288
S. Dittmann and J.A. Vargas
infaunal community at this site (Dittmannn 1998,2000). Therefore the ecological role of Trypea australiensis equals the one of the lugworm Arenicola
marina in temperate tidal flats. Promotive effects were also recorded for
Callianassa japonica in southern Japan (Tamaki and Suzukawa 1991).
Callianassid shrimps are documented from intertidal habitats of the Pacific
coast of Colombia and from the Gulf of Mexico, where polyclad worms,
pinnotherid crabs, car ide an shrimps and alpheid shrimps were associated
with the burrows (Felder et al. 1993; Manning and Felder 1995; Felder and
Manning 1997, 1998). In Costa Rica, alpheid shrimps build similar burrows to
T. australiensis, but as yet they have not been investigated for associated
fauna, nor have the burrows of fiddler crabs (Uca spp.).
Burrows of other crustaceans and of brachiopods were also seen to
accommodate higher infaunal numbers, but this effect varied both with
burrow type and season (Dittmann 1996). Tube-worms are also known to
affect infaunal distributions (Ziihlke et al. 1998) and, in the subtidal of the
Gulf of Nicoya, Maurer and Vargas (1984) found a higher diversity of benthic
fauna around tubes of Spiochaetopterus costarum.
Although promotive interactions have only been studied in a few tropical
tidal flats of Australia so far, it is suspected that larger macrobenthic organisms exert comparable promotive effects in the tropics as in temperate latitudes.
13.4.3.2 Repressive Interactions
Predation is seen as a prevailing process regulating the benthic fauna in tidal
flat communities in temperate latitudes (Reise 1985). Several predatory species (e.g. crabs, nemerteans, snails, birds, fish and juvenile prawns) occur in
tropical tidal flats and effects on macro- and meiobenthic prey have been
reported (Dittmann 1993; Christy et al. 1998). The experimental exclusion of
soldier crabs resulted in a fivefold increase in meiofauna numbers in a
tropical tidal flat of northeast Australia (Dittmann 1993). Using predator
exclusion cages in a mudflat near Punta Morales, Vargas (1988) concluded that
macro-predators (fish, birds, crabs and snails) have only a negligible effect on
benthic community structure in this tropical tidal flat. He found almost no
changes in abundance in the exclusion cages, but did see changes in the rank
order of abundance of dominant species.
At present, the findings on the relevance of predation in tropical benthic
communities are somewhat contradictory. There is little evidence for a regulating effect of epibenthic predators on infaunal assemblages in the tropics.
However, it cannot be excluded that multiple predatory effects (e. g. Ambrose
1984) exist in tropical tidal flats, as the predatory effects of endobenthic
predators have not yet been addressed. The report by Christy et al. (1998) of a
S. Dittmann and J.A. Vargas
infaunal community at this site (Dittmannn 1998,2000). Therefore the ecological role of Trypea australiensis equals the one of the lugworm Arenicola
marina in temperate tidal flats. Promotive effects were also recorded for
Callianassa japonica in southern Japan (Tamaki and Suzukawa 1991).
Callianassid shrimps are documented from intertidal habitats of the Pacific
coast of Colombia and from the Gulf of Mexico, where polyclad worms,
pinnotherid crabs, car ide an shrimps and alpheid shrimps were associated
with the burrows (Felder et al. 1993; Manning and Felder 1995; Felder and
Manning 1997, 1998). In Costa Rica, alpheid shrimps build similar burrows to
T. australiensis, but as yet they have not been investigated for associated
fauna, nor have the burrows of fiddler crabs (Uca spp.).
Burrows of other crustaceans and of brachiopods were also seen to
accommodate higher infaunal numbers, but this effect varied both with
burrow type and season (Dittmann 1996). Tube-worms are also known to
affect infaunal distributions (Ziihlke et al. 1998) and, in the subtidal of the
Gulf of Nicoya, Maurer and Vargas (1984) found a higher diversity of benthic
fauna around tubes of Spiochaetopterus costarum.
Although promotive interactions have only been studied in a few tropical
tidal flats of Australia so far, it is suspected that larger macrobenthic organisms exert comparable promotive effects in the tropics as in temperate latitudes.
13.4.3.2 Repressive Interactions
Predation is seen as a prevailing process regulating the benthic fauna in tidal
flat communities in temperate latitudes (Reise 1985). Several predatory species (e.g. crabs, nemerteans, snails, birds, fish and juvenile prawns) occur in
tropical tidal flats and effects on macro- and meiobenthic prey have been
reported (Dittmann 1993; Christy et al. 1998). The experimental exclusion of
soldier crabs resulted in a fivefold increase in meiofauna numbers in a
tropical tidal flat of northeast Australia (Dittmann 1993). Using predator
exclusion cages in a mudflat near Punta Morales, Vargas (1988) concluded that
macro-predators (fish, birds, crabs and snails) have only a negligible effect on
benthic community structure in this tropical tidal flat. He found almost no
changes in abundance in the exclusion cages, but did see changes in the rank
order of abundance of dominant species.
At present, the findings on the relevance of predation in tropical benthic
communities are somewhat contradictory. There is little evidence for a regulating effect of epibenthic predators on infaunal assemblages in the tropics.
However, it cannot be excluded that multiple predatory effects (e. g. Ambrose
1984) exist in tropical tidal flats, as the predatory effects of endobenthic
predators have not yet been addressed. The report by Christy et al. (1998) of a