Reproductive cycle of the oviparous lizard Sceloporus jalapae,from Zapotitlán Salinas,Puebla, Mexico

Reproductive patterns vary widely among species and populations of squamates. In general, patterns can be divided into cyclic and acyclic. Cyclic patterns are common in tropical and temperate species of seasonal environments, while acyclic ones are characteristic of tropical species that inhabit less variable environments. We studied the reproductive cycle of Sceloporus jalapae, one of the smallest species of Sceloporus, in an arid environment at Zapotitlán Salinas, Puebla, Mexico. Both sexes mature in the first year following hatching and exhibit a seasonal reproductive pattern with maximum activity in spring and summer that appears to be influenced by temperature. Unlike small species of Sceloporus that inhabit pine–oak and tropical forests, S. jalapae exhibits an extended period of reproductive activity that allows females to produce at least two clutches of 3–7 eggs each, and contrary to other species of Sceloporus, in this species there is no correlation between female length and clutch size. The reproductive pattern of S. jalapae is like that shown by other oviparous species of the genus; nevertheless, some life history traits of this species are shared with oviparous and viviparous species of small size.     

Distribution and abundance of Tillandsia spp. (Bromeliaceae) in the Zapotitlán Valley,Puebla, México

Seed germination of woody species was studied in treefall gaps in NewZealand to assess how environmental heterogeneity affects regeneration fromseed. Gaps were created in a relictual Pinus radiataplantation destined for restoration to native forest. Seeds of the nativespecies Alectryon excelsus, Macropiperexcelsum, and Fuchsia excorticata, and theinvasive alien species Cytisus scoparius andBerberis darwinii were sown in sites differing inexposure,with and without 3 cm of pine litter. Litter promoted germinationof Alectryon and Macropiper,independent of site. Without litter, percent germination ofMacropiper was negatively correlated with percent open skyoverhead. Germination of Fuchsia was significantly higherin treefall gaps than in the forest understory, with litter having littleeffect. Cytisus germinated most successfully in sitesexposed to direct solar radiation, with or without litter. Percent germinationof Berberis was high in all sites, and was consistentlypromoted by litter. Glasshouse trials for each species showed the same effectsof litter cover as found in the field. These results suggest thatmicroenvironmental heterogeneity can be an important influence on the speciescomposition of regenerating vegetation within and around treefall gaps.     

Geospatial analysis of pollen records from the Yucatán peninsula, Mexico

Changes in distribution of semi-evergreen forest in the Yucatán peninsula and variation of precipitation during the late Holocene were inferred using a geographical information system. Deterministic methods for spatial interpolation using fossil pollen data from seven cores elucidated environmental changes. The changes in the distribution of the semi-evergreen forest allowed to us infer variations in precipitation in the area and to distinguish whether changes of forest cover are a consequence of climate and/or of human activities. The reconstruction of the Preclassic period (at 550 and 50 b.c.) indicates higher precipitation than at present and suggests a more closed vegetation cover. Around a.d. 450 the vegetation acquired an open character indicating a reduction in precipitation. During this time the decrease in forest was not homogeneous in the Yucatán peninsula, indicating human impacts in certain areas. A reduction in forest cover but not a complete deforestation of the region is assessed during the Classic period (a.d. 450). The reconstruction of a.d. 950 shows the recovery of the forest and is related to the Medieval warm period. Geographical information systems are useful tools to reconstruct the spatial history of the vegetation of the Yucatán peninsula during the late Holocene.     

