Lecture 2

Conservation BiologyBIOL3620Lecture 2Introduction to BiodiversityPrimack - Chapter 2 2What is Biodiversity?The sum total of all living things – the richness and variation in the living world. 3What is Biodiversity?Biodiversity can be considered on three different levels:Genetic diversityNumber of Genes/AllelesThe genetic variation within species, both among geographically separate populations and among individuals within single populations Species diversitynumber of speciesAll the species on Earth, from single-celled bacteria and protists to the multicellular kingdoms (plants, fungi, and animals), Ecosystemnumber of community typesThe different biological communities and their associations with the chemical and physical environment (“the ecosystem”) 4Importance of Biodiversity?Figure 2.1 Biological diversity includes genetic, species, and community/ecosystem diversity 5Species DiversitySpecies are “fundamental units of evolution”One major goal of conservation biology – recognizing and classifying speciesWhat is a species?Two different definitions:1.2. 6Species DiversityMorphological Definition of Species:“A group of individuals that is morphologically, physiologically or biochemically distinct from other groups in some important characteristic”is a group of individuals that can potentially breed among themselves and do not breed with individuals of other groups’.Some species that look similar differ in DNA sequences or other molecular markersE.g. bacteria 7Species DiversityMorphological definition most often used by taxonomistsFigure 2.2 (A) A botanist preparing a plant specimen; (B) Natural history collectionsstyle.visibilityppt_xppt_ystyle.visibility 8Species DiversityBiological Definition of Species:“A group of individuals that can potentially breed among themselves in the wild and that do not breed with individuals of other groups”Typically used by evolutionary biologistsEmphasis on breeding and genetic relationships not just physical features 9Species DiversityMorphological vs. Biological species definitionMethods and assumptions used for each are differentSometimes give different resultsWhich is better/more appropriate definition? 10Species DiversityWhich Definition is Best?In practice, biological definition difficult to useRequires knowledge of breeding potentialAsexually reproducing species?Fossils?When reproductive information not available, morphological differences that might represent a different species are usedSpecies determined in this manner referred to as morphospecies. 11Species DiversityMorphospeciesUseful because organisms that look alike generally share many alleles that code for morphological similarities.Many species designations based on morphology have been supported by more recent genetic data. 12Problems Identifying SpeciesProblems identifying and distinguishing species are common:E.g. DogsLarge variety of observable morphological formsCan still interbreedSingle speciesFigure 2.3 Dogs are all one species and readily interbreed 13Problems Identifying Species“Sibling” speciesMorphologically and physiologically similar butbiologically separateE.g. TuataraTuatara: Sphenodon punctatushttp://www.ryanphotographic.com/images/JPEGS/Tuatara%20on%20forest%20floor%20three%20quarters.jpg 14Savannah subspeciesForest subspeciesDesert subspeciesSibling species: African ElephantsProblems Identifying Species 15Problems Identifying SpeciesHybridsMating between related but distinct species produce intermediate forms (hybrids)Blur distinction between speciesSometimes hybrids better suited to environment than either parent speciescan form new speciesHybridization common in plant species in disturbed habitatsAlso occurs when a few individuals of rare species surrounded by large numbers of closely related species 16Problems Identifying SpeciesHybridshttp://www.grida.no/aeo/images/img2b8s.jpgEthiopian wolf (Canis simensis)http://www.abf90.dial.pipex.com/eurocat2.jpgEuropean Wildcat (Felix silvestris)                                                      http://eelink.net/EndSpp.old.bak/optiredwolf.htmlRed Wolf (Canis rufus) 17How many species are there?Described and given scientific names:1.75 million extant species300,000 fossil speciesEstimates of the total number of extant species range from 10 to 50 million!Approx. 1/3 of world species have been describedOften little known about their life histories/ecologyMany species not yet discoveredfast rate habitat lossInaccessibleVery important to describe species and measure species diversity! 18Measures of Species DiversityCommonly used measures fall into three categories that emphasize:1.2.3. Conservation biologists usually use numbers.Ecologists often use evenness measuresassess the effect of pollution or a disturbance.Ecologists also use indices of similaritiesto identify shifts in relative abundance and why they happen. 