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Interspecific interactions between parasites sharing the same host are often antagonistic; the presence of one species decreases the number of individuals or negatively affects both the distribution and reproduction of the other species. Antagonistic interactions between co-infecting parasites may translate into direct competition or interactive segregation, but elements of both may be present. Potential interactions between two acanthocephalan species, Pomphorhynchus laevis and Acanthocephalus anguillae, were studied in the field in two of their natural fish definitive hosts. There was no evidence for competitive exclusion between P. laevis and A. anguillae. However, a negative interaction was found for the first time in the field between these two species. Based on the analysis of parasite abundance and total biomass using a static regression approach, I found that the abundance and total biomass of parasite was also limited by host characteristics. These results are consistent with previous laboratory studies on competition between P. laevis and A. anguillae.
Herbaceous plants are often under-studied in tropical forests, despite their high density and diversity, and little is known about the factors that influence their distribution at microscales. In a 25-ha plot in lowland Amazonian rain forest in Yasuní National Park, Ecuador, we censused six species of Heliconia (Heliconiaceae) in a stratified random manner across three topographic habitat types. We observed distribution patterns consistent with habitat filtering. Overall, more individuals occurred in the valley (N = 979) and slope (N = 847) compared with the ridge (N = 571) habitat. At the species level, Heliconia stricta (N = 1135), H. spathocircinata (N = 309) and H. ortotricha (N = 36) all had higher abundance in the valley and slope than ridge. Further, H. vellerigera (N = 20) was completely absent from the ridge. Conversely, H. velutina (N = 903) was most common in the drier ridge habitat. The two most common species (H. stricta and H. velutina) had a reciprocal or negative co-occurrence pattern and occurred preferentially in valley versus ridge habitats. These results suggest that taxa within this family have different adaptations to the wetter valley versus the drier ridge and that habitat partitioning contributes to coexistence.
Pheromones play an important role in mediating interspecific interactions in insects. In an insect community, pheromones can reveal information about the senders, which could be used by other members of the food web (competitor, natural enemies, etc.) to their own advantage. The aggregation pheromones of two closely related thrips species, Frankliniella occidentalis and Frankliniella intonsa, have been identified with the same major compounds, (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, but in different ratios. However, the roles of the aggregation pheromones in the interspecific interactions between these two closely related species are unknown. Here, we investigated the roles of major aggregation pheromone compounds in interspecific interactions between F. occidentalis and F. intonsa for both long and short ranges. The results showed that, at tested doses, neither aggregation pheromone-induced long range cross-attraction nor short range cross-mating was detected between F. occidentalis and F. intonsa. Field-trapping trials showed that the species-specificity in aggregation pheromones was regulated by the ratio of two major compounds. However, species-specific blends of the two major compounds had no effect on short-range interactions between these two species. Our data from the thrips species provide support for the ‘aggregation model of coexistence’, explaining the species-specific pheromone-mediated coexistence of closely related species. Thus, species-specific pheromones could be one of the factors affecting population dynamics and community structure in closely related insects with similar niches.
Differentiation of niche by means of resource partitioning facilitates coexistence of species with similar requirements. Here we analyse the association between different habitats (i.e. nest types) and two Diptera species of the poorly known Family Carnidae that coexist during their larval and pupal stage in the nests of troglodytic bird species. We also describe for the first time the puparium of Hemeromyia anthracina and Hemeromyia longirostris and offer morphometric data of the puparia of these two species and of Carnus hemapterus. Both the smaller size and the occurrence of well-developed spiracles allow easy discrimination of the puparium of C. hemapterus. The puparia of both Hemeromyia species is very similar and only differ in the distance between the small spiracles. Hemeromyia anthracina and C. hemapterus coexisted in nest boxes but the former species did not occur in natural sandy cavities where, in turn, C. hemapterus was highly prevalent. Carnus hemapterus prevalence did not differ between nest boxes and natural cavities but its abundance was higher in the first type of nest. This study shows clear associations of the two dipteran species with specific types of nests. Yet, some conditions are seemingly acceptable for both species.