Plant resources of the Tehuacán-Cuicatlán valley, Mexico

Information on richness of plant resources, and their forms of use and management in the biosphere reserve Tehuacan-Cuicatlan, Mexico is analyzed. This 10 000 km² region hosts nearly 2700 vascular plant species, and it is acknowledged as one of the arid areas with the highest floristic diversity in North America. The seven indigenous ethnic groups that live in this region have cultural roots that date back almost 10 000 years. Based upon ethnobotanical and floristic studies, as well as bibliographical sources, a total of 808 useful plant species were identified, most of them (90%) being native, and 44 species being endemic to the region. A total of 681 species are wild plants, 109 are weeds and ruderal plants, and 86 are domesticated crops. However, it was noted that considerable overlap exists between the species of these 3 categories. For example, while wild and ruderal plants (706 species) are foraged by both humans and domestic animals, 59 species of this group are also managed in situ. On the other hand, 168 wild, ruderal and domesticated species are cultivated. The Tehuacán-Cuicatlan Valley is one of the richest regions of Mexico in plant resources. Local knowledge on use and management of plants is a valuable source of information for designing conservation and social development strategies for the biosphere reserve.     

Renegotiating gender and class in the berry fields of Michoacán,Mexico

This article examines the renegotiation of gender and class in a rural Mexican community where economic crisis in the sugar industry led foreign agribusinesses to promote blackberry and raspberry production for export and hire primarily women as berry pickers. Analysis focuses on the transition from a sugar economy where mostly men worked in the cane fields to non-traditional agricultural exports when women entered agricultural waged labor in unprecedented numbers. This restructuring of the regional economy raises important questions regarding the marginalization of differentiated subaltern groups and the nature of new sets of power relations between transnational agribusinesses, berry growers, and waged workers. I analyze the contradictions of this changing social field that connects Northern consumers, transnational company executives, berry growers, and waged laborers in a web of differential power relations as they reverberate along the commodity chain from campesino households to the global market.     

Discovery of radiolaria and conodonts in the Carboniferous–Permian of San Salvador Patlanoaya (Puebla,Mexico); biostratigraphic implications

New identifications of radiolaria and conodonts allow clarifying the biostratigraphy of the Pennsylvanian and Permian deposits in San Salvador Patlanoaya (Puebla State, Mexico). The radiolaria are sometimes relatively common in the series, but weakly diversified and endemic. Among the conodonts, Streptognathodus bellus is characteristic of the Late ‘Virgilian’ sensu Baars, probably coeval with the Early Wolfcampian sensu Thompson or Wilde, the Bursumian of Ross & Ross or the Orenburgian–Asselian stage or substage of Russia (sensu Davydov). San Salvador Patlanoaya is a key-section for the Pennsylvanian–Permian boundary in Mexico.     

Aquatic ecosystems of the Yucatán Peninsula (Mexico), Belize, and Guatemala

This study presents limnological and morphological characteristics, physical and chemical properties of waters, and geochemistry of surface sediments for 63 aquatic ecosystems located on the karst Yucatán Peninsula and surrounding areas of Belize and the Guatemalan highlands and eastern lowlands. Our principal goal was to classify the aquatic systems based on their water variables. A principal component analysis (PCA) of the surface water chemistry data showed that a large fraction of the variance (29%) in water chemistry is explained by conductivity and major ion concentrations. The broad conductivity range, from 168 to 55,300 μS cm⁻¹ reflects saline water intrusion affecting coastal aquatic environments, and the steep NW–S precipitation gradient, from ~450 to >3,200 mm year⁻¹. Coastal waterbodies Celestún and Laguna Rosada displayed the highest conductivities. Minimum surface water temperatures of 21.6°C were measured in highland lakes, and warmest temperatures, up to 31.7°C, were recorded in the lowland waterbodies. Most lakes showed thermal stratification during the sampling period, with the exception of some shallow (<10 m) systems. Lakes Chichancanab, Milagros, and Bacalar displayed sulfate-rich waters. Waters of sinkholes had relatively high conductivities (<3,670 μS cm⁻¹) and a broad range of δ¹⁸O values (−4.1 to +3.8‰). Ca, HCO₃, and SO₄ dominated the waters of the lowland lakes, whereas Na was the dominant cation in highland lakes. Coastal aquatic ecosystems were dominated by Na and Cl. Cluster analysis based on surface water variables classified aquatic environments of the lowlands and highlands into three groups: (1) lowland lakes, ponds, wetlands, and coastal waterbodies (2) highland lakes, and (3) sinkholes and rivers. A broad trophic state gradient was recorded, ranging from the eutrophic Lake Amatitlán and the Timul sinkhole to oligotrophic Laguna Ayarza, with the highest water transparency (11.4 m). We used major and trace elements in surface sediments to assess pollution of waterbodies. Lakes Amatitlán, Atescatempa, El Rosario, Cayucón, Chacan-Lara, La Misteriosa, rivers Subín and Río Dulce, the wetland Jamolún, and the sinkhole Petén de Monos showed evidence of pollution and urban development. Their surface sediments displayed high concentrations of As, Cu, Fe, Ni, Pb, Se, Zn, and Zr, which suggest moderate to strong pollution.     

