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Seven taxa of 2 families Muridae, Heteromyidae of small rodents were captured Hodomys alleni, Liomys pictus, Oryzomys couesi, Peromyscus aztecus, Reithrodontomys fulvescens, R. Information about age structure, population dynamics, biomass, and reproduction were obtained with mark—recapture techniques for the most abundant species P. These species comprised Species varied in population density, relative abundance, and timing of reproduction, which was seasonal.
Reproductive activity for P. Density fluctuated annually for P. A fundamental question in population and community ecology is what determines distribution and abundance of species within local regions Begon et al. These attributes of a population are determined primarily by the extent to which individual organisms can tolerate conditions and acquire essential resources Brown and Harney ; Morton et al.
Temporal and spatial variation in population density is largely a consequence of interactions between limiting factors of the environment and life-history characteristics of species e. Demographic patterns and strategies are affected by phylogenetic affinities of species, interspecific interactions, and a multitude of environmental factors. Thus, comparative population ecology is crucial to understand community structure, as a partial explanation of coexistence of similar or related species Brown and Zeng ; Fleming Comparative studies of population ecology of coexisting species are important to understanding community organization and ecological processes.
Extensive research on population and community ecology of mammals generally has been conducted in the north-temperate zone and desert regions Brown and Harney ; Brown and Zeng ; Mares and Cameron ; Rosenzweig and Winakur , but little is known about basic population and community ecology of small rodents in tropical zones.
Studies on population ecology of coexisting small mammals in Mexico are even more scarce. We compare population and community ecology of small rodents in 2 habitats, cloud forests and disturbed areas, in the mountains of western Jalisco, Mexico. Our objectives were to compare demographic and reproductive patterns and population dynamics of the most abundant species in both habitats and determine composition and diversity of species of small rodents in each habitat. Annual rainfall is 1, mm, but pronounced seasonal variation results in 3 predictable seasons; dry-hot season March—June , rainy season July—October , and dry-cold season November—February; Cuevas Five main forest habitats occur at ECLJ: pine forest, pine—oak forest, cloud forest, oak forest, and gallery forest, in addition to disturbed areas Cuevas ; Jardel We studied mature cloud forest and disturbed cloud forest.
The cloud forest occupied the most humid sites. That vegetation, located in protected dales and slopes, is composed of trees reaching 40 m in height, with low penetration of light in most areas. The cloud forest occupied Dominant arboreal and shrubby species in this habitat included Carpinus tropicalis, Cinnamomum pachypodum, Cornus disciflora, Magnolia iltisiana, Persea hintonii, Quercus candicans, Q. Disturbed areas were agricultural fields placed in patches of cleared cloud forest and abandoned 15—20 years ago.
That vegetation occupied Average distance between grids was m. One hundred Sherman live traps 23 by 7. Traps were operated for 3 days each month from April through May , for 12, trap nights in disturbed areas and 15, trap nights in cloud forest.
Traps were baited in the afternoon with a mixture of cracked corn wet season or oats dry season , peanut butter, and liquid vanilla.
Captured animals were marked by toe-clipping and released after recording location of capture, identification number, body mass, length of hind foot, age, sex, and reproductive condition. Individuals were aged as juvenile or adult based on body size and pelage Fleming For males, reproductive condition was determined by relative size and position of testes abdominal or scrotal ; for females, condition of vagina open or closed , condition of nipples small, lactating, or recently lactating , and presence or absence of palpable embryos were recorded.
The minimum-number-known-alive technique MNKA; Krebs was used to estimate population size and sex ratios. Relative abundance of each species was expressed as a ratio of MNKA of the more common species.
Population size was divided by effective trapping areas of the grids to estimate density Mares and Ernest Effective trapping areas were determined by adding a boundary strip around the area of each grid that was computed as the mean distance between captures of the most abundant species 10 m. For estimates of biomass of the total population, we multiplied body mass at 1st capture of each individual times monthly population density.
For individuals that were not captured in a particular month but were known to be alive in subsequent trapping seasons, we used their average body mass in previous and subsequent captures. We determined population structure age and sex categories for the most common species based on actual number of individuals captured during each trapping period. Species diversity was computed with the Shannon—Wiener index Magurran and compared with a t -test Hutcheson Analyses were based on captures of individuals of 6 species in cloud forest and captures of individuals of 6 species in disturbed areas.
These habitats shared 5 species Hodomys alleni, Oryzomys couesi, Peromyscus aztecus, Reithrodontomys fulvescens, and Sigmodon alleni [captured once in cloud forest] , Liomys pictus was captured only in disturbed areas, and R. During the 14 months of trapping, only R. Species richness in both habitats was lowest during the mid-dry season and peaked at the end of the wet season. The pattern of relative abundance revealed that 3 species were rare H.
In disturbed area, 2 species P. Data for biomass and density are based on numbers of captures. Although some juveniles and subadults were captured, they were not included in estimates of biomass. Density was calculated for the 2 most abundant species P.
Density of P. Population fluctuations of P. Density also differed between habitats for R. Monthly population density of R. Population density average monthly minimum number known alive per hectare for 2 species of rodents. Reproductive activity Fig. Reproductively active males appeared during all 14 months of trapping, but mainly during the end of the dry-cold and middle of the dry-hot seasons. Pregnant females of P. Reproductively active females on disturbed area were recorded from November through February , pregnant females were captured in December , and males were reproductively active September—October and February—April The lowest reproductive activity was found for females of R.