Tropical bamboos persist in a wide range of light conditions and quickly respond to changes in light availability. However, the mechanisms underpinning this ability remain unknown. In order to test the hypothesis that the modular and hollow culm architecture of bamboos explains their performance in a wide range of light environments, we determined the allometric relationships of two dominant bamboo species of the upper hill dipterocarp forests of Malaysia, Gigantochloa ligulata (n = 29) and Schizostachyum grande (n = 25), via destructive sampling. We also monitored biomass turnover of bamboos and woody trees in 24 permanent plots (1.92 ha in total) over a one-year period. Compared with woody trees, bamboo culms attained 1.5 times the height and their clumps supported four times as much total leaf area at the same above-ground biomass. In addition, at a given height, bamboo clumps had six times larger crown projection area than trees while having a similar amount of total leaf area per unit of crown projection area. Finally, bamboos’ biomass turnover rate was three times higher than trees, and G. ligulata increased its specific rate of biomass increase after canopy disturbance, while trees decreased. We conclude that the unique architecture of bamboos allows them to persist under closed forest canopy light conditions and to respond to gap formation via high biomass turnover rate.
Lichen thalli represent the most conspicuous examples of fungal-algal interactions. Studies that describe phycobiont diversity within entire thalli are based mainly on Sanger sequencing. In some lichen species, this technique could underestimate the intrathalline coexistence of multiple microalgae. In this study different multi-tool approaches were applied to two lichen taxa, Circinaria hispida and Flavoparmelia soredians, to detect algal coexistence. Here, we combined Sanger sequencing, a specific polymerase chain reaction (PCR) primer, 454-pyrosequencing, phycobiont isolation and ultrastructural characterization. Furthermore, we compared pyrenoid ultrastructural features of lichenized phycobionts with microalgae isolated in culture. An improved methodology was used to isolate and propagate phycobionts which, in combination with fast genetic identification, resulted in a considerable reduction in time and cost to complete the process. This isolation method, coupled with a specific PCR primer, allowed for the detection of coexisting algae in C. hispida (four Trebouxia lineages). 454-pyrosequencing detected only a fraction of such diversity, while Sanger sequencing identified only the primary phycobiont. Ultrastructural features of the isolated algae were observed by transmission electron microscopy; the maintenance of the pyrenoid characteristics suggested the existence of different Trebouxia lineages. In F. soredians a single Trebouxia lineage was identified using all these approaches.
In cases of lichens with algal coexistence, a combination of different molecular and ultrastructural approaches may be required to reveal the underlying algal diversity within a single thallus. The approach proposed in this study provides information about the relationship between molecular and ultrastructural data, and represents an improvement in the delimitation of taxonomic features which is needed to recognize intrathalline Trebouxia diversity.
In this work, we examine the mathematical analysis and numerical simulation of pattern formation in a subdiffusive multicomponents fractional-reaction-diffusion system that models the spatial interrelationship between two preys and predator species. The major result is centered on the analysis of the system for linear stability. Analysis of the main model reflects that the dynamical system is locally and globally asymptotically stable. We propose some useful theorems based on the existence and permanence of the species to validate our theoretical findings. Reliable and efficient methods in space and time are formulated to handle any space fractional reaction-diffusion system. We numerically present the complexity of the dynamics that are theoretically discussed. The simulation results in one, two and three dimensions show some amazing scenarios.
In eighteenth-century law and print, English Catholics were portrayed as entirely untrustworthy, and their exclusion from all aspects of English society encouraged. Yet, as many local studies have shown, there were numerous individual cases of relatively peaceful coexistence between Protestants and Catholics in this period. This article explores why this was the case by examining how Catholics overcame labels of untrustworthiness on a local level. Using the remarkable political influence of one high-status Catholic in the first half of the eighteenth century as a case study, it questions the utility of “pragmatism” as an explanation for instances of peaceful coexistence in this period. Instead it focuses on the role that deliberate Catholic resistance to legal disabilities played in allowing them to be considered as trustworthy individuals in their localities. The resulting picture of coexistence points towards a moderation of the historiographical emphasis on mutual compromise between confessions in favour of attention to the determined resilience of minority groups. In explaining this, this article makes the broader point that the influence of trust, long important in studies of early modern economic, political, and social relationships, is ripe for exploration in the context of interconfessional relations.
