Red Mangrove habitats are of great importance to a wide diversity of organisms, including fish (Thayer et al. 1987; Kaplan 1988). Animal diversity in mangrove ecosystems is generally much higher than plant diversity.
Burrowing isopods, such as Phycolimnoria clarkae and Sphaeroma peruvianum, and encrusting barnacles (Balanus spp.) reduce root growth in Red Mangrove; leaves are consumed by land crabs and caterpillars, such as the larvae of the skipper Phocides pigmalion (Perry 1988: Ellison and Farnsworth 1996 and references therein).
The intertidal air-breathing gastropod Melampus coffeus is a critical component in the breakdown of mangrove leaf litter, and it forms an important link between mangrove forest productivity and estuarine food webs. Although a number of other invertebrate species act to accelerate litter breakdown in mangrove and salt-marsh systems (e.g., shredder snails, sesarmid crabs), M. coffeus belongs to a smaller group that can directly assimilate the resources in mangrove leaves. Thus, where M. coffeus is abundant, substantial portions of mangrove leaf material are converted to snail biomass and larvae. Adult snails are preyed upon by white ibis (Eudocimus albus); juvenile snails may be preyed on by Fundulus heteroclitus killifish, which may forage in the leaf litter at high tide; and larvae are exported to the estuary. (Proffitt and Devlin 2005 and references therein)
Land crabs are very important components of mangrove ecosystems. They differentially prey on seeds, propagules, and seedlings along nutrient, chemical, and physical environmental gradients. Such abiotic factors are well known to influence plant species distributions. Lindquist et al. (2009), however, argue that in mangrove ecosystems crab predation is more important than many of these environmental factors in shaping the dynamics and organization of coastal forests. These authors also found that crabs facilitate forest growth and development through such activities as excavation of burrows, creation of soil mounds, aeration of soils, removal of leaf litter into burrows, and creation of carbon-rich soil microhabitats. Crabs influence the distribution, density and size-class structure of tree populations. Given the evident importance of crabs as among the major drivers of tree recruitment (i.e., establishment of a new generation) in tropical coastal forest ecosystems, Lundquist et al. suggest that their conservation should be included in management plans for these forests. (Lundquist et al. 2009)
The dominant members of the crab fauna in mangroves belong to the families Gecarcinidae, Grapsidae, and Ocypodidae. The grapsid crabs are the primary consumers of propagules in the Indo-West Pacific region. In the eastern Pacific, Atlantic, and Caribbean, the gecarcinids (e.g. Cardisoma spp.) and Ocypodids (e.g. Ucides spp.) are more important than the grapsids. (Lindquist et al. 2009 and refrerences therein)
Lundquist et al. (2009) found that crab predation on Red Mangrove was less severe in canopy gaps than in the understory, similar to the pattern found by Sousa et al. (2003a) for predation by the stem-boring scolytid beetle Coccotrypes rhizophorae. In the study by Sousa et al. on the Caribbean coast of Panama, the authors found that the Red Mangrove's water-borne propagules establish
wherever they strand, but long-term sampling revealed that only those that do so in or near lightning-created canopy gaps survive and grow to maturity. These microsites provide better growth conditions than the does surrounding understory and, equally important, provide refuge from predation by C. rhizophorae. Sousa et al. (2003b) found that if an infestation of C. rhizophorae did
not completely girdle a Rhizophora seedling, the seedling could survive, but grew at a reduced rate.
In a study in southwestern Puerto Rico, Wier (2004) found cankers, dead branches and trunks, and as much as 32% mortality consistently associated with the fungus Cytospora rhizophorae. The presence of this fungus, an agent of the cytospora canker disease, correlated with proximity to arboreal nests of the termite Nasutitermes costalis. High incidence of this termite (40%), was detected in injured red mangroves. Wier presents circumstantial evidence that this fungus is carried and disseminated by Nasutitermes costalis, with spores that enter branch and root wounds germinating and forming canker-weakened trees that may die prematurely.
Gilbert and Sousa (2002) studied the host-associations of wood-decaying basidiomycete polypore fungi on three mangrove species (Rhizophora mangle, Avicennia germinans, and Laguncularia racemosa) in a Panamanian mangrove forest. They note that the pattern typically observed for these fungi in diverse tropical forests is that there are a large number of rare species, with the smaller number of common species necessarily being nonspecialists due to the challenge of host rarity. In contrast, the authors found that in the tropical mangrove forest they studied, the polypore assemblage was strongly dominated by a few host-specialized species. Three fungal species, each with a strong preference for a different mangrove host species, comprised 88 percent of all fungi collected (the authors note, however, that these fungi are all reported from other hosts outside of mangrove forests as well). At least for polypore fungi within tropical mangrove forests, where host diversity is low and the abundance of individual host species is high, the restriction against host specialization typically imposed by host rarity in tropical forests may be relaxed, resulting in a polypore community dominated by a few common host-specialist species. (Gilbert and Sousa 2002)
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