301,935 research outputs found
General relationships between consumer dispersal, resource dispersal and metacommunity diversity
One of the central questions of metacommunity theory is how dispersal of
organisms affects species diversity. Here we show that the diversity-dispersal
relationship should not be studied in isolation of other abiotic and biotic
flows in the metacommunity. We study a mechanistic metacommunity model in which
consumer species compete for an abiotic or biotic resource. We consider both
consumer species specialized to a habitat patch, and generalist species capable
of using the resource throughout the metacommunity. We present analytical
results for different limiting values of consumer dispersal and resource
dispersal, and complement these results with simulations for intermediate
dispersal values. Our analysis reveals generic patterns for the combined
effects of consumer and resource dispersal on the metacommunity diversity of
consumer species, and shows that hump-shaped relationships between local
diversity and dispersal are not universal. Diversity-dispersal relationships
can also be monotonically increasing or multimodal. Our work is a new step
towards a general theory of metacommunity diversity integrating dispersal at
multiple trophic levels.Comment: Main text: 15 pages, 4 figures. Supplement: 25 pages, 12 figure
Foray search: An effective systematic dispersal strategy in fragmented landscapes
In the absence of evidence to the contrary, population models generally assume that the dispersal trajectories of animals are random, but systematic dispersal could be more efficient at detecting new habitat and may therefore constitute a more realistic assumption. Here, we investigate, by means of simulations, the properties of a potentially widespread systematic dispersal strategy termed "foray search." Foray search was more efficient in detecting suitable habitat than was random dispersal in most landscapes and was less subject to energetic constraints. However, it also resulted in considerably shorter net dispersed distances and higher mortality per net dispersed distance than did random dispersal, and it would therefore be likely to lead to lower dispersal rates toward the margins of population networks. Consequently, the use of foray search by dispersers could crucially affect the extinction-colonization balance of metapopulations and the evolution of dispersal rates. We conclude that population models need to take the dispersal trajectories of individuals into account in order to make reliable predictions
Study design and mark-recapture estimates of dispersal: A case study with the endangered damselfly Coenagrion mercuriale
Accurate data on dispersal ability are vital to the understanding of how species are affected by fragmented landscapes. However, three factors may limit the ability of field studies to detect a representative sample of dispersal events: (1) the number of individuals monitored, (2) the area over which the study is conducted and (3) the time over which the study is conducted. Using sub-sampling of mark-release-recapture data from a study on the endangered damselfly Coenagrion mercuriale (Charpentier), we show that maximum dispersal distance is strongly related to the number of recaptured individuals in the mark-release-recapture study and the length of time over which the study is conducted. Median dispersal distance is only related significantly to the length of the study. Spatial extent is not associated with either dispersal measure in our analysis. Previously consideration has been given to the spatial scale of dispersal experiments but we demonstrated conclusively that temporal scale and the number of marked individuals also have the potential to affect the measurement of dispersal. Based on quadratic relationships between the maximum dispersal distance, recapture number and length of study, we conclude that a previous study was of sufficient scale to characterise the dispersal kernel of C. mercuriale. Our method of analysis could be used to ensure that the results of mark-release-recapture studies are independent of levels of spatial and temporal investment. Improved confidence in dispersal estimates will enable better management decisions to be made for endangered species
Anthropogenic seed dispersal: rethinking the origins of plant domestication
It is well documented that ancient sickle harvesting led to tough rachises, but the other seed dispersal properties in crop progenitors are rarely discussed. The first steps toward domestication are evolutionary responses for the recruitment of humans as dispersers. Seed dispersal–based mutualism evolved from heavy human herbivory or seed predation. Plants that evolved traits to support human-mediated seed dispersal express greater fitness in increasingly anthropogenic ecosystems. The loss of dormancy, reduction in seed coat thickness, increased seed size, pericarp density, and sugar concentration all led to more-focused seed dispersal through seed saving and sowing. Some of the earliest plants to evolve domestication traits had weak seed dispersal processes in the wild, often due to the extinction of animal dispersers or short-distance mechanical dispersal
Dispersal-mediated trophic interactions can generate apparent patterns of dispersal limitation in aquatic metacommunities
Dispersal is a major organising force in metacommunities, which may facilitate compositional responses of local communities to environmental change and affect ecosystem function. Organism groups differ widely in their dispersal abilities and their communities are therefore expected to have different adaptive abilities. In mesocosms, we studied the simultaneous compositional response of three plankton communities (zoo-, phyto- and bacterioplankton) to a primary productivity gradient and evaluated how this response was mediated by dispersal intensity. Dispersal enhanced responses in all three planktonic groups, which also affected ecosystem functioning. Yet, variation partitioning analyses indicated that responses in phytoplankton and bacterial communities were not only controlled by dispersal directly but also indirectly through complex trophic interactions. Our results indicate that metacommunity patterns emerging from dispersal can cascade through the food web and generate patterns of apparent dispersal limitation in organisms at other trophic levels.
When do beetles and bugs fly? A unified scheme for describing seasonal flight behaviour of highly dispersing primary aquatic insects
Many authors investigated the dispersal flight of aquatic insects, but the exact length of the seasonal flying periods and its main characteristics have not been determined. A wide spectrum of species must be investigated before drawing general conclusions on seasonal changes about dispersal flight. Seasonal dispersal flight of aquatic beetles and bugs were studied during a 30-week long monitoring period. Insects were attracted to highly polarizing horizontal shiny black plastic sheets. 90 species/taxa and more than 45 000 individuals were captured during the sampling period. Aquatic insects were rising into the air during all periods of the year (from April till October). We hypothesized that species or group of species can be characterized by different seasonal rhythms of their dispersal flight. A unified scheme was established based on seasonal dispersal activity of 45 species to assess the dispersal behaviour. Detailed information about seasonal dispersal of 22 more species, and seasonal dispersal pattern were predicted in cases of further 23 species. In all, three seasonal patterns and twelve sub-patterns were identified based on specific characteristics of flight. The scheme is widely and generally applicable to characterize the seasonal dispersal flight of primarily aquatic insects. To demonstrate this, we performed the classification on previously reported data. Both previous and current results of the flight dispersal studies can be classified in the scheme, and the results are comparable by using this unified categorization
- …