Space is one of the primary limiting resources for organisms on the intertidal rocky shore. This paper examined the effect of reduced density on key traits (mortality and growth) on the intertidal barnacles, Chthamalus montagui and Semibalanus balanoides, on the mid-shore in Plymouth, UK. Intra- and interspecific treatments comprising of C. montagui and S. balanoides were manipulated to reduce densities at two similar sites. Changes in mortality and operculum growth were assessed over an 8-week period using digital photography. Covariates of growth included nearest neighbour distance, competition between closest pairs and initial size. Conflicting patterns were observed when comparing growth rates between treatments and sites. At Site 1, interspecific treatments had a lower growth rate than intraspecific treatments, whereas at Site 2, interspecific growth rates were higher. ANCOVA showed that nearest neighbour distance had no significant effect on growth, but when comparing differences in growth of closest neighbouring pairs, C. montagui treatment showed evidence of competition whereas S. balanoides did not. ANCOVA analysis indicated no difference in growth between each outcome of pair competition, suggesting winners are initially bigger than losers. Comparisons of mortality between treatments indicated mortality over time with no significant differences observed between treatments, but response surface methodology (RSM) revealed no effects of competition on mortality of S. balanoides, but negative effects of both intra- and interspecific competition on C. montagui survivorship. Examination of natural populations of barnacles in the mid-shore indicated there was strong spatial variation in growth rates, perhaps driven by small-scale differences within sites.
In this paper we consider a system of reaction–diffusion–advection equations with a free boundary, which arises in a competition ecological model in heterogeneous environment. The evolution of the free-boundary problem is discussed, which is an extension of the results of Du and Lin (Discrete Contin. Dynam. Syst. B19 (2014), 3105–3132). Precisely, when u is an inferior competitor, we prove that (u, v) → (0, V) as t→∞. When u is a superior competitor, we prove that a spreading–vanishing dichotomy holds, namely, as t→∞, either h(t)→∞ and (u, v) → (U, 0), or limt→∞h(t) < ∞ and (u, v) → (0, V). Moreover, in a weak competition case, we prove that two competing species coexist in the long run, while in a strong competition case, two species spatially segregate as the competition rates become large. Furthermore, when spreading occurs, we obtain some rough estimates of the asymptotic spreading speed.
The shanny/common blenny (Lipophrys pholis) and long-spined scorpionfish/bullhead (Taurulus bubalis) are commonly encountered, sympatric species within much of Great Britain's rocky intertidal zones. Despite being prey items of the cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) respectively, and both contributors to the diet of the near-threatened European otter (Lutra lutra), little is known on the population dynamics of the temperate specimens of Great Britain. It is further less known of the degrees of sympatricity between the two fish species and to what extent they are able to coexist. The current study examines spatio-temporal distributions and abundances at various resolutions: monthly population dynamics of both species along England's Yorkshire coast and seasonal population dynamics along the Yorkshire coast and around the Isle of Anglesey, Wales. Studies of their abundances, sizes, degrees of rock pool co-occurrence and diel activities are further examined, which indicate coexistence is maintained when interspecific co-occurrence takes place only between specimens of similar sizes, thus demoting size-related dominance hierarchies.
Dominant woody species can determine the structure and composition of a plant community by affecting environmental conditions experienced by other species. We explored how dominant tree species affect the tree species richness, diversity, evenness and vertical structural heterogeneity of non-dominant species in wet and dry miombo woodlands of Tanzania. We sampled 146 plots from eight districts with miombo woodlands, covering a wide range of topographic and climatic conditions. We recorded 217 woody plant species belonging to 48 families and 122 genera. Regression analysis showed significant negative linear associations between tree species richness, relative species profile index of the non-dominant and the relative abundance of the dominant tree species (Brachystegia spiciformis and Brachystegia microphylla in wet, and Brachystegia spiciformis and Julbernardia globiflora in dry miombo woodlands). Shannon diversity and evenness had strong non-linear negative relationships with relative abundance of dominant tree species. A large number of small individual stems from dominant and non-dominant tree species suggesting good regeneration conditions, and intensive competition affecting survival. We suggest that dominant miombo tree species are suppressing the non-dominant miombo tree species, especially in areas with high recruitments, perhaps because of their important adaptive features (extensive root systems and ectomycorrhizal associations), which enhance their ability to access limited nutrients.
