ISSN 10623604, Russian Journal of Developmental Biology, 2015, Vol. 46, No. 5, pp. 294–306. © Pleiades Publishing, Inc., 2015.
Original Russian Text © F.N. Shkil, O.E. Lazebnyi, D.V. Kapitanova, Belay Abdissa, V.B. Borisov, S.V. Smirnov, 2015, published in Ontogenez, 2015, Vol. 46, No. 5, pp. 346–359.
Species flocks, common for vertebrate and inverte
brate animals, are monophyletic groups of closely
related sympatric forms (species, morphotypes,
ecotypes, races) inhabiting a narrowly circumscribed
area. Extremely rapid adaptive radiation, morpholog
ical divergence, and speciation are typical for many
species flocks. Moreover, the phenomenon of rapid
evolutionary transformations is so widespread among
species flocks that some authors consider the criteria
of “rapid evolution” (Ribbink, 1984) or “explosive
speciation” (Sullivan et al., 2002) to be necessary for
the definition of species flock.
Within vertebrats, species flocks have a peak inci
dence in bony fishes (Teleostei) (Golubtsov, 2010).
The best known are species flocks of the African Great
Lakes cichlid fishes (Salzburger et al., 2002; Meyer,
2005) and cottoid fishes of Lake Baikal (Sideleva, 1994;
Kontula et al., 2003) consisting of hundreds and doz
ens sympatric endemics, respectively. Lake species
flocks and mechanisms of their evolution are the sub
jects of much ecological, evolutionary, and genetic
The article was translated by the authors.
investigations. But much in the phenomenon of spe
cies flocks remains unclear including the mechanism
through which their explosive divergence occurs.
Traditionally, sympatric speciation and divergence
are considered to be associated with large genomic
changes such as polyploidization, hybridization, chro
mosome fragmentation and fusion, among others
(Yablokov and Yusupov, 1976). However, in the evolu
tion of species flocks different mechanisms seem to be
involved since wide morphological diversity can be
achieved on the background of only slight genomic
divergence (Turgeon et al., 1999; Osinov, 2002; Loh et al.,
2008; Sideleva, 2010).
To reveal these mechanisms, the species flock of
the large hexaploid African barbs of g.
inhabiting Lake Tana in Ethiopia was stud
ied. This flock, the largest recent one for cyprinid
fishes, includes 14 (15) closely related sympatric
endemic species/morphotypes and
which is widely distributed across East Africa and con
sidered to be ancestral to the remaining large Tana
Ontogenetic Mechanisms of Explosive Morphological Divergence
in the Lake Tana (Ethiopia) Species Flock of Large African Barbs
; Cyprinidae; Teleostei)
F. N. Shkil
, O. E. Lazebnyi
, D. V. Kapitanova
, Belay Abdissa
V. B. Borisov
, and S. V. Smirnov
A.N. Severtsov Institute of Ecology and Evolution, RAS, 33 Leninsky prospect, Moscow
Koltzov Institute of Developmental Biology, RAS, 26 Vavilova str., Moscow
BahirDar Fishery and Other Aquatic Life Research Center, ARARI, BahirDar, Ethiopia
Received November 5, 2014; in final form, May 11, 2015
—Species flock of Lake Tana (Ethiopia) large African barbs (
; Cyprinidae; Teleostei),
the largest recent cyprinid species flock, was studied as a model system for investigating ontogenetic mecha
nisms of the explosive morphological divergence often accompanying sympatric speciation in bony fishes.
Comparative morphological analysis carried out with the use of geometric morphometric techniques revealed
differences in the head shapes of species under study. Comparative analysis of skull development
revealed significant interspecies differences in the temporal characteristics of craniogenesis in these species.
These two lines of evidence suggest that heterochronies in craniogenesis underlie divergence in the head
shapes of adult Tana barbs. This prediction was verified via experimental changes of temporal characteristics
of craniogenesis in
, a putative ancestor for the Lake Tana species flock. For this aim, timing
and rate of skull development were changed by artificial manipulation of thyroid hormone levels. This exper
iment verified, that it is heterochronies that underlie an explosive morphological divergence of the Lake Tana
barbs species flock. Our findings together with those reported in the literature suggest variability in the activity
of the hypothalamicpituitarythyroid axis to contribute to these heterochronies.
: species flock, morphological divergence, heterochronies, thyroid hormones, geometric mor
ONTOGENY AND EVOLUTION