1.4 Biogeographical patterns

Biogeographical patterns reveal how species are distributed across landscapes and ecosystems. These patterns are shaped by factors like range size, spatial autocorrelation, and metapopulation dynamics, which influence biodiversity and species abundance globally.

Understanding biogeographical patterns is crucial for conservation and predicting species responses to environmental changes. Key concepts include biodiversity gradients, island biogeography, endemism, and the impact of dispersal barriers on species distribution and evolution.

Species distribution patterns

• Examines how organisms are spatially arranged across landscapes and ecosystems
• Fundamental to understanding ecological processes and biodiversity patterns in world biogeography
• Influences conservation strategies and predictions of species responses to environmental changes

Range size vs abundance

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• Range size refers to the geographical area occupied by a species
• Abundance represents the number of individuals within a population
• Positive correlation often observed between range size and local abundance
• Species with larger ranges tend to have higher local abundances (brown bears)
• Rare species typically have smaller ranges and lower abundances (giant pandas)
• Factors influencing range-abundance relationships
  • Habitat availability
  • Dispersal abilities
  • Environmental tolerances

Spatial autocorrelation in ecology

• Describes the degree of similarity between spatially proximate observations
• Crucial concept in understanding species distribution patterns
• Positive spatial autocorrelation indicates clustering of similar values
• Negative spatial autocorrelation suggests dispersion of dissimilar values
• Methods for measuring spatial autocorrelation
  • Moran's I
  • Geary's C
  • Variograms
• Applications in landscape ecology and conservation planning
  • Identifying habitat connectivity
  • Predicting species range expansions

Metapopulation dynamics

• Describes interconnected populations of the same species in fragmented habitats
• Consists of local populations connected by dispersal
• Key processes in metapopulation dynamics
  • Colonization of empty habitat patches
  • Local extinction events
  • Recolonization of previously occupied patches
• Influences regional persistence of species (butterfly populations in meadows)
• Importance in conservation biology for managing fragmented landscapes
• Metapopulation models used to predict population viability and extinction risk

Biodiversity gradients

• Describes systematic variations in species richness across geographical or environmental gradients
• Fundamental patterns in global biodiversity distribution
• Crucial for understanding evolutionary and ecological processes shaping life on Earth

Latitudinal diversity gradient

• Increase in species richness from poles to tropics
• One of the most well-documented patterns in ecology
• Hypotheses explaining the gradient
  • Available energy hypothesis
  • Evolutionary speed hypothesis
  • Time and area hypothesis
• Variations across different taxonomic groups (mammals, plants, marine organisms)
• Exceptions to the general pattern (parasites, marine invertebrates)
• Implications for conservation priorities and predicting climate change impacts

Altitudinal diversity gradient

• Changes in species richness along elevation gradients
• Generally shows a hump-shaped pattern with peak diversity at mid-elevations
• Factors influencing altitudinal diversity patterns
  • Temperature and precipitation changes
  • Available area at different elevations
  • Productivity gradients
• Variations in patterns between different mountain ranges (Andes, Himalayas)
• Importance in understanding species' responses to climate change
• Applications in conservation planning for montane ecosystems

Marine depth diversity gradient

• Describes changes in species richness with increasing ocean depth
• Generally shows a decline in diversity from shallow to deep waters
• Unique patterns observed in different marine ecosystems
  • Coral reefs exhibit high diversity in shallow waters
  • Hydrothermal vents show localized diversity hotspots in deep seas
• Factors influencing marine depth diversity
  • Light availability
  • Pressure changes
  • Nutrient availability
• Implications for understanding deep-sea ecosystems and their conservation

Island biogeography

• Studies the distribution and diversity of species on islands
• Fundamental to understanding evolutionary processes and biodiversity patterns
• Provides insights into colonization, extinction, and speciation dynamics

Species-area relationship

• Describes the increase in species richness with increasing island area
• Typically expressed as a power function: S = cA^z
  • S represents species richness
  • A represents island area
  • c and z are constants
• Factors influencing the species-area relationship
  • Island isolation
  • Habitat diversity
  • Time since isolation
• Applications in conservation biology for estimating species loss due to habitat fragmentation
• Variations in the relationship across different taxonomic groups and island types

Island colonization vs extinction

• Colonization rates depend on island isolation and species dispersal abilities
• Extinction rates influenced by island size, habitat diversity, and population sizes
• Balance between colonization and extinction determines island species richness
• Factors affecting colonization success
  • Distance from source populations
  • Presence of suitable habitats
  • Dispersal mechanisms (wind, water, animal-mediated)
• Causes of island extinctions
  • Limited resources
  • Inbreeding depression
  • Environmental disturbances
• Examples of successful colonizers (coconut palms) and extinct island species (dodo)

Equilibrium theory of biogeography

• Proposed by MacArthur and Wilson in 1967
• Postulates that island species richness reaches an equilibrium over time
• Equilibrium results from a balance between immigration and extinction rates
• Key predictions of the theory
  • Larger islands have higher equilibrium species richness
  • More isolated islands have lower equilibrium species richness
• Applications in understanding species turnover on islands
• Limitations and critiques of the theory
  • Assumes ecological equivalence of species
  • Does not account for evolutionary processes

Endemism and cosmopolitanism

• Explores the geographical distribution range of species
• Crucial for understanding biodiversity patterns and conservation priorities
• Influences biogeographical classification and evolutionary studies

Endemic species hotspots

• Areas with high concentrations of species found nowhere else on Earth
• Characteristics of endemic species hotspots
  • High species richness
  • High levels of habitat specialization
  • Often geographically isolated or unique environments
• Examples of global endemic hotspots
  • Madagascar's unique flora and fauna
  • Hawaiian archipelago's diverse plant species
  • Australia's marsupial diversity
• Importance in global conservation efforts
  • Prioritization of protected areas
  • Focus on preserving irreplaceable biodiversity
• Threats to endemic hotspots
  • Habitat destruction
  • Climate change
  • Invasive species

Widespread vs restricted taxa

• Compares species with broad geographical ranges to those with limited distributions
• Factors influencing range size
  • Dispersal abilities
  • Environmental tolerances
  • Historical biogeography
• Characteristics of widespread taxa
  • Generalist ecological requirements
  • High dispersal capabilities
  • Often found in multiple biogeographical regions
• Features of restricted taxa
  • Specialized habitat requirements
  • Limited dispersal abilities
  • Often endemic to specific areas
• Examples of widespread taxa (barn owls) and restricted taxa (lemurs)
• Implications for conservation and management strategies

Factors influencing endemism

• Geographical isolation promotes endemism through limited gene flow
• Environmental uniqueness creates specialized niches for endemic species
• Historical factors such as past climate changes and geological events
• Evolutionary processes leading to endemism
  • Adaptive radiation in isolated environments
  • Allopatric speciation
  • Relict populations of formerly widespread species
• Biological factors affecting endemism
  • Dispersal limitations
  • Reproductive strategies
  • Competitive abilities
• Human impacts on endemism patterns
  • Habitat fragmentation increasing isolation
  • Climate change altering suitable habitats

Biogeographical regions

• Large-scale divisions of Earth's surface based on distinctive assemblages of plants and animals
• Fundamental to understanding global biodiversity patterns and evolutionary history
• Crucial for conservation planning and management at continental scales

Wallace's realms

• Proposed by Alfred Russel Wallace in the 19th century
• Divides the world into six major biogeographical regions
  • Nearctic
  • Neotropical
  • Palearctic
  • Ethiopian (Afrotropical)
  • Oriental (Indomalayan)
  • Australian
• Based on distribution patterns of animal species, particularly mammals
• Boundaries between realms often correspond to major geographical barriers
  • Wallace Line separating Oriental and Australian realms
• Importance in understanding evolutionary history and species dispersal patterns
• Modern refinements and additions to Wallace's original classification

Terrestrial ecoregions

• Smaller units within biogeographical realms representing distinct assemblages of species and environmental conditions
• Defined by WWF (World Wildlife Fund) as part of global conservation efforts
• Characteristics of terrestrial ecoregions
  • Unique species compositions
  • Similar climatic conditions
  • Shared evolutionary history
• Examples of major terrestrial ecoregions
  • Amazon rainforest
  • Serengeti grasslands
  • Siberian taiga
• Importance in conservation planning and protected area design
• Challenges in ecoregion classification and management
  • Defining boundaries in transition zones
  • Addressing cross-border conservation issues

Marine biogeographic provinces

• Large-scale divisions of the world's oceans based on species distributions and environmental factors
• Characteristics of marine biogeographic provinces
  • Distinct assemblages of marine organisms
  • Influenced by ocean currents and physical barriers
  • Varying levels of endemism
• Major marine biogeographic provinces
  • Indo-Pacific
  • Eastern Pacific
  • Western Atlantic
  • Eastern Atlantic
• Factors influencing marine biogeographic patterns
  • Temperature gradients
  • Ocean circulation patterns
  • Geological history of ocean basins
• Importance in marine conservation planning and fisheries management
• Challenges in defining marine biogeographic boundaries due to the fluid nature of marine environments

Dispersal and barriers

• Examines how organisms move across landscapes and the factors limiting their distribution
• Crucial for understanding species range expansions, invasions, and responses to environmental changes
• Influences genetic diversity and population connectivity in biogeography

Dispersal mechanisms in nature

• Active dispersal involves organism-driven movement
  • Flight in birds and insects
  • Swimming in fish and marine mammals
  • Walking or running in terrestrial animals
• Passive dispersal relies on external forces
  • Wind dispersal of seeds and spores
  • Water dispersal of aquatic organisms and plant propagules
  • Animal-mediated dispersal through ingestion or attachment
• Importance of dispersal in
  • Colonization of new habitats
  • Gene flow between populations
  • Species' responses to environmental changes
• Variations in dispersal abilities across taxa and life stages
• Human-assisted dispersal and its impact on biogeographical patterns

Geographical vs ecological barriers

• Geographical barriers physically impede organism movement
  • Mountain ranges (Andes, Himalayas)
  • Large water bodies (oceans, seas)
  • Deserts (Sahara, Gobi)
• Ecological barriers limit species distribution through environmental factors
  • Temperature gradients
  • Salinity differences in aquatic environments
  • Soil type variations
• Interactions between geographical and ecological barriers
  • Mountains creating rain shadows and temperature gradients
  • Ocean currents influencing climate and dispersal patterns
• Impact of barriers on
  • Species range limits
  • Genetic differentiation between populations
  • Speciation processes
• Changes in barrier effectiveness over time due to climate change and human activities

Long-distance dispersal events

• Rare occurrences of organisms traveling far beyond their normal range
• Importance in biogeography
  • Explaining disjunct distributions
  • Colonization of remote islands
  • Rapid range expansions
• Mechanisms of long-distance dispersal
  • Extreme weather events (hurricanes, tsunamis)
  • Rafting on floating vegetation or debris
  • Migratory animals as vectors
• Examples of long-distance dispersal
  • Coconut palms colonizing remote Pacific islands
  • Birds blown off course during migration reaching new continents
• Challenges in studying long-distance dispersal
  • Rarity of events
  • Difficulty in direct observation
• Genetic evidence for historical long-distance dispersal events
• Implications for predicting species responses to climate change

Vicariance and disjunction

• Explores the separation of populations by geographical or ecological barriers
• Fundamental to understanding speciation and biogeographical patterns
• Influences the distribution of related taxa across different regions

Vicariance biogeography theory

• Explains the distribution of related taxa through the fragmentation of ancestral populations
• Key concepts in vicariance biogeography
  • Allopatric speciation resulting from population isolation
  • Congruent distribution patterns among multiple taxa
  • Importance of geological events in shaping biodiversity
• Historical development of vicariance theory
  • Shift from dispersalist to vicariance explanations in the mid-20th century
  • Integration with plate tectonic theory
• Methods used in vicariance biogeography
  • Cladistic biogeography
  • Phylogenetic analysis of distribution patterns
• Limitations and criticisms of strict vicariance explanations
  • Neglect of dispersal events
  • Oversimplification of complex biogeographical histories

Continental drift effects

• Impacts of plate tectonics on the distribution of flora and fauna
• Major continental drift events shaping biogeography
  • Breakup of Pangaea
  • Formation of the Atlantic Ocean
  • Collision of India with Asia
• Examples of continental drift effects on biodiversity
  • Marsupial distribution in Australia and South America
  • Ratite bird distribution across southern continents
  • Plant families with Gondwanan distribution patterns
• Importance of understanding past continental configurations
  • Explaining relict distributions
  • Interpreting fossil evidence in biogeographical context
• Challenges in distinguishing continental drift effects from other biogeographical processes
  • Long time scales involved
  • Confounding effects of extinction and dispersal

Disjunct distribution patterns

• Occurrences of closely related taxa in widely separated geographical areas
• Types of disjunct distributions
  • Intercontinental disjunctions
  • Intracontinental disjunctions
  • Elevational disjunctions
• Causes of disjunct distributions
  • Vicariance events (continental drift, mountain uplift)
  • Long-distance dispersal
  • Climate-driven range shifts
  • Anthropogenic introductions
• Examples of disjunct distributions
  • Beech trees (Fagus) in Europe, Asia, and North America
  • Aloe plants in Africa and Arabian Peninsula
  • Bipolar distributions in marine organisms
• Methods for studying disjunct distributions
  • Molecular clock analyses
  • Fossil record examination
  • Ecological niche modeling
• Implications of disjunct distributions for conservation and evolutionary studies

Biogeographical evolution

• Examines how evolutionary processes shape the distribution of organisms over time
• Integrates concepts from ecology, evolution, and geology to explain biodiversity patterns
• Crucial for understanding the origins and maintenance of global biodiversity

Adaptive radiation in isolation

• Rapid diversification of a single ancestral species into multiple species
• Occurs when organisms encounter new ecological opportunities in isolated environments
• Characteristics of adaptive radiation
  • Rapid speciation rates
  • Morphological and ecological divergence
  • Occupation of diverse niches
• Famous examples of adaptive radiation
  • Darwin's finches in the Galápagos Islands
  • Cichlid fishes in African Great Lakes
  • Silversword alliance plants in Hawaii
• Factors promoting adaptive radiation
  • Ecological opportunity in new environments
  • Release from competition and predation
  • Genetic flexibility of founding populations
• Importance in understanding island biogeography and evolution in isolated habitats
• Challenges in studying adaptive radiation
  • Distinguishing from other diversification processes
  • Reconstructing ancestral traits and environments

Convergent evolution across regions

• Independent evolution of similar traits in distantly related organisms
• Occurs when different species face similar environmental challenges
• Characteristics of convergent evolution
  • Similar morphological or physiological adaptations
  • Analogous structures with different evolutionary origins
  • Often observed in geographically separated regions
• Examples of convergent evolution in biogeography
  • Succulent plants in African and American deserts
  • Flightless birds on different continents (ostriches, emus)
  • Marsupial and placental mammals with similar ecological roles
• Factors influencing convergent evolution
  • Similar selective pressures in different environments
  • Constraints on possible evolutionary solutions
  • Shared ancestral genetic toolkit
• Importance in understanding adaptation and predictability in evolution
• Methods for identifying convergent evolution
  • Comparative phylogenetic analyses
  • Functional genomics studies

Coevolution in biogeography

• Reciprocal evolutionary changes between interacting species
• Influences the distribution and diversity of multiple species simultaneously
• Types of coevolutionary relationships
  • Mutualism (pollination, seed dispersal)
  • Predator-prey interactions
  • Host-parasite relationships
• Biogeographical aspects of coevolution
  • Geographic mosaics of coevolution
  • Coevolutionary arms races across landscapes
  • Influence on species range limits
• Examples of coevolution in biogeography
  • Fig trees and fig wasps across tropical regions
  • Coral reefs and their symbiotic algae in different oceans
  • Plant defenses and herbivore adaptations in different continents
• Importance in understanding community assembly and ecosystem functioning
• Challenges in studying coevolution in a biogeographical context
  • Disentangling coevolution from other evolutionary processes
  • Accounting for historical biogeographical events

Human impacts on biogeography

• Examines how human activities alter species distributions and biodiversity patterns
• Crucial for understanding and mitigating anthropogenic effects on global ecosystems
• Integrates concepts from conservation biology, ecology, and global change science

Anthropogenic species introductions

• Deliberate or accidental movement of species outside their native ranges by human activities
• Major pathways of species introductions
  • International trade and transport
  • Horticulture and agriculture
  • Pet and aquarium trade
  • Ballast water in ships
• Impacts of introduced species on native ecosystems
  • Competition with native species
  • Predation on native fauna
  • Alteration of habitat structure
  • Disruption of ecosystem processes
• Examples of significant species introductions
  • Cane toads in Australia
  • Zebra mussels in North American waterways
  • Kudzu vine in the southeastern United States
• Factors influencing invasion success
  • Propagule pressure
  • Environmental matching
  • Lack of natural enemies
• Management strategies for introduced species
  • Prevention and early detection
  • Eradication efforts
  • Control and containment measures

Habitat fragmentation consequences

• Breaking up of continuous habitats into smaller, isolated patches
• Causes of habitat fragmentation
  • Deforestation and land conversion
  • Urbanization and infrastructure development
  • Agricultural expansion
• Ecological consequences of fragmentation
  • Reduced habitat area
  • Increased edge effects
  • Isolation of populations
  • Disruption of metapopulation dynamics
• Impacts on biodiversity
  • Decreased species richness in fragments
  • Loss of habitat specialists
  • Genetic isolation and inbreeding
  • Altered species interactions
• Examples of fragmentation effects
  • Atlantic Forest fragmentation in Brazil
  • Prairie fragmentation in North America
• Mitigation strategies
  • Habitat corridors and connectivity restoration
  • Buffer zone creation
  • Landscape-scale conservation planning

Climate change effects

• Alterations in species distributions and ecosystem functioning due to global climate shifts
• Observed and predicted impacts of climate change
  • Range shifts towards poles and higher elevations
  • Phenological changes (timing of life cycle events)
  • Mismatches in species interactions
  • Increased extinction risk for climate-sensitive species
• Vulnerability of different ecosystems
  • Polar and alpine regions
  • Coral reefs and other marine ecosystems
  • Tropical rainforests
• Examples of climate change impacts on biogeography
  • Poleward expansion of mangroves
  • Upslope migration of mountain plants
  • Changes in migratory bird patterns
• Challenges in predicting and managing climate change effects
  • Uncertainties in climate projections
  • Complex interactions with other stressors
  • Time lags in species responses
• Adaptation strategies
  • Protected area network design for climate resilience
  • Assisted migration of vulnerable species
  • Ecosystem-based adaptation approaches

Biogeographical methods

• Explores techniques and approaches used to study and analyze biogeographical patterns
• Integrates data from various disciplines to understand species distributions and biodiversity
• Crucial for making informed decisions in conservation and environmental management

Species distribution modeling

• Predicts the geographical range of species based on environmental variables
• Key components of species distribution models
  • Occurrence data for target species
  • Environmental predictor variables
  • Statistical or machine learning algorithms
• Types of species distribution models
  • Correlative models (MaxEnt, BIOCLIM)
  • Mechanistic models based on physiological constraints
  • Hybrid approaches combining correlative and mechanistic elements
• Applications in biogeography
  • Predicting potential ranges of invasive species
  • Identifying suitable habitats for reintroduction programs
  • Projecting species range shifts under climate change scenarios
• Limitations and challenges
  • Biases in occurrence data
  • Selection of appropriate environmental variables
  • Accounting for biotic interactions and dispersal limitations
• Importance in conservation planning and biodiversity assessments

Phylogeographic analysis techniques

• Combines phylogenetics and biogeography to study the geographical distribution of genetic lineages
• Key methods in phylogeography
  • DNA sequencing of multiple individuals across populations
  • Construction of gene trees and haplotype networks
  • Statistical tests for population structure and demographic history
• Applications in biogeography
  • Reconstructing historical migration routes
  • Identifying glacial refugia and recolonization patterns
  • Detecting cryptic species and evolutionary significant units
• Examples of phylogeographic studies
  • Post-glacial recolonization patterns in European trees
  • Diversification of Galápagos giant tortoises
  • Phylogeography of human populations
• Challenges in phylogeographic analysis
  • Distinguishing between historical and contemporary processes
  • Integrating data from multiple genetic markers
  • Accounting for incomplete lineage sorting
• Importance in understanding evolutionary history and informing conservation strategies

Biogeographical data visualization

• Techniques for representing complex spatial and temporal patterns in biodiversity
• Types of biogeographical visualizations
  • Species distribution maps
  • Biodiversity hotspot maps
  • Phylogenetic trees with geographical information
  • Animated visualizations of range shifts over time
• Tools and software for biogeographical visualization
  • Geographic Information Systems (GIS) (ArcGIS, QGIS)
  • R packages for spatial analysis and mapping
  • Web-based platforms for interactive visualizations
• Applications in biogeography
  • Communicating complex patterns to diverse audiences
  • Identifying spatial trends and anomalies in biodiversity data
  • Supporting decision-making in conservation planning
• Challenges in biogeographical visualization
  • Representing uncertainty in spatial data
  • Balancing detail and clarity in complex datasets
  • Choosing appropriate color schemes and symbology
• Importance of effective visualization in advancing biogeographical research and conservation efforts