Category: Ecology

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Ecology, derived from the Greek word "oikos" (meaning home) is the scientific study of the distribution and abundance of organisms. Where organisms occur and how many there are is determined by the interactions between them and their environment. An organism's environment is made up of other organisms (biotic factors) on the one hand and physical and chemical phenomena (abiotic factors) on the other. The combined biological and physical constituents of the environment are referred to as an ecosystem. Within an ecosystem, ecology can deal with individual organisms, populations (individuals of the same species occurring together in space and time) or communities (assemblages of species populations). The actual place where an organism lives is its habitat, whereas the term ecological niche describes 'how' an organism lives (its tolerances and requirements defining the resources and conditions it needs to survive). Ecology is furthermore concerned with the pathways of energy and matter flowing through an ecosystem, for example through looking at food webs or nutrient cycles. The applications of ecology are manifold and include biodiversity conservation, management of habitats and protected areas, pest control and harvest management to name but a few.

In terms of evolutionary convergence, the repeated conquest of new habitats can provide fascinating insights. For example, terrestrialisation or taking to the sky (in the form of gliding or powered flight) has occurred multiple times independently in different groups of animals. It is also particularly instructive to explore parallels between communities of organisms inhabiting similar environments.

Mediterranean-type ecosystems, which are characterised by long hot, dry summers and short winters with variable rainfall, occur in different regions of the world, and the plant communities there show a number of striking similarities, notably drought-evading annuals and evergreen shrubs.

In ancient times, Madagascar and New Zealand were both home to giant herbivorous birds, against which the resident plants (that are only very distantly related to each other) evolved defences, such as tough wiry branches with widely spaced leaves. With these giant birds now extinct, the wire anatomy still remains as a ghost of past adaptation.

Bacteria show an extraordinarily wide distribution and have colonised even the most extreme of environments. For example, thermophilic bacteria flourish in high-temperature environments, while halotolerant bacteria can cope with extreme salinities. These extremophiles represent a key example of convergence as they have evolved independently in each of the two major subgroups of bacteria, the Archaea and Eubacteria.

Further interesting examples of ecological convergence can be found among the birds (e.g. between the nectar-feeding hummingbirds and sunbirds) and snakes (e.g. between African and European whip snakes).

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Flying through the air on a summer's evening or sparkling in the ocean you may see magical flashes of light that signal some of nature's most enchanting creatures, those that are bioluminescent.

Tropical rainforest trees n/a Not Available
Mangrove swamp ecology n/a Not Available
Placental and marsupial mammal ecology n/a Not Available
Deep sea communities: cold seeps and hot vents n/a Not Available
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Cichlids are one of the cause celebré of evolution, and rightly so because these freshwater fish show a remarkable diversity and exemplify many key aspects of adaptive radiation. But why so successful? The answer lies in the versatility of the jaws (and yes, they are convergent).

Evolution of birds from feathered reptiles

Birds, in the sense of flying descendants of feathered reptiles (a more expansive group than the "true" birds in today's skies), evolved several times from within the theropods.

Halotolerance in bacteria and protistans n/a Not Available
Crabs: insights into convergence

You might think of crabs mainly as food, but this group is also highly instructive in terms of convergence…

Ecological convergence in snakes

Whip snakes are elongate, highly alert, move quickly and hunt lizards.  All are very distinctive, but the European and African whip snakes are convergent.

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Extremophiles: Archaea and Bacteria

Surely, no organism can survive in boiling water or brines nine times the salinity of seawater? Wrong - some archaea and bacteria have independently evolved adaptations to such extreme environments...

Gliding lizards, frogs and ants

Tree-dwelling (‘arboreal’) ants capable of controlled gliding do so when dislodged or threatened by predation. Gliding species include members of three disparate families: Myrmicinae, Pseudomyrmecinae and Formicinae.

Gliding in feathered reptiles

A number of reptile species have been discovered in the Mesozoic fossil record, bearing feathers that were apparently used to support gliding locomotion, rather than true, powered flight as we see in present day birds.

Gliding in Draco lizards and tree snakes

“The agamid lizard genus Draco (consisting of the so-called ‘flying dragons’) exhibits an array of morphological traits associated with gliding.” – A.P. Russell & L.D. Dijkstra (2001) Journal of the Zoological Society of London, vol. 253, page 457

Gliding mammals

Gliding mammals rely primarily on extensive skin membranes or ‘patagia’ that stretch between fore- and hind-limbs, creating a wing-like structure.

Gliding reptiles

In the reptiles, different forms of skin membrane (called ‘patagia’) and in some extinct species, primitive feathers, have evolved convergently as adaptations for gliding.

Mammalian adaptations to underwater vision

One of the more obvious eye adaptations in whales is the extraordinary capacity of the pupil to change the size of its opening, from very small when in surface sunlit water to very large when exploring the abyssal gloom.

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Wire plants, moas and elephant birds

Madagascar and New Zealand were once home to giant herbivorous birds. And the plants have not forgotten...



Birds: insights into convergence

Intriguing ecological and morphological parallels can be found among the Neoaves. Many of these forms were initially believed to be each other's closest relatives, but are now widely recognised as classic examples of convergence. Think how similar swifts and swallows are, but they are only distantly related.

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Tool use in birds

What animals can drop stones into a water-filled tube to bring floating food within reach or bend wire to form a hook? Obviously chimpanzees? No, New Caledonian crows have evolved sophisticated tool use too.

Myriapods (centipedes and millipedes): defence and terrestrialisation

This group of arthropods is also important because they show independent invasion of the land (terrestrialization), which not surprisingly has led to important convergences.

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Mediterranean plant ecosystems

Mediterranean climates are characterized by long hot, dry summers and short winters with variable rainfall. The plant communities have long been recognized to have a number of striking similarities, notably drought-evading annuals and ever-green shrubs forming dense scrub.

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Crustaceans: insights into convergence

Whilst predominantly marine, quite a number of crustaceans have invaded freshwater habitats and even more interestingly a few demonstrate terrestrialization, effectively freeing themselves from their aquatic ancestry.

Terrestrialization by amphibians

In the amphibians we see the recurrent evolution of a direct life cycle, a necessary pre-requisite for the invasion of land by losing the aquatic tadpole.

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Amphibian life cycles and terrestrialisation

Certain groups show a dramatic transition between a juvenile stage and the adult. This is perhaps most familiar in the frogs which in particular, are well-known for their aquatic tadpoles.

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Annelids: insights into convergence

Notable instances of convergence involving annelids include luminescence, moulting and the independent evolution of both compound eyes (e.g. in sabellids) and camera eyes (in alciopids).

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