quantitative and seasonal rain fluctuations. During the dry season the landscape is barren. A large proportion of xeric vegetation consists of annual plants. Microphyllous shrubs, small succulent trees, plants in rosettes (such as agaves and terrestrial bromcliads) or pcretmial and semi-deciduous slmtbs can also be present. Xeric vegetation has high levels of endemism at the species and genus level. Flowering and faunal reproduction processes arc adapted to rainy seasons. Ants and rodents arc fundamentally important species. Habitat diversity in the hot xeric system is spatially very heterogeneous and patchy. Dominant species include Rillereocereus lz)Wirix, Opunlia spp.. Cylindropuntia histrix. Rlwdocactus cubensis, Caesalpinia spp:. Capparis spp., Gaujacum o.fficinale. Consolea macracantlw, Demlrocereus nudijlorus, Pilosocereus brooksianus. Harrisiafernowii, Agave a!bescens, and Melocactus acunae. Diagnostic species group arc Jacquinia, Goc/matia, Cordia, Gueltarda, Lantana and Coccothrinax palms. In the Caribbean xeric shrublands and cactus scrubs arc found on the Leeward Islands, Windward Islands, and Cuba. The biological diversity of Caribbean islands is very spatially compact. It was recently noted (Lugo eta/., 2000) that major environmental gradients and vegetation change occur over short distances ofless than 100 km. Natural disturbances, such as earthquakes, volcanic eruptions and hurricanes, in combination with human interference such as mining/quarrying, air/water pollution, forest tires, agriculture development, urban sprawl, tourism, introduced animals, and invasive exotics have modified vegetation and the landscape ofthc Caribbean. Strategies must be developed to prioritize conservation actions to prevent the remaining endemic species habitats becoming severely fragmented. Freshwater The Caribbean's freshwater biodiversity is found in a variety of habitats including large lowland rivers, montane rivers and streams, lakes, wetlands and underground karst networks. In addition to being habitats tor many important, unique and migratory animals and plants, these freshwater habitats provide clean water, food and many services to local communities. These services arc especially impot1ant as the small islands of the insular Caribbean arc completely sutTOundcd by salt water, and rely greatly on limited, landbased fi·cshwatcr fi·om functional ecosystems. Information on the distribution of many Caribbean freshwater species is scarce, distribution is not known tor most freshwater taxa, even for fish that arc otherwise well studied. 167 freshwater fish species have been identified (Ncodat, 2007; Lee eta!., 1983; Rcis et al., 2003), although there have been a large number of introduced species from aquaculture and aquarium collections. Fifty of these species arc endemic to the Caribbean, with the genera Limia and Gambusia being predominant. Reptiles are represented by several species that arc included in the IUCN Red List such as the American and Cuban Crocodiles ( Crocody/us acutus and C. rhombij'er) and the Hispaniolan Slider (Trachemys decorata). Amphibians arc primarily terrestrial in the Caribbean represented by the Genus Eleuthcrodactylus but some truly aquatic species exist within the Genera Bufo, Hy/a and Osteopi/us (e.g. Bt!fo jluviaticus. B. guentheri. Hyla !tei/prini, H. l'asta and Osteopilus dominicensis) with a tendency to be locally endemic. Macroinvcrtcbrates arc imp011ant to Caribbean fi·cshwatcr biodiversity due to their disproportionate influence on ecosystem li.mctioning. lvfacrobrachium is a widespread genus indicated in the ecological literature as a keystone species in insular Caribbean freshwater environments (Pringle eta!., 1993; Ramirez & Pringle 1998; March et a!., 200 I). At least six species of Macro brachium shrimp (M. acantlwrus, ill. carcinus, M. crenu/atum. lvl. .f!wstinum. lvl. heterochirus. and M. o/j'ersii) arc known to occur in tl·cshwatcr habitats on Caribbean islands (Holthuis, 1952; Chace & Hobbs, 1969; Hunte, 1976; Covich & McDowell, 1996; Bowles et a!., 2000). Widespread fi·cshwatcr prawns tound in the Caribbean belong to the genus Atya that has at least three known species (A. imwcrwus. A. lanipes. and A. scabra). Aquatic insects have 7 - 10-