Depositional environment and biofacies characterization of the Upper Pennsylvanian–Lower Permian deposits of the San Salvador Patlanoaya section (Puebla, Mexico)

The San Salvador Patlanoaya section (Puebla State of Mexico) has been subdivided into seven informal members labeled A–F. Members C–F have been dated as Missourian to Leonardian (equivalent to Kasimovian to Kungurian, i.e. lower Upper Pennsylvanian to upper Lower Permian). Members C–E display a shallowing-upward trend as does member F. The biodiversity of these carbonate deposits outcropping in the San Salvador Patlanoaya section is relatively low, although multiple microfossils (algae, small foraminifera, fusulinids and fish remains) are represented. Member C consists of calcarenitic limestone interpreted as distal tempestites interbedded with shaly limestone facies. These storm beds are composed mainly of silt, sand-sized quartz grains and bioclasts. Member D corresponds to coarse bioclastic limestones represented by calcareous tempestites and channel beds with erosional bases. Member E is composed of green shales and cross-bedded sandstones and gravelly conglomerates. Member F corresponds to a condensed package of limestones and interbedded siliciclastics and is Cisuralian (Early Permian) in age. Member G consists of condensed black shales and limestone nodules. The results of the study have significant implications for recognition of climatic and/or sea-level fluctuations in bioclastic–siliciclastic facies during the Late Pennsylvanian–Early Permian. The skeletal limestones and channel sandstones, common throughout the Pennsylvanian–Permian section, provide a constraint on palaeobathymetry, with the water depth fluctuating frequently around a position below, but near, the storm wave base.     

Plant management and biodiversity conservation in Náhuatl homegardens of the Tehuacán Valley,Mexico

Background

The Tehuacán Valley is one of the areas of Mesoamerica with the oldest history of plant management. Homegardens are among the most ancient management systems that currently provide economic benefits to people and are reservoirs of native biodiversity. Previous studies estimated that 30% of the plant richness of homegardens of the region are native plant species from wild populations. We studied in Náhuatl communities the proportion of native plant species maintained in homegardens, hypothesizing to find a proportion similar to that estimated at regional level, mainly plant resources maintained for edible, medicinal and ornamental purposes.

Methods

We analysed the composition of plant species of homegardens and their similarity with surrounding Cloud Forest (CF), Tropical Rainforest (TRF), Tropical Dry forest (TDF), and Thorn-Scrub Forest (TSF). We determined density, frequency and biomass of plant species composing homegardens and forests through vegetation sampling of a total of 30 homegardens and nine plots of forests, and documented ethnobotanical information on use, management, and economic benefits from plants maintained in homegardens.

Results

A total of 281 plant species was recorded with 12 use categories, 115 ornamental, 92 edible, and 50 medicinal plant species. We recorded 49.8 ± 23.2 (average ± S.D.) woody plant species (shrubs and trees) per homegarden. In total, 34% species are native to the Tehuacán Valley and nearly 16% are components of the surrounding forests. A total of 176 species were cultivated through seeds, vegetative propagules or transplanted entire individual plants, 71 tolerated, and 23 enhanced. The highest species richness and diversity were recorded in homegardens from the CF zone (199 species), followed by those from the TRF (157) and those from the TDF (141) zones.

