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While dispersal is the basis of inter‐population connectivity, it is difficult to directly observe. New molecular techniques provide ways of studying the intensity and direction of dispersal among populations through quantifying gene flow. When herbivores disperse their gut microbes travel with the host, and gut microbiota is known to play an important role in host health. However, the current understanding of the driving mechanism between moose dispersal patterns and gut microbial structure is vague. Therefore, when we observe the effects of climate warming on gene flow, it is important to understand the ecological mechanisms that affect the gut microbiota. We applied integrative methods from molecular biology, nutritional ecology and microbiomics to quantify dispersal patterns of moose populations in northeast China and explore the ecological mechanisms driving gut microbe–host associations. We found that moose populations in northeast China are undergoing two dispersal patterns while retreating in a northwesterly direction. Dispersing and isolated moose populations differed in their gut microbial composition and frequency of functional types that relate to digestion and diet composition. We also found that the environmental variables related to the moose gut microbial communities also changed with different dispersal patterns. The gut microbiota of isolated moose populations was only related to ambient temperature, whereas the microbiota in dispersing moose populations was related to longitude and diet protein content. We expect that the differences in the taxonomic and functional structure of gut microbiota relating to digestion are adaptive. Consequently, this study highlights that special attention should be placed on the management of isolated moose populations, and ecological corridors or translocation of moose individuals may be needed to allow persistence in the face of global warming; doing this will likely improve the adaptability of gut microbiota. [ABSTRACT FROM AUTHOR]

Naturally occurring populations of most species are distributed non‐uniformly across their ranges. Observed changes in range‐wide population size are attributed to local‐scale processes such as fecundity and survival and to regional scale demographic processes such as immigration. It is often infeasible to study a species across its entire range, and we frequently make inferences on populations as a whole based on the demographic rates of a more restricted area. Extrapolating inferences about demographic processes from study areas to the entire species' range can lead to erroneous estimations, particularly when permanent emigrants contribute significantly to individual population processes. In this paper, we evaluated demographic processes and population trends at multiple scales for tricolored blackbirds (Agelaiustricolor) in California using site‐specific banding data and range‐wide citizen‐science data. First, we found that a previous estimate of statewide decline of 34% is largely driven by an estimated decline of 51.7% for the southern population. Second, we found evidence of a pseudo‐source and sink system, with the northern region acting as a sink for individuals moving from the declining southern region. The southern region is a "pseudo‐source" since it has lower rates of adult survival and an annual growth rate of r = −0.099, while still acting as a source of immigrants for the northern region. In turn, the north fits the traditional definition of a sink by an annual growth rate near zero, in addition to declining at a rate of 2.5% even though it is estimated to receive immigrants from the south at rates ranging from 8.3% to 13.2% per year. Our results suggest that the loss of wetland habitats in Southern California, coupled with increasing severity of droughts driven by changing climatic conditions, has created this pseudo‐source and sink system. Long term, tricolored blackbirds are likely to experience range contraction in the south, and the northern region is likely to undergo declines due to a loss of immigrants from the south. [ABSTRACT FROM AUTHOR]

Competition for limited resources is considered a key factor controlling invasion success. Resource availability can be viewed in either the long or short-term. Long-term availability depends on the baseline nutrient availability in the ecosystem and how those conditions shape the ecological community. Short-term resource availability fluctuates with disturbances that alter nutrient availability and/or the density and composition of the ecological community. We investigated how species' traits interact with short and long-term resource availability to determine the outcome of invasions. We manipulated long-term baseline resource availability, disturbance intensity, disturbance frequency, and propagule pressure in a fully factorial design using protist microcosms. Our results show that short and long-term resource availability and the direct mortality from disturbance interact with the traits of resident community members and traits of invaders to determine community invasibility. While competitively dominant invaders with slow growth rates may suffer rather than benefit from short-term resource fluctuations, quickly growing but competitively inferior invaders can benefit from both the resource fluctuations and the heterogeneity in community composition created by disturbance. Our findings empirically synthesize two explanations for invasion success, namely short-term resource fluctuations and long-term resource availability, and highlight the importance of considering traits of invaders and residents, such as growth rate and competitive ability, in the context of productivity and disturbance gradients. This species' traits approach could resolve idiosyncratic results from natural systems undergoing disturbance and invasion that do not follow patterns predicted by traditional invasion frameworks. [ABSTRACT FROM AUTHOR]

The metacommunity concept is an important way to think about linkages between different spatial scales in ecology. Here we review current understanding about this concept. We first investigate issues related to its definition as a set of local communities that are linked by dispersal of multiple potentially interacting species. We then identify four paradigms for metacommunities: the patch-dynamic view, the species-sorting view, the mass effects view and the neutral view, that each emphasizes different processes of potential importance in metacommunities. These have somewhat distinct intellectual histories and we discuss elements related to their potential future synthesis. We then use this framework to discuss why the concept is useful in modifying existing ecological thinking and illustrate this with a number of both theoretical and empirical examples. As ecologists strive to understand increasingly complex mechanisms and strive to work across multiple scales of spatio-temporal organization, concepts like the metacommunity can provide important insights that frequently contrast with those that would be obtained with more conventional approaches based on local communities alone. [ABSTRACT FROM AUTHOR]

Theory suggests that the response of communities to habitat subdivision depends on both species’ characteristics and the extent to which species interact. For species with dynamics that are independent of other species, subdivision is expected to promote regional extinction as populations become small and isolated. By contrast, intermediate levels of subdivision can facilitate persistence of strongly interacting species. Consistent with this prediction, experimental subdivision lengthened persistence of some species, altering the extent of food web collapse through extinction. Extended persistence was associated with immigration rescuing a basal prey species from local extinction. As predicted by food web theory, habitat subdivision reduced population density of a top predator. Removal of this top predator from undivided microcosms increased the abundance of two other predator species, and these changes paralleled those produced by habitat subdivision. These results show that species interactions structured this community, and illustrate the need for investigations of other communities. [ABSTRACT FROM AUTHOR]