Demopoulos, Amanda W. J., Brian Fry, and Craig R. Smith. 2007. Food web structure in exotic and native mangroves: A hawaii-puerto rico comparison. Oecologia 153 (3) (SEP): 675-86.
Abstract:
Plant invasions can fundamentally alter detrital
inputs and the structure of detritus-based food webs. We
examined the detrital pathways in mangrove food webs in
native (Puerto Rican) and introduced (Hawaiian) Rhizophora
mangle forests using a dual isotope approach and a
mixing model. Based on trophic-level fractionation of 0-
\%of or <513Can d 2-3%c for Sl5N, among the invertebrates,
only nematodes, oligochaetes, and nereid polychaetes from
native mangroves exhibited stable isotopes consistent with
a mangrove-deriveddi et. Certainf auna,i n particulartu bificid
oligochaetes, had Sl3C values consistent with the consumption
of mangrove leaves, but they were depleted in 15N,
suggesting their primary nitrogen source was low in 15N,
and was possibly N2-fixing bacteria. In introduced mangroves,
all feeding groups appeared to rely heavily on nonmangroves
ources, especially phytoplanktonin puts.M ixing
model results and discriminant analysis showed clear separation
of introduced and native mangrove sites based on
differential food source utilization within feeding groups,
with stronger and more diverse use of benthic foods
observed in native forests. Observed differences between
native and invasive mangrove food webs may be due to
Hawaiian detritivores being poorly adapted to utilizing the
tannin-rich, nitrogen-poor mangrove detritus. In addition,
differential utilization of mangrove detritus between native
and introduced mangroves may be a consequence of forest
age. We postulate that increasing mangrove forest age may
promote diversification of bacterial food webs important in
N and S cycling. Our results also suggest a potentially
important role for sulfur bacteria in supporting the most
abundantin faunalc onsumers,n ematodes,i n the most mature
systems.