Importance Of Interspecific Interactions Research Articles

Dynamics of ostracod populations from shallow lakes of Patagonia: life history insights

Wetlands are one of the most valuable natural resources, providing a number of ecosystem services and socio-economic values. Small ponds sustain a rich aquatic biodiversity and because of their short hydrological regimen and small size are excellent environments for population studies of microcrustaceans such as ostracods. This study describes the population dynamics of the Ostracoda fauna in three temporary shallow lakes during one hydroperiod in Argentine Patagonia. Three cosmopolitan species were determined: Cypris pubera, Tonnacypris lutaria and Eucypris virens. Among them, T. lutaria is here reported for the first time from the Neotropical region. Multivariate ordination techniques were used to examine the relationships among environmental variables and ostracod density on each sampling site. High values of conductivity, absorption at 320 nm (as a measure of dissolved organic matter), dissolved oxygen concentration, temperature and chlorophyll a concentration correlated positively with ostracod density. All the populations studied reproduced parthenogenetically, and the life cycles of E.virens and C. pubera were followed in detail by weekly sampling of their populations. The former displayed continuous reproduction, whereas the latter showed a multivoltine strategy. The life history of C. pubera was affected by the seasonality of the habitat. The development rate correlated positively with water temperature; conductivity and temperature had a positive effect on adult size in C. pubera, while conductivity had a negative effect on adult size in E. virens. In this study, we present the first data set on the development and life history of ostracods in Patagonian freshwater environments. However, several questions remain and encourage us to further investigate the relative importance of ostracods in food webs, as well as the importance of inter-specific interactions between ostracods and other taxa.

Community‐dependent foraging habits of flower visitors: cascading indirect interactions among five bumble bee species

AbstractDespite the ubiquity and the importance of interspecific interactions among flower visitors, few studies have examined their effects on the realized feeding niches of visitor species in a community context. To evaluate the community‐wide effects of interactions among flower visitors, I have examined changes in the flower utilization patterns of each visitor species at several sites where the component of the visitor's community differed. Specifically, I compared the flower preferences and foraging habits (legitimate foraging vs. primary nectar robbing vs. secondary nectar robbing) of five bumble bee species in flower patches consisting of Trifolium pratense L. (red clover) and T. repens L. (white clover) on Hokkaido Island, Japan. I also examined the nectar production and standing crops of each flower species to evaluate the exploitation competition based on nectar. The bumble bee species exhibited different flower utilization patterns among sites. At sites where the long‐tongued Bombus diversus tersatus was common and the exotic short‐tongued B. terrestris was rare, B. diversus tersatus visited red clover (long‐tubed flowers) exclusively, whereas medium‐tongued B. pseudobaicalensis and short‐tongued B. hypocrita sapporoensis and B. hypnorum koropokkrus preferentially visited white clover (short‐tubed flowers). Conversely, at sites where the long‐tongued bee was rare, four other species frequently visited red clover in different modes: B. pseudobaicalensis visited legitimately, B. hypocrita sapporoensis and B. terrestris visited as primary nectar robbers, and B. hypnorum koropokkrus visited as a secondary nectar robber. The presence or absence of resource exploitation by the long‐tongued species and the interaction between primary and secondary nectar robbers via robbing holes was the major ecological sources of these differences. Diverse effects of interactions among flower visitors played important roles in shaping pattern of plant and flower visitor interactions.

Toward an Identification of Resources Influencing Habitat Use in a Multi-Specific Context

Interactions between animal behaviour and the environment are both shaping observed habitat use. Despite the importance of inter-specific interactions on the habitat use performed by individuals, most previous analyses have focused on case studies of single species. By focusing on two sympatric populations of large herbivores with contrasting body size, we went one step beyond by studying variation in home range size and identifying the factors involved in such variation, to define how habitat features such as resource heterogeneity, resource quality, and openness created by hurricane or forest managers, and constraints may influence habitat use at the individual level. We found a large variability among individual's home range size in both species, particularly in summer. Season appeared as the most important factor accounting for observed variation in home range size. Regarding habitat features, we found that (i) the proportion of area damaged by the hurricane was the only habitat component that inversely influenced roe deer home range size, (ii) this habitat type also influenced both diurnal and nocturnal red deer home range sizes, (iii) home range size of red deer during the day was inversely influenced by the biomass of their preferred plants, as were both diurnal and nocturnal core areas of the red deer home range, and (iv) we do not find any effect of resource heterogeneity on home range size in any case. Our results suggest that a particular habitat type (i.e. areas damaged by hurricane) can be used by individuals of sympatric species because it brings both protected and dietary resources. Thus, it is necessary to maintain the openness of these areas and to keep animal density quite low as observed in these hunted populations to limit competition between these sympatric populations of herbivores.