Conclusion

Homegardens provide a high diversity of resources for subsistence of local households and significantly contribute to conservation of native biodiversity. The highest diversity was recorded in homegardens where the neighbouring forests had the least diversity, suggesting that management of homegardens aims at compensating scarcity of naturally available plant resources. Cultivated species were markedly more abundant than plants under other management forms. Diversity harboured and management techniques make homegardens keystones in strategies for regional biodiversity conservation.

     

Traditional Knowledge and Useful Plant Richness in the Tehuacán–Cuicatlán Valley,Mexico

Traditional Knowledge and Useful Plant Richness in the Tehuacán–Cuicatlán Valley, Mexico. This study systematizes ethnobotanical information about the interactions between people and plants, ethnofloristic richness, the relative importance of useful species richness in relation to general species richness, and plant management in the Tehuacán–Cuicatlán Valley of central Mexico. The study recorded a total of 1,605 useful vascular plant species (61.2% of the total species richness of the regional vascular flora), this being the region with the highest absolute richness of useful plant species in Mexico. The null hypothesis that plant families with a higher number of useful species would be those having a higher general species richness was analyzed through residuals method. The plant families richest in useful species were Poaceae, Asteraceae, Cactaceae, Cyperaceae, Mimosaceae, and Solanaceae, most of which also have the highest general floristic richness. However, analyses of use categories did not generally corroborate our hypothesis. About 1,335 of the useful species are wild, more than 500 species are submitted to some type of management (62 species are tolerated, 34 protected, 50 enhanced, and 358 cultivated), but only a few have been studied to document their process of domestication. This information can be useful for developing regional strategies of sustainable management of plant resources.     

Proposal for the Establishment of the Core Zones in the Biosphere Reserve of Tehuacán-Cuicatlán, Mexico

This work proposes the establishment of core zones in the Biosphere Reserve of Tehuacán-Cuicatlán (BRTC), based on plant species richness and endemism. A total of 561 species of the four most important plant families in the region (Asteraceae, Cactaceae, Leguminosae and Poaceae) as well as 174 endemic species of these and other families were used in the analyses. Distribution of these taxa was analyzed using two different iterative complementarity methods. Significant correlations were found between patterns of species richness and endemic plants distribution in the study area. These results were combined with other analysis where two different indices (species richness index and human population index) were used. The results suggest the delimitation of four core zones within the Biosphere Reserve, covering a total area of 105,300 ha. The core zones represent 21.8% of the area, and would protect 72.54% of the species from the selected plant families and 67.8% of endemic species.     

Lycopodiopsids and equisetopsids from the Triassic of Quebrada de los Fósiles Formation,San Rafael Basin,Argentina

In the late 1960s, rests of a low-diversity flora dominated by the lycopsid Pleuromeia were reported. The specimens were recovered from a creek near San Rafael, Mendoza Province, western Argentina, in the lower section of the Puesto Viejo Group, the Quebrada de los Fósiles Formation, considered as Early Triassic in age. Despite the importance of this flora with respect to the end-Permian mass extinction event, it was not yet described nor illustrated. Since then, the age of the Puesto Viejo Group has been revised and the Quebrada de los Fósiles Formation is now considered to be early Middle Triassic. The fossil plants are here first described and interpreted. The most common element, Pleuromeia cf. sternbergii, a species known worldwide that characterizes the post-extinction flora recovery, is accompanied by sphenopsids such as Neocalamites and Equisetostachys, and an herbaceous lycopsid. This community grew up associated with transient water bodies in flood plain environments that developed under warm temperate, strongly seasonal climatic conditions. The landscape was stressed by volcanism, and the conjunction of these factors probably restricted the colonization and development of a full ecosystem, as happened worldwide after the end-Permian mass extinction.     

