Abstract
The genus
Phakellia
comprises predominantly fan-shaped deep-sea sponges, but its species diversity and boundaries remain unresolved. Here, we use an integrative approach combining morphological and molecular data to investigate the
Phakellia robusta
species complex and describe two new species,
Phakellia pallida
sp. nov. and
Phakellia pusilla
sp. nov. Overlap in external and spicular morphology makes these taxa challenging to identify. Molecular analyses based on mitochondrial (
cox1
) and nuclear (
28S
) markers support the recognition of the three taxa as distinct species, and reveal their close evolutionary relationship. The two new species co-occur in the NE Atlantic Ocean and the Mediterranean Sea, with overlapping depth ranges, although
P. pallida
sp. nov. is generally found at greater depths. Our results also suggest that several previous records of
P. robusta
from the Mediterranean and southern parts of the NE Atlantic may instead correspond to either
P. pallida
sp. nov. or
P. pusilla
sp. nov., indicating that its distribution requires reassessment. In addition, a group I intron previously reported in the
cox1
gene of
P. robusta
was polymorphically detected at the same insertion site in some, but not all, individuals of
P. pusilla
sp. nov., but it was absent from
P. pallida
sp. nov. individuals. Overall, our results reveal pseudocryptic diversity within
Phakellia
and highlight the value of integrative approaches for resolving species boundaries and reassessing deep-sea sponge diversity and distributions.