Microbial ecology of the cystic fibrosis lung

Understanding the microbial flora of the cystic fibrosis (CF) respiratory tract is of considerable importance, as patient morbidity and death are primarily caused by chronic respiratory infections. However, chronically colonized CF airways represent a surprisingly complex and diverse ecosystem. The precise contributions of different microbes to patient morbidity, and in particular the importance of inter-specific interactions, remain largely unelucidated. The importance of within-species genetic and phenotypic variation has similarly received limited explicit attention. While a host of studies provide data on the microbial species recovered from patients, these are often incomparable due to differences in sampling and data reporting, or do not present the data in a way that aids our understanding of the ecosystem within each patient. This review brings together a cross-section of recent research on the CF airways and the microbes which infect them. The results presented suggest that understanding the CF lung in terms of its community and evolutionary ecology could benefit our understanding of disease progression and influence treatment regimens.

Consumer-Resource Dynamics. By William W. Murdoch, Cheryl J. Briggs & Roger M. Nisbet, pp. 462. Monographs in Population Biology, 36. Princeton University Press, Princeton, USA and Oxford, UK, 2003. ISBN 0 691 00658 X (hbk) and 0 691 00657 1 (pbk). £55.00 (cloth) and £24.95 (paper).

Consumer-Resource Dynamics. By William W. Murdoch, Cheryl J. Briggs & Roger M. Nisbet, pp. 462. Monographs in Population Biology, 36. Princeton University Press, Princeton, USA and Oxford, UK, 2003. ISBN 0 691 00658 X (hbk) and 0 691 00657 1 (pbk). £55.00 (cloth) and £24.95 (paper).

Niche Dynamics of Deer Mice in a Fragmented, Old-Growth-Forest Landscape

Peromyscus oreas and P. maniculatus were non-randomly distributed across macrohabitats (including continuous old-growth forests, old-growth corridors, old-growth fragments, and clearcuts) of the Olympic National Forest, Washington. At this landscape scale, population densities of P. oreas were significantly higher in old-growth sites, particularly continuous forest and corridors, while densities of P. maniculatus were highest in clearcuts. At a finer scale, niche breadths measured across local habitats (within each macrohabitat) were broadest in preferred macrohabitat of each species. The potential importance of interspecific interactions was reflected in an inverse correlation between densities of the two species across all sites, niche segregation at the landscape (between macrohabitat) and local scales, and by the relatively high densities of P. oreas in forest fragments that lacked P. maniculatus . Relative densities of the two species combined were nearly as high in corridors as they were in continuous old-growth, and were nearly double that found in fragments and clearcuts. Given the importance of these rodents as prey for other vertebrates, including the endangered northern spotted owl ( Strix occidentalis caurina ), maintaining stands of continuous old-growth and forested corridors should remain a priority for conserving diversity of native forest communities.

Interspecific Interaction and Similarity in Species Composition

To resolve the controversy initiated by Connor and Simberloff's (1978) analysis of similarity among the biota of the Galapagos Islands, we analyze the theoretical relationship between interspecific interactions and similarity. A counterintuitive result from our analysis is that all interspecific interactions, including competition, tend to increase similarity (given their effects on unconditional probabilities of occurrence). To have this effect, however, they must combine with the effects of interisland colonization. The results of Power (1975) and those of Connor and Simberloff (1978) suggest that interisland colonization and possibly interspecific interactions have had important effects on similarity in the Galapagos, but several difficulties prevent us from accepting their results. We conclude, with Connor and Simberloff, that the similarity of bird species lists for the Galapagos Islands does not support the importance of interspecific interactions in determining species distributions. In general, we...