scholarly journals Niche shifts and local competition between two coral reef fishes at their geographic boundary

2007 ◽  
Vol 58 (12) ◽  
pp. 1120 ◽  
Author(s):  
Andrew J. Limbourn ◽  
Geoffrey P. Jones ◽  
Philip L. Munday ◽  
Maya Srinivasan
Keyword(s):  
Resource Use ◽  
Large Scale ◽  
Reef Fishes ◽  
Geographic Ranges ◽  
Local Competition ◽  
Competition Theory ◽  
Niche Shifts ◽  
Random Assortment ◽  
Port Moresby ◽  
Foraging Ranges

Competition theory predicts that, when resources are limiting, interacting species should differ more in resource use where they co-occur, compared with where they do not (resource partitioning). The damselfishes Dascyllus aruanus and D. melanurus provide a useful test of this prediction because they exhibit largely allopatric geographic ranges that overlap near Port Moresby, Papua New Guinea. To test whether this species pair exhibited responses in resource use that were consistent with competition theory, the depth distributions, coral substrata and diet of each species at allopatric and sympatric locations were compared. Where sympatric, the frequency of co-occurrence was examined and foraging ranges and diet on corals where the species do and do not co-occur were compared. Contrary to expectations, the species were more similar in depth, habitat use and diet in the sympatric region. Within this location, they sometimes co-existed in the same coral shelters, but much less often than would be expected with random assortment. Where they did co-exist, their diets converged. D. melanurus exhibited restricted foraging ranges and consumed smaller prey in the presence of D. aruanus, but not vice versa. It was concluded that niche shifts along different resource axes at the geographic boundary are explained both by large-scale constraints in resource availability and local-scale competitive interactions.

scholarly journals Phylogeography in an “oyster” shell provides first insights into the genetic structure of an extinct Ostrea edulis population

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sarah Hayer ◽  
Dirk Brandis ◽  
Alexander Immel ◽  
Julian Susat ◽  
Montserrat Torres-Oliva ◽  
...  
Keyword(s):  
Large Scale ◽  
Wadden Sea ◽  
Atlantic Coast ◽  
Phylogenetic Reconstruction ◽  
Oyster Shell ◽  
Glacial Refugia ◽  
Late Nineteenth Century ◽  
Ostrea Edulis ◽  
Geographic Ranges ◽  
The North

AbstractThe historical phylogeography of Ostrea edulis was successfully depicted in its native range for the first time using ancient DNA methods on dry shells from museum collections. This research reconstructed the historical population structure of the European flat oyster across Europe in the 1870s—including the now extinct population in the Wadden Sea. In total, four haplogroups were identified with one haplogroup having a patchy distribution from the North Sea to the Atlantic coast of France. This irregular distribution could be the result of translocations. The other three haplogroups are restricted to narrow geographic ranges, which may indicate adaptation to local environmental conditions or geographical barriers to gene flow. The phylogenetic reconstruction of the four haplogroups suggests the signatures of glacial refugia and postglacial expansion. The comparison with present-day O. edulis populations revealed a temporally stable population genetic pattern over the past 150 years despite large-scale translocations. This historical phylogeographic reconstruction was able to discover an autochthonous population in the German and Danish Wadden Sea in the late nineteenth century, where O. edulis is extinct today. The genetic distinctiveness of a now-extinct population hints at a connection between the genetic background of O. edulis in the Wadden Sea and for its absence until today.

scholarly journals Precision Agriculture for Resource Use Efficiency in Smallholder Farming Systems in Sub-Saharan Africa: A Systematic Review

2021 ◽  
Vol 13 (3) ◽  
pp. 1158
Author(s):  
Cecilia M. Onyango ◽  
Justine M. Nyaga ◽  
Johanna Wetterlind ◽  
Mats Söderström ◽  
Kristin Piikki
Keyword(s):  
Resource Use ◽  
Precision Agriculture ◽  
Large Scale ◽  
English Language ◽  
Management Practices ◽  
Smallholder Farmers ◽  
Management Strategies ◽  
Sub Saharan Africa ◽  
Smallholder Farming ◽  
Sub Saharan

