You're into an area that I particularly enjoy, namely the taxonomy of fish, but I will try to not be too wordy.
There has been and will continue to be significant changes in the classification of fish. This is actually not so much a matter of debate, but an issue of having almost to rethink our classification of most fish, largely because of the discovery of DNA and its application in what we term phylogenetics. Before this, ichthyologists classified fish according to mainly physiological characteristics which may have included dentition, fin ray counts, inner bone structure, etc., and to a lesser extent external colour/pattern. With the discovery of DNA, scientists began to see the remarkable inter-relationship that all living things on this planet have, both animals and plants; we call this evolutionary biology. Phylogenetics as Wikipedia defines it (and rather well) is the study of evolutionary relationships among groups of organisms which are discovered through molecular sequencing data and morphological data matrices.
The idea behind phylogenetics is to trace every living species back to the last common ancestor. This obviously takes time, and requires the examination of several individuals of the species, and often from different geographical areas in order to ascertain if it is just one species or the different fish have evolved into distinct species due to geographical separation. As collectors move further into areas previously unexplored, fish are being discovered that bear such close physical similarities to others that it is impossible without examination to determine if they are conspecifics, geographic variants, or distinct species.
As for the molly species, I do not know if there is a photo listing on someone's site, but there is Fishbase which lists all known species of fish. If you search the genus Poecilia, it will bring up a list of 116 species. However, as i said previously, there are some 40 recognized distinct species. Many of the names in the Fishbase list are invalid, and they give the valid name in another column. If you click on the name link, it will take you to the page describing that species, and there will be a photo if one is available (some species have never been photographed), or a drawing if no photo, or perhaps blank if neither. But you can with patience look up all the molly species. Here's the index page for Peocilia.
http
/www.fishbase.org/Nomenclature/ScientificNameSearchList.php?crit1_fieldname=SYNONYMS.SynGenus&crit1_fieldtype=CHAR&crit1_operator=EQUAL&crit1_value=poecilia&crit2_fieldname=SYNONYMS.SynSpecies&crit2_fieldtype=CHAR&crit2_operator=CONTAINS&crit2_value=&typesearch=simple&group=summary&backstep=-2&sortby=sciname
The mollies in the hobby are likely going to be one of two species, P. sphenops (the common molly) or P. latipinna (the Sailfin Molly). The many forms of these are just man-made variants of the wild fish, obtained through selective breeding and such. The feral (wild) form P. sphenops has an olive-green back and bluish flanks spotted with orange, and the belly region is orange. The iris of the eye is blue; fins are brownish. The popular all-black molly was developed from this species; it is less hardy and requires warmer temperatures. There are now several varieties, such as the Gold, Green, Lyretail, and Dalmation, some of which are crosses between this species and P. latipinnis. The fish has an average lifespan of 4 years, except for the Black form which is about 3 years.By the way, the plural of genus is genera. Species is both singular and plural. We can thank the great Carl Linnaeus (1707-1778) for our biological classification system.
Byron.
There has been and will continue to be significant changes in the classification of fish. This is actually not so much a matter of debate, but an issue of having almost to rethink our classification of most fish, largely because of the discovery of DNA and its application in what we term phylogenetics. Before this, ichthyologists classified fish according to mainly physiological characteristics which may have included dentition, fin ray counts, inner bone structure, etc., and to a lesser extent external colour/pattern. With the discovery of DNA, scientists began to see the remarkable inter-relationship that all living things on this planet have, both animals and plants; we call this evolutionary biology. Phylogenetics as Wikipedia defines it (and rather well) is the study of evolutionary relationships among groups of organisms which are discovered through molecular sequencing data and morphological data matrices.
The idea behind phylogenetics is to trace every living species back to the last common ancestor. This obviously takes time, and requires the examination of several individuals of the species, and often from different geographical areas in order to ascertain if it is just one species or the different fish have evolved into distinct species due to geographical separation. As collectors move further into areas previously unexplored, fish are being discovered that bear such close physical similarities to others that it is impossible without examination to determine if they are conspecifics, geographic variants, or distinct species.
As for the molly species, I do not know if there is a photo listing on someone's site, but there is Fishbase which lists all known species of fish. If you search the genus Poecilia, it will bring up a list of 116 species. However, as i said previously, there are some 40 recognized distinct species. Many of the names in the Fishbase list are invalid, and they give the valid name in another column. If you click on the name link, it will take you to the page describing that species, and there will be a photo if one is available (some species have never been photographed), or a drawing if no photo, or perhaps blank if neither. But you can with patience look up all the molly species. Here's the index page for Peocilia.
http
/www.fishbase.org/Nomenclature/ScientificNameSearchList.php?crit1_fieldname=SYNONYMS.SynGenus&crit1_fieldtype=CHAR&crit1_operator=EQUAL&crit1_value=poecilia&crit2_fieldname=SYNONYMS.SynSpecies&crit2_fieldtype=CHAR&crit2_operator=CONTAINS&crit2_value=&typesearch=simple&group=summary&backstep=-2&sortby=scinameThe mollies in the hobby are likely going to be one of two species, P. sphenops (the common molly) or P. latipinna (the Sailfin Molly). The many forms of these are just man-made variants of the wild fish, obtained through selective breeding and such. The feral (wild) form P. sphenops has an olive-green back and bluish flanks spotted with orange, and the belly region is orange. The iris of the eye is blue; fins are brownish. The popular all-black molly was developed from this species; it is less hardy and requires warmer temperatures. There are now several varieties, such as the Gold, Green, Lyretail, and Dalmation, some of which are crosses between this species and P. latipinnis. The fish has an average lifespan of 4 years, except for the Black form which is about 3 years.By the way, the plural of genus is genera. Species is both singular and plural. We can thank the great Carl Linnaeus (1707-1778) for our biological classification system.
Byron.
