10.4 Evolutionary biogeography

Evolutionary biogeography explores how geological, climatic, and biological processes shape species distributions over time. It combines principles from ecology, evolution, geology, and paleontology to understand global biodiversity patterns and provide insights into species origins, migrations, and adaptations.

Key concepts include vicariance, dispersal, extinction, and speciation. The field integrates evidence from fossils, genetics, and ecological studies to reconstruct biogeographic histories and explain current biodiversity patterns. It also examines human impacts and climate change effects on species distributions.

Foundations of evolutionary biogeography

• Evolutionary biogeography examines how geological, climatic, and biological processes shape species distributions over time
• Integrates principles from ecology, evolution, geology, and paleontology to understand global biodiversity patterns
• Provides crucial insights into species origins, migrations, and adaptations in the context of Earth's dynamic history

Historical development of field

Top images from around the web for Historical development of field

• 

  Alfred Russel Wallace — Wikipédia View original

  Is this image relevant?

• 

  File:PSM V74 D405 Alfred Russel Wallace.png - Wikimedia Commons View original

  Is this image relevant?

• 

  Wallacea and Biogeography – Simple Book Publishing View original

  Is this image relevant?

• 

  Alfred Russel Wallace — Wikipédia View original

  Is this image relevant?

• 

  File:PSM V74 D405 Alfred Russel Wallace.png - Wikimedia Commons View original

  Is this image relevant?

1 of 3

Top images from around the web for Historical development of field

• 

  Alfred Russel Wallace — Wikipédia View original

  Is this image relevant?

• 

  File:PSM V74 D405 Alfred Russel Wallace.png - Wikimedia Commons View original

  Is this image relevant?

• 

  Wallacea and Biogeography – Simple Book Publishing View original

  Is this image relevant?

• 

  Alfred Russel Wallace — Wikipédia View original

  Is this image relevant?

• 

  File:PSM V74 D405 Alfred Russel Wallace.png - Wikimedia Commons View original

  Is this image relevant?

1 of 3

• Emerged from biogeography and evolutionary biology in the mid-20th century
• Alfred Russel Wallace pioneered biogeographical thinking through his explorations and observations
• Plate tectonic theory in the 1960s revolutionized understanding of species distributions across continents
• Molecular techniques in the 1980s enabled more precise dating of evolutionary events and lineage divergences

Key concepts and principles

• Vicariance explains population separation due to geographical barriers (mountain ranges)
• Dispersal involves movement of organisms across existing barriers (ocean currents)
• Extinction shapes biogeographic patterns by eliminating species from certain areas
• Speciation generates new taxa through isolation and adaptation to local environments
• Phylogenetic relationships provide a framework for understanding evolutionary history and biogeographic patterns

Relationship to other disciplines

• Geology informs understanding of past continental configurations and climate changes
• Paleontology provides fossil evidence for historical species distributions and extinctions
• Ecology contributes insights into species interactions and habitat requirements
• Genetics enables analysis of population structure and gene flow between regions
• Climatology helps explain species range limits and adaptations to environmental conditions

Mechanisms of species distribution

• Species distributions result from complex interactions between historical events and ongoing ecological processes
• Understanding these mechanisms helps explain current biodiversity patterns and predict future changes
• Combines evidence from fossils, genetics, and ecological studies to reconstruct biogeographic histories

Dispersal vs vicariance

• Dispersal involves active or passive movement of organisms across existing barriers
  • Can occur through various means (wind, water, animal vectors)
  • Often results in founder effects and genetic bottlenecks
• Vicariance occurs when populations become separated by newly formed geographical barriers
  • Can lead to allopatric speciation over time
  • Examples include continental drift and mountain range formation
• Both processes contribute to current species distributions and can operate simultaneously

Long-distance dispersal events

• Rare occurrences that can significantly impact biogeographic patterns
• Explains disjunct distributions of closely related species across large distances
• Mechanisms include:
  • Rafting on floating vegetation or debris (reptiles colonizing oceanic islands)
  • Wind dispersal of small organisms or seeds (ferns reaching isolated volcanic islands)
  • Bird-mediated transport of seeds or small animals (plant colonization of remote areas)
• Molecular clock analyses help estimate timing of these events

Barriers to dispersal

• Physical obstacles that limit species movement and gene flow
• Vary in effectiveness depending on species' dispersal abilities and ecological requirements
• Major types include:
  • Geographical barriers (mountain ranges, oceans, deserts)
  • Climatic barriers (temperature gradients, precipitation patterns)
  • Ecological barriers (habitat discontinuities, biotic interactions)
• Understanding barrier effects crucial for predicting species responses to environmental changes

Speciation and extinction processes

• Speciation and extinction dynamically shape biodiversity patterns over time
• Balance between these processes determines species richness in different regions
• Influenced by both intrinsic biological factors and extrinsic environmental conditions

Allopatric vs sympatric speciation

• Allopatric speciation occurs when populations become geographically isolated
  • Most common form of speciation
  • Driven by vicariance events or long-distance dispersal
  • Examples include Darwin's finches on Galápagos Islands
• Sympatric speciation happens within the same geographical area
  • Rarer but possible through mechanisms like polyploidy in plants
  • Can occur through ecological specialization or sexual selection
  • Cichlid fish in African lakes demonstrate rapid sympatric speciation

Adaptive radiation

• Rapid diversification of a single lineage into multiple species
• Often occurs when organisms encounter new ecological opportunities
• Key features include:
  • Common ancestry of diversifying group
  • Phenotype-environment correlation
  • Trait utility (adaptations provide fitness advantages)
• Classic examples include Hawaiian honeycreepers and Anolis lizards in the Caribbean

Mass extinctions and recovery

• Periods of elevated extinction rates affecting multiple taxonomic groups
• Five major mass extinctions recognized in Earth's history
  • End-Ordovician (445 mya)
  • Late Devonian (375-360 mya)
  • End-Permian (252 mya, most severe)
  • End-Triassic (201 mya)
  • End-Cretaceous (66 mya, dinosaur extinction)
• Recovery periods characterized by adaptive radiations and ecosystem restructuring
• Current biodiversity crisis considered potential sixth mass extinction due to human activities

Phylogenetic approaches

• Phylogenetic methods provide a framework for understanding evolutionary relationships and biogeographic histories
• Integrate molecular data, fossil evidence, and geographical information
• Enable testing of hypotheses about dispersal, vicariance, and speciation events

Molecular clock techniques

• Use genetic differences to estimate divergence times between lineages
• Based on the assumption of relatively constant mutation rates over time
• Calibrated using fossil evidence or known geological events
• Relaxed clock models account for rate variation among lineages
• Help reconstruct timing of key biogeographic events (continental separations, island colonizations)

Ancestral area reconstruction

• Infers geographical ranges of ancestral lineages based on current species distributions
• Methods include:
  • Parsimony-based approaches (minimize number of dispersal or vicariance events)
  • Likelihood-based models (incorporate probabilities of different biogeographic processes)
  • Bayesian approaches (account for uncertainty in phylogenetic relationships and ancestral states)
• Provides insights into historical biogeographic patterns and processes

Phylogeography

• Examines relationships between genetic lineages and their geographic distributions
• Focuses on intraspecific patterns and recent evolutionary history
• Utilizes mitochondrial DNA and other rapidly evolving genetic markers
• Reveals patterns of population expansion, contraction, and migration
• Helps identify refugia during past climate changes and potential cryptic species

Biogeographic patterns

• Large-scale patterns of species distributions across the globe
• Reflect complex interactions between historical and contemporary processes
• Provide insights into evolutionary history and ecological dynamics

Centers of origin

• Geographical areas where major taxonomic groups are thought to have originated
• Often characterized by high species diversity and ancient lineages
• Examples include:
  • Tropical Andes for many plant groups
  • Southeast Asia for primates
  • Australia for marsupials
• Identification based on fossil records, phylogenetic patterns, and current distributions

Endemism and biodiversity hotspots

• Endemic species unique to a particular geographic location
• Biodiversity hotspots contain high concentrations of endemic species
  • Often in areas with long-term environmental stability or isolation
  • Typically cover small areas but harbor disproportionate biodiversity
• Key hotspots include:
  • Madagascar (lemurs, chameleons)
  • California Floristic Province (diverse plant communities)
  • Eastern Afromontane (unique bird and mammal species)
• Critical for conservation efforts due to high species richness and uniqueness

Island biogeography theory

• Developed by MacArthur and Wilson in the 1960s
• Explains species richness on islands as a balance between immigration and extinction
• Key principles:
  • Larger islands support more species than smaller islands
  • Islands closer to mainland have higher immigration rates and species richness
  • Equilibrium number of species depends on island size and isolation
• Applies beyond literal islands to habitat fragments and isolated ecosystems
• Informs conservation strategies for designing nature reserves and managing fragmented landscapes

Climate change impacts

• Climate change significantly affects species distributions and ecosystem dynamics
• Alters environmental conditions faster than many species can adapt
• Poses major challenges for biodiversity conservation and ecosystem management

Range shifts and expansions

• Species respond to changing temperatures by moving to higher latitudes or elevations
• Observed in various taxa (butterflies, birds, plants)
• Rate and extent of shifts vary among species, leading to community reorganizations
• Creates new species interactions and potential mismatches with food sources or pollinators
• Limitations include dispersal barriers and habitat fragmentation

Extinction risks

• Climate change increases extinction probability for many species
• Particularly threatens:
  • Species with limited dispersal abilities
  • Habitat specialists with narrow environmental tolerances
  • Organisms dependent on climate-sensitive habitats (coral reefs, polar regions)
• Synergistic effects with other stressors (habitat loss, pollution) amplify risks
• Extinction debts may lead to delayed biodiversity losses even if climate stabilizes

Adaptation and resilience

• Some species show potential for rapid adaptation to changing conditions
• Mechanisms include:
  • Phenotypic plasticity (adjusting behavior or physiology without genetic changes)
  • Microevolutionary responses (genetic adaptations over relatively short time scales)
  • Range shifts to track suitable climates
• Factors influencing adaptive capacity:
  • Genetic diversity within populations
  • Generation time and reproductive rate
  • Ability to disperse to new habitats
• Understanding adaptive potential crucial for predicting species persistence and guiding conservation efforts

Human influences

• Human activities profoundly impact global biogeographic patterns
• Alter species distributions, community compositions, and ecosystem functions
• Create novel selection pressures and evolutionary trajectories for many organisms

Anthropogenic dispersal

• Humans facilitate movement of species across natural barriers
• Intentional introductions include:
  • Agricultural crops and livestock
  • Ornamental plants
  • Game animals for hunting
• Unintentional introductions occur through:
  • Ship ballast water (zebra mussels in North American lakes)
  • Cargo transport (brown tree snakes to Guam)
  • Pet trade escapes (Burmese pythons in Florida Everglades)
• Leads to homogenization of biotas and potential ecological disruptions

Habitat fragmentation effects

• Breaking up continuous habitats into smaller, isolated patches
• Impacts species persistence and genetic diversity
• Consequences include:
  • Reduced population sizes and increased inbreeding
  • Disrupted metapopulation dynamics
  • Altered species interactions and ecosystem processes
  • Edge effects changing microclimate and resource availability
• Particularly problematic for species with large home ranges or specific habitat requirements

Conservation implications

• Biogeographic knowledge crucial for effective conservation planning
• Informs strategies such as:
  • Designing protected area networks to capture maximum biodiversity
  • Identifying priority areas for conservation based on endemism and uniqueness
  • Planning corridors to maintain connectivity between fragmented habitats
  • Assessing species vulnerability to climate change
  • Guiding assisted migration efforts for threatened species
• Challenges include balancing local and global conservation priorities

Case studies in evolutionary biogeography

• Specific examples illustrating key concepts and processes in evolutionary biogeography
• Demonstrate interplay between geological events, climate changes, and biological evolution
• Provide insights into formation of current biodiversity patterns

Continental drift and biota

• Breakup of Gondwana influenced distribution of many plant and animal groups
• Marsupial mammals in Australia and South America share a common ancestor
  • Diverged as continents separated ~80 million years ago
  • Explains unique fauna of Australia and absence of placental mammals until human arrival
• Ratite birds (ostriches, emus, kiwis) show similar Gondwanan distribution pattern
• Plant families like Proteaceae demonstrate links between South America, Africa, and Australia

Pleistocene glaciations

• Cycles of glacial and interglacial periods over past 2.6 million years
• Profoundly influenced species distributions and evolution
• Effects include:
  • Formation of glacial refugia where species persisted during ice ages
  • Post-glacial recolonization leading to current distribution patterns
  • Speciation events due to population isolation in refugia
• Examples:
  • European hedgehog shows genetic evidence of expansion from southern refugia
  • North American boreal forest species exhibit patterns of glacial retreat and recolonization

Oceanic island evolution

• Islands as natural laboratories for studying evolution and biogeography
• Processes observed include:
  • Adaptive radiation (Hawaiian honeycreepers, Galápagos finches)
  • Island gigantism or dwarfism (Komodo dragons, extinct dwarf elephants)
  • Loss of dispersal abilities in plants and insects
• Geological history of island formation and erosion shapes colonization patterns
• Distance from mainland and island age influence species richness and endemism levels
• Human impacts often severe due to isolated nature of island ecosystems

Future directions

• Emerging technologies and interdisciplinary approaches expanding possibilities in evolutionary biogeography
• Integration of diverse data sources to address complex questions about biodiversity patterns and processes
• Increasing focus on applied aspects to address global environmental challenges

Integrating genomics

• High-throughput sequencing technologies provide unprecedented genetic data
• Applications in evolutionary biogeography include:
  • Whole-genome comparisons to reconstruct fine-scale phylogenetic relationships
  • Population genomics to detect signatures of selection and local adaptation
  • Environmental DNA (eDNA) for non-invasive biodiversity monitoring
  • Ancient DNA to study extinct species and historical population dynamics
• Challenges include bioinformatics processing and integrating genomic data with other lines of evidence

Predictive modeling

• Developing models to forecast species distributions under future climate scenarios
• Incorporates:
  • Climate projections
  • Species' physiological tolerances
  • Dispersal abilities
  • Biotic interactions
• Machine learning approaches improve model accuracy and complexity
• Applications include:
  • Identifying future conservation priorities
  • Planning assisted migration efforts
  • Assessing invasion risks of non-native species
• Limitations include uncertainties in climate projections and species' adaptive capacities

Interdisciplinary collaborations

• Increasing integration of evolutionary biogeography with other fields
• Collaborations with:
  • Earth scientists to refine paleogeographic reconstructions
  • Climatologists to improve understanding of past and future climate impacts
  • Ecologists to incorporate species interactions into biogeographic models
  • Conservation biologists to apply biogeographic insights to management strategies
• Emergence of new subdisciplines (conservation paleobiology)
• Challenges include bridging different scientific cultures and methodologies
• Potential for novel insights and more comprehensive understanding of biodiversity patterns and processes