Sociocultural and ecological factors influencing management of edible and non-edible plants: the case of Ixcatlán,Mexico

Background

Identifying factors influencing plant management allows understanding how processes of domestication operate. Uncertain availability of resources is a main motivation for managing edible plants, but little is known about management motives of non-edible resources like medicinal and ceremonial plants. We hypothesized that uncertain availability of resources would be a general factor motivating their management, but other motives could operate simultaneously. Uncertainty and risk might be less important motives in medicinal than in edible plants, while for ceremonial plants, symbolic and spiritual values would be more relevant.

Methods

We inventoried edible, medicinal, and ceremonial plants in Ixcatlán, Oaxaca, Mexico, and conducted in-depth studies with 20 native and naturalized species per use type; we documented their cultural importance and abundance by interviewing 25 households and sampling vegetation in 33 sites. Consumption amounts and preferences were studied through surveys and free listings with 38 interviewees. Management intensity and risk indexes were calculated through PCA and their relation analyzed through regression analyses. Canonical methods allowed identifying the main sociocultural and ecological factors influencing management of plants per use type.

Results

Nearly 64, 63, and 55% of all ceremonial, edible, and medicinal wild plants recorded, respectively, are managed in order to maintain or increase their availability, embellishing environments, and because of ethical reasons and curiosity. Management intensity was higher in edible plants under human selection and associated with risk. Management of ceremonial and medicinal plants was not associated with indexes of risk or uncertainty in their availability. Other sociocultural and ecological factors influence management intensity, the most important being reciprocal relations and abundance perception.

Conclusions

Plant management through practices and collectively regulated strategies is strongly related to control of risk and uncertainty in edible plants, compared with medicinal and ceremonial plants, in which reciprocal interchanges, curiosity, and spiritual values are more important factors. Understanding how needs, worries, social relations, and ethical values influence management decisions is important to understand processes of constructing management strategies and how domestication could be started in the past and are operated at the present.

     

Patterns of Knowledge and Use of Medicinal Plants in Santiago Camotlán,Oaxaca, Mexico

Medicinal plants continue to play an important role in healthcare, both in Mexico and around the world. We investigated the relationship between various sociodemographic factors, such as age, economic activity, years of schooling, socioeconomic levels, gender, and language proficiency, and the knowledge and frequency of medicinal plant use in Santiago Camotlán, Sierra Norte of Oaxaca, with a mainly Zapotec population. In a first stage, we interviewed specialists in depth and collected and identified plants for a catalogue of the medicinal plant flora (90 species). With this catalogue, we then interviewed a sample of the general population and the specialists on knowledge and frequency of use. The relationship between the sociodemographic variables and knowledge was analyzed by multiple regression. To explore differences of knowledge within the population, we identified three groups with a two-step cluster analysis; the results were compared statistically with a Kruskal-Wallis non-parametric test and then a post hoc Dunn’s test to see if all the differences between groups were significant. Age and occupation explained 54% of the variation of knowledge. Medicinal plant knowledge in the region persists mainly because of the necessity to treat the diseases that the “doctor does not cure,” the culture-bound syndromes, and the most common ailments, malfunctions of the digestive system.     

Stomach content analysis of juvenile, scalloped hammerhead shark Sphyrna lewini captured off the coast of Mazatlán, Mexico

We quantified the diet of juvenile, scalloped hammerhead shark Sphyrna lewini in the area off Mazatlan, Sinaloa, Mexico, to understand their feeding ecology this shark. The prey species of Sphyrna lewini were identified and quantified from stomach content analysis. In addition, we determined the variations between genders. During two fishing seasons (2000–2001 and 2001–2002), we analyzed 232 stomachs, of which 85% contained food. The trophic spectrum was composed of three species of cephalopods, six of crustaceans and 19 species of fish from mainly pelagic and benthic habitats. According to the Index of Relative Importance (%IRI), the cephalopod Loliolopsis diomedeae with IRI = 18%, fish of the family Carangidae IRI = 25% and family Synodontidae IRI = 19% constituted the main prey in general. The trophic niche width was <0.4, which indicated that S. lewini juveniles in this area feed on a wide range of prey items, though they showed a preference for a few prey items.     

