2021 Oct 12}, abstract = {

African savannas are the last stronghold of diverse large-mammal communities, and a major focus of savanna ecology is to understand how these animals affect the relative abundance of trees and grasses. However, savannas support diverse plant life-forms, and human-induced changes in large-herbivore assemblages-declining wildlife populations and their displacement by livestock-may cause unexpected shifts in plant community composition. We investigated how herbivory affects the prevalence of lianas (woody vines) and their impact on trees in an East African savanna. Although scarce (\<2\% of tree canopy area) and defended by toxic latex, the dominant liana, (Apocynaceae), was eaten by 15 wild large-herbivore species and was consumed in bulk by native browsers during experimental cafeteria trials. In contrast, domesticated ungulates rarely ate lianas. When we experimentally excluded all large herbivores for periods of 8 to 17 y (simulating extirpation), liana abundance increased dramatically, with up to 75\% of trees infested. Piecewise exclusion of different-sized herbivores revealed functional complementarity among size classes in suppressing lianas. Liana infestation reduced tree growth and reproduction, but herbivores quickly cleared lianas from trees after the removal of 18-y-old exclosure fences (simulating rewilding). A simple model of liana contagion showed that, without herbivores, the long-term equilibrium could be either endemic (liana-tree coexistence) or an all-liana alternative stable state. We conclude that ongoing declines of wild large-herbivore populations will disrupt the structure and functioning of many African savannas in ways that have received little attention and that may not be mitigated by replacing wildlife with livestock.

}, issn = {1091-6490}, doi = {10.1073/pnas.2101676118}, author = {Coverdale, Tyler C and O{\textquoteright}Connell, Ryan D and Hutchinson, Matthew C and Savagian, Amanda and Kartzinel, Tyler R and Palmer, Todd M and Goheen, Jacob R and Augustine, David J and Sankaran, Mahesh and Tarnita, Corina E and Pringle, Robert M} } @article {45930, title = {Change in dominance determines herbivore effects on plant biodiversity.}, journal = {Nat Ecol Evol}, year = {2018}, month = {2018 Oct 29}, abstract = {

Herbivores alter plant biodiversity (species richness) in many of the world{\textquoteright}s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis-that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.

}, issn = {2397-334X}, doi = {10.1038/s41559-018-0696-y}, author = {Koerner, Sally E and Smith, Melinda D and Burkepile, Deron E and Hanan, Niall P and Avolio, Meghan L and Collins, Scott L and Knapp, Alan K and Lemoine, Nathan P and Forrestel, Elisabeth J and Eby, Stephanie and Thompson, Dave I and Aguado-Santacruz, Gerardo A and Anderson, John P and Anderson, T Michael and Angassa, Ayana and Bagchi, Sumanta and Bakker, Elisabeth S and Bastin, Gary and Baur, Lauren E and Beard, Karen H and Beever, Erik A and Bohlen, Patrick J and Boughton, Elizabeth H and Canestro, Don and Cesa, Ariela and Chaneton, Enrique and Cheng, Jimin and D{\textquoteright}Antonio, Carla M and Deleglise, Claire and Demb{\'e}l{\'e}, Fadiala and Dorrough, Josh and Eldridge, David J and Fernandez-Going, Barbara and Fern{\'a}ndez-Lugo, Silvia and Fraser, Lauchlan H and Freedman, Bill and Garc{\'\i}a-Salgado, Gonzalo and Goheen, Jacob R and Guo, Liang and Husheer, Sean and Karemb{\'e}, Moussa and Knops, Johannes M H and Kraaij, Tineke and Kulmatiski, Andrew and Kyt{\"o}viita, Minna-Maarit and Lezama, Felipe and Loucougaray, Gregory and Loydi, Alejandro and Milchunas, Dan G and Milton, Suzanne J and Morgan, John W and Moxham, Claire and Nehring, Kyle C and Olff, Han and Palmer, Todd M and Rebollo, Salvador and Riginos, Corinna and Risch, Anita C and Rueda, Marta and Sankaran, Mahesh and Sasaki, Takehiro and Schoenecker, Kathryn A and Schultz, Nick L and Sch{\"u}tz, Martin and Schwabe, Angelika and Siebert, Frances and Smit, Christian and Stahlheber, Karen A and Storm, Christian and Strong, Dustin J and Su, Jishuai and Tiruvaimozhi, Yadugiri V and Tyler, Claudia and Val, James and Vandegehuchte, Martijn L and Veblen, Kari E and Vermeire, Lance T and Ward, David and Wu, Jianshuang and Young, Truman P and Yu, Qiang and Zelikova, Tamara Jane} } @article {34250, title = {Conservation lessons from large-mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments.}, journal = {Ann N Y Acad Sci}, year = {2018}, month = {2018 May 11}, abstract = {

African savannas support an iconic fauna, but they are undergoing large-scale population declines and extinctions of large (\>5\ kg) mammals. Long-term, controlled, replicated experiments that explore the consequences of this defaunation (and its replacement with livestock) are rare. The Mpala Research Centre in Laikipia County, Kenya, hosts three such experiments, spanning two adjacent ecosystems and environmental gradients within them: the Kenya Long-Term Exclosure Experiment (KLEE; since 1995), the Glade Legacies and Defaunation Experiment (GLADE; since 1999), and the Ungulate Herbivory Under Rainfall Uncertainty experiment (UHURU; since 2008). Common themes unifying these experiments are (1) evidence of profound effects of large mammalian herbivores on herbaceous and woody plant communities; (2) competition and compensation across herbivore guilds, including rodents; and (3) trophic cascades and other indirect effects. We synthesize findings from the past two decades to highlight generalities and idiosyncrasies among these experiments, and highlight six lessons that we believe are pertinent for conservation. The removal of large mammalian herbivores has dramatic effects on the ecology of these ecosystems; their ability to rebound from these changes (after possible refaunation) remains unexplored.

}, issn = {1749-6632}, doi = {10.1111/nyas.13848}, author = {Goheen, Jacob R and Augustine, David J and Veblen, Kari E and Kimuyu, Duncan M and Palmer, Todd M and Porensky, Lauren M and Pringle, Robert M and Ratnam, Jayashree and Riginos, Corinna and Sankaran, Mahesh and Ford, Adam T and Hassan, Abdikadir A and Jakopak, Rhiannon and Kartzinel, Tyler R and Kurukura, Samson and Louthan, Allison M and Odadi, Wilfred O and Otieno, Tobias O and Wambua, Alois M and Young, Hillary S and Young, Truman P} }