Ecosystem & Genetic Diversity

What is an ecosystem? A group of interacting organisms (a community) and the physical environment they inhabit biotic and abiotic factors in a given area Delineating difficult they gradually transition along ecotones spatial scales vary Types of ecosystems can’t protect all ecosystems, but can protect some of each type

Classifying Ecosystems No quantitative standard for assessing similarities or differences but ecosystem classifications based on vegetation exist for some places Hierarchical but no formal system Should consider geography Using climatic zones, continental boundaries, etc.

Why Classify? Inventory, assessment, and management often at the ecosystem scale Evaluate human impacts some ecosystems extinct others have declined severely Great Lakes Alvars type of sparsely vegetated grassland with shallow soils nearly all of North Americas are near the Great Lakes many are imperiled, and they support many rare species Classification led to conservation prioritization for some alvars, protecting the rare species within

Ecosystem Values: More than a sum of its parts? Intrinsic Value some of each kind must be protected example of severely impacted ecosystems? Instrumental Value Economic ~ goods and services Spiritual ~ popular religions advocate stewardship for “creation” Scientific and Educational ~ Ecological ~ decomposition, nutrient and water cycling keystone ecosystems: salt marshes, rivers, pyrogenic ecosystems Strategic ~ protect a representative array of ecosystems, protect everything that lives there too (course-filter approach) effective for unknown, cryptic, and hard-to-detect species Uniqueness ~ depends on classification scheme, different than rarity

Diversity & Stability Rivets on a plane analogy Some species more important that others keystone, dominant, ecosystem engineers Mechanisms for diversity-stability relationship Food web ~ more redundancy Resists invasion ~ fewer available niches, unexploited resources Resists disease ~ because abundance is lower, disease spreads more slowly, dilution effects Variety of responses to disturbance

Species Richness: Why are some ecosystems more diverse? Climate temperature moisture energy availability Disturbance intermediate disturbance hypothesis Environmental Heterogeneity Spatial Size and Configuration Positive Feedback, more plant species support more animal species…. But richness isn’t everything. Salt marshes, mangroves, and the Galapagos aren’t very species rich, but are still worthy of conservation.

Landscape Ecology Landscape ~ mosaic of ecosystems Need for landscape level conservation species with large ranges use multiple ecosystems processes that occur on a landscape scale

5 Levels of Genetic Diversity Among higher taxonomic levels Among species Among populations Within populations Within individuals

Allele Frequencies A gene is polymorphic if the most abundant allele has a frequency less than 95% An allele is rare if it has a frequency less than.5%, 1%, or 5% Remember polymorphism is based on allele frequencies

Heterozygosity Percent of genes at which the average individual is heterozygous Expected heterozygosity calculated using Hardy Weinberg Equilibrium Calculate an index to determine how much of a species heterozygosity is due to within vs. among population diversity AmongWithin

Quantitative Variation Continuous traits controlled by several genes and more likely to be associated with fitness Evaluate the potential of species to adapt to rapid change.

Genetic Diversity is Important! Evolutionary Potential Genetic diversity is the raw material that evolution shapes Environments change through time, anthropogenic changes particularly rapid through space, heterogeneous environments More diverse offspring, next generation isn’t riding on a single genotype Loss of Fitness low fertility, costs of inbreeding, even in constant environments inbreeding increases homozygosity, which leads to the expression of recessive, deleterious alleles heterosis, or heterozygote vigor, generally more robust

Inbreeding isn’t all bad Many plants tolerant of inbreeding After enough inbreeding, deleterious alleles removed Outbreeding depression local adaptations can be lost when individuals from different populations breed Ibex

Utilitarian Values Domestic species can be very diverse Wild relatives of domestic species an important source of genetic variation disease resistance drought tolerance

Processes that Diminish Genetic Diversity Bottlenecks and founder events severe reduction in population leads to loss of alleles, especially rare ones

Processes that Diminish Genetic Diversity Drift ~ random changes in allele frequencies larger effects in smaller populations alleles may become fixed drift erodes diversity faster than mutation introduces it

Processes that Diminish Genetic Diversity Inbreeding identical by descent ~ relatives can share identical copies of genes because they were inherited from the same ancestor

Effective Population Size Total, or census, population size is not the same as the effective size Effective population size is the breeding population in some species, many adults never breed also takes into account ratio of males to females

Cultural Diversity Animals have culture too! We should also be concerned with preserving traditional ecological knowledge