Web Niche on Biodiversity & Conservation Biology

Welcome to my Web Niche on Biodiversity and Conservation Biology (BCB) the department I work in at the University of the Western Cape, Cape Town. Biodiversity is the variety of forms of living organisms at various levels and Conservation Biology is the study of how we can prevent species and habitats being lost while still maintaining sustainable human societies. I teach Landscape Ecology and Ecological Informatics.

Wednesday, December 07, 2005

Biodiversity and how we assess it?

BIODIVERSITY at its most basic level includes the full range of species on the planet from the simplest structures that contain DNA, the viruses through to organisms with possess nucleuses, it includes single-celled organisms through to multi-cellular organisms which include plants, animals and fungi. This can be considered SPECIES DIVERSITY.

At a different level, biodiversity would include the genetic variation within a single population or between several populations, the genetic variation within a variety or subspecies or species. This can be considered GENETIC DIVERSITY.

At its widest level it can include variations in the biological communities in which species live, the ecosystems in which the communities occur in and the interactions among these levels. This can be considered COMMUNITY-LEVEL DIVERSITY.


GENETIC DIVERSITY is needed by any species in order to maintain reproductive vitality, resistance to disease, and the ability to adapt to changing conditions. Genetic diversity within domestic plants and animals is of particular value in the breeding programme necessary to maintain them.

SPECIES DIVERSITY represents the range of evolutionary and ecological adaptations of species. The variety of species can be considered a resource and maintaining such variety gives the option of it being used as an alternative. For example the diversity of tropical rain forest species is particularly important in finding new pharmaceutical products.

COMMUNITY-LEVEL DIVERSITY represents how species coexist in specific habitats and the relationships between species in ecosystems. The maintenance of proper ecosystem functionality is one of the main tasks that has to be undertaken by Nature Conservation Agencies.

SPECIES DIVERSITY

Species are generally defined from a morphologically, physiologically or biochemically distinct (taxonomists use this)and are a group of individuals that can potentially breed among themselves (ecologist use this)

Nomenclature of Species

Unique naming
Binomial system
Hierarchical organisation (Kingdom, Phylum, Class, Order, Family, Genus, Species)

PROBLEMS WITH THE SPECIES CONCEPT

Species versus varieties (e.g. dogs)
Sibling species
Hybridization
Identification (species-rich communities)

ORIGIN OF SPECIES

Biological organisms evolved 3.5 billion years ago
Conceptualization of the species concept:- Darwin and Wallace

SPECIATION

Based on more offspring produced than survive

Differences in genetic material will enable some individuals to grow, survive and reproduce better than other individuals.
When a population is sufficiently changed genetically than it can no longer interbreed with the original species call it PHYLETIC EVOLUTION.

SPECIATION is particularly rapid on islands Galapagos (Darwin’s finches) and Hawaii (Honey creepers) and is termed ADAPTIVE RADIATION

TWO TYPES OF SPECIATION

Allopatric speciation created through geographical separation

Sympatric speciation occurs without geographical separation

RATES OF SPECIATION

Generally a slow process

Fast speciation achieved through unequal division of chromosomes which arise to polyploids (plants and even animals e.g. Gila monster)

Speciation rates currently much slower than extinction rates.
(National parks generally too small to support speciation process)

GENETIC DIVERSITY

Important concept is the population defined as a group of individuals that mate with one another and produce offspring, a species may include one or more populations.

Individuals within a population are usually genetically different from one another and this is reflected in their genes.

Genes are units of a chromosome that code for a specific protein.

Alleles are alternative forms of genes coding for the same trait.

GENETIC VARIATION is achieved via recombinations of genes

GENE POOL is the total array of genes and alleles in a population

GENOTYPE combination of alleles possessed within an individual

PHENOTYPE morphological, physiological, anatomical and biochemical characterization of the individuals

GENETIC VARIABILITY IN A POPULATION

Determined by the number of genes that have more than one allele (= polymorphic genes) and the number of alleles for each polymorphic gene

For a population to be heterozygous for a gene it must receive two different alleles of the gene from their two parents

Heterozygous individuals tend to grow , survive and reproduce more successfully (=fitter) and is referred to as HYBRID VIGOR

ARTIFICIAL SELECTION is often the reverse of hybrid vigor.

COMMUNITIES AND ECOSYSTEMS

Species interactions within biological communities come about through processes such as

competition
predation
mutualism


Species occupy distinct trophic or feeding levels within communities and reflect their way in which they obtain energy. Individual species often have specific feeding relationships with other species that can be represented as a food chain or food web.

KEYSTONE SPECIES/RESOURCES

Certain keystone species appear to be important in determining the ability of other species to persist in a community. These keystone species are often top carnivores but can be other species (including a fruiting tree species for a suite of frugivores). The loss of a keystone species from a community can result in a cascade of extinctions of other species.

LEOPARD or CROWNED EAGLE (REDUCED)

impacts on

MONKEYS (INCREASE)

impacts on

BIRDS (REDUCED DUE TO PREDATION)


impacts on

FOREST TREES (REDUCED POLINATION/SEED DISPERSAL PROCESSES UPSET)

Certain keystone resources, such as water holes and salt licks may occupy small fractions of a habitat, but may be crucial to the persistence of many species in an area.


MEASURING BIOLOGICAL DIVERSITY

Mathematical indices of biological diversity have been developed to examine and compare patterns of species distribution at local and regional levels. Such mathematical indices are chiefly useful for examining particular groups of species rather than the full range of species and interactions founds in nature.

Many of these measures examine the evenness of species occurrence in relation to the number of species. Differing techniques have different biases with some being strongly affected by sampling size and others by species rarity.

ALPHA DIVERSITY: The number of species in a single community

BETA DIVERSITY: degree to which species composition changes along environmental gradients and the effects looks at species turnover.

GAMMA DIVERSITY: applies to larger geographical scales and looks at the rate at which additional species are encountered as geographical replacements within a habitat type occur in different localities.

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