Smithsonian at the Poles: Contributions to International Polar

Species Diversity and Distributions
of Pelagic Calanoid Copepods
from the Southern Ocean
E. Taisoo Park and Frank D. Ferrari
E. Taisoo Park, Texas A&M University, 29421
Vista Valley Drive, Vista, CA 92084, USA.
Frank D. Ferrari, Invertebrate Zoology, National
Museum of Natural History, Smithsonian
Institution, 4210 Silver Hill Road, Suitland, MD
20746, USA. Corresponding author: F. D. Ferrari
( ferrarif@si.edu). Accepted 27 June 2008.
ABSTRACT. In the Southern Ocean, 205 species of pelagic calanoid copepods have
been reported from 57 genera and 21 families. Eight species are found in the coastal
zone; 13 are epipelagic, and 184 are restricted to deepwater. All 8 coastal species and
eight of 13 epipelagic species are endemic, with epipelagic species restricted to one
water mass. Of the 184 deepwater species, 50 are endemic, and 24 occur south of
the Antarctic Convergence. Most of the remaining 134 deepwater species are found
throughout the oceans with 86% percent reported as far as the north temperate region.
The deepwater genus Paraeuchaeta has the largest number of species in the Southern
Ocean, 21; all are carnivores. Scolecithricella is also speciose with 16 species, and more
specimens of these detritivores were collected. Species with a bipolar distribution are
not as common as bipolar species pairs. A bipolar distribution may result from continuous
extinction in middle and low latitudes of a wide spread deepwater species with
shallow polar populations. Subsequent morphological divergence results in a bipolar
species pair. Most of the numerically abundant calanoids in the Southern Ocean are
endemics. Their closest relative usually is a rare species found in oligotrophic habitats
throughout the oceans. Abundant endemics appear adapted to high primary and secondary
productivity of the Southern Ocean. Pelagic endemicity may have resulted from
splitting a widespread, oligotrophic species into a Southern Ocean population adapted
to productive habitats, and a population, associated with low productivity that remains
rare. The families Euchaetidae and Heterorhabdidae have a greater number of their
endemic species in the Southern Ocean. A phylogeny of these families suggests that
independent colonization by species from different genera was common. Thus, two
building blocks for the evolution of the Southern Ocean pelagic fauna are independent
colonization and adaptation to high productivity.
INTRODUCTION
Copepods often are referred to as the insects of the seas. They certainly are
comparable to insects in survival through deep time, ecological dominance, geographic
range, and breadth of adaptive radiation (Schminke, 2007). However,
they are not comparable to insects in numbers of species. Only 11,302 species
of copepods were known to science toward the end of the last century (Humes,
1994), and 1,559 have been added since then. In contrast, the number of described
insects approaches one million (Grimaldi and Engel, 2005). In terms of
the number of individuals alive at any one time, however, copepods undoubtedly