Lake Tana large barbs: phenetics, growth and diversification

Abstract

Among the Lake Tana large barbs of about 10 cm SL only representatives of the ' acute ' morphotype can be distinguished, in the size range 10-20 cm SL ' bigmouth big eye ' can be identified also. As for the rest, very few individuals can be confidently affiliated with a particular morphotype most of them looking like ' intermedius '. Even within the range of 20-30 cm SL some individuals are still difficult to identify. Principal component analysis of cranial characters revealed discrete groups of morphotypes. Differences in both external and cranial characters of the morphotypes result from divergence which is most pronounced when fish are 4-5 years old and 20-25 cm SL. This divergence cannot be related exclusively with differences in the growth rates of individuals representing different morphotypes. Differences in food composition between the morphotypes probably increase in parallel with their morphological divergence. Differences between the morphotypes in the lateral line (ll) and the gill rakers (Sb) counts were revealed using ANOVA. Comparison of the Lake Tana Barbus complex of forms with that previously known from Lake Lanao (Philippines) suggests that in both lakes the different forms arose sympatrically but that sympatric speciation in Lake Lanao has advanced further than in Lake Tana. 1996 The Fisheries Society of the British Isles

Evidence of a Cenozoic Betic–Kabilian Connection Based on Freshwater Fish Phylogeography (Luciobarbus, Cyprinidae)

“…However, this type of approach is difficult due to the high degree of polymorphism shown by species of this genus, in which species flock phenomena have been described (Nagelkerke et al, 1994;Mina et al, 1996;Reig et al, 1998). Recent electrophoretic studies have analyzed genetic variation at the population and species levels, as well as phylogenetic relationships (e.g., Berrebi et al, 1990;El Gharbi, 1993;El Gharbi et al, 1993;Karakousis et al, 1995;Machordom et al, 1995Machordom et al, , 1998Slechtová et al, 1998).…”

Genetic divergence among morphotypes of Lake Tana (Ethiopia) barbs

“…The morphotypes Intermedius, Zurki, Acute, Troutlike, Barbel, White hunch, Dark, Bighead, Bigmouth small-eye, Bigmouth big-eye and Carplike have been defined by Nagelkerke et al (1994). Acute hunch is designated according to Mina et al (1996a). The description of the morphotype Green intermedius is not yet published (M. Mina, pers.…”

Sympatric Speciation by Sexual Selection Alone Is Unlikely

“…The recruitment of assortative mating preferences and species identity signals by disruptive natural selection is a more likely cause of the evolution of reproductive isolation when it occurs sympatrically. The most widely accepted cases of sympatric speciation (Taylor and Bentzen 1993;Schliewen et al 1994;Mina et al 1996;Wood and Foote 1996;Filchak et al 2000) appear to have occurred along ecological axes (Schluter 1998). Due to the high packing of ecologically similar species, disruptive natural selection in rock cichlid communities is certainly multifarious (Rice and Hostert 1993;Via 2001).…”