Biogeography and Species Distribution

Flashcards on biogeography and species distribution.

Biogeography

• the study of geographical distribution of organisms

• Lomolino et al., 2017

Environmental Controls on Species Distribution

• climate control major driver of distribution

Geographic Controls on Species Distribution

• Vicariance = seperation of a pop by a physical barrier leading to similar species

• Dispersal = movement of species from one location to another, resulting in different evolutionary pathways.

• Connectivity of habitats can change - can vary over time

• Barriers affecting species individually

• Abandoned patches may re-connect - become homegnised again

• Lomolino et al., 2017

Biogeographic regions

• distinct areas with unique plant and animal life shaped by ecological and historical factors

• Lomolino et al., 2017

Importance of islands

• physical attributes make them an ideal place of research

• key figures have contributed to biogeography using islands

• Islands as model systems + provide research opportunities

• many of them

• find islands in all climate zones

• discrete - have edges - where water starts

• Warren et al., 2015

Types of islands

• Continental e.g. British Isles

• Oceanic e.g. Galápagos Islands

• Barrier

• Tidal

• Coral

• Artificial

• Lomolino et al., 2017

Evolutionary filter and species selection on islands

• Group of species arriver at an island

• community assemblage

• evolutionary filter - make species go extinct

• Whittaker et al., 2013

Island Syndromes

Unique evolutionary traits and vulnerabilities that species develop upon reaching isolated islands.

Lomolino et al., 2017

Importance of islands - physical factors - Isolation (Sympatric Isolation) - new species from the same ancestor

• once apart of neighbouring continent - likely to have flora and fauna from mainland

• speciation occurs in isolation

• Santos et al., 2016

Island analogues

• Lakes - can be defined spatially

• Lakes used as models to study island biogeography

• most tests here focus on relationship between species richness and lake surface area / isolation

• Hortal et al., 2014

Island size

• positive relationship between the area of a habitat and the number of species found in the area

• large islands have more species

• small spaces can only support a small number of species

• rising sea levels during warm phases = fragmented the region into large islands and archipelagos

• leads to speciation through isolation

• Whittaker wt al., 2007

Distance from the mainland

• Rising sea levels - make islands further away from mainland

• oceans barriers to distribution if land animals (Allopatric isolation) - new species

• island communities of not always have lower diversity than mainland - Santos et al., 2016

• near islands will have higher immigration rates than far islands - Warren et al., 2015

• MacArthur and Wilson - Island species area relationship steeper with increasing geographic isolation

• Small island effect - certain species can not occur on an island below a certain size

Ecoregions

• identified by analysing patterns and composition of biotic and abiotic components

• E.g. geology, soil, land use etc

• Lomolino et al., 2017

Darwin and Islands

• Mocking bird species on 3 islands in the Pacific - different from each other

• Fossils found in South America - sloth and armadillo - contradicted idea that species were fixed

• Galapagos islands - size of finches beak varies

• biogeographical processes from one study

• Immigration —> colonisation —> adaptive radiation

• Cox and Moore, 2019

Colonisation

• plant or animal establishing itself in an area

• Cox and Moore, 2019

Adaptive radiation

• process in which organisms diversify from ancestral species into new forms

• Cox and Moore, 2019

Wallace

• realised that closely related species were found close together geographically

• distance from mainland will affect diversity of biota

• Santos et al., 2015

Wallace Line

• shows how species remain separate

• can not travel between islands due to sea level rise

• Santos et al., 2015

Natural selection

• organisms with traits better suited to environment - more likely to survive - pass on traits + reproduce

• by Darwin and Wallace

• Cox and Moore, 2019

MacArthur and Wilson

• theory of island biogeography = number of species on an island is the result of dynamic equilibrium between species becoming extinct

• biota affected by degree of isolation

• rate of immigration balanced by rate of extinction

• may take time to establish equilibrium

• theory does not always work

• Warren et al., 2015

SLOSS debate (Single Large or Several Small) - link to Island biogeography theory

• optimal strategy for conserving biodiversity in fragmented habitats

• will a single large reserve conserve more or serval small ones

• catastrophe - everything will go - better to have smaller areas

• Cox and Moore, 2019

Edge effect - ink to Island biogeography theory

• more edge - ratio is higher when you have smaller islands rather than one big one

• Cox and Moore, 2019

Ecological factors - Succession and disturbance

• large disturbances can lead to areas being exposed and reshaped

• Spiller et al., 1998

• e.. Krakatoa volcano in 1883

• biological invasions can change the local environment

Ecological factors - Evolution and adaptation

• evolution change in response to conditions

• process takes long - unlikely to occur anywhere but islands - provide opportunity for species to live long enough for adaptation

• Evolution key role in community assembly

• Thorpe, 2005

Conservation theory

• Habitat fragmentation = reduction in the area of the original habitat and spatial configuration of that remains

• assumptions - fragments are similar to oceanic islands

• Haila, 2002

Paleogeography

Past geographic conditions have shaped current biogeographic regions.

Processes that affect differentiation at palaeographic scales

• plate tectonics

• climate history

• evolutionary history

• Willis and McElwain, 2014

Case study for Palaeography

• Gibraltar straight closing connected Europe and Africa 5 to 6 mill years ago

• species competition if North Africa and Europe

• Unable to cross

• Willis and McElwain, 2014

Tobler’s Law

• everything is related to everything - but near things are more related than distant

• exception - environment shows string contrasts so near places differ greatly

• Near things may not be more similar -

• Anisotropic Long-Distant Dispersal Hypothesis - dispersal of animals affected by directional factors like water and wind

• E.g. stronger correlation of floristic similarities with wind connectivity than proximity

• Lomolino et al., 2017

Anthropogenic Controls on Species Distribution

Human activities influence species distributions.

Rufugia - climate change

• earth got cooler - water locked up in ice - drier

• impact on poles greater

• tropical forest = drier - retract in refugia

• glacial maxima - tropical forest shrank + fragmented

• speciation occurred

• end of glacial period - warmer

• habitat islands grew again

• more speciation

• evidence for this : areas in the Amazon where there are highly biodiverse in certain types of species

• e.g. butterflies in all patches

• Cox and Moore, 2019

Dispersal

• The movement of a species from one area of land to another, particularly relevant in island biogeography.

• Lomolino et al., 2017

Invasive Species

• Species that colonize areas they were previously unable to inhabit due to geographic barriers.

• Lomolino et al., 2017

Zoogeographic Regions

• Regions defined based on the distribution of vertebrate families and genera.

• Lomolino et al., 2017