Macroinvertebrate fauna and depositional environment of the lower Upper Cenomanian Oberhäslich Formation in the Saxonian Cretaceous Basin (Germany)

In Saxony (southeast Germany), the global early Late Cretaceous transgression is reflected by the onlap of shallow-marine siliciclastics of the lower Upper Cenomanian Oberhäslich Formation (Calycoceras naviculare Zone) onto the eastern Erzgebirge, the central part of the emergent Mid-European Island. Based on detailed logging of sections south of Dresden and the study of extensive collection material, the depositional environment and macroinvertebrate assemblages of the Oberhäslich Formation have been reconstructed. This unit, with a mean thickness of 10–15 m, usually shows a fining-upward trend that may become reversed towards the top, was laid down in a single 3rd-order sea-level cycle and is capped by an unconformity at the base of the overlying upper Upper Cenomanian Dölzschen Formation (sequence boundary Cenomanian 5; junction of the Calycoceras naviculare and Metoicoceras geslinianum zones). The macroinvertebrate assemblage of the Oberhäslich Formation, collected mainly from bioturbated, fine- or rarely medium-grained, quartz-rich sandstones, is fairly diverse, comprising nearly 50 taxa, predominantly bivalves (94.3%). Most conspicuous and abundant are relatively large forms such as Rhynchostreon (R.) suborbiculatum (25%) and Inoceramus pictus spp. (21%), eponymous taxa of the Rhynchostreon suborbiculatum/Inoceramus pictus assemblage. Non-bivalve benthic invertebrates are rare and represented by rather poorly preserved irregular and regular echinoids, siliceous sponges, a few gastropods, crustacean remains and a single starfish. Common Thalassinoides and Ophiomorpha burrows indicate that crustaceans were an important part of the infauna. Pervasive bioturbation resulted in a post-depositional homogenization of the sediments while all body fossils are preserved as (composite) internal moulds. The guild structure of the Rhynchostreon suborbiculatum/Inoceramus pictus assemblage shows a predominance of epifaunal and semi-infaunal suspension feeders (95.3%), suggesting eutrophic and unstable “green-water conditions” of an inner-shelf setting. Deposit-feeding biota are rare. The common occurrence of articulated bivalves and storm-induced shell beds indicate episodic rapid burial, most probably by tempestites. A current-influenced, well-oxygenated and nutrient-rich environment slightly below fair-weather base is inferred for the fine-grained sandy, fossiliferous sediments of the Oberhäslich Formation.     

Current status of the habitat and population of the black howler monkey (Alouatta pigra) in Balancán, Tabasco, Mexico

