Browsing by Subject "BEHAVIORAL ECOLOGY"

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  • Xia, Zhichao; Yu, Lei; He, Yue; Korpelainen, Helena; Li, Chunyang (2019)
    Tree performance in mixed-species forest plantations is ultimately the net result of positive and negative interactions among species. Despite increasing knowledge of interspecific interactions, relatively little is known about the chemical mechanisms mediating such interactions. We constructed mixed planting systems with two species including Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) and broadleaf species Cinnamomum camphora L. Presl, Elaeocarpus decipiens Hemsl, Liquidambar formosana Hance, or Michelia macclurei Dandy. Based on a series of manipulative experiments, we investigated the performance of Chinese fir and analyzed root placement patterns and the composition of main soil microbial groups. The broadleaf trees influenced the growth of Chinese fir roots more than the growth of shoots. Furthermore, C. camphora roots released allelochemicals into the soil environment, resulting in growth inhibition of Chinese fir and changes in main soil microbial groups. However, when grown with E. decipiens and M. macclurei, the growth of Chinese fir was consistently promoted. It responded by enhancing its root growth and altering root behavior, resulting in a shift from growth inhibition to chemical facilitation. These positive inter-specific interactions also stimulated changes in the composition of soil microbes. Complementary experiments indicated that non-toxic signaling molecules in the root exudates of E. decipiens and M. macclurei may be responsible for mediating positive root-root interactions and regulating the composition of main soil microbial groups. Thus, our study demonstrated that broadleaf species chemically mediate the growth of Chinese fir through root exudates. Such a novel mechanism offers many implications and applications for reforestation programs undertaken to rehabilitate forest plantations that suffer from declining productivity related to densely planted monocultures.
  • Reyes-Garcia, Victoria; Powell, Bronwen; Diaz-Reviriego, Isabel; Fernandez-Llamazares, Alvaro; Gallois, Sandrine; Gueze, Maximilien (2019)
    The diets of contemporary hunter-gatherers are diverse and highly nutritious, but are rapidly changing as these societies integrate into the market economy. Here, we analyse empirical data on the dietary patterns and sources of foods of three contemporary hunter-gatherer societies: the Baka of Cameroon (n=160), the Tsimane' of Bolivia (n=124) and the Punan Tubu of Indonesia (n=109). We focus on differences among villages with different levels of integration into the market economy and explore potential pathways through which two key elements of the food environment (food availability and food accessibility) might alter the diets of contemporary hunter-gatherers. Results suggest that people living in isolated villages have more diverse diets than those living in villages closer to markets. Our results also suggest that availability of nutritionally important foods (i.e., fruits, vegetables and animal foods) decreases with increasing market integration, while availability of fats and sweets increases. The differences found seem to relate to changes in the wider food environment (e.g., village level access to wild and/or market foods and seasonality), rather than to individual-level factors (e.g., time allocation or individual income), probably because food sharing reduces the impact of individual level differences in food consumption. These results highlight the need to better understand the impact of changes in the wider food environment on dietary choice, and the role of the food environment in driving dietary transitions.
  • Kelm, Detlev H.; Toelch, Ulf; Jones, Mirkka M. (2021)
    Background: Mixed-species groups in animals have been shown to confer antipredator, foraging and other benefits to their members that may provide selective advantages. In most cases, however, it is unclear whether functional benefits are a principal driver of heterospecific groups, or whether groups simply result from simultaneous exploitation of common resources. Mixed-species groups that form independently of environmental conditions may, however, evidence direct benefits of species associations. Bats are among the most gregarious mammals, with sometimes thousands of individuals of various species roosting communally. Despite numerous potential functional benefits of such mixed-species roosting groups, interspecific attraction has never been shown. To explore alternative explanations for mixed-species roosting, we studied roost selection in a speciose neotropical understory bat community in lowland rainforest in Costa Rica. Long term roost data were recorded over 10 years in a total of 133 roosts comprising both natural roosts and structurally uniform artificial roosts. We modelled bat roost occupancy and abundance in each roost type and in forest and pasture habitats to quantify the effects of roost- and environmental variability. Results: We found that bat species presence in natural roosts is predictable from habitat and structural roost parameters, but that the presence and abundance of other bat species further modifies roost choice. One third of the 12 study species were found to actively associate with selected other bat species in roosts (e.g. Glossophaga commissarisi with Carollia sowelli). Other species did not engage in communal roosting, which in some cases indicates a role for negative interspecific interactions, such as roost competition. Conclusions: Mixed-species roosting may provide thermoregulatory benefits, reduce intraspecific competition and promote interspecific information transfer, and hence some heterospecific associations may be selected for in bats. Overall, our study contributes to an improved understanding of the array of factors that shape diverse tropical bat communities and drive the dynamics of heterospecific grouping in mammals more generally.