Harald Beck

SEED PREDATION BY NEOTROPICAL RAIN FOREST MAMMALS INCREASES DIVERSITY IN SEEDLING RECRUITMENT

Seed dispersal and seedling recruitment (the transition of seeds to seedlings) set the spatiotemporal distribution of new individuals in plant communities. Many terrestrial rain forest mammals consume post-dispersal seeds and seedlings, often inflicting density-dependent mortality. In part because of density-dependent mortality, diversity often increases during seedling recruitment, making it a critical stage for species coexistence. We determined how mammalian predators, adult tree abundance, and seed mass interact to affect seedling recruitment in a western Amazonian rain forest. We used exclosures that were selectively permeable to three size classes of mammals: mice and spiny rats (weighing <1 kg), medium-sized rodents (1-12 kg), and large mammals (20-200 kg). Into each exclosure, we placed seeds of 13 tree species and one canopy liana, which varied by an order of magnitude in adult abundance and seed mass. We followed the fates of the seeds and resulting seedlings for at least 17 months. We assessed the effect of each mammalian size class on seed survival, seedling survival and growth, and the density and diversity of the seedlings that survived to the end of the experiment. Surprisingly, large mammals had no detectable effect at any stage of seedling recruitment. In contrast, small- and medium-sized mammals significantly reduced seed survival, seedling survival, and seedling density. Furthermore, predation by small mammals increased species richness on a per-stem basis. This increase in diversity resulted from their disproportionately intense predation on common species and large-seeded species. Small mammals thereby generated a rare-species advantage in seedling recruitment, the critical ingredient for frequency dependence. Predation by small (and to a lesser extent, medium-sized) mammals on seeds and seedlings significantly increases tree species diversity in tropical forests. This is the first long-term study to dissect the effects of various mammalian predators on the recruitment of a diverse set of tree species.

Do Neotropical peccary species (Tayassuidae) function as ecosystem engineers for anurans

The concept of ecosystem engineering has catalysed novel approaches and models for non-trophic species interactionsandecosystemfunctions.Ecosystemengineersphysicallymodifyabioticandbioticenvironments,thereby creating new habitats that can be colonized by a new suite of species. In the Peruvian Amazonas, we tested whether peccaries (Tayassuidae) function as ecosystem engineers by creating and maintaining wallows. Such wallows could be critical aquatic habitats and breeding sites for anuran species during dry seasons. We compared hydroperiods of 21 peccary wallows and 13 naturally formed ponds across three dry seasons and found that wallows had a consistently higher mean water surface area than ponds. We also examined the pH, dissolved oxygen and temperature, and found no significant differences in these parameters between water bodies. Wallows had a significantly higher density of tadpoles, metamorphs and adult anurans, as well as higher β-diversity and species richness than ponds. This study not only provides thefirst systematic evidence of the ecosystem engineering processes of peccaries, but also reveals the positive consequences of such for anuran species.

Range-wide declines of a key Neotropical ecosystem architect, the Near Threatened white-lipped peccary Tayassu pecari

We report a range-wide status assessment of a key Neotropical ecosystem architect, the white-lipped peccary Tayassu pecari , categorized as Near Threatened on the IUCN Red List, using published information and unpublished data from 41 scientists in 15 range countries. We estimate that the white-lipped peccary has been extirpated in 21% of its historical range over the last 100 years, with reduced abundance and a low to medium probability of long-term survival in another 48% of its current range. We found major range declines in Argentina, Paraguay, southern Brazil, Colombia, Venezuela, north-east Brazil, Mexico and Costa Rica. This species is particularly at risk in more xeric ecosystems, especially the caatinga, cerrado and pampas. Hunting and habitat destruction are the most severe threats, although there are also unexplained sudden die-offs suggestive of disease. We evaluate our results in light of this species’ important interspecific interactions and its role as an ecosystem architect. One of our recommendations is that conservation efforts should focus on landscape conservation of large, continuous and ecologically intact areas containing a mosaic of different habitat types.

Synergistic impacts of ungulates and falling palm fronds on saplings in the Amazon

Most seedlings and saplings remain in the forest understorey for decades before becoming adults or dying, and thus may be exposed to various sources of physical disturbance (Clark & Clark 1991, 2001). Because tree species vary in their ability to recover after physical damage (Gillman et al . 2003, Guariguata 1998), this damage can act as an ecological filter and influence the juvenile community structure and species composition (Peters et al . 2004). Studies have demonstrated the occurrence and magnitude of stem breakage in juveniles caused by falling branches and other canopy debris (Clark & Clark 1989, 1991; Gillman & Ogden 2001, Scariot 2000). Surprisingly, little is known about the magnitude and ecological consequences of physical damage to juvenile plants by mammals, particularly large ungulates, including herbivory, trampling and uprooting (Gillman & Ogden 2003, Roldan & Simonetti 2001).

Meat from the Wild: Extractive Uses of Wildlife and Alternatives for Sustainability

Hunting and gathering remained the main mode of subsistence of humanity for hundreds of thousands of years, beginning some 1.8 million years ago, and until the Neolithic Revolution (some 10,000 years ago), when agriculture gradually spread through human societies (Marlowe 2005). Hunter-gatherer societies obtained their food directly from “natural” ecosystems, by hunting wild animals and collecting wild plants (Richerson et al. 1996). Early agrarian societies started planting desired crops on suitable lands, competing with wildlife for space and resources. As agrarian societies evolved, techniques for planting and harvesting became technologically more advanced and more efficient (Richerson et al. 1996). Innovations thus allowed the human population to grow and to colonize nearly every terrestrial ecosystem type on Earth.

An Experimental Test of Epi- and Endozoochory of Arbuscular Mycorrhizal Fungi Spores by Small Mammals in a Maryland Forest

Abstract Small mammals have been proposed as important dispersers of the spores of arbuscular mycorrhizal fungi (AMF), yet few data exist to support this hypothesis. We experimentally tested 2 models of small-mammal dispersal of AMF spores by quantifying their impact on the mycorrhizal inoculum potential of sterile soil flats in a northeast mesophytic forest in Maryland. Epizoochory did not provide a mechanism for spore dispersal in our study. However, our data demonstrated that endozoochory by several small-mammal species can be an effective dispersal mode for AMF. In the field experiment, inoculum potential of soil from plots that were accessible to Peromyscus leucopus (White-footed Mouse) was significantly higher than in control plots, which excluded small mammals. This study provides experimental evidence that White-footed Mice disperse AMF spores.