Luquillo Experimental Forest: Research History and Opportunities.

Harris, N.L.; Lugo, A.E.; Brown, S.; and Heartsill Scalley, T. (Eds.).
Luquillo Experimental Forest: Research history and opportunities. EFR-1.
Washington, DC: U.S. Department of Agriculture. 152 p.

Feeding preferences of West Indian manatees in Florida, Belize, and Puerto Rico as indicated by stable isotope analysis

Alves-Stanley C.D., Worthy G.A.J., Bonde R.K. Feeding preferences of West Indian manatees in Florida, Belize, and Puerto Rico as indicated by stable isotope analysis. Marine Ecology Progress Series, Vol 402. pp. 255-267, 2010.

Understanding survival and abundance of overwintering warblers: Does rainfall matter?

Dugger, KM, J. Faaborg, WJ Arendt, and KA Hobson. 2004. Understanding survival and abundance of overwintering warblers: Does rainfall matter? Condor 106 (4) (NOV): 744-60.

We investigated relationships between warbler abundance and survival rates measured on a Puerto Rican wintering site and rainfall patterns measured on the wintering site and in regions where these warblers breed, as estimated using stable-isotope analysis (dD) of feathers collected from wintering birds. We banded birds using constant-effort mist netting from January 1989–2003 in the Gunica Forest of southwestern Puerto Rico. Blackand- white Warblers (Mniotilta varia), American Redstarts (Setophaga ruticilla), and Ovenbirds (Seiurus aurocapilla) dominated the Neotropical migrant capture totals each winter, with resulting sample sizes large enough to estimate survival rates. Estimates of capture probability from survival modeling allowed us to estimate abundance from mist-netting capture totals for Black-and-white Warblers and Ovenbirds. Stable-hydrogen isotopes showed that the three focal species came mostly from the eastern United States. Black-andwhite Warbler abundance was related to rainfall total deviations from normal in Gua´nica Forest, and Ovenbird abundance was related to total annual rainfall in the United States. Survival models with rainfall covariates were weakly supported overall, but apparent survival of Black-and-white Warblers and American Redstarts was negatively related to rain during the first 6 months of the year at Gua´nica, and Ovenbird survival was related to rainfall during the spring in the southeastern U.S. Abundance and apparent survival exhibited similar, species-specific patterns of association with rainfall for Black-and-white Warblers and Ovenbirds. Winter rainfall was important to demographic parameters of Blackand- white Warblers, and breeding-season rain was important to Ovenbirds.

Stable Isotopic Studies of Earthworm Feeding Ecology in Tropical Ecosystems of Puerto Rico

Hendrix, PF, SL Lachnicht, MA Callaham, and XM Zou. 1999. Stable isotopic studies of earthworm feeding ecology in tropical ecosystems of puerto rico. Rapid Communications in Mass Spectrometry 13 (13): 1295-9.

Feeding strategies of earthworms and their influence on soil processes are often inferred from morphological, behavioral and physiological traits. We used 13C and 15N natural abundance in earthworms, soils and plants to explore patterns of resource utilization by different species of earthworms in three tropical ecosystems in Puerto Rico. In a high altitude dwarf forest, native earthworms Trigaster longissimus and Estherella sp. showed less 15N enrichment (delta 15N = 3–6%) than exotic Pontoscolex corethrurus (15N = 7–9%) indicating different food sources or stronger isotopic discrimination by the latter. Conversely, in a lower altitude tabonuco forest, Estherella sp. and P. corethrurus overlapped completely in 15N enrichment (delta15N = 6–9%), suggesting the potential for interspecific competition for N resources. A tabonuco forest converted to pasture contained only P. corethrurus which were less enriched in 15N than those in the forest sites, but more highly enriched in 13C suggesting assimilation of C from the predominant C4 grass. These results support the utility of stable isotopes to delineate resource partitioning and potential competitive interactions among earthworm species. Copyright # 1999 John Wiley & Sons, Ltd.

Moisture as a determinant of habitat quality for a nonbreeding Neotropical migratory songbird

Smith, Joseph A. M., Leonard R. Reitsma, and Peter P. Marra. 2010. Moisture as a determinant of habitat quality for a nonbreeding neotropical migratory songbird. Ecology 91 (10) (OCT): 2874-82.

Identifying the determinants of habitat quality for a species is essential for understanding how populations are limited and regulated. Spatiotemporal variation in moisture and its influence on food availability may drive patterns of habitat occupancy and demographic outcomes. Nonbreeding migratory birds in the neotropics occupy a range of habitat types that vary with respect to moisture. Using carbon isotopes and a satellite-derived measure of habitat moisture, we identified a moisture gradient across home ranges of radiotracked Northern Waterthrush (Seiurus noveboracensis). We used this gradient to classify habitat types and to examine whether habitat moisture correlates with overwinter mass change and spring departure schedules of Northern Waterthrush over the late-winter dry season in the tropics. The two independent indicators of moisture revealed similar gradients that were directly proportional to body mass change as the dry season progressed. Birds occupying drier habitats declined in body mass over the study period, while those occupying wetter habitats increased in body mass. Regardless of habitat, birds lost an average of 7.6% of their mass at night, and mass recovery during the day trended lower in dry compared with wet habitats. This suggests that daily incremental shortfalls in mass recovery can lead to considerable season-long declines in body mass. These patterns resulted in consequences for the premigratory period, with birds occupying drier habitats having a delayed rate of fat deposition compared with those in wet habitats. Taken together with the finding that males, which are significantly larger than females, are also in better condition than females regardless of habitat suggests that high-quality habitats may be limited and that there may be competition for them. The habitat-linked variation in performance we observed suggests that habitat limitation could impact individual and population-level processes both during and in subsequent periods of the annual cycle. The linkage between moisture and habitat quality for a migratory bird indicates that the availability of high-quality habitats is dynamic due to variation in precipitation among seasons and years. Understanding this link is critical for ascertaining the impact of future climate change, particularly in the Caribbean basin, where a much drier future is predicted.