Opportunities exist for adoption of precision agriculture technologies in all parts of the world. The form of precision agriculture may vary from region to region depending on technologies available, knowledge levels and mindsets. The current review examined research articles in the English language on precision agriculture practices for increased productivity among smallholder farmers in Sub-Saharan Africa. A total of 7715 articles were retrieved and after screening 128 were reviewed. The results indicate that a number of precision agriculture technologies have been tested under SSA conditions and show promising results. The most promising precision agriculture technologies identified were the use of soil and plant sensors for nutrient and water management, as well as use of satellite imagery, GIS and crop-soil simulation models for site-specific management. These technologies have been shown to be crucial in attainment of appropriate management strategies in terms of efficiency and effectiveness of resource use in SSA. These technologies are important in supporting sustainable agricultural development. Most of these technologies are, however, at the experimental stage, with only South Africa having applied them mainly in large-scale commercial farms. It is concluded that increased precision in input and management practices among SSA smallholder farmers can significantly improve productivity even without extra use of inputs.

scholarly journals Stable Coexistence in a Field-Calibrated Individual-Based Model of Mangrove Forest Dynamics Caused by Inter-Specific Crown Plasticity

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 955
Author(s):  
Uwe Grueters ◽  
Mohd Rodila Ibrahim ◽  
Hartmut Schmidt ◽  
Katharina Tiebel ◽  
Hendrik Horn ◽  
...  
Keyword(s):  
Forest Dynamics ◽  
Mangrove Forest ◽  
Resource Competition ◽  
Standing Stock ◽  
Mean Field ◽  
Individual Based Model ◽  
Local Competition ◽  
Competition Theory ◽  
Crown Plasticity ◽  
Classical Competition

(1,2) In this theoretical study, we apply MesoFON, a field-calibrated individual-based model of mangrove forest dynamics, and its Lotka–Volterra interpretations to address two questions: (a) Do the dynamics of two identical red mangrove species that compete for light resources and avoid inter-specific competition by lateral crown displacement follow the predictions of classical competition theory or resource competition theory? (b) Which mechanisms drive the dynamics in the presence of inter-specific crown plasticity when local competition is combined with global or with localized seed dispersal? (3) In qualitative support of classical competition theory, the two species can stably coexist within MesoFON. However, the total standing stock at equilibrium matched the carrying capacity of the single species. Therefore, a “non-overyielding” Lotka–Volterra model rather than the classic one approximated best the observed behavior. Mechanistically, inter-specific crown plasticity moved heterospecific trees apart and pushed conspecifics together. Despite local competition, the community exhibited mean-field dynamics with global dispersal. In comparison, localized dispersal slowed down the dynamics by diminishing the strength of intra-/inter-specific competition and their difference due to a restriction in the competitive race to the mean-field that prevails between conspecific clusters. (4) As the outcome in field-calibrated IBMs is mediated by the competition for resources, we conclude that classical competition mechanisms can override those of resource competition, and more species are likely to successfully coexist within communities.

Intra- and inter-specific dominance relationships among arctic and snowshoe hares

1990 ◽  
Vol 68 (3) ◽  
pp. 457-464 ◽  
Author(s):  
Shannon M. Fitzgerald ◽  
Lloyd B. Keith
Keyword(s):  
A Priori ◽  
Interference Competition ◽  
Agonistic Interaction ◽  
Test Results ◽  
Geographic Ranges ◽  
Competition Theory ◽  
Dominance Relationships ◽  
Snowshoe Hares ◽  
Breeding Condition ◽  
Free Ranging

