Fauna of Puerto Rico - Invertebrates

Invertebrates

The invertebrate fauna of Puerto Rico is high in richness but low in diversity relative to mainland neotropical faunas of similar size and habitat diversity. Puerto Rico, in comparison to other Antillean islands, is the most extensively studied in regards to invertebrates.

Puerto Rico's insect fauna, similar to the majority of major invertebrate taxa in the archipelago, is considered depauperate when compared to its mainland counterparts. For example, approximately 300 species of butterfly occur in Puerto Rico, in contrast to more than 600 species in Trinidad and more than 1,500 species documented from a 7.5 km² region in Brazil. As of 1998, out of the estimated 925,000 described insect species, only 5,573 were documented from Puerto Rico. In terms of diversity, of the 31 extant insect orders, 27 have representatives in Puerto Rico. The orders without reported representatives are Microcoryphia, Grylloblattaria, Plecoptera, and Mecoptera. The largest insect depository in Puerto Rico resides at the Museo de Entomología y Biodiversidad Tropical (Museum of Entomology and Tropical Biodiversity), part of the Agricultural Experimental Station of the University of Puerto Rico.

Arachnids are important to the forest ecology, as both predators and prey. In some forest types, such as tabonuco forest, they are the major arboreal invertebrate predators; spiders being the most abundant representative. The Maricao Commonwealth Forest's 27 spider species belong to five families: Uloboridae, Pholcidae, Theridiidae, Linyphiidae and Araneidae. Theotima minutissima, a small spider species found in abundance in the Caribbean National Forest, is believed to be parthenogenetic, meaning that it reproduces without fertilization by a male.

Other terrestrial invertebrates described from Puerto Rico include earthworms and cave dwelling animals. Eighteen native species of earthworm have been described, with 11 species belonging to the Glossoscolecidae family, 3 to the Megascolecidae family, and 4 to the Exxidae family. Seventy-eight invertebrate species are known to inhabit Puerto Rico's caves. Six of these species are restricted to the Antilles, 23 come from North America and 23 are endemic to Puerto Rico. Only two of the species are confirmed as troglobites, or restricted to caves. Forty-five percent of the species are predators while the remaining 55% are guano scavengers, detrivores and herbivores. It is believed that most of this fauna arrived at Puerto Rico in the Pleistocene.

The marine invertebrate fauna of Puerto Rico is composed of 61 sponges, 171 cnidarians, 8 nemerteans, 1,176 mollusks, 129 annelids (polychaetes), 342 crustaceans, 165 echinoderms, 131 bryozoans, 117 hard corals, 99 soft corals and gorgonians, 13 corallimorphs, and 8 hydrocorals. Coral species found in Puerto Rican reefs are representative of the general Caribbean fauna. Commonly occurring corals include Boulder Star coral (Montrastaea annularis), Finger coral (Porites porites), and Elkhorn coral (Acropora palmata).

Invertebrate introductions have had an observable effect on Puerto Rican fauna. Native freshwater snails such as Physa cubensis have been adversely affected by introduced species. Currently, the most abundant freshwater snail in Puerto Rico is the Quilted Melania (Tarebia granifera), an introduced species. Another invertebrate introduced to Puerto Rico is the honeybee. This animal competes with the endangered Puerto Rican Parrot for secondary nesting cavities at the Caribbean National Forest. Africanized bees, which pose an even greater threat for secondary cavity nesters, have recently extended their range to Puerto Rico. Other introductions include 18 species of ant, one of the most abundant taxa in leaf litter habitats.