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14.6 Taxonomic Confusion, Species Crypsis,
and Morphological Plasticity
W.M. Graham and K.M. Bayha
Historical taxonomic confusion has often complicated initial efforts to study
jellyfish invasions, and nowhere is that more true than in the case of the Black
Sea ctenophore invasions. Initially, the Black Sea Mnemiopsis was identified
alternatively as M. mccradyi (Zaika and Sergeeva 1990) or M. leidyi (Vinogradov
et al. 1989), the two most recently recognized Mnemiopsis species.
However, many doubted these terminologies (Seravin 1994; Harbison and
Volovik 1994), and the validity of the two Mnemiopsis species has been questioned
based on morphological grounds (Seravin 1994; Harbison and Volovik
1994; Oliveira and Migotto 2006). A recent molecular study has indicated that
one species exists worldwide, i.e., M. leidyi (Bayha 2005). Another notable
example of such confusion is that of the ctenophore Beroë. The same name (B.
ovata) had historically been used for two morphologically different animals
(one from the western Atlantic and Caribbean, the other from the Mediterranean),
and it was initially believed that Beroë may have invaded from the
Mediterranean. However, both genetic (Bayha et al. 2004) and morphological
(Seravin et al. 2002) evidence indicated that the invasive animal has a western
Atlantic origin (eastern seaboard of the Americas and the Caribbean). Consequently,
Bayha et al. (2004) proposed that, pending a thorough systematic
revision of the genus Beroë, the species be termed Beroë ovata sensu Mayer
(as opposed to the incorrect Beroë ovata Mayer 1912).
Species crypsis and morphological plasticity can also hinder efforts to
study invasive animals. Invasive patterns of Aurelia and Cassiopea are excellent
examples of the problems associated with species crypsis. Neither invasion
was fully appreciated until genetic techniques were employed (Greenberg
et al. 1996; Holland et al. 2004; Dawson et al. 2005), because the invaders
were historically confused with morphologically similar natives. Where
species crypsis confuses multiple species for one, morphological plasticity
may confound species invasion patterns by having only one invading species
recognized as multiple others. This phenomenon has hindered studies of the
invasion of Phyllorhiza punctata into the Gulf of Mexico and elsewhere
(Bolton and Graham 2004). Again, only molecular genetic approaches will
allow us to fully unravel interrelationships between invasive jellyfish exhibiting
morphological plasticity.