262 ZOOGEOGRAPHY 



ANALYSIS OF THE ISOPOD FAUNA 



In the following discussion, the West Indian and Caribbean provinces are 

 treated as one, the isopod faunas offering little evidence to warrant a separate 

 treatment of each. 



It is a truism that for any discussion of the zoogeography of an area to have 

 meaning, the true extent of the fauna must be known. With the area under 

 review, collecting effort has been uneven, and the true faunal composition of 

 many regions is still incompletely known. Obviously, any conclusions based 

 on such incomplete data are approximate and subject to revision. Neverthe- 

 less, certain general patterns or trends emerge when the present isopod fauna 

 is broken down into its components. 



The deepwater isopod fauna of the Caribbean (i.e., from deeper than 200 

 m) has barely been explored, and little is to be gained from discussing the 

 relatively few species known. A list of these deeper dwelling species is in- 

 cluded (Table 4). 



Although about 280 shallow-water species are covered by this work, cer- 

 tain categories of species must be excluded, for various reasons, before anal- 

 ysis can be attempted. Such excluded groups include the species of Oniscidea 

 (being essentially terrestrial forms and not part of the marine regime); the 

 cymothoid species and the species of Aegidae (being fish parasites for at least 

 part of their life history, and whose distribution is complicated by the dis- 

 tribution and mobility of the hosts); the limnoriids (being wood-borers whose 

 distribution is more a function of the distribution of floating wood); and the 

 true cave species (which have a history more reflective of the geological his- 

 tory of the area than of the marine regime). The epicarideans have a distribu- 

 tion somewhat complicated by the distribution of their crustacean hosts and 

 their pelagic epicaridean and cryptoniscan larvae. Nevertheless, the decapod 

 hosts of the great majority of species covered here are Caribbean endemics, 

 and inclusion of the epicarideans changes very little the overall patterns of 

 distribution, as demonstrated by the two figures provided (Figure 109). After 

 making these exclusions there remain about 166 species (218 with the epi- 

 carideans) that can be broken down into the following components (figures 

 in brackets include epicarideans): 



1. True Caribbean/Bahamian species — 124 species, 74.8% [147, 67.5%]. 

 These are the species recorded only from the Caribbean and the Bahamas. 

 The term endemic is avoided, as too little is known of the actual distribution 

 of many species. Of these species, 86 [87] have been recorded from a single 

 locality. 



2. Species occurring south of the discussion area, and extending into 

 Brazil — 5 species, 3.0% [9, 4.1%]. These low numbers indicate that the 