In disturbed area, we recorded reproductive activity of females from May to September; males were present from May—August and January—February. Sex ratios males : females in cloud forest varied for R. The sex ratio for P. Age structure of P. Juvenile R. The percentage of adults of R. The rodent community at our study areas was composed of 7 species. Community composition varied temporally between habitats, with species increasing and decreasing in different patterns.
Other studies of tropical rodent communities reported a range from 4 to 11 species of small rodents August ; Fleming ; Mares and Ernest Indeed, our study at ECLJ illustrated that cloud-forest habitat is among the richest Neotropical and Nearctic habitats for small rodents. The high richness of small rodents may be attributable in part to our study site occurring in a transition areas between 2 biogeographic regions Neotropical—Nearctic and the heterogeneous landscape at RBSM.
Fluctuation in densities of the most common species paralleled each other in both habitats. Two of the murid rodents showed pronounced fluctuations in population density. Populations of R. This seasonality in peaks of density concurs with that of R. In southeastern Texas, R. Little seasonality has been reported in reproduction of R.
In our study, sexually active female R. Males almost always were reproductively active. The number of males of R. In several studies in Texas, numbers of males commonly were greater than numbers of females Cameron ; Joule and Jamerson Reproductive activity of male P.
In central Chiapas, Mexico, activity of females was reported in May Alvarez et al. In our study, females of P. Our results indicate that cloud forest supports a richer rodent community than disturbed areas, and perhaps is richer than other temperate and tropical localities.
Our data provide a point of departure for future long-term studies of rodent communities that would allow comparison of population and community parameters of species in these kinds of habitats.
We thank C. Ayala, K. Blanco, H. Olivo, D. Ruiz, and H. Olivo assisted with logistics and reviewed the manuscript. We are grateful to E. We thank an anonymous reviewer who made several excellent suggestions.
Cameron, INT Alvarez T. Arroyo J. Google Scholar. August P. Population ecology of small mammals in the llanos of Venezuela.
In this paper we emphasize that sampling decisions in population and community ecology are context dependent. Thus, the selection of an appropriate sampling procedure should follow directly from considerations of the objectives of an investigation. We recognize eight sampling alternatives, which arise as a result of three basic dichotomies: parameter estimation versus pattern detection, univariate versus multivariate, and a discrete versus continuous sampling universe. These eight alternative sampling procedures are discussed as they relate to decisions regarding the required empirical sample size, the selection or arrangement of sampling units, and plot size and shape. Our results indicate that the decision-making process in sampling must be viewed as a flexible exercise, dictated not by generalized recommendations but by specific objectives: there is no panacea in ecological sampling. We also point to a number of unresolved sampling problems in ecology. This is a preview of subscription content, access via your institution.
McNaughton, Samuel J. Last reviewed: June The subdiscipline of biology that concentrates on the relationships between organisms and their environments. Ecology, also called environmental biology, is concerned with patterns of distribution where organisms occur and with patterns of abundance how many organisms occur in space and time. It seeks to explain the factors that determine the range of environments that organisms occupy and that determine the abundance of organisms within those ranges.
Specifically, he seeks to identify the mechanisms by which behavioral, population, and community dynamics mediate nutrient and energy pathways. The objective is to improve our ability to predict ecological outcomes and enhance conservation efficacy such as the sustainability of ecosystem services e. Much of this research takes place in tropical coastal ecosystems mangroves, seagrass beds and coral reefs where he studies gradients created by anthropogenic impacts to test theory directly within the context of environmental change and biodiversity loss. Robyn Burnham studies the high diversity tropical forests of Ecuador, Peru and Brazil, identifying the dominant species in liana communities across the Amazon Basin, and determines the traits that predispose climbing species to proliferate under forest alterations. They work across scales from the micro soil food webs to the macro regional carbon fluxes as well as across diverse terrestrial ecosystems forests, meadows, bogs, tropics, boreal, temperate.
Activities, discussion leader, and required readings. General syllabus. Reading the literature pdf.
Community ecology is the study of the interactions between species in communities on many spatial and temporal scales, including the distribution, structure, abundance, demography, and interactions between coexisting populations. The primary focus of community ecology is on the interactions between populations as determined by specific genotypic and phenotypic characteristics. It is one of the most important aquaculture food resources worldwide.
Seven taxa of 2 families Muridae, Heteromyidae of small rodents were captured Hodomys alleni, Liomys pictus, Oryzomys couesi, Peromyscus aztecus, Reithrodontomys fulvescens, R. Information about age structure, population dynamics, biomass, and reproduction were obtained with mark—recapture techniques for the most abundant species P. These species comprised Species varied in population density, relative abundance, and timing of reproduction, which was seasonal. Reproductive activity for P. Density fluctuated annually for P.
In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis , biotic community , biological community , ecological community , or life assemblage. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization". Community ecology or synecology is the study of the interactions between species in communities on many spatial and temporal scales, including the distribution, structure, abundance, demography , and interactions between coexisting populations. Community ecology also takes into account abiotic factors e.
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ГЛАВА 113 - Ни в коем случае! - крикнул мужчина с короткой стрижкой, глядя в камеру. - У нас приказ. Мы отчитываемся перед директором Лиландом Фонтейном, и только перед. Фонтейна это позабавило. - Вы знаете, кто. - Какая разница? - огрызнулся светловолосый. - Позвольте вам сразу кое-что объяснить, - сказал директор.
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Keywords: Ecology, Population, Evolution Theory, Population Demography, Energy. Contents. 1. Introduction. 2. Ecological Systems as a Subject of Ecology. 3.Reply
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