In many areas, wildlife managers are turning to hunting programmes to increase public acceptance of predators. This study examines attitudes measured before and after a hunting and trapping season (wolf hunt) in Wisconsin (WI), USA, and casts some doubt on whether such programmes actually promote public acceptance. In Wisconsin, attitudes toward wolves (Canis lupus) were recorded before and after the inaugural regulated wolf hunt. Measuring longitudinal changes is particularly important in assessing management interventions. The attitudes of 736 previous respondents were resampled in 2013. Changes in individual responses to statements about emotions, behavioural intentions, beliefs, and attitudes toward wolves and wolf management between 2009 and 2013 were assessed using a nine-item scaled variable called ‘tolerance’. Although the majority (66%) of wolf range respondents approved of the decision to hold the hunt, the results indicate a negative trend in attitudes toward wolves among male respondents and hunters living in wolf range, both before and after the state's first legal hunt, suggesting that hunting was not associated with an increase in tolerance for the species after one year. Tolerance levels among female respondents remained stable throughout the study period.
In many coastal areas substrate is the limiting resource for benthic
organisms. Some sessile species can be used as secondary substrate, reducing
competition and increasing coexistence. In southern Chile, annual
populations of Macrocystis pyrifera recruit and grow on the
shells of Crepipatella fecunda. This study describes
ecological interactions between the kelp and the slipper limpet over an
annual cycle. The degree of kelp overgrowth was established by collecting
sporophytes and through in situ submarine photography over
a 10 month period (starting when kelp recruits became visible and ending
when sporophytes were no longer present). Changes in the biochemical
composition of the limpet tissue were also recorded by chemical analyses, to
evaluate the potential effects (positive/neutral/negative) of kelp on
C. fecunda nutritional condition. The results indicate
that both species coexist, although kelp overgrowth may cause a decrease in
carbohydrates in C. fecunda tissues, restricted to the
period when the kelp forest reaches its maximum biomass. Individually, the
short duration of the maximum overgrowth period and the size reached by
C. fecunda females (up to 65 mm shell length) may enable
rapid limpet recovery, avoiding competitive exclusion. On a population
level, the M. pyrifera annual cycle generates the needed
‘break’ for C. fecunda populations, reducing the effects of
kelp overgrowth. Thus, in the view of the neutral effect of kelp overgrowth,
together with the positive effect of C. fecunda on
M. pyrifera recruitment described somewhere else, this
ecological interaction can be categorized as commensalism.
Examining possibilities for the coexistence of two competing populations is a classic problem which dates back to the earliest ‘predator-prey’ models. In this paper we study this problem in the context of a model introduced in Björnberg et al. (2012) for the spread of a virus infection in a population of healthy cells. The infected cells may be seen as a population of ‘predators’ and the healthy cells as a population of ‘prey’. We show that, depending on the parameters defining the model, there may or may not be coexistence of the two populations, and we give precise criteria for this.
Bats are important components in tropical mammal assemblages. Unravelling the mechanisms allowing multiple syntopic bat species to coexist can provide insights into community ecology. However, dietary information on component species of these assemblages is often difficult to obtain. Here we measured stable carbon and nitrogen isotopes in hair samples clipped from the backs of 94 specimens to indirectly examine whether trophic niche differentiation and microhabitat segregation explain the coexistence of 16 bat species at Ankarana, northern Madagascar. The assemblage ranged over 4.4‰ in δ15N and was structured into two trophic levels with phytophagous Pteropodidae as primary consumers (c. 3‰ enriched over plants) and different insectivorous bats as secondary consumers (c. 4‰ enriched over primary consumers). Bat species utilizing different microhabitats formed distinct isotopic clusters (metric analyses of δ13C–δ15N bi-plots), but taxa foraging in the same microhabitat did not show more pronounced trophic differentiation than those occupying different microhabitats. As revealed by multivariate analyses, no discernible feeding competition was found in the local assemblage amongst congeneric species as compared with non-congeners. In contrast to ecological niche theory, but in accordance with studies on New and Old World bat assemblages, competitive interactions appear to be relaxed at Ankarana and not a prevailing structuring force.
