gingerbeer Posted January 8, 2008 Share Posted January 8, 2008 This question is prompted by a thread on another forum but figure here is where the best answer will probably come from (Hi Dave ) What is a species and how do they decide nowdays what is a variant and what is a species. Link to comment Share on other sites More sharing options...
Ged Posted January 9, 2008 Share Posted January 9, 2008 Here is a simple definition A species is a single, distinct class of living creature with significant physical or behavioural features that allows you to distinguish it from others whilst a variant is the small differences that can occur within the species i.e. colour Link to comment Share on other sites More sharing options...
akroyd Posted January 9, 2008 Share Posted January 9, 2008 Hi Ged, That's a blurry line with a lot of cichlids. We've got hybrid elec. blues, red devils, jewels and zebras to name a few. I don't have any idea what the current rules are. Link to comment Share on other sites More sharing options...
gingerbeer Posted January 9, 2008 Author Share Posted January 9, 2008 akroyd was responsable for this thread - at school it was taught about fertile and infertile offspring - that doesn't work - so what is it. Link to comment Share on other sites More sharing options...
cyber_crimes Posted January 9, 2008 Share Posted January 9, 2008 Species is a sub division of a Genus. EG: mutlifasciatus is a species of the Genus Lamprologus. A species is determined by its similar attributes to those labelled under a genera. A demasoni is obviously from the same family as a zebra as they share similar features, therefore they are both listed under the genus Pseudotropheus. But they do have differences so they are titled as different species. Variant is often used to describe certain distinguishing features such as colour, morph, locality etc. within a species. A good EG: would be the variants used to describe Pseudotropheus zebra (red zebra, cobalt blue zebra etc) or the locality differences of Tropheus moorii. JMO! Link to comment Share on other sites More sharing options...
Ged Posted January 9, 2008 Share Posted January 9, 2008 That's a blurry line with a lot of cichlids. We've got hybrid elec. blues, red devils, jewels and zebras to name a few. The concensus is that to qualify as a species the organism must not be able to interbreed with another organism outside the group and this is not the case as you have mentioned when you look at cichlids. To add to the mix you have the term genera which is the rank above species in the classification in taxonomy which may include several related species. In cichlids these are know as "cichlid flocks" and would normally come from a monophyletic (one ancestor) origin. My understanding is that due to the monophyletic origin of cichlid species that cichlids within the same cichlid flock may interbreed. When it comes to Haplochromine cichlids of Lake Malawi it is was termed as a single cichlid flock but is now thought (depending on who you listen too) that there are two haplochromine species flocks in the lake, one comprising the 11 genera of mbuna, the other including all the remaining endemic haplochromines (Michael Oliver) There is a another term that needs to be added to this discussion and that is speciation. This is the evolutionary development of a new species, usually as one population separates into two different populations no longer capable of interbreeding. Below is a part of an article I wrote on Cynotilapia afra of Thumbi West Island Cynotilapia afra has become a very popular species amongst aquarists because of its striking colour pattern. Each location provides slight variations to a blue fish with black bands. Some variations include striking yellow contrasts and markings. These variations have been explained by a number of different theories, some more likely than others. The two main schools of thought on the topic of speciation from the mother population are the sympatric theorists and the allopatric theorists. Sympatric theorists espouse that speciation can occur within the presence of the mother population. The likelihood that two fish with the same variation will breed is reduced by both males and females using colour and patterns to help recognise conspecifics. If the variant fails to find a mate with the same variation then the genes of the parent population will eventually re-establish itself. It is hard for those that espouse this theory to support their argument by finding examples in the cichlid population in Lake Malawi. The allopatric theorists on the other hand propose that speciation occurs because of geographical isolation from the mother population. There are two major allopatric schools of thought. The vicarious theory (Rosen, 1975) advocates that the isolation of the daughter population occurs because of a geographical event such as a rise in the lake level. Once the daughter population is isolated then it is able to follow a different evolutionary path. The peripatric speciation or the founder effect theory (Mayr, 1963) believe that as the mother population spreads out a few individuals may reach a previously un-colonised location. These few are then able to breed and stabilise any variation prior to arrival of others from the mother population. Variation can also be attributed to the introgressive hybridization of cichlids. Riseberg and Wendel (1993) as well as Arnold (1997) through their studies formulated that offspring from two different, closely related parental species will result in hybrid offspring that possess a complex mixture of parental genes. It is the mating back or introgression to the parent species over a number of generations that new species are formed. There have been a number of research studies undertaken to examine hybridization events in cichlids. Stauffer and Hert (1992) examined hybridization in translocated species, Seehausen et al. (1997) under turbid water conditions, Ruber et al. (2001) when secondary contact was made due to fluctuations in the water levels in the lake and McElroy and Kornfield (1993) in the aquarium. All these theories may help explain why speciation of cichlids in Lake Malawi and other Rift lakes has taken place at a frenetic pace. The use of DNA evidence is not only helping us understand the phylogenetic tree of Lake Malawi cichlids but also identifying possible hybridization events. I don't know if I have help your understanding or just added to the confusion. Gerard Link to comment Share on other sites More sharing options...
Josh Posted January 9, 2008 Share Posted January 9, 2008 To me a species is still a species regardless of what hybrids we have. Hybrids dont have a species name. Crossbreeds within a species would still have a species name but I doubt we should used it when describing our fish Josh Link to comment Share on other sites More sharing options...
YeW Posted January 10, 2008 Share Posted January 10, 2008 It's a question most scientists wont give you a good answer to (me included): Look here for a bunch of definitions: http://en.wikipedia.org/wiki/Species_conce...ions_of_species and here for more info: http://en.wikipedia.org/wiki/Species_problem A variant is some intraspecies division (like subspecies, variety, morph etc). btw: Monophyly doesn't allow interbreeding. Monophyly just means that they share a common ancestor. The key issue here is time. Chimps and humans are part of a monophyletic linneage -- but they cant interbreed. That's because there's enough genetic difference between the two "species". Hell, cichlids and humans are part of a monophyletic linneage (the chordates). In the case of cichlids many "species" have evolved very recently and are still genetically very similar. This similarity allows interbreeding between quite different looking organisms! For this reason the reproductive species concept (which is being discussed by many above) doesn't really hold up and virtually no one uses it today. It's particularly poor when it comes to plants (which are much more robust when it comes to genetic abnormality than animals), fungi or prokaryotes. Link to comment Share on other sites More sharing options...
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