Modelling the abundance and productivity distribution to understand the habitat–species relationship: the guanaco (Lama guanicoe) case study

2020 ◽  
Vol 47 (6) ◽  
pp. 448
Author(s):  
Celina E. Flores ◽  
Laura M. Bellis ◽  
Schiavini Adrián
Keyword(s):  
Interspecific Competition ◽  
Breeding Season ◽  
Food Availability ◽  
Geographic Location ◽  
Distribution Patterns ◽  
Species Relationship ◽  
Productivity Distribution ◽  
Forage Availability ◽  
Feral Dogs ◽  
Family Groups

Abstract ContextThe conservation of large wild herbivores presents a challenge posed by the fact that their broad habitat requirements overlap with various human activities. Elucidating the factors that explain their distribution patterns provides us with a better understanding of habitat–species relationships and facilitates the design of effective management policies. AimsIdentify the natural (forage availability, weather) and anthropogenic (hunting, interspecific competition) factors that explain the abundance and productivity distribution of the guanaco. Estimate guanaco abundance and productivity and describe their distribution. MethodsWe estimated the abundance and productivity of guanaco by using aerial surveys during the breeding and non-breeding season of two consecutive years, following the strip-transect methodology; we then modelled these as a function of environmental factors by means of density surface models. Key resultsThe highest abundance and productivity of guanaco occurred mostly where mesic grassland was dominant. Guanaco abundance presented three hotspots on the basis of geographic location, and family groups were more productive at low to intermediate livestock level. Abundance was significantly higher in the breeding season for both years (5614 and 14092 individuals) than in the non-breeding season (2922 and 6926 individuals), and it was higher in 2015 than in 2014. Productivity was higher in 2015 than in 2014 (0.54 and 0.46 calves per adult respectively). ConclusionsGuanaco responded to forage availability, occupying zones with low to intermediate food availability in the breeding season, and those with the highest availability in the non-breeding season. This could be due to interspecific competition between livestock and guanaco family groups. We propose that the overall guanaco response could also be explained by social structure or by unassessed factors such as predation risk by feral dogs. ImplicationsThe guanaco could compensate for the use of habitats with a lower food availability during the breeding season by using better-quality habitats during the non-breeding season.

Food availability and initial relative abundance determine the outcome of interspecific competition between two different-sized cladocerans

2016 ◽  
Vol 101 (3-4) ◽  
pp. 105-112 ◽  
Author(s):  
Rui Chen ◽  
Hengxing Tang ◽  
Feixi Zhao ◽  
Yingyuan Wu ◽  
Yuan Huang ◽  
...  
Keyword(s):  
Interspecific Competition ◽  
Food Availability ◽  
Relative Abundance

Ecological and environmental indicators of Brazil Nut Tree (Bertholletia excelsa Bonpl.) in Flona do Jamari, Rondônia

2020 ◽  
Vol 11 (7) ◽  
pp. 740-751
Author(s):  
Nilson Reinaldo Fernandes dos Santos Júnior ◽  
Diogo Martins Rosa ◽  
José Das Dores de Sá Rocha ◽  
Marta Silvana Volpato Sccoti ◽  
Scheila Cristina Biazatti ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Distribution Pattern ◽  
Geographic Location ◽  
Distribution Patterns ◽  
Environmental Indicators ◽  
Diameter Distribution ◽  
Brazil Nut ◽  
Productive Potential ◽  
Morisita Index ◽  
Individual Trees

Mapping Brazil nut trees in the Amazon is essential for indicating its distribution patterns within different ecosystems, while also being useful to estimate the species productive potential. This study aimed to evaluate the spatial distribution of Brazil nut trees in Flona do Jamari – RO, considering its environmental and topographic conditions. A census was performed for all individual trees sized ≥ 35 cm in diameter at 1.30 m breast height (DBH) above the ground of six Annual Production Units (APU) in Forest Management Unit III (FMU-III), a 11,011.2 ha area of Flona do Jamari, RO. DBH and geographic location (GPS) were collected for each tree. Structure and diameter distribution were evaluated by abundance, density, dominance, and frequency. The Morisita index was used to identify the spatial distribution pattern. The environment was defined by the local relative height found along the drainage network, by the digital model Height Above the Nearest Drainage (HAND). Most trees were among DBH intermediate classes (60 to 140 cm), and only a few were young trees (DBH < 50 cm). Brazil nut trees present a random spatial distribution and a predominant distribution pattern of 'terra-firme (solid ground)'. Such information on the species structural, spatial, and ecological patterns serve as key elements for further studies on production potential.

scholarly journals Scales of Food Availability for an Endangered Insectivore, The Hawaii Akepa

The Auk ◽  
2002 ◽  
Vol 119 (1) ◽  
pp. 166-174 ◽  
Author(s):  
J. Scott Fretz
Keyword(s):  
Food Availability ◽  
Prey Availability ◽  
Spatial Scales ◽  
Canopy Cover ◽  
Distribution Patterns ◽  
Prey Population ◽  
Suitable Habitat ◽  
Population Declines ◽  
Loxops Coccineus ◽  
A Site

