Seed priming increases the vigor of seeds and seedlings through metabolic and biochemical processes occurring during controlled hydration, followed by dehydration. In the field, seeds are exposed to ...hydration-dehydration events in and on the soil after dispersal, as in seed priming. Nevertheless, seed priming has been sparsely tested on desiccation-sensitive seeds, which are vulnerable to climate change effects. We evaluated the effect of two priming methods on seeds from two tropical rainforest species:
Cupania glabra
and
Cymbopetalum baillonii
. For hydropriming, the seeds were fully hydrated and then dehydrated to three dehydration levels. For natural priming, the seeds were buried for 12 days in either closed forest or forest gap. Primed seeds were sown in 1% agar medium and placed in an environmental chamber. The growth of the seedlings from the highest germination priming treatments was evaluated for 1 year in the field. Our results showed that for
C. glabra
and
C. baillonii
, hydroprimed seeds varied in their germination response, depending on the degree of their dehydration. However, for
C. baillonii
, hydropriming seems to invigorate seeds, compared to non-imbibed seeds of the same dehydration level. Natural priming increased germination speed in both species without any difference between closed forest and forest gap. Moreover, seeds with natural priming had a higher final germination percentage than seeds with hydropriming. Seedlings from seeds with natural priming showed a higher growth rate than the controls in both species, whereas hydropriming produced a similar effect in
C. glabra
. Both priming methods could be used for restoration practices with the studied species, natural priming being a novel method