Evolutionary responses to climate change in parasitic systems.

Species may respond to climate change in many ecological and evolutionary ways. In this simulation study, we focus on the concurrent evolution of three traits in response to climate change, namely dispersal probability, temperature tolerance (or niche width), and temperature preference (optimal habitat). More specifically, we consider evolutionary responses in host species involved in different types of interaction, that is parasitism or commensalism, and for low or high costs of a temperature tolerance-fertility trade-off (cost of generalization). We find that host species potentially evolve all three traits simultaneously in response to increasing temperature but that the evolutionary response interacts and may be compensatory depending on the conditions. The evolutionary adjustment of temperature preference is slower in the parasitism than in commensalism scenario. Parasitism, in turn, selects for higher temperature tolerance and increased dispersal. High costs for temperature tolerance (i.e. generalization) restrict evolution of tolerance and thus lead to a faster response in temperature preference than that observed under low costs. These results emphasize the possible role of biotic interactions and the importance of 'multidimensional' evolutionary responses to climate change.

THE CONTRIBUTION OF SOIL PHYSICOCHEMICAL PROPERTIES TO THE PRESENCE AND GENETIC DIVERSITY OF BURKHOLDERIA PSEUDOMALLEI.

Burkholderia pseudomallei (Bp), the causative agent of melioidosis, is unevenly distributed in the complex soil environment. Physicochemical factors in the soil have been reported to affect microbial communities in the soil. The effect of physicochemical factors on the number and diversity of organisms in the soil has not been reported. Twenty-five each B. pseudomallei-positive and -negative soil samples were collected from a melioidosis-endemic area. The amount of Bp in each soil sample was measured by culture and quantitative PCR (qPCR). The following physicochemical properties from each soil sample were measured: pH, total organic carbon (TOC), total nitrogen (TN), carbon to nitrogen ratio (C:N ratio), exchangeable calcium (EC) and extractable iron (EI). All the physico- chemical properties measured were significantly different between the Bp-positive and -negative soil samples. The Bp-positive soil samples had lower C:N ratios and lower EC and a higher EI (p < 0.05) than the Bp-negative samples. The average pH was lower (3.7-5.0) in the Bp-negative samples. Among the Bp-positive soil samples, the EC was negatively correlated with the PCR copy number. The amount of bacteria detected with the qPCR method was higher than with the culture method, suggesting the presence of unculturable forms of bacteria that might re-grow when the environmental conditions was suitable. A total of 117 Bp isolates obtained from the soil samples were classified into 25 groups using BOX-PCR. The genetic diversity of Bp, did not correlate with the physicochemical factors investigated. A suitable pH range and C:N ratio may be important for the presence of Bp. The EI supports the needs and EC probably alters the growth of Bp. The genetic diversity of the bacteria was not influenced by the soil factors investigated in this study. This information shows the environment conducive to the growth of Bp. This gives us information about how to potentially control or decrease Bp in the soil in the future.

Emergence of spatially structured populations by area-concentrated search.

The idea that populations are spatially structured has become a very powerful concept in ecology, raising interest in many research areas. However, despite dispersal being a core component of the concept, it typically does not consider the movement behavior underlying any dispersal. Using individual-based simulations in continuous space, we explored the emergence of a spatially structured population in landscapes with spatially heterogeneous resource distribution and with organisms following simple area-concentrated search (ACS); individuals do not, however, perceive or respond to any habitat attributes per se but only to their foraging success. We investigated the effects of different resource clustering pattern in landscapes (single large cluster vs. many small clusters) and different resource density on the spatial structure of populations and movement between resource clusters of individuals. As results, we found that foraging success increased with increasing resource density and decreasing number of resource clusters. In a wide parameter space, the system exhibited attributes of a spatially structured populations with individuals concentrated in areas of high resource density, searching within areas of resources, and "dispersing" in straight line between resource patches. "Emigration" was more likely from patches that were small or of low quality (low resource density), but we observed an interaction effect between these two parameters. With the ACS implemented, individuals tended to move deeper into a resource cluster in scenarios with moderate resource density than in scenarios with high resource density. "Looping" from patches was more likely if patches were large and of high quality. Our simulations demonstrate that spatial structure in populations may emerge if critical resources are heterogeneously distributed and if individuals follow simple movement rules (such as ACS). Neither the perception of habitat nor an explicit decision to emigrate from a patch on the side of acting individuals is necessary for the emergence of such spatial structure.

Effect of Landscape Composition and Invasive Plants on Pollination Networks of Smallholder Orchards in Northeastern Thailand.

Destruction of natural habitat, land-use changes and biological invasion are some of the major threats to biodiversity. Both habitat alteration and biological invasions can have impacts on pollinator communities and pollination network structures. This study aims to examine the effect of an invasive plant, praxelis (Praxelis clematidea; Asteraceae), and land-use types on pollinator communities and the structure of pollination networks. We conducted the study in smallholder orchards which are either invaded or non-invaded by P. clematidea. We estimated the pollinator richness, visitation rates, and pollinator diversity and evaluated the network structures from 18 smallholder orchards in Northeastern Thailand. The effect of landscape structure in the vicinity of the orchards was investigated, with the proportion of agricultural, forest, and urban landscape within a 3 km radius analyzed. The invasive species and land-use disturbance influence the pollinator communities and pollination network structure at species level was affected by the presence of P. clematidea. Bees were the most important pollinator group for pollinator communities and pollination networks of both invaded or non-invaded plots, as bees are a generalist species, they provide the coherence of both the network and its own module. The urban landscape had a strong negative influence on pollinator richness, while the proportions of agriculture and forest landscape positively affected the pollinator community.