We evaluated the habitat and populations of the black howler monkey (Alouatta pigra) in the municipality of Balancán, Tabasco, southeastern Mexico, using a combination of field surveys and remotely sensed data. We identified 21,937 ha of remnant vegetation composed of 1,348 fragments. Fragments separated by up to 200 m were grouped into "clusters" of fragments in accordance with the maximum observed open distance crossed by A. pigra. A total of 11% or 84 of the 772 clusters identified through remote sensing were selected at random, and for these we determined the vegetation type, canopy height, area, and distance to the closest human settlement. In these same 84 clusters, which included a total area of 9,817 ha, from October to June of 2006 we located a total of 1,064 black howler monkeys, including 228 troops and 49 solitary monkeys. A. pigra was found in 62 (74.7%) of all clusters visited, with a cumulative area of 6,032 ha. Troops varied in size from 2 to 15 individuals (average 6.0+/-2.9 ind/troop). Adults were 67% (n=716) of detected individuals, whereas juveniles were 20.5% (n=218) and infants were 12.5% (n=133). We found black howlers to occur at an ecological density of 10.8 ind/km(2), which is low in comparison with A. pigra in other fragmented and conserved sites. We found a statistically significant relationship between the area of clusters and the abundance of howler monkeys (r(2)=0.2, F=10.47, gl=3, P=0.002). In addition, the probability of finding A. pigra was greater in secondary vegetation, riparian vegetation, tropical dry forest, undisturbed tropical oak forest, and palm forest (F=12, gl=3, P<0.0001), as compared with disturbed tropical oak forest. Our results provide data on the distribution, abundance, and population structure of black howler monkeys in a fragmented landscape in the southeast of Mexico. These data are a necessary prerequisite for conservation planning for this species.     

Effect of the spatial and seasonal soil heterogeneity over arbuscular mycorrhizal fungal spore abundance in the semi-arid valley of Tehuacán-Cuicatlán, Mexico

Recent studies have shown that some species of Mimosa (Leguminosae-Mimosoideae) create resource islands (RI), rich in soil organic matter and nutrients, as well as in arbuscular mycorrhyzal fungal (AMF) spores, in the semi-arid Valley of Tehuacán-Cuicatlán. The relevance of this fact is that arid and semi-arid regions are characterized by low fertility soils and scarce precipitation, limiting plant species growth and development; this explains why the presence of AM fungi may be advantageous for mycorrhizal desert plants. Fluctuations in AMF spore numbers could be related to environmental, seasonal and soil factors which affect AMF sporulation, in addition to the life history of the host plant. The aim of this study was to asses the impact of spatial (resource islands vs open areas, OA) and seasonal (wet season vs start of dry season vs dry season) soil heterogeneity in the distribution and abundance of AMF spores in four different study sites within the Valley. We registered AMF spores in the 120 soil samples examined. Significant differences in the number of AMF spores were reported in the soil below the canopy of Mimosa species (RI) comparing with OA (RI > OA), and between Mimosa RI themselves when comparing along a soil gradient within the RI (soil near the trunk > soil below the middle of the canopy > soil in the margin of the canopy > OA); however, there were no significant differences between the soil closest to the trunk vs middle, and margin 's OA. Finally, more spores were reported in the soil collected during the wet season than during the dry season (wet > start of dry > dry). Therefore, the distribution of AMF spores is affected by spatial and seasonal soil heterogeneity. This study points out the relevance of Mimosa RI as AMF spore reservoirs and the potential importance of AM fungi for plant species survivorship and establishment in semi-arid regions. AM fungi have recently been recognized as an important factor determining plant species diversity in arid and temperate ecosystems.     

Palynofacies analysis of the late Holocene San Nicolás terrace of the Cauca paleolake and paleohydrology of northern South America

The detailed palynofacies analysis of the late Holocene laminated succession of the San Nicolás terrace in the middle Cauca Valley, northern Colombia, is interpreted as the product of sedimentation in a lacustrine to fluvial dominated setting. Radiocarbon analyses reveal that the succession was deposited between ~ 3500 and a few hundreds of years with sedimentary rates in excess of ~ 600 cm/ka. The milimetric laminae and the high frequency fluctuations in the content of the palynodebris of terrestrial origin, i.e., the high altered ligno-cellulosic debris/amorphous organic matter ratio, together with diatoms typical of fluvial conditions, such as Aulacoseira granulata do suggest an intermittent and continuous hydrological and biological connectivity with the Cauca River, akin to a varzea lacustrine environment. Drier to wetter conditions appear to occur, moving upward in the succession. This might reflect regional precipitation conditions all along the Cauca Valley and the southern migration of the intertropical convergence zone.