The spatial patterns of distribution of five species of the Gerreidae (Diapterus rhombeus, Eucinostomus argenteus, Eucinostomus gula, Eucinostomus melanopterus and Eugerres brasilianus) in Mambucaba estuary, south-eastern Brazil, were determined to assess habitat partitioning of the estuarine reaches. Sampling was conducted between October 2007 and August 2008. Diapterus rhombeus and E. gula were exclusively found in the lower estuary, whereas E. melanopterus and E. brasilianus were exclusively found from the middle estuary. Eucinostomus argenteus was common in the two estuarine zones. Total length and total weight data showed that the smallest individuals of D. rhombeus and E. gula were found near to the estuarine mouth compared with deeper areas of high salinity and lesser influence of the estuarine plume. The smallest individuals of E. argenteus, E. brasilianus and E. melanopterus were found in a protected estuarine lagoon connected to the main estuarine channel, and the largest in the other sites in the main channel of the middle estuary. Spatial partition seems to be the strategy developed by the 5 members of the Gerreidae family to coexist in the Mambucaba estuary, which may be attributed to competition in the past between the species of Gerreidae or to differentiated tolerance to environmental constraints
Soil and adjacent leaf-litter environments support a diverse decomposer fauna. This has led to what is known as ‘the enigma of the soil fauna’, or the question of how it is possible for such large numbers of species to coexist without obvious biotic mechanisms, such as competitive exclusion, limiting coexistence (Anderson 1975). Dietary specialization or effective partitioning of food resources could be a mechanism to avoid niche overlap among sympatric soil/litter species (Chahartaghi et al. 2005, Jennings & Barkham 1975). However, unravelling the complexities of trophic relationships can be difficult, especially in soil/leaf-litter habitats where both consumers and prey are small, diverse and often unidentifiable (Scheu & Falca 2000). As such, the trophic relationships among species in these habitats typically remain unresolved.
Prunus species are important commercial fruit (plums, apricot, peach and cherries), nut (almond) and ornamental trees cultivated broadly worldwide. This review compiles information from available literature on Prunus species in regard to gene flow and hybridization within this complex of species. The review serves as a resource for environmental risk assessment related to pollen mediated gene flow and the release of transgenic Prunus. It reveals that Prunus species, especially plums and cherries show high potential for transgene flow. A range of characteristics including; genetic diversity, genetic bridging capacity, inter- and intra-specific genetic compatibility, self sterility (in most species), high frequency of open pollination, insect assisted pollination, perennial nature, complex phenotypic architecture (canopy height, heterogeneous crown, number of flowers produced in an individual plant), tendency to escape from cultivation, and the existence of ornamental and road side Prunus species suggest that there is a tremendous and complicated ability for pollen mediated gene movement among Prunus species. Ploidy differences among Prunus species do not necessarily provide genetic segregation. The characteristics of Prunu s species highlight the complexity of maintaining coexistence between GM and non-GM Prunus if there were commercial production of GM Prunus species. The results of this review suggest that the commercialization of one GM Prunus species can create coexistence issues for commercial non-GM Prunus production. Despite advances in molecular markers and genetic analysis in agroecology, there remains limited information on the ecological diversity, metapopulation nature, population dynamics, and direct measures of gene flow among different subgenera represented in the Prunus genus. Robust environmental impact, biosafety and coexistence assessments for GM Prunus species will require better understanding of the mechanisms of gene flow and hybridization among species within the Prunus species complex.
Spatial distribution patterns and habitat associations of Fagaceae species in a Fagaceae-codominated hill forest in Sumatra were investigated. Ten Fagaceae species believed to be zoochorous (animal-dispersed seed) and five codominant canopy and emergent anemochorous (wind-dispersed seed) species from Anacardiaceae and Dipterocarpaceae were studied. Five Fagaceae species and all codominant anemochorous species were significantly aggregated while the other five Fagaceae species showed a random distribution pattern. The median distance of small saplings from the nearest reproductively mature tree tended to be shorter for aggregated species than spatially random species. This implied that some Fagaceae species dispersed over longer distances than anemochorous species. Relationships between four habitat variables and distribution of the target species were examined with torus-translation tests. Three Quercus and one Lithocarpus species showed positive habitat associations. Two Quercus species aggregated at the preferred habitat, but the others were randomly distributed. Thus tree species with specific habitat preference do not only aggregate at the preferred habitat. The three ridge-specialist Quercus species showed gradual changes in habitat association, which could reflect avoidance of competition among the species. Most of the Lithocarpus species showed little correlation with habitat variables. Coexistence of the three Quercus species partly reflected subtle differences in topographical preferences. Distribution of five of the six Lithocarpus species was unrelated to topography, so other mechanisms must be sought to account for the maintenance of coexistence in this species-rich genus.