Phylogenesis of reproductive strategies in labyrinth fishes (Anabantoidei) and their sister groups

Abstract

Clado- and semogenetic approaches, when used in concert, make it possible to resolve questions concerning the phylogenetic relationships between group representatives, as well as the phylogenesis of those representatives’ characters. Parental care patterns and other forms of reproductive behavior, along with the reproductive strategy as a whole, can be the subject of semogenetic analysis to no less an extent than morphological structures sensu stricto. One highly specialized form of parental care in fish, including representatives of the suborder of labyrinth fishes and their sister groups, appears to be parental food provisioning. In our view, the evolutionary origin of postembryonic brood provisioning in bony fishes is characterized by three main features: (1) in fish, different forms of postembryonic food provisioning are convergent in their origin; (2) any kind of brood provisioning is realized through exploitation of the already existing character and is maintained by selection due to an enhancement of offspring fitness; (3) the main evolutionary path of the emergence and development of this phenomenon consists in function expansion and replacement. The hypothesis does have heuristic power, since it enables prediction of the presence of the reproductive strategy component in question through the identification of adequate basic adaptations. Although parental care occurs in the majority of anabantoid fishes, there are still several species for which such care is not known. On the cladogram, these species by no means take the basal position but are surrounded by fishes that provide care for their eggs, or even their hatchlings. The parsimony principle leads to the suggestion that parental care is a plesiomorphic character in the suborder Anabantoidei (or in the order Anabantiformes). It seems that the ancestors of present day noncarrying species that take various positions within this phylogenetic group were fishes showing parental care. Their reproductive strategy later changed as a result of r selection. If this hypothesis is correct, the absence of parental care should be considered a case of reproductive strategy degradation. It is quite probable that parental food provisioning was a component of the ancestral reproductive strategies. It is also possible that the reproductive strategy of present-day anabantoids that supposedly do not care for their offspring actually includes some optional forms of parental care.