Food Web Structure in Exotic and Native Mangroves: A Hawaii-Puerto Rico Comparison

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.

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.


STONER, A. W. & ZIMMERMAN, R. J. 1988. Food pathways associated with penaeid shrimps in a mangrove-fringed estuary. Fisheries Bulletin 86:543-551.

High abundance and production of juvenile Penaeus spp. in tropical estuaries has been attributed to high concentrations of mangrove-derived detritus in the nursery habitats. Examination of the diets of Penaeus notialis, P. subtilis, and P. brasiliensis in the mangrove-fringed Laguna Joyuda, Puerto Rico showed that even the smallest juveniles are predators consuming capitellid polychaetes (20-38% of diets) and amphipods (20-76%). Less than 25% of the diets was detritus. Ontogenetic variation in diets was greater than interspecific variation, and there was no evidence for dietary separation among the sympatric species. Seasonal shifts in foods reflected abundance patterns of macrobenthic prey species. Despite the consumption of prey organisms generally classified as detritivorous, stable carbon isotope ratios in the penaeids (-18.1 to -15.0%0), their food items (-18.8 to -17.7°/00), and primary producers indicated that shrimps and the majority of sediment dwellers in Laguna Joyuda obtain most of their carbon from benthic a1gae (-14.4°/00) and not from mangrove detritus (- 25.0 to - 22.9°/00).

Estimating the assimilation of mangrove detritus by fiddler crabs in Laguna Joyuda, Puerto Rico, using dual stable isotopes

France, R. 1998. Estimating the assimilation of mangrove detritus by fiddler crabs in laguna joyuda, puerto rico, using dual stable isotopes. Journal of Tropical Ecology 14 (JUL): 413-25.

Dual stable isotope analyses (delta 13C and delta 15N) of fiddler crabs from a forest-fringed, land-locked lagoon in Puerto Rico indicated the differential assim- ilation of material from ingested sediments. Fiddler crabs preferentially selected foi niitrogen-fixing benthic microalgae (cyanobacteria) over vascular plant detritus. These results question the assumption that mangrove detritus is always the prin- cipal source of energy to estuariiie consumers. Previous research fiom this lagoon as well as from Amazonia suggests that the magnitude of lan-d-wvater ecotonal coupling may be low for these particular tropical systems where benthic algal productivity is presumably high.

Differences in urbanization and degree of marine influence are reflected in d13C and d15N of producers and consumers in seagrass habitats of Puerto Rico

Olsen, Ylva S., Sophia E. Fox, Erin L. Kinney, Mirta Teichberg, and Ivan Valiela. 2010. Differences in urbanization and degree of marine influence are reflected in delta(13)C and delta(15)N of producers and consumers in seagrass habitats of puerto rico. Marine Environmental Research 69 (3) (APR): 198-206.

Couplings between land use and marine food webs in tropical systems are poorly understood. We compared land–sea coupling in seven sites around Puerto Rico, differing in the degree of precipitation and urbanization, by measuring d13C and d15N in producers and consumers. d15N values were influenced by human activity: the food web from sites near urbanized centers was on average 1‰ heavier in d15N compared to undeveloped sites. This is most likely due to wastewater inputs from septic systems relatively near the shoreline. Changes in d13C were best explained by differences in the degree of marine influence. Where terrestrial inputs from a major river dominated, d13C values were lighter, whereas sites further from land and in locations exposed to oceanic currents had heavier d13C values, characteristic of a marine source of dissolved organic carbon. We found no significant effect of precipitation on connectivity in spite of a twofold difference in annual average rainfall between the north and south coast. The results suggest there is some connectivity between land and sea in Puerto Rico, despite high rates of evaporation relative to precipitation.

Review of Use of Isotopes in Studying the Natural History of Puerto Rico

Evaristo J. Review of Use of Isotopes in Studying the Natural History of Puerto Rico. University of Pennsylvania. 2012.

This review summarizes the earth and environmental science research papers in Puerto Rico that used isotopic techniques between 1965 and 2011. The range of applications in isotope-related research in Puerto Rico has grown steadily, led by the ubiquitous utility of stable isotope ratios in biogeochemical (δ13C, δ15N) and ecological (δ13C, δ15N, δD) research. Moreover, research in climatology has grown in recent years, spanning from the evaluation of the fidelity of isotope records (δ18O, δ13C) as an environmental proxy to the elucidation of multidecadal variability for paleoclimate reconstructions (δ18O and Sr/Ca). On the other hand, in addition to using isotope ratios, hydrological studies in Puerto Rico have also used trace element data to answer flow source (δD, δ18O, 87Sr/86Sr) and solute source (Ge/Si) questions, as well as in examining groundwater/surface flow relationships (222Rn). Finally, various isotope data have been used in trying to understand geomorphological (10Be, δ30Si) and geophysical (Pb, Nd, and Sr) phenomena. It is hoped that this review will be able to contribute to stimulating future interests in isotope-related research as applicable in the LCZO or Puerto Rico, in particular, and/or in comparable humid tropical settings, in general.
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