L. Shimek, Ph. D.
Hart, M. W., S. L. Johnson, J. A. Addison,
and M. Byrne. 2004. Strong character incongruence and character
choice in phylogeny of sea stars of the Asterinidae.
Biology. l23(4): 343-356.
Historically, characters from early animal
development have been a potentially rich source of phylogenetic
information, but many traits associated with the gametes and
larval stages of animals with complex life cycles are widely
suspected to have evolved frequent convergent similarities.
Such convergences will confound true phylogenetic relationships.
We compared phylogenetic inferences based on early life history
traits with those from mitochondrial DNA sequences for sea
stars in the genera Asterina, Cryptasterina,
and Patiriella (Valvatida: Asterinidae). Analysis of
these two character sets produced phylogenies that shared
few clades. We quantified the degree of homoplasy in each
character set when rnapped onto the phylogeny inferred from
the alterative characters. The incongruence between early
life history and nucleotide characters implies more homoplasy
in the life history character set. We suggest that the early
life history traits in this case are most likely to be misleading
as phylogenetic characters because simple adaptive models
predict convergence in early life histories, We show that
adding early life history characters may slightly improve
a phylogeny based on nucleotide sequences, but adding nucleotide
characters may be critically important to improving inferences
from phylogenies based on early life history characters.
Many aquarists are familiar with the small
sea stars in the family Asterinidae that are common in
reef aquaria. Although often placed in the genus Asterina,
they actually have not been identified by any reputable taxonomist.
The authors of this paper examined 17 similar and related
sea star species and tried to determine the relationships
between them. Because of the complexities of their development
and structures, they were unable to unambiguously determine
the relationships. This paper is interesting in that its authors
looked at several sea stars that were roughly the same size
and morphology as the ones found in aquaria. Several of these
stars were similar in appearance to the stars found in aquaria;
however, none of the stars investigated in the study reproduced
by fission, which is the aquarium species’ method of
reproduction. Given the data presented in this paper, it is
unlikely that the relationships between small asterinid species
of sea stars found in aquaria will soon be conclusively identified.
It appears that much of the critical information about the
species is available only from an analysis of the species’
DNA, and that those data will have to be added to the various
traditional morphological data to determine the relationships
within this large group of small sea stars species.