1.7 Temporal scales in biogeography

Temporal scales in biogeography span from geological eras to rapid ecological changes. These timescales help us understand how life on Earth has evolved and adapted over millions of years. By examining different temporal perspectives, we can unravel the complex patterns of species distribution and diversity.

From continental drift to climate cycles, temporal scales shape the world's ecosystems. They influence speciation rates, extinction events, and the movement of organisms across landscapes. Understanding these timescales is crucial for predicting future biodiversity patterns and developing effective conservation strategies.

Geological time scales

• Encompasses vast spans of Earth's history divided into distinct eras, periods, and epochs
• Provides framework for understanding evolution of life and major geological events
• Crucial for biogeographers to contextualize species distributions and ecosystem changes

Eras and periods

Top images from around the web for Eras and periods

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

• 

  File:Geologic time scale.jpg - Wikimedia Commons View original

  Is this image relevant?

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

1 of 3

Top images from around the web for Eras and periods

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

• 

  File:Geologic time scale.jpg - Wikimedia Commons View original

  Is this image relevant?

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

• 

  2.3 Geological time scale | Digital Atlas of Ancient Life View original

  Is this image relevant?

1 of 3

• Divided into three main eras Paleozoic, Mesozoic, and Cenozoic
• Paleozoic era (541-252 million years ago) marked by emergence of complex life forms
• Mesozoic era (252-66 million years ago) known as the "Age of Reptiles" (dinosaurs)
• Cenozoic era (66 million years ago to present) characterized by mammalian dominance
• Each era further subdivided into periods (Triassic, Jurassic, Cretaceous)

Major extinction events

• Five major mass extinctions identified in Earth's history
• End-Ordovician (444 million years ago) eliminated ~86% of species
• Late Devonian (375-360 million years ago) wiped out ~75% of species
• End-Permian (252 million years ago) known as "Great Dying" destroyed ~96% of species
• End-Triassic (201 million years ago) eliminated ~80% of species
• Cretaceous-Paleogene (66 million years ago) caused dinosaur extinction
• Each event reshaped global biodiversity and influenced biogeographical patterns

Continental drift vs plate tectonics

• Continental drift theory proposed by Alfred Wegener in 1912
• Suggested continents once formed a supercontinent called Pangaea
• Plate tectonics theory emerged in 1960s as more comprehensive explanation
• Describes movement of lithospheric plates on Earth's surface
• Drives formation of mountain ranges, ocean basins, and volcanic activity
• Influences species distributions through creation of barriers and corridors

Evolutionary time scales

• Focuses on the pace and patterns of evolutionary change over time
• Helps biogeographers understand species origins, adaptations, and distributions
• Provides insights into how organisms respond to environmental changes

Speciation rates

• Vary widely across different taxonomic groups and environments
• Influenced by factors such as genetic variation, selection pressures, and isolation
• Punctuated equilibrium model suggests rapid bursts of speciation followed by stasis
• Gradual model proposes slow, continuous evolutionary change over time
• Measured using fossil record data and molecular clock techniques

Adaptive radiation

• Rapid diversification of species from a common ancestor
• Occurs when organisms encounter new ecological opportunities or niches
• Classic Darwin's finches on Galápagos Islands
• Hawaiian honeycreepers demonstrate extensive adaptive radiation
• Leads to formation of endemic species clusters in isolated environments

Molecular clocks

• Use genetic differences to estimate time since species diverged
• Based on assumption of relatively constant mutation rates over time
• Calibrated using fossil record or known geological events
• Helps reconstruct evolutionary histories and divergence times
• Provides temporal framework for biogeographical analyses
• Limitations include variation in mutation rates and calibration uncertainties

Ecological time scales

• Encompasses shorter-term processes shaping ecosystems and communities
• Ranges from seasonal changes to multi-decadal patterns
• Critical for understanding dynamic nature of species distributions and interactions

Succession patterns

• Describes changes in community composition over time
• Primary succession occurs on newly exposed surfaces (lava flows, glacial retreat)
• Secondary succession follows disturbances in existing ecosystems (forest fires)
• Climax community represents relatively stable end stage of succession
• Influenced by factors such as climate, soil conditions, and species interactions

Population dynamics

• Studies changes in population size and structure over time
• Influenced by birth rates, death rates, immigration, and emigration
• Density-dependent factors regulate population growth (competition, predation)
• Density-independent factors affect populations regardless of size (natural disasters)
• Understanding population dynamics crucial for conservation and management

Disturbance regimes

• Recurring patterns of environmental disruptions in ecosystems
• Natural disturbances include fires, floods, storms, and pest outbreaks
• Anthropogenic disturbances encompass logging, agriculture, and urbanization
• Shape community structure and species composition over time
• Create mosaic of habitats at different successional stages

Climate change time scales

• Encompasses both natural and human-induced climate variations
• Ranges from short-term fluctuations to long-term trends
• Profoundly impacts species distributions and ecosystem functioning

Glacial vs interglacial periods

• Alternating cycles of global cooling and warming over geological time
• Glacial periods characterized by extensive ice sheet coverage
• Interglacial periods marked by warmer temperatures and reduced ice extent
• Current Holocene epoch represents an interglacial period
• Drives major shifts in species ranges and community compositions

