Cryptic and Sibling Species among the Decapod Crustacea

Cryptic species are those which are difficult to recognize using traditional systematic methods. Among the decapod Crustacea, there are probably many unrecognized complexes of cryptic species because of dependence on preserved material. Electrophoretic and mating studies have been very useful in determining whether individuals that differ in ecology, behavior, life history, or color can potentially interbreed. Color pattern of living specimens is a particularly useful character, since it is easy to assess and appears to differentiate morphologically similar species in a number of decapod groups. Examples include species of Uca and various symbionts of coral reef organisms (e.g., in the genera Trapezia and Alpheus and the subfamily Pontoniinae). Although nonmorphological characters cannot be scores in most museum specimens, statistical analysis of morphometric data first collected for individuals of known identity can subsequently be used to identify preserved material. Electrophoretic analyses such as those done for species complexs of Uca, Trapezia, and Alpheus, have also shown that cryptic species pairs may or may not be more closely related to each other than morphologically distinct congeners. For this reason the term "sibling" should be reversed for those species which have been shown to be very closely related using biochemical techniques. Various speciation patterns, including possible examples of host race speciation and speciation facilitated by sexual selection, occur within decapod species complexes.