Abstract The Hawaii Akepa (Loxops coccineus coccineus) is an endangered bird that has declined dramatically in the last 100 years, and is now rare or absent from many areas that appear to support suitable habitat. Food availability may play a role in these distribution patterns, but differences in food between sites may arise from different sources. I compared prey availability between a site supporting a large, stable Hawaii Akepa population, and a site from which Hawaii Akepa have declined in the last 100 years for unknown reasons. I used three spatial scales to compare food between sites to explore the basis of differences in food between sites. At a scale appropriate for comparing prey population dynamics (scale 1), I found that prey population densities are similar between sites, suggesting that introduced (or native) predators or parasitoids have not affected prey populations differently between sites. At two larger scales incorporating habitat structure, I found that food availability is much lower at the site of Hawaii Akepa declines. Differences in canopy density per square meter (scale 2), and in canopy cover per square kilometer (scale 3), result in lower food availability that may have effects on individual foraging birds as well as on potential Hawaii Akepa population density. These findings illustrate the importance of explicitly incorporating spatial scale into inquiries about food for Hawaii Akepa, and suggest that the site of population declines may not be suitable habitat with respect to food for this species.

scholarly journals The Effects of Water Levels and Interspecific Competition on Two Carex Species in a Temperate Wetland of Northeast China

2020 ◽  
Vol 12 (24) ◽  
pp. 10654
Author(s):  
Wenwen Tan ◽  
Li Sun ◽  
Xinhou Zhang ◽  
Changchun Song
Keyword(s):  
Spatial Distribution ◽  
Water Level ◽  
Interspecific Competition ◽  
Distribution Patterns ◽  
Wetland Plants ◽  
Water Levels ◽  
Carex Lasiocarpa ◽  
Temperate Wetland ◽  
The Relationship ◽  
Spatial Distribution Characteristic

Zonation along a water level is the main spatial distribution characteristic of wetland plants. This is mainly because of the influences of hydrological conditions and interspecific competition, which finally narrow the fundamental niche of a species to its realized niche. In the present study, a controlled experiment was conducted in order to analyze the relationship between Carex lasiocarpa/Carex pseudocuraica and Glyceria spiculosa, in conditions of three competitive treatments at four water levels. The results showed that in no competition, C. lasiocarpa preferred low water levels, but this preference receded when competing with G. spiculosa. In contrast, C. pseudocuraica had greater preference for low water level when competing with G. spiculosa. The root/shoot ratios of the two Carex species decreased with increasing water levels, but they were almost unaffected by different competition treatments. With the increase in water level during full competition with G. spiculosa, the competitive ability of C. lasiocarpa showed an increasing trend, whereas a contrary trend was observed in C. pseudocuraica. Our results suggested the effects of water levels and their interactions with interspecific competition varied between the two Carex species and played an important role in determining spatial distribution patterns and potential community succession of wetland plants.

Co-existence, Demography and Distribution Patterns of Two Co-occurring Ecologically Equivalent Fynbos Proteaceae Species

1998 ◽  
Vol 46 (4) ◽  
pp. 505 ◽  
Author(s):  
J. J. Midgley ◽  
N. J. Enright ◽  
R. M. Cowling
Keyword(s):  
Interspecific Competition ◽  
Competitive Exclusion ◽  
Distribution Patterns ◽  
Size Class ◽  
Fire Intensity ◽  
Shallow Soil ◽  
Cape Peninsula ◽  
Rocky Habitats

Leucospermum conocarpodendron (L.) Beuk. and Mimetes fimbriifolius Salisb. ex J.Knight co-occur in the southern Cape Peninsula, where we studied their distribution patterns, demography and fire responses. Leucospermum conocarpodendron has relatively larger seedlings and is therefore the likely competitive dominant. Adults and seedlings of both species are widely spaced and interspecific competition is unlikely to cause competitive exclusion. Differences between the two species in recruitment levels and fire-mortality are small. Thus their size-class distributions are very similar. They are restricted to shallow-soil rocky habitats, not only because of reduced fire intensity in these sites, but because these are habitats avoided by the faster growing more competitive reseeding Proteaceae. Co-existence of these two species appears to mainly be due to fire keeping populations sparse, and ants keeping individuals fairly isolated.

Silver gull breeding at two colonies in the Sydney-Wollongong regio, Australia

1992 ◽  
Vol 19 (4) ◽  
pp. 429 ◽  
Author(s):  
GC Smith ◽  
N Carlile
Keyword(s):  
Clutch Size ◽  
Breeding Season ◽  
Food Availability ◽  
Breeding Success ◽  
Artificial Structures ◽  
Sydney Harbour ◽  
The 1960S ◽  
Almost All

Silver gulls have increased in abundance in Sydney-Wollongong this century. Both the number of colonies and their sizes have grown. The largest colony of 43 000-50000 pairs is on Big I., off Wollongong. Breeding was compared at this colony with that at a satellite colony on artificial structures in Rozelle Bay, Sydney Harbour. Breeding occurred from July to February at Big I., a lengthening of the season since the 1960s. At Rozelle Bay, breeding occurred almost all year round. Egg and clutch size varied within and between years at Big I. First-eggs of clutches, laid during the first breeding peak, were significantly larger than those laid later in each breeding season. The size of third-eggs in clutches differed between years. It is proposed that these disparities were a result of differences in food availability between years. Clutch sizes were significantly larger during the first breeding peak than later clutches of each season. Clutch size was larger at Rozelle Bay. Variation in clutch size was linked to quality of individuals and food availability. Breeding success at colonies was low, indicating that carrying capacities have been reached.

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