Tropical Fish Research
Native Habitat – Study of Pupfishes
A new study of pupfishes – a paper on the diverse species of pupfishes has just been published. It should be interesting to aquarists who like to know more about their chosen passion. This study of pupfishes focuses on a family of fish that rarely finds its way into the aquariums of home aquarists, but is extremely interesting because of the places they tend to occupy in nature.
Pupfishes are found in very diverse habitats and have been found to be extremely adaptable, through evolution to a wide variety of niches that other animals often cannot occupy. In the report “Pupfish form Evolutionary Mountain Ranges” Seriously Fish suggests the reasons for increased evolution in these very exploitive fish:
They are however of great interest to conservation biologists and evolutionary scientists since many species are highly-localised in terms of distribution and tend to inhabit extreme environments, while some are notable for extremely rapid rates of evolution which are among the fastest known in the animal world.
This kind of accelerated evolution is often referred to as ‘adaptive radiation’, of which the most famous examples among fishes are perhaps the enormously diverse populations of cichlids inhabiting eastern Africa’s great lakes, home to hundreds of endemic species, some of which have developed extreme ecological specialisations such as scale-eating (lepidophagy), fry-stealing, parasite-feeding and ambush predation.
Such radiation events are typically associated with an initial increase in rates of morphological and species diversification as new ecological niches are colonised followed by a slowdown in diversification, and this theory is sometimes referred to as ‘early burst’.
Pupfish ‘heat map’ taken from Martin and Wainwright (2011). Colours indicate the rate of morphological diversification in (A) Lake Chichancanab and (B) San Salvador relative to other cyprinodontids. Numbers refer to the 16 traits measured. © Chris Martin
The precise mechanisms driving radiations have not always been clear, though, and one theory suggests that moving into a unique niche or niches may drive species to diversify more quickly than when they make a sideways movement to a similar niche in a new environment.
There are many fast evolving fish available for the home aquarium, but more often they are driven by artificial breeding regimens where a hobbyist is most interested in developing a new strain by enhancing already evident traits.
Study of Pupfishes in a Young Lake
An experiment with the evolution and growth patterning of three species of pup fish was undertaken in a very young lake that is helping speed up the evolution and diversification of the species. The results are quite interesting as they show the ways the species are differentially evolving and creatiung new patterns of behaviour