Cyprinodontiformes vivíparos e ovovivíparos

Livebearer Cyprinodontiformes

Biologia > Cyprinodontiformes vivíparos e ovovivíparos ameaçados

Biology > Threatened Livebearer Cyprinodontiformes

Livebearer Cyprinodontiformes in the IUCN Red List of Threatened Species

4 species recent extinction becomes a very sad reality that turns this page in something very sorrowful about.

There are at least 2 more species vanished from the wild and the menaces over a considerable number of other are really a great anguish.

To realise how serious this problem can be, it’s quite imperative to be aware of how IUCN Red List of Threatened Species operates, as well to have a fine notion about the used terminology on the below classifications. Information about this topics is accessible thru the links, either directed to external sources or documentation available on this website. Search for them after next classification tables.

Sub-Família Goodeinae :

Sub-família Poeciliinae :

Citation - IUCN Red List of Threatened Species 

www.iucnredlist.org ( downloaded on 23 December 2005 )

To understand this concepts please acess :

IUCN Red List of Threatened Species categories

IUCN Red List of Threatened Species criteria

Conservation Biology

One of the greatest challenges that biosphere is facing can be no doubt the accelerating speed of species extinction.

Speculations say that never since the Cretaceous so many species become extinct in so short period of time.

The defy posed by present high levels of species massive vanishing, and the prospect of even upper levels in the future, has led to the emergence of a new scientific matter - Conservation Biology. 

This new science works as an applied discipline to seeks and learn how to preserve species, communities, and ecosystems from extinction. The causes of biodiversity declines and the attempts to develop methods to prevent such impasse are the main object for Conservation Biology.

Species under vulnerable or extinct classification

To become sure and secure about this two kinds of classification, conservation biologists concentrate on changes in population size and habitat availability.

Sudden declines in populations and above all whose habitats are being destroyed, or which are endemic to small areas can be considered as good start.

What can be responsible for extinction ?

Realtive small number of individuals or when a specie is significantly rare in the wild, does not necessarily mean that it is in danger of extinction.

Nature utilizes many simple mechanisms to prevent population numbers from growing out of control reaching a demographic explosion. Shortage or increase of some resources may limit or increase the size of populations.

We might consider also the top levels of the feeding chain, where effectives are usually rare because little energy is available to support their populations.

Vulnerable species must not always be considered threaten with extinction or lost. 

Many restrain endemics are quite stable for millenniums and not at all threatened meanwhile their individuals number was never too large.

If it's not just the size or vulnerability, what can be responsible for extinction ?

Taking in consideration a unfortunately long and wide collection of recorded species lost and many currently threatened with that probable fortune, conservation biologists have identified a few factors that cannot be ignored and seem to play a key role in many extinctions with special focus on the Livebearer Cyrinodontiformes:

• Introduced alien species in habitat

• Disturbance of ecological relationships

• Loss of genetic variability

• Habitat devastation or habitat fragmentation

• Water pollution and contamination

• Desease

• Climate change

• Water resources overexploitation

• Dams construction

Population viability analysis

Quantifying the risk faced by a particular species is far from been a simple process or precise method.

Increasingly, conservation biologists make a rough estimate of a population's risk of local extinction, thinking in terms of a minimum individual’s number to viability. 

This way they estimate the number and density of effectives necessary for the population to maintain or increase its numbers.

Some small populations can show high threat of vanishing, while others, equally undersized, are at little or no jeopardised at all.

Two components are of particular importance to estimate a population viability, the demography ( the amount of random variation in birth and death rates) and the genetic ( fluctuations in a population's level of genetic variation ).

The less significant the population, the greater the random fluctuation are expected to be. 

Extinction is more expected in small populations when high death rates coincide with low birth rates, or when higher levels of inbreeding lead to a lowering of heterozygosity.

A number of species, particularly those in aquarium, are distributed in metapopulations, to be more precise, in collections of small subpopulations separated from each other. Each individual subpopulation may be quite small and in real threat of extinction due to genetic problems in small populations dangerous effects, but the metapopulation it self represents a large number of reproductive individuals and could be quite safe from vanish so long they could be in contact and breed out of it's isolated group.

IUCN Red List of Threatened Species ?

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