Sibling Sea Urchin Species in Hawaii: Diversity in the Genus Echinothrix

EPA Grant Number: F6E70548
Title: Sibling Sea Urchin Species in Hawaii: Diversity in the Genus Echinothrix
Investigators: Jessop, Holly
Institution: University of Hawaii at Hilo
EPA Project Officer: Zambrana, Jose
Project Period: September 1, 2006 through September 1, 2008
Project Amount: $110,322
RFA: GRO Fellowships for Graduate Environmental Study (2006) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Ecology , Fellowship - Evolutionary Biology


Despite a species-rich community of sea urchins in Hawai`i, and their potential ecological importance within Hawaiian reef ecosystems, there is a paucity of studies specific to their biology and ecology. Moreover, two of the most common urchins on Hawaiian reefs, Echinothrix calamaris and Echinothrix diadema, have been investigated relatively little. These similar co-existing species of long-spined urchins can be difficult to distinguish, although they do possess some color and subtle morphological differences. Especially in the field, their close overall resemblance and overlapping general habitat preferences can lead to frequent incorrect identifications. Such similar species are ideal candidates for investigations of close ecological interactions. Furthermore, these sympatric urchins may also provide opportunities to explore processes of speciation that also ultimately relate to the origin and maintenance of biodiversity. My research thesis seeks to exploit these scientific opportunities provided by the plentiful but relatively little-known sibling Echinothrix urchins of Hawai`i.

Specifically, I plan to both quantify and correlate the morphological and genetic diversity in Echinothrix urchins of Hawai`i. That is, this research aims to provide the first step at unification of morphological and genetic characters in this genus. Thus, whether slight morphological variation is a result of numerous polymorphisms and/or plasticity, or corresponds to multiple genetically unique clades, will be ascertained. In addition, the abundances and distributions of Echinothrix urchins will be surveyed, and possible interspecific differences in microhabitat utilization documented. The overall objective of my thesis is a synthesis of these molecular, morphological, and ecological investigations, to better define and quantify the species, as well as any cryptic subspecific clades, of Echinothrix urchins present in Hawai`i.


Multiple specimens of every Echinothrix morphotype encountered will be collected in Hawai`i, during surveys of their abundance and spatial distribution patterns. Using both light and electron scanning microscopy, the fine details of morphological diversity in this genus will then be extensively examined and documented, via measurements of the tests, spines, and pedicellariae of each specimen. DNA will also be extracted from each specimen, and any differences in mitochondrial molecular markers between morphotypes will be determined. These data will be combined to test the hypothesis that a number of albeit small but readily visible physical differences between Echinothrix specimens are indicative of genetic identity.

Expected Results:

This study will resolve the diversity present in the genus Echinothrix in Hawai`i: 1) A thorough set of all morphological characters possessed by each genetic clade in Hawai`i will be compiled; 2) The species of Echinothrix in Hawai`i will thereby be defined and quantified; 3) A key of morphological characters that enables correct visual identification of these species will be created. Thus, the necessary foundation upon which to build investigations regarding processes that have driven cladogenesis in this genus will be provided. For example, this study will also document possible mechanisms of reproductive isolation, such as differences in fine-scale ecological partitioning between species. By providing such information on biodiversity, as well as insights into its generation and maintenance, this study will also generate findings useful for conservation planning.

Supplemental Keywords:

Biodiversity, biology, cladogenesis, conservation biology, coral reef, cryptic species, diversity, Echinothrix, ecology, ecosystems, evolution, genetics, habitat partitioning, Hawai`i, Hawaiian islands, mitochondrial DNA, molecular characterization, morphological characterization, morphology, reproductive isolation, sea urchin, sibling species, speciation,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Monitoring/Modeling, Habitat, Environmental Monitoring, Biology, marine ecosystem, habitat dynamics, reef ecosystem, biodiversity, genetic consequences, community genetic diversity, ecological consequences, sea urchins

Progress and Final Reports:

  • 2007
  • Final