Biogeography Concepts and Regions

Key Definitions and Concepts

• Biogeography studies the geographical distribution of organisms.
• Modern biogeography incorporates zoogeography (animals), phytogeography (plants), focusing on historical and ecological aspects. Historical biogeography considers evolutionary processes, while ecological aspects investigate environmental influences.

Zoogeographical and Phytogeographical Regions

• Holarctic Realm comprises Nearctic and Palearctic regions.
• Other realms include Afrotropical, Oriental, and Australian, totaling seven regions.
• Arctic and Palaeotropical regions connect.
• Transition zones such as Wallacea mark sharp divisions between biotas.

Historical Biogeography

• Dispersion is organism movement across geographical barriers.
• Vicariance describes separation due to geographical changes (e.g., continental drift).
• Pangea, a supercontinent, split into Laurasia (north) and Gondwana (south) roughly 225 million years ago.
• Evidence for continental drift includes fossils and geological formations.
• Subspecies patterns in Fringilla coelebs (Chaffinch) and False Beech (Nothofagus) reflect dispersion patterns and Gondwana breakup, respectively.

Ecological Biogeography

• Biodiversity decreases from the equator to the poles, influenced by factors such as net primary productivity.
• Biodiversity hotspots are regions with high species diversity and endemism, notably tropical forests and Mediterranean areas.

Species Range and Representation

• Species ranges vary from cosmopolitan (global) to endemic (restricted).
• Species ranges can be continuous or disjunct.
• Mapping species range uses outline, grid, and point maps.
• Range changes include seasonal and historical shifts and expansions (e.g., Quercus spp.)

Key Concepts in Island Biogeography

• Island biogeography examines species diversity on islands and habitat islands, influenced by area, isolation, habitat heterogeneity, and species characteristics.

Equilibrium Model (MacArthur & Wilson, 1963)

• Species richness increases with island area.
• Species richness decreases with island isolation.
• Colonization and extinction rates reach equilibrium.

Effects on Species Richness

• Larger islands support more species due to greater habitat diversity.
• Smaller islands experience higher extinction rates.
• Isolation limits colonization and increases extinction risk.
• Habitat heterogeneity supports more species.

Evolutionary Dynamics

• Endemicity is higher on larger, more isolated islands.
• It relates to dispersal abilities and ecological niches.
• Species specialists (predators, parasites) are more vulnerable to extinction.
• Neoendemics emerge on new islands, while paleo-endemics survive from fragmented habitats.

Conservation Implications

• Preserve large, heterogeneous habitats to maintain biodiversity.
• Protect isolated islands to protect endemic species.
• Manage invasive species and habitat loss.
• Address climate change impacts on insular ecosystems.

Introduction to Ordinations

• Ordinations reduce complex multivariate data to simpler diagrams.
• They compare species data, environmental variables, and sample traits.
• Ordination (gradual continuous variability) differs from classification (discrete categories).

Common Ordination Techniques

• PCA (Principal Component Analysis), RDA (Redundancy Analysis), CA (Correspondence Analysis), and CCA (Canonical Correspondence Analysis) are common approaches.
• Axes represent variability, with eigenvalues indicating their significance.
• Species points indicate relationships with environmental variables.
• Environmental arrows show influence strength and direction.
• Angles between arrows illustrate correlation strengths and directions (180° = negative, 90° = no correlation).

Data Requirements for Ordination

• Input data includes species abundance and environmental variables.
• The number of samples should exceed the number of explanatory variables.
• Handle missing data (zeros and NAs) carefully.

Macroevolution

• Macroevolution encompasses processes above the species level, including speciation, extinction, and evolutionary trends.
• Microevolution involves species-internal processes like mutations and genetic variation.
• Global biodiversity changes are influenced by adaptive radiation, speciation, and extinction events.
• Speciation drivers include traits like parasitism, planktonic lifestyles, and genetic polymorphism.
• Species selection favors species with high speciation and low extinction rates.

Evolutionary Trends

• Williston's Rule describes simplification of body structures over time.
• Cope's Rule indicates trends toward larger body size in lineages.
• Mass extinction events significantly alter global biodiversity.
• Factors contributing to extinction include narrow ecological niches and limited distribution ranges.

