Distribution Of Other Organisms Research Articles

Amphibian and Reptilian Chorotypes in the Arid Land of Central Asia and Their Determinants

The analysis of the biogeographic distribution of species is the basis for establishing a strategy for land management and responding to climatic change, but research on the distribution of amphibians and reptiles in the arid land in the middle of Asia is extremely limited. After classifying the chorotypes of amphibians and reptiles in the arid land of Central Asia using a clustering analysis, we delineated their distribution characteristics and discovered the ecological determinants for the chorotypes in terms of feature selection and the Akaike information criterion (AIC). We identified 6 chorotypes at the higher level and 16 sub-chorotypes at the lower level. Compared to small-scale or subjective research, which produces unstable results, research characterized by both large scale and clustering methods yields more consistent and stable results. Our results show that the Mean Altitude (MA), Mean Annual Temperature (MAT), and Mean Temperature in the Wettest Quarter (MTWE) are the critical variables determining the higher-level chorotypes. Furthermore, geographical factors appear to have a stronger influence on chorotypes than climatic factors. Several climatic variables and MA were identified as the best fit in the AIC model at the lower level, while the sub-chorotypes are determined more by multiple climatic factors with complex relationships. The research on amphibian and reptilian distribution patterns will shed light on the overall distribution of other species in the same understudied area. Widespread species in the study area are not clearly distinguished due to the cluster analysis computing process. This problem however, appears in studies of the distribution of other organisms thus warrants further research. Our methodology based on the selection of multiple models is effective to explore how the environment determines the distributions of different animal groups.

Patterns of occurrence of grazing molluscs on sandstone and concrete seawalls inSydney Harbour (Australia)

Proliferation of artificial structures is a common feature in urbanized environments. In Sydney Harbour (NSW, Australia), much of the coastline is composed of seawalls that have replaced natural habitats, such as rocky shores. Many of these seawalls are made of sandstone blocks or concrete, but the effects of the type of substratum on assemblages living on seawalls has not been documented. Nevertheless, differences in characteristics of substratum have been shown to affect composition and development of intertidal assemblages. Grazing molluscs are important agents in the structuring of intertidal assemblages affecting numbers and distribution of other organisms. This study compares species and numbers of grazing molluscs at midshore levels between concrete and sandstone seawalls across Sydney Harbour. The two habitats supported a similar suite of species, although in different numbers and frequencies of occurrence, particularly higher on the shore. Therefore, concrete and sandstone seawalls provide different habitat for intertidal molluscs depending on tidal height. Experimental work is needed to assess properly the impact of construction of seawalls with different materials on intertidal biodiversity.

Inferring species distributions in the absence of occurrence records: An example considering wolverine ( Gulo gulo) and Canada lynx ( Lynx canadensis) in New Mexico

Information about geographic distributions is required for species conservation and management. Ultimately, this information is derived from records of occurrence. However, the reliability and availability of occurrence records are variable. A conceptual framework for evaluating the reliability of occurrence records is provided. Only records associated with physical evidence, especially a museum voucher specimen, are considered verified. However, errors in species identification or location are possible even for verified records. In addition, biases exist in occurrence records because they generally are collected haphazardly. Other sources of bias include sampling error associated with small areas or range limits and aspects of the species’ biology that make it unlikely to be documented. A practical method is provided for interpreting a species’ distribution in a particular area given a paucity of reliable occurrence records. Factors that must be considered for including such areas of interest within the range of a species include: (1) plausible reason for the paucity of records; (2) continuous suitable habitat between the area of interest and localities of reliable occurrence; and (3) absence of biogeographic breaks in the distribution of other organisms with similar evolutionary histories. The possible distribution of wolverine ( Gulo gulo) and Canada lynx ( Lynx canadensis) in New Mexico provides a case study of this approach. It is concluded that the mountains of north-central New Mexico should be considered within the natural range of wolverine and Canada lynx.

Functional Matrix: A Conceptual Framework for Predicting Multiple Plant Effects on Ecosystem Processes

▪ Abstract Plant species differ in how they influence many aspects of ecosystem structure and function, including soil characteristics, geomorphology, biogeochemistry, regional climate, and the activity and distribution of other organisms. Attempts to generalize plant species effects on ecosystems have focused on single traits or suites of traits that strongly covary (functional groups). However, plant effects on any ecosystem process are mediated by multiple traits, and many of these traits vary independently from one another. Thus, most species have unique combinations of traits that influence ecosystems, and there is no single trait or functional-group classification that can capture the effects of these multiple traits, or can predict the multiple functions performed by different plant species.We present a new theoretical framework, the functional matrix, which builds upon the functional group and single trait approaches to account for the ecosystem effects of multiple traits that vary independently among species. The functional matrix describes the relationship between ecosystem processes and multiple traits, treating traits as continuous variables, and determining if the effects of these multiple traits are additive or interactive. The power of this approach is that the ecosystem effects of multiple traits are the underlying mechanisms determining species effects, how the effects of an individual species change across seasons and under varying environmental conditions, the nonadditive effects of plant species mixtures, and the effects of species diversity.

Component concept for the study of the paleocommunities with an example from the Early Carboniferous of Southern Indiana (U.S.A.)

Predominantly suspension-feeding faunas of three contemporaneous, laterally contignous Early Carboniferous (Early Mississippian) facies are studied from exposures in southern Indiana (U.S.A.). Each major taxonomic group is examined for the primary limiting factors controlling its distribution. The paleoecology of the entire fauna is more easily evaluated from a component viewpoint. Five components are recognized with important limiting factors listed for each component as follows: (1) organisms that lived at the sediment—water interface which are influenced by sediment mobility and grain size, including brachiopods, bryozoans, etc.; (2) organisms controlled by prevalent energy conditions, such as crinoids; (3) organisms controlled by turbidity such as sponges; (4) commensal, parasitic, or predaceous organisms that are dependent upon the distribution of other organisms; and (5) nektonic and planktonic organisms whose distribution and abundance are not only controlled by their original biological distribution but also by the depositional rate, including fish and conodonts. The distributions of different community components are independent; however, community integrity within a component is maintained from place to place at any time within a paleogeographic province.

The Vertical Distribution of Marine Macroplankton. An Observation on Diurnal Changes

INTRODUCTION.1. A series of hauls with the ring-trawl were made at five depths in water 50 metres deep, so that samples were obtained approximately in daylight, at dusk, at midnight, at dawn, and again in daylight.A depth-recorder was used with the net giving a graphic record of its path through the water.2. Examination of the catches demonstrated the diurnal changes in vertical distribution of the species caught by the ring-trawl.3. Four types of behaviour were shown:—(a) A definite migration to the surface in the dark hours of certain forms living in the deeper layers in the daytime.(b) An expanding of the distribution of other organisms, that in the daytime had a zone of maximum abundance in the deeper layers, so that they were evenly scattered from the surface downwards.(c) Certain animals showed no or very little change in their vertical distribution during the dark hours.(d) A movement up to the midwater region by those forms that during the daytime adopt either a truly benthic existence or are congregated in the water layers immediately adjacent to the sea floor.(Lists of species grouped under their respective types of behaviour are to be found on page 780.)4. Many such observations are required before conclusions can be drawn as to the normal diurnal behaviour of plankton animals: this is a definite record of what occurred in this locality in mid-July at a period of full moon in fair weather.