Vegetation cover of Brazil in the last 21 ka: New insights into the Amazonian refugia and Pleistocenic arc hypotheses

Aim

The two main hypotheses about the Neotropical palaeovegetation, namely that of Amazonian refugia by Haffer and of the Pleistocene arc by Prado and Gibbs, are still constantly debated. We offer new insights on this debate using ecological niche modelling with combined climate–soil predictors to test both hypotheses, reconstruct the palaeovegetation of the Last Glacial Maximum (LGM; 21 ka) and Mid‐Holocene (Mid‐H; 6 ka) and indicate the configuration of refugia areas.

Location

Brazil.

Time period

Last 21 ka.

Major taxa studied

Biomes.

Methods

We modelled the environmental space of the 10 most representative biomes with the RandomForest classifier, using climate predictors from three atmospheric general circulation models (CCSM4, MPI‐ESM‐P and MIROC‐ESM) and soil predictors, the same for the different situations. Based on the consensus among the models, we reconstructed the palaeovegetation cover for LGM and Mid‐H and used fossil pollen sites to validate the reconstructions in a direct comparison.

Results

The climate in the past was cooler and wetter throughout most of the territory. The Amazon basin region was the most affected by climate change in the last 21 ka, with equatorial rain forest retracting to refugia areas, while the tropical rain forest (with climatic preferences similar to the Atlantic forest) expanded in the basin. In southern Brazil, the mixed forest (Araucaria forest) shifted to lower latitudes, while the grasslands expanded. In most biomes, the greatest changes occurred in the ecotonal zones, supported by pollen fossils.

Main conclusions

With regard to Haffer's hypothesis, the forests of the Amazonian lowlands retreated to refugia areas, while the colder and wetter climate of the basin created a favourable niche for another type of forest, instead of savanna. The advance of dry vegetation was restricted to ecotonal conditions, preventing the formation of a continuous Pleistocene arc, predicted by Prado and Gibbs's hypothesis.     

No bottom-up effects of food addition on predators in a tropical forest

Several studies in temperate forests have demonstrated effects of litter addition on decomposers and predators. However, adding litter does not allow separating the effects of food availability and habitat space. We investigated the response of decomposers and predators to increased food resources and space in forests of the southern Mata Atlântica of Brazil. In two forest ecosystems representing an early successional stage of secondary forests and old-growth forest, we added nutrient-rich organic material, artificial litter of no nutritional value, or a combination of both to the soil surface of 120 plots to separate the effects of habitat space and food on soil food webs. We sampled litter- and soil-dwelling arthropods after three months using pitfall traps, soil sample extraction, and sticky traps just above the soil. Adding artificial litter had no positive effect on any of the 17 analyzed arthropod groups. Combining all sampled arthropods the effect was even significantly negative. Adding food had a positive effect on the abundance of decomposers, but not predators. We found no interactions between added artificial litter and added organic material. Our results suggest that the soil fauna in tropical forests is food limited. The lack of a bottom-up effect on predators suggests that they are not predominantly regulated by the abundance of epigeic prey but rather by competition or predation.     

Simultaneous Analysis of Six Microsatellite Markers in Atlantic Cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>): A Novel Multiplex Assay System for Use in Selective Breeding Studies

A novel hexaplex assay system including Gmo8, Gmo19, Gmo35, Gmo37, Tch11, and Tch12 microsatellites from Atlantic cod, consisting of trinucleotide or tetranucleotide repeat units, is introduced. All 6 loci were coamplified in a single reaction employing dye-labeled primers. Alleles from these loci were sized using an internal standard by automated sample processing in an ABI 310 Genetic Analyser. Amplified alleles in profiles containing selected microsatellites were typed clearly, providing easily interpretable results. Sequencing data indicated that alleles at all loci consisted of simple repeat units. This may help minimize the likelihood of stuttering upon polymerase chain reaction amplification. The results suggest that the presented hexaplex assay system may be a useful tool in a selective breeding program in which genetic identification will allow different genotypes to be reared together from fertilization. This should have a great impact as it will make selective breeding more efficient.     

Nuclear and mitochondrial phylogeography of the Atlantic forest endemic Xiphorhynchus fuscus (Aves: Dendrocolaptidae): biogeography and systematics implications

We studied the intraspecific evolutionary history of the South American Atlantic forest endemic Xiphorhynchusfuscus (Aves: Dendrocolaptidae) to address questions such as: Was the diversification of this bird's populations associated to areas of avian endemism? Which models of speciation (i.e., refuges, river as barriers or geotectonism) explain the diversification within X. fuscus? Does the genetic data support subspecies as independent evolutionary units (species)? We used mitochondrial (n=34) and nuclear (n=68) DNA sequences of X. fuscus to study temporal and spatial relationships within and between populations. We described four main monophyletic lineages that diverged during the Pleistocene. The subspecies taxonomy did not match all the evolutionary lineages; subspecies atlanticus was the only one that represented a monophyletic and isolated lineage. The distribution of these lineages coincided with some areas of endemism for passerines, suggesting that those areas could be regions of biotic differentiation. The ancestor of X. fuscus diverged approximately 3 million years ago from Amazonian taxa and the phylogeographic pattern suggested that X. fuscus radiated from northeastern Brazil. Neither the riverine nor the geotectonic vicariance models are supported as the primary cause for diversification of geographic lineages, but rainforest contractions and expansions (ecological vicariance) can explain most of the spatial divergence observed in this species. Finally, analyses of gene flow and divergence time estimates suggest that the endangered subspecies atlanticus (from northeastern Brazil) can be considered a full species under the general lineage species concept.     