Plant Biogeography Overview

• Plant biogeography studies plant distribution using ecological, evolutionary, and historical processes.
• Climatic drivers (temperature, precipitation, seasonal changes) and historical ones (continental drift, glacial refugia, and post-glacial migration) influence plant distribution.
• Climatic drivers, such as beech distribution, depend on climatic conditions.
• Historical drivers, like the breakup of Gondwana/Laurasia, impact historical and distribution patterns (e.g., Nothofagus).
• Glacial refugia and postglacial migration are vital factors in plant distribution.

Historical Biogeography (for plants)

• Continental drift divided Gondwana and Laurasia, influencing plant distributions.
• Postglacial migration models, e.g., sediment coring and fossil analysis, help understand migration routes.
• Relict species are found in specific habitats like tundra or peat bogs.
• Methods used to detect glacial refugia include DNA markers, pollen analysis, microfossils, and sediment coring.

Species Diversity Concepts

• Species richness is the count of species in a community.
• Heterogeneity (H) combines species richness and evenness.
• Evenness (E) reflects species distribution uniformity.
• Diversity measurements typically focus on counts based on individuals, biomass, cover, or productivity, focusing on one trophic level.

Species Richness

• Species richness is the simplest diversity concept, reflecting the species diversity in a community.
• Rarefaction and Jackknife/Bootstrap statistical techniques are used to estimate richness.

Heterogeneity

• Heterogeneity accounts for species richness and evenness.
• Various distributions (e.g., Logarithmic, Lognormal) are seen in observed species.
• Simpson's Index measures the probability that two randomly selected individuals are from the same species.
• Shannon-Wiener Index measures species diversity based on information theory.
• Brillouin index accounts for non-random samples.
• Pielou's Evenness measures the consistency of species abundance.

Species Concepts and Reproductive Isolation

• A species is a basic evolutionary unit, with multiple concepts.
• Historical concepts include typological, nominalistic, and intuitive views.
• Modern concepts include morphological, biological (interbreeding), recognition, and cladistic (shared traits).
• Reproductive isolation mechanisms (RIM) prevent interspecies hybridization: prezygotic (ecological, temporal, behavioral, mechanical, gametic) or postzygotic (zygotic, embryonic/juvenile, hybrid sterility, low fitness)

Species Distribution

• Distribution types can be continuous, fragmented (disjunct, vicariant or non-vicariant), or sytropic (same habitat).

Reproductive Isolation Mechanisms (RIM)

• RIM (Prezygotic) includes ecological, temporal, behavioral, mechanical, and gametic aspects. - Postzygotic RIMs include zygotic, embryonic/juvenile mortality, hybrid sterility, and lower fitness.

Speciation Overview

• Speciation is the process of new species arising, involving reproductive isolation and genetic divergence.
• Dobzhansky-Muller Hypothesis involves genetic incompatibility arising in hybrids.
• Haldane's Rule highlights the increased sterility in the heterogametic sex of hybrids.
• Reinforcement hypothesis proposes selection intensifying reproductive barriers.

Types of Speciation

• Phyletic speciation involves change within a lineage, without increase in diversity.
• Allopatric speciation occurs due to geographic barriers.
• Peripatric speciation is divergence in small isolated populations.
• Sympatric speciation occurs without geographic barriers.
• Parapatric speciation occurs across adjacent habitats.
• Ring species experience a gradual geographic change.
• Hybridization can form new species through backcrossing or introgression.
• Hybridogenesis and polyploidy are other speciation mechanisms.

Community Similarity and Classification

• Hierarchical classification groups data based on similarity.
• Methods are often hierarchical and agglomerative, producing dendrograms to visualize relationships.
• Data preparation involves input data transformation (e.g., square-root, logarithmic) and standardization.
• Similarity coefficients (e.g., Jaccard, Sørensen, Bray-Curtis, Morisita) measure similarity in different ways.
• Clustering methods involve starting with individual samples and merging based on similarity.

Methods For Detecting Glacial Refugia

• Techniques used include DNA markers, pollen analysis, and microfossils (e.g., pollen, wood, charcoal) from sediment cores.

Explore key definitions and concepts in biogeography, including the historical and ecological aspects of zoogeography and phytogeography. This quiz covers the different biogeographical realms, their characteristics, and the historical processes that shaped their distribution. Test your understanding of dispersion, vicariance, and the effects of continental drift.