The geographic ranges of arctic and snowshoe hares (Lepus arcticus and L. americanus) rarely overlap. In Newfoundland and elsewhere in North America, arctic hares occupy treeless barrens or tundra, whereas snowshoe hares inhabit forest. We explored the hypothesis that such allopatry reflects interference competition, an agonistic interaction in which snowshoe hares are behaviourally dominant. To assess both inter- and intra-specific dominance, we conducted a series of dyadic trials in outdoor pens and also observed interactions of free-ranging individuals. Five testable predictions were inferred, a priori, from competition theory and previous leporid studies: (i) heavier individuals are dominant, (ii) adults dominate juveniles, (iii) females dominate males when both are in breeding condition, (iv) males dominate females when neither are in breeding condition, and (v) adults in breeding condition dominate those that are not. With snowshoe hares, tests for predictions i and ii were inconclusive, and iii was probably verified (P = 0.03). With arctic hares, test results were inconclusive for i, verified for ii (P < 0.01), and rejected for iii and iv, dominance being unrelated to sex or breeding condition. Prediction v could not be tested intraspecifically, but arctic hares dominated snowshoe hares in 84 of 85 dyads, including those where snowshoes weighed more, or were in breeding condition and arctic hares were not. It is, therefore, highly unlikely that interference competition with snowshoe hares is responsible for the current restriction of arctic hares to barrens and tundra.

scholarly journals Mapping Miskitu subsistence land use change in Concejo Territorial Katainasta, Honduras

2018 ◽  
Vol 3 (61E) ◽  
pp. 609-622
Author(s):  
Taylor A. Tappan ◽  
Peter H. Herlihy
Keyword(s):  
Spatial Patterns ◽  
Resource Use ◽  
Large Scale ◽  
Good Governance ◽  
Indigenous Communities ◽  
Conservation Policies ◽  
Territorial Jurisdiction ◽  
Before And After ◽  
Analysis Of Results ◽  
Spatial Parameters

Understanding the large-scale spatial patterns of natural resource use in indigenous homelands is critical for guaranteeing indigenous peoples’ ancestral land rights, designing effective conservation policies, and promoting good governance in Central America. However, few studies have mapped the diachronic distribution of indigenous communities’ resource use in these areas. Here we present a case study describing the spatial functionality of the Concejo Territorial Katainasta (CTK)--the first indigenous territorial jurisdiction in Honduras to receive an intercommunity land title. Two participatory research mapping (PRM) studies--the first in 1992 and the second in 2014-15--mapped the spatial patterns of Miskitu subsistence activities in CTK. The results were subsequently converted into a geographic information system (GIS) that allowed for spatial and temporal comparisons of Miskitu subsistence livelihoods in CTK before and after the titling process. Here we focus on the spatial parameters of three Miskitu subsistence livelihoods: agriculture, hunting and fishing. Analysis of results suggests that 1) the 2014-15 subsistence use areas for Miskitu communities in CTK have not diverged dramatically from those of the 1992 study, and 2) the new legal boundaries of CTK adequately encompass the subsistence use areas of its constituent communities and recognize the historical overlaps in Miskitu resource use and tenure patterns.

scholarly journals Management effectiveness suggests a role in structuring herbivorous fish communities in Sinai marine protected areas, Gulf of Aqaba

2021 ◽  
Author(s):  
Khaled M. El-Haddad ◽  
Saad Z. Mohamed ◽  
Tarek A. Temraz ◽  
Abdel-Hamid A. Ali ◽  
Mohamed S. Abdel-Rahman
Keyword(s):  
Large Scale ◽  
Size Structure ◽  
Reef Fishes ◽  
Fish Populations ◽  
Herbivorous Fish ◽  
Gulf Of Aqaba ◽  
Management Approach ◽  
Numerical Density ◽  
Total Biomass ◽  
The Status

