The pelagic realm of the deep-sea is home to some of the most spectacular fishes in terms of morphological adaptations, a probable consequence
of the distinct hostile living conditions in this poorly known habitat. Detecting speciation patterns in open ocean fishes is often complicated from
the lack of defined physical barriers inhibiting gene flow, resulting in difficulties when establishing species richness and ecology, a particularly
evident problem when considering volume of habitat available in the deep-sea. However, considering the “hostile” factors such as scarce prey
and infrequent sexual encounters, comparing species richness and habitat alone tells us little about successful speciation in the pelagic deep-sea
environment.
The last two decades has expanded our knowledge on teleostean phylogeny from molecular data, although comparing nuclear, mitochondrial and
hundreds of years of morphological work on both extant and extinct fishes, clearly illustrates numerous discrepancies between these three
phylogenetic hypotheses. The phylogenetic results, updated paleontological information, a continuous production of new molecular data and
advanced relaxed clock analysis provide us with the opportunity to initiate the calculation of speciation rates across independent fish lineages
occupying similar habitats.
In this study we produced new mitogenomic data of previously insufficiently sampled deep-sea fish lineages, and constructed a dataset of over
250 taxa to represent the current mitogenomic view of actinopterygian phylogeny. Taxon sampling was chosen with special emphasis on recent
results, that showed phylogeny and age estimates from nuclear evidence, allowing us to compare the ages of stem- and crown group nodes of all
major deep-sea pelagic fish radiations.
Two extreme extinction rates were used to calculate the diversification rates of all major deep-sea fish radiations using the different phylogenetic
hypotheses and associated estimates of divergence time. Two deep-sea radiations, the order Stomiiformes and the deep-sea Anglerfishes in the
suborder Ceratoidei, were found to present higher diversification rates than all other lineages in this habitat when compared to a background
diversification rate of pelagic deep-sea fishes in the Teleostei.