Coexistence of NADPH-diaphorase and vasoactive intestinal polypeptide in the enteric nervous system of the Atlantic cod (Gadus morhua) and the spiny dogfish (Squalus acanthias)

The distribution of NADPH (nicotinamide adenine dinucleotide phosphate)-diaphorase in nerve cells in the gastrointestinal tract has been investigated and compared in three fish species representing different evolutionary branches. In mammals, NADPH-diphorase is identical to nitric oxide synthase (NOS) and can, in the presence of NADPH, reduce the dye nitroblue tetrazolium, resulting in a blue product. Using this method, we have found numerous NADPH-diaphorase-containing nerve cells in the myenteric plexus of the Atlantic cod (Gadus morhua) and the spiny dogfish (Squalus acanthias) but none in the hagfish (Myxine glutinosa). In the cod, nerve fibres were sparsely stained, whereas in the dogfish, they formed a dense pattern of fibre bundles. Double-staining for NADPH-diaphorase and the neuropolypeptides VIP (vasoactive intestinal polypeptide) and PACAP (pituitary adenylate cyclase activating peptide) revealed three separate populations designated VIP/NADPH, VIP/- and NADPH/-. The majority but not all of the NADPH-diaphorase-positive cells also showed VIP or PACAP immunoreactivity and vice versa. The presence of NADPH-diaphorase in neurons and the distribution of these neurons in the gastrointestinal tract of the two species indicate a physiological role for nitric oxide in the control of gut motility.     

The risks of parenthood. I. General theory and applications

Summary We use contemporary life history theory to analyze parental decisions concerned with the defense of offspring, and with the provisioning of offspring in the presence of risk. In achieving the optimal level of parental investment, the parent faces a tradeoff between present and future reproductive success. Our models, which are based on stochastic dynamic programming, lead to predictions of the following kind: (i) offspring will be defended more vigorously as they grow older; (ii) long-lived species will accept fewer risks in caring for offspring than short-lived species; (iii) parents living in permanently riskier environments will defend their offspring more vigorously than parents in less risky environments; (iv) however, temporary increases in risk will result in temporarily less vigorous defense and provisioning of offspring. The models also show that parents and their offspring have different conceptions of the optimal level of parental investment. The flexibility of our modeling approach as a method of analyzing facultative behavior is also emphasized. Finally, we apply the methods of this paper to analyze fledging behavior of Atlantic puffins.     

A preliminary study of two species of flatfish (family: Bothidae) from the south-west Atlantic

Two species of the family Bothidae (lefteye flounders), Mancopsetta maculata metadata and M. milfordi occur in the south-west Atlantic but are caught rarely by commercial bottom trawlers. Little is therefore known about their general biology from this area. A total of 251 M. maculata and 276 M. milfordi were sampled during deep-water exploratory fishing conducted in November 1994 within the Falkland Islands Interim and Outer Conservation Zones, at depths of 400-1000 m, using standard commercial bottom trawling gear. The two species were found to have similar geographical distributions between 48.30'-53.30'S and 55°-62° W and were often obtained at the same stations in depths of 400-900 m on the continental slope. Mancopsetta maculata maculata showed a uni-modal cohort structure with a modal length at the 29-cm total length size-class. Males of M. m. maculata outnumbered females in a ratio of 3.5 : 1. Mancopsetta milfordi showed a tri-modal length distribution, the main mode at the 37-cm total length size-class, with females outnumbering males in a ratio of 1.1 : 1. Length-weight relationships and length-at-age information are presented for the two species. Diet was determined from the analysis of stomach contents and, although the major prey type for both species consisted of crustaceans, the morid fish Austrophycis marginata also formed an important part of the diet of M. milfordi. Key words: Mancopsetta maculata maculata; Mancopsetta milfordi; distribution; south-west Atlantic; size; diet.     

Marine Amebae From Clean and Stressed Bottom Sediments of the Atlantic Ocean and Gulf of Mexico*,†,‡

SYNOPSIS Amebae isolated from sediments of the Atlantic Ocean and Gulf of Mexico were maintained in continuous culture and most were identified to genus and species. Twenty-six species representing 12 genera were recognized from existing literature and several others (Flabellula, Mastigamoeba, Cochliopododium) were identified only to genus. One ameboflagellate and several small limax-type amebae which require further study also were isolated. Other sarcodmids belonging to the Heliozoida, Testocida, Leptomyxida, and Proteomyxida were identified only tentatively. the distribution of the amebae and ameba-like organisms was tabulated for the following geographic areas: Atlantic Ocean near Long Island, New York: Atlantic Ocean 16-65 miles offshore from New York and New Jersey: Atlantic Ocean 1-50 miles offshore from Maryland and Delaware: and the Gulf of Mexico 3.5-41 miles offshore from the southeastern United States. Amebae present in shellfish holding trays at Lewis. Delaware, were isolated, and identified to compare the distribution of species in laboratory tanks with those present in natural ocean bottoms. Published accounts of each collection site were reviewed to obtain specific data on contamination with sewage wastes, acid wastes, dredge spoils, and petroleum hydrocarbons. Two previously undescribed amebae were found to represent new genera and species and are described herein, one from the Delaware mariculture facility, and the other from the digestive tract of the blue crab, Callinectes sapidus, and the gill surface of the lady crab, Ovalipes ocellatus. Sarcodinids present in clean or stressed environments were listed, and genera and species that were widespread or apparently geographically restricted were recorded.     

Food selection by a sit-and-wait predator,the monkfish,Lophius upsicephalus,off Namibia (South West Africa)

Synopsis We investigated prey selection by the monkfish, Lophius upsicephalus. This sit-and-wait predator preferentially selected prey types that would be expected to react to the lure of the illicium. Prey size selection was dependent on predator size, with larger predators feeding on a wider range of prey sizes.