19Species Richness:Number of species present in a community, habitat or evolutionary lineage.Three main categories based on spatial patterns and geographical scales.1.2.3. Measures of Species Diversity 20Alpha Diversity:Number of species in a certain community.Comes closest to the popular concept of species richness.Used to compare the number of species in:Can be:Weighted – Unweighted – Measures of Species Diversity 21Alpha Diversity:For example:A 100-ha patch of forest in southern Ontario has fewer tree species than a 100-ha patch of Amazon rainforest.This is an example of an unweighted measure.It compares direct numbers.Measures of Species Diversity 22More highly quantitative indices take into account the relative abundance of different species.Shannon diversity indexCommunities with large numbers of species that are equally abundant -Communities with few species or with many species but with only one or a few which are abundant -This is a weighted indexMeasures of Species Diversity 23Ecologists prefer weighted measuresConservation biologists prefer unweighted measures.Reasons:Common species dominate the weighted indexes.In conservation, rare species are of greater importance Often only species lists are available rather than accurate estimates of population densities (needed for weighted measures).Measures of Species Diversity 24Gamma Diversity:Applies to larger geographical scalesLarge region or continentAllows for comparisons of large areas that encompass diverse landscapes or a wide geographical area.For example:Kenya has 1000 species of forest birds.Britain has only 200 species of forest birds.Measures of Species Diversity 25Beta Diversity:Links alpha and gamma diversityRefers to the rate of change of species composition along and environmental or geographical gradient.?-richness is high when:?-richness is low when: Measures of Species Diversity 26For Example:Several lakes in a region with fish:Measures of Species Diversity 27Another Example:Measures of Species DiversityHigh ?-richness in tropics 28Measures of Species Diversity 29Advantages/DisadvantagesUseful for examining species distribution patterns and comparing different regionsDoes not give any information about species interactions:DynamicsFunctional role the species plays in the habitat or ecosystem.Also does not differentiate between native and non-native species.Currently there are no good indicators of the functioning of the more complex aspects of communities. 30Genetic DiversityGenetic diversity affected by reproductive behaviour within populationsPopulation = a group of individuals that mate with one another and produce offspringA species may include one or more separate populationsPopulations may consist of a few or millions of individuals 31Genetic DiversityIndividuals in a population are genetically different from each otherHave different alleles which arise through mutationGenetic variation increases via recombination during sexual reproductionGenetically different individuals also differ in their ability to:survivereproduce 32Genetic DiversityFigure 2.8 Genetic variation 33Genetic DiversityHow is genetic variation measured?various molecular biology techniques.Why important?Measures of the genetic variation within local populations can help understanding of the forces acting on genetic variation.Three practical applications:1. Design of captive breeding programmes for rare species – 34Genetic Diversity2. Re-establishing populations3. Rates of Evolution 35Genetic DiversityAmount of genetic variability in a population determined by:Number of polymorphic genes (genes that have more than one allele)Number of alleles for each of the genesGenetic variability contributes to adaptability of population to changing environmentRare species often have less genetic variabilityMore vulnerable to extinction when environment changes 36Genetic DiversityVariation at the population level is important because this is the level where you see:Responses to environmental stressesAdaptationsMaintenance/reshuffling of genetic diversity. The more variability, the greater the potential rate of evolutionary changeVariation at the population level mainly due to adaptations to local ecological conditions. 37Genetic DiversityIn many plant and animal populations, heterozygous individuals have greater fitness than homozygous individuals:Hybrid vigor or heterosisReasons:More flexibility dealing with environmental challenges when have two allelesNon-functional, or harmful alleles received from one parent, masked by functioning alleles received from the other 38Genetic DiversityThe evolutionary history of a population can be determined by looking at genetic differences among individuals within a population and among different populations of a species.Individual populations often have great conservation value, particularly if those populations are isolated or semi-isolated i.e. each adapted to a different environment. 39Genetic DiversityExample: Guppies in Trinidad streamsGuppies (Poecilia reticulata) occur in streams either with or without predatory fish.These guppies have different genetically based characteristics such as colour patterns, clutch size, offspring size, depending of which streams they inhabit.If you were to introduce an extirpated population into a stream with predators you would need to choose those individuals with the traits that enabled them to coexist with predators. 40Genetic DiversityThis type of variation which is environmentally induced and genetically based is referred to as plasticity.It is important to consider in conservation biology. 41Ecosystem DiversityCommunities and Ecosystems:Biological community – the species that occupy a particular area and the interactions between those speciesEcosystem – a biological community plus the associated physical and chemical environmentShaped by ongoing processes such as water cycles, nutrient cycles, energy captureThe processes occur at geographical scales ranging from square metres to tens of thousands of square kilometres 42Ecosystem DiversityPhysical environment affects structure and characteristics of a biological communityE.g. aquatic ecosystemsBiological community can also alter physical characteristics of an environmentE.g. Kelp forests (Box 2.2) – Required reading 43Ecosystem DiversityBox 2.2 Forests of giant kelp provide the starting point and structure for a diverse biological community