Herbivorous reef fishes are critically important for maintaining the health and resilience of coral reefs. In the Egyptian Gulf of Aqaba (GoA), many of these herbivores are important fishery targets and little is known about their population size structure and biomass patterns. Here, we conduct a large-scale (~250 km of coastline) assessment of the status of herbivorous fish populations along a fishing pressure gradient at 30 sites and eight regions in the GoA. These regions are subjected to three levels of fishing and protection, ranging from almost no fishing (No take, NT), and moderately fished (via Gear restriction, GR) to heavily fished (Open access, OA). We found that the NT fishery reserve was the most effective to maintain herbivorous fish size, biomass, and richness across all functional groups, though numerical density was not. Total herbivore biomass was 4.3 and 2.8 times higher on NT reefs and GR reefs, respectively than on OA reefs. Among GoA regions, only Ras Mohammed and Sharm El-Sheikh (unfished), and Nabq (fished) met the global mean herbivore biomass target of ~30 kg/500 m2. Our work also highlights three important results regarding the impacts of fishing and fisheries management on herbivorous fish populations: (i) size structure was heavily skewed toward smaller individuals, with fishes less than (20 cm) accounting for 81.1% of the population in heavily fished OA reefs vs. 52.8% at unfished NT reefs, (ii) biomass of larger herbivore individuals (>35 cm) accounting for less than 1% of the total biomass in OA reefs vs. 37% at NT reefs, and (iii) large-bodied target species, Cetoscarus bicolor, Naso unicorn, and Kyphosus spp., accounting for 15.9% of the total biomass at NT reefs on average, while they were virtually absent from OA reefs. Collectively, these findings suggest that many principal fisheries species in the central northern regions of the GoA have been overexploited, which in turn can lead to reef degradation. Therefore, there is an urgent need to develop a participatory management approach and enforce restrictions on destructive fishing gear in order to promote recovery of herbivore biomass.

scholarly journals Landscape-Level Interactions Among Ungulates, Vegetation, and Large-Scale Fires in Northern Yellowstone National Park

1991 ◽  
Vol 15 ◽  
pp. 263-275
Author(s):  
Monica Turner ◽  
Yegang Wu ◽  
William Romme ◽  
Linda Wallace
Keyword(s):  
Spatial Pattern ◽  
Cervus Elaphus ◽  
Resource Use ◽  
Yellowstone National Park ◽  
National Park ◽  
Large Scale ◽  
Field Studies ◽  
Bison Bison ◽  
Fire Size ◽  
Winter Range

The scale of the 1988 fires in Yellowstone National Park (YNP) raised numerous questions for the management of natural areas subject to large, infrequent disturbances. An important management issue in YNP involves the interaction of large-scale fire with the large assemblage of native ungulates and vegetation dynamics in the landscape. In this 2-year research project, we are using landscape modeling and field studies to address basic questions about the effects of fire scale and heterogeneity on (1) resource utilization and survival of free-ranging elk (Cervus elaphus) and bison (Bison bison) and (2) the production and regeneration of preferred forage grasses and aspen in northern YNP. We are testing a series of eight hypotheses within the framework of two basic questions. First, we ask whether there are thresholds in fire size that interact with winter severity and ungulate density to determine ungulate resource use and survival on the winter range in northern YNP. This question focuses on the effects of fire size, regardless of the spatial pattern of burning. Second we ask, if large fires occur, does the spatial distribution of burned areas (and hence of higher quality forage) influence ungulate resource use during winters subsequent to the first post-fire year. In this question, we are addressing the effects of spatial pattern on herbivory. We focus on elk and bison because these are by far the most numerous ungulates in the area (Houston 1982), and we have chosen to examine winter grazing and browsing for several reasons. Winter range conditions are the primary determinant of ungulate survival and reproduction in Yellowstone, and winter utilization of the vegetation by ungulates appears to be intense in some areas. Ungulates make distinct foraging choices in the winter as in the rest of the year, and burn patterns may influence those choices in ways that we represent as hypotheses described later. In addition, the activities of animals can be readily monitored in the winter, and the exact locations of feeding and bedding sites can be determined. Travel routes are easily monitored, and the ability to sight animals is high; therefore, group locations and sizes can be readily determined. This research complements ongoing studies in YNP by expanding the spatial scale at which plant-herbivore dynamics are considered and by explicitly addressing the effects of spatial heterogeneity. Our research will produce a spatially explicit simulation model of the 78,000 ha winter range that predicts plant and ungulate dynamics under varying fire sizes, fire patterns, winter weather scenarios, and ungulate densities. The model and field studies will allow quantitative comparisons of the effects of large and small fires on ungulate survival and will thereby permit the simulation of the effects of alternative fire management scenarios.

scholarly journals Environmental and taxonomic controls of carbon and oxygen stable isotope composition in <i>Sphagnum</i> across broad climatic and geographic ranges

2018 ◽  
Author(s):  
Gustaf Granath ◽  
Håkan Rydin ◽  
Jennifer L. Baltzer ◽  
Fia Bengtsson ◽  
Nicholas Boncek ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Large Scale ◽  
Net Primary Productivity ◽  
Isotope Composition ◽  
Isotopic Signature ◽  
Δ13c Values ◽  
Geographic Ranges ◽  
Lower Elevation ◽  
Site Variation ◽  
Species Specific

Abstract. Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.), which for their growth depend on elements from the atmosphere. As the isotopic composition of carbon (12,13C) and oxygen (16,18O) of these Sphagnum mosses are affected by environmental conditions, the dead Sphagnum tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is a lack of adequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of Sphagnum is species-specific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation), and elevation; (ii) if the C isotopic signature can be a proxy for net primary productivity (NPP) of Sphagnum; and (iii) to what extent Sphagnum tissue δ18O tracks the δ18O isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia using two important peat-forming Sphagnum species (S. magellanicum, S. fuscum) common to the Holartic realm. There were differences in δ13C values between species. For S. magellanicum δ13C decreased with increasing height above the water table (HWT, R2 = 17 %) and was positively correlated to productivity (R2 = 7 %). Together these two variables explained 46 % of the between-site variation in δ13C values. For S. fuscum, productivity was the only significant predictor of δ13C (total R2 = 6 %). For δ18O values, ca. 90 % of the variation was found between sites. Globally-modelled annual δ18O values in precipitation explained 69% of the between-site variation in tissue δ18O. S. magellanicum showed lower δ18O enrichment than S. fuscum (−0.83 ‰ lower) . Elevation and climatic variables were weak predictors of tissue δ18O values after controlling for δ18O values of the precipitation. To summarise, our study provides evidence for (a) good predictability of tissue δ18O values from modelled annual δ18O values in precipitation, and (b) the possibility to relate tissue δ13C values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used at a large scale for climatic reconstructions but that such models should be species-specific.

Determinants of resource use efficiencies among lowland rice farmers of Enugu State, Nigeria

Agro-Science ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 61-67
Author(s):  
T.C. Okoh ◽  
P.I. Opata ◽  
I.I. Umaru
Keyword(s):  
Resource Use ◽  
Large Scale ◽  
Average Rate ◽  
Allocative Efficiency ◽  
The State ◽  
Lowland Rice ◽  
Gross Margin ◽  
Rice Farmers ◽  
State Education ◽  
Enugu State

The gap in supply and demand of rice could be due to observable differentials in the allocative efficiency of the rice farmers in Nigeria. Therefore, the study focused on the determinants of resource-use efficiencies and profitability of lowland rice farmers of Enugu State, Nigeria. A multistage sampling technique was used to collect cross-sectional data from 300 smallholder rice farmers across the six agricultural zones of the State. The gross margin (GM) analysis was used to estimate the profitability while the marginal value productmarginal factor cost (MVP-MFC) was used to evaluate the efficiency of rice farming. The Stochastic Frontier Cost Function was also used to estimate the determinants of resource use efficiency among lowland rice farmers in Enugu state. The results from the GM showed that rice production is profitable with an average rate of returns on investment (ROI) of 2.80. The MVP-MFC analysis showed that all the input factors hypothesized were over-utilised indicating the existence of large-scale resource-use inefficiency among lowland rice farmers of the state. Education and age were the only socio-economic variables that affected the allocative efficiency of the rice farmers. The study recommends a farm-level policy directed towards the encouragement of younger adults since they are more likely to adopt innovation and boost efficiency and investment in extension education for advisory services to facilitate resource-use efficiencies.

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