6.2.2 Ecuadorian Continental Shelf
In general, the location with the greatest diversity of marine invertebrate species
(including echinoderms) seems to be in the Gulf of Guayaquil (which is the main
estuary of Ecuador). Maluf (1988a, b) identified this Gulf as a transition area
because there are a large number of southern echinoderm species whose ranges are
between 1° and 4°S. Transition zones may have a greater number of species
because co-occurrence in the ecotone between two similar habitat types is possible. However, this zone may have a higher biodiversity because it has been better
studied compared to the other areas along the continental coast (Cruz et al. 2003).
Even so, information is still insufficient for echinoderms (Villamar and Cruz 1983;
Avilés 1984; Mair et al. 2002; Sonnenholzner and Lawrence 2002). So far, scientific studies have been limited to basic research and the taxonomy of the biota.
To date, there is no proper analysis of the distribution of the fauna of echinoderms
based on the limited available records (Appendix).
The echinoderm fauna presently known is composed of 26 species: nine species
of Asteroidea, two species of Ophiuroidea, ten species of Echinoidea, and four
species of Holothuroidea. Of these, 17 species have been reported from the
intertidal area and shallow water environments, less than 20 m depth (Mair et al.
2002). Sea urchins, such as Echinometra vanbrunti and Eucidaris thouarsii; sea
cucumbers such as Holothuria theeli, and Holothuria arenicola; and sea stars such
as Pharia pyramidata and Phataria unifascialis are extremely common along the
central and southern coast of mainland Ecuador.
6.2.3 The Galápagos Islands
The Galápagos Islands are the southern distributional limit for many species.
Although these islands are separated from the nearest American mainland by
1,000 km of open water, there are several factors influencing the dispersal process
that favor affinity between the Panamá Bight (Panamá/Colombia/Ecuador), and the
Galápagos, while a smaller affinity is expected between the Galápagos and Perú
(Glynn et al. 1983). Only one-third of Perú’s echinoderms are shared with the
Galápagos Islands (Maluf 1991). The pronounced offshore movement of waters in
northern Perú would favor selection for non-planktotrophic species along the
mainland coast with reduced larval dispersal to the Galápagos. The islands lie to the
south of the normal path of the North Equatorial Countercurrent, the best potential
dispersal route for shallow-water tropical forms between the Central and the
Eastern Pacific. The greatest influence of this current is between 4° and 10°N
latitude, along the coasts of Costa Rica, Panamá, Colombia and the northern part of
Ecuador. Trans-Pacific species may have secondarily dispersed to the Galápagos
Islands from established mainland populations. The Equatorial Undercurrent could
transport (at great depth) central Pacific tropical larvae to the Galápagos.
6 Echinoderms of Ecuador
191
In general, the location with the greatest diversity of marine invertebrate species
(including echinoderms) seems to be in the Gulf of Guayaquil (which is the main
estuary of Ecuador). Maluf (1988a, b) identified this Gulf as a transition area
because there are a large number of southern echinoderm species whose ranges are
between 1° and 4°S. Transition zones may have a greater number of species
because co-occurrence in the ecotone between two similar habitat types is possible. However, this zone may have a higher biodiversity because it has been better
studied compared to the other areas along the continental coast (Cruz et al. 2003).
Even so, information is still insufficient for echinoderms (Villamar and Cruz 1983;
Avilés 1984; Mair et al. 2002; Sonnenholzner and Lawrence 2002). So far, scientific studies have been limited to basic research and the taxonomy of the biota.
To date, there is no proper analysis of the distribution of the fauna of echinoderms
based on the limited available records (Appendix).
The echinoderm fauna presently known is composed of 26 species: nine species
of Asteroidea, two species of Ophiuroidea, ten species of Echinoidea, and four
species of Holothuroidea. Of these, 17 species have been reported from the
intertidal area and shallow water environments, less than 20 m depth (Mair et al.
2002). Sea urchins, such as Echinometra vanbrunti and Eucidaris thouarsii; sea
cucumbers such as Holothuria theeli, and Holothuria arenicola; and sea stars such
as Pharia pyramidata and Phataria unifascialis are extremely common along the
central and southern coast of mainland Ecuador.
6.2.3 The Galápagos Islands
The Galápagos Islands are the southern distributional limit for many species.
Although these islands are separated from the nearest American mainland by
1,000 km of open water, there are several factors influencing the dispersal process
that favor affinity between the Panamá Bight (Panamá/Colombia/Ecuador), and the
Galápagos, while a smaller affinity is expected between the Galápagos and Perú
(Glynn et al. 1983). Only one-third of Perú’s echinoderms are shared with the
Galápagos Islands (Maluf 1991). The pronounced offshore movement of waters in
northern Perú would favor selection for non-planktotrophic species along the
mainland coast with reduced larval dispersal to the Galápagos. The islands lie to the
south of the normal path of the North Equatorial Countercurrent, the best potential
dispersal route for shallow-water tropical forms between the Central and the
Eastern Pacific. The greatest influence of this current is between 4° and 10°N
latitude, along the coasts of Costa Rica, Panamá, Colombia and the northern part of
Ecuador. Trans-Pacific species may have secondarily dispersed to the Galápagos
Islands from established mainland populations. The Equatorial Undercurrent could
transport (at great depth) central Pacific tropical larvae to the Galápagos.
6 Echinoderms of Ecuador
191