So how cold tolerant are the cichlids?
Not -see below.
How did the tilapia become more tolerant of cold?
Likely adaptation /evolution over eons.
Could the others African varieties learn to turn on the 'polar vortex' gene and adapt as well?
Possibly , but for every successful major evolutionary change there are 1000 that go into the ash heap of history.At least 1,650 species have been scientifically described,[2] making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000.
Cichlids are particularly well known for having evolved rapidly into a large number of closely related but morphologically diverse species within large lakes, particularly Tanganyika, Victoria, Malawi, and Edward.[8][9] Their diversity in the African Great Lakes is important for the study of speciation in evolution
Cichlids share a single key trait: the fusion of the lower pharyngeal bones into a single tooth-bearing structure. A complex set of muscles allows the upper and lower pharyngeal bones to be used as a second set of jaws for processing food, allowing a division of labour between the "true jaws" (mandibles) and the "pharyngeal jaws". Cichlids are efficient and often highly specialized feeders that capture and process a very wide variety of food items. This is assumed to be one reason why they are so diverse
Multilocus Phylogeny of Cichlid Fishes (Pisces: Perciformes): Evolutionary
Comparison of Microsatellite and Single-Copy Nuclear Loci
J. Todd Streelman,* Rafael Zardoya,†1 Axel Meyer,†2 and Stephen A. Karl*
The freshwater fish family Cichlidae is a multiform
mosaic of ancient and recent lineages.
The current distribution
throughout Africa, India, Madagascar, and the
Neotropics suggests a Gondwana-wide ancestral range
(Brown and Gibson 1983) and a pattern of divergence
matching the splitting of the continental masses (Stiassny
1987, 1991; fig. 1). In this vicariant scenario, cichlids
would have roots dating back at least 130 MYA (Storey1995). In contrast to the relative antiquity of the family,
the apparent recent and rapid evolution within some
genera has attracted widespread attention (e.g., Fryer
and Iles 1972; Meyer et al. 1990; Goldschmidt 1996).
For example, in east Africa, the 300-plus species of the
haplochromine flock of Lake Victoria are believed to
share a common ancestor less than 200,000 years ago
(Meyer et al. 1990; Johnson, Scholz, and Talbot 1996;
Kaufman, Chapman, and Chapman 1997).
If the consensus phylogeny represents
true evolutionary relationships, or at least that
the Cichlidae is not ancestral to the outgroup taxa
(which include Perca and Lates), then it would appear
that the microsatellite region of Tmo-M27 was dramatically
reduced or nearly lost in the cichlid ancestor. The
repeat motif is then expanded in the ancestor to African
taxa. Notably, the largest differences in repeat numbers
are found within the east African clade; the youngest
and most species-rich group.
This is a great study - but complex.
http://mbe.oxfordjournals.org/cgi/reprint/15/7/798.pdf