Milankovitch cycles

• Describes periodic variations in Earth's orbit and axis tilt
• Three main components eccentricity, obliquity, and precession
• Eccentricity cycle occurs over ~100,000 years
• Obliquity cycle has a period of ~41,000 years
• Precession cycle takes ~26,000 years
• Influences long-term climate patterns and ice age cycles

Anthropogenic climate change

• Rapid warming trend observed since the Industrial Revolution
• Primarily driven by increased greenhouse gas emissions (carbon dioxide, methane)
• Alters temperature patterns, precipitation regimes, and extreme weather events
• Impacts species distributions, phenology, and ecosystem functioning
• Poses significant challenges for conservation and biodiversity management

Biogeographical processes over time

• Examines mechanisms shaping species distributions across spatial and temporal scales
• Integrates concepts from ecology, evolution, and geology
• Helps explain current biodiversity patterns and predict future changes

Dispersal vs vicariance

• Dispersal involves movement of organisms across barriers
• Can occur through active locomotion or passive transport (wind, water, animals)
• Vicariance results from formation of barriers splitting populations
• Barriers include geological events (mountain formation) or climate changes
• Both processes contribute to speciation and biogeographical patterns

Island biogeography theory

• Developed by MacArthur and Wilson in 1960s
• Explains species richness on islands as balance between immigration and extinction
• Larger islands support more species due to increased habitat diversity
• Islands closer to mainland have higher immigration rates
• Equilibrium number of species depends on island size and isolation
• Applies to other isolated habitats (lakes, mountain tops, habitat fragments)

Metacommunity dynamics

• Studies interconnected local communities linked by dispersal
• Four main paradigms patch dynamics, species sorting, mass effects, and neutral
• Patch dynamics focuses on colonization-extinction processes
• Species sorting emphasizes environmental filtering and niche differentiation
• Mass effects consider source-sink dynamics between habitats
• Neutral model assumes ecological equivalence among species
• Helps understand biodiversity patterns at multiple spatial scales

Human impacts on temporal scales

• Examines anthropogenic influences on biogeographical processes
• Ranges from local habitat modifications to global climate change
• Alters natural temporal scales of ecological and evolutionary processes

Habitat fragmentation effects

• Breaks continuous habitats into smaller, isolated patches
• Reduces overall habitat area and increases edge effects
• Disrupts species movements and gene flow between populations
• Leads to local extinctions and altered community compositions
• Time-delayed extinctions may occur due to extinction debt

Invasive species introductions

• Involves transport of non-native species to new environments
• Often facilitated by human activities (trade, travel, agriculture)
• Can outcompete native species and alter ecosystem functioning
• Lag times between introduction and invasion may span decades
• Examples include kudzu in North America and rabbits in Australia

Conservation and restoration timelines

• Conservation efforts aim to protect existing habitats and species
• Restoration projects seek to recover degraded ecosystems
• Short-term actions include habitat protection and invasive species control
• Medium-term goals focus on population recovery and habitat connectivity
• Long-term objectives involve ecosystem resilience and evolutionary potential
• Timelines vary depending on ecosystem type and degree of degradation

Methods for studying temporal scales

• Encompasses various techniques to reconstruct past environments and species histories
• Integrates data from multiple disciplines (geology, paleontology, genetics)
• Crucial for understanding long-term biogeographical patterns and processes

Fossil record analysis

• Examines preserved remains or traces of ancient organisms
• Provides direct evidence of past species distributions and morphologies
• Allows reconstruction of extinct ecosystems and climates
• Limitations include incomplete preservation and taphonomic biases
• Integrates with other methods to build comprehensive picture of past life

Phylogenetic reconstruction

• Uses genetic or morphological data to infer evolutionary relationships
• Constructs tree-like diagrams showing common ancestry and divergence
• Methods include maximum parsimony, maximum likelihood, and Bayesian inference
• Molecular phylogenies often combined with fossil data for calibration
• Helps understand historical biogeography and speciation events

Paleoecological techniques

• Studies past ecosystems using various proxies and indicators
• Pollen analysis reveals past vegetation compositions and climate conditions
• Tree ring analysis provides information on past growth conditions and disturbances
• Stable isotope analysis infers past diets, migration patterns, and climate
• Sediment core analysis reconstructs long-term environmental changes
• Integrates multiple lines of evidence to build comprehensive picture of past ecosystems

Temporal scales in different biomes

• Examines how biogeographical processes vary across major ecosystem types
• Considers unique characteristics and temporal dynamics of each biome
• Crucial for understanding global biodiversity patterns and conservation priorities

Tropical vs temperate patterns

• Tropical regions characterized by relatively stable climates over time
• Led to higher species diversity and specialization in tropics
• Temperate regions experienced more dramatic climate fluctuations
• Resulted in more generalist species adaptations in temperate zones
• Differences in speciation rates and extinction risks between regions

Marine vs terrestrial systems

• Marine environments more connected, facilitating long-distance dispersal
• Terrestrial systems often have more distinct barriers to movement
• Ocean currents influence marine species distributions over time
• Land-based dispersal more affected by topography and climate gradients
• Different timescales of environmental change between marine and terrestrial systems

Mountain vs lowland environments

• Mountains create diverse microclimates and isolated habitats
• Promote rapid speciation and high endemism rates
• Lowlands often have more gradual environmental gradients
• Mountain species more vulnerable to climate change due to limited upslope migration
• Elevational gradients serve as natural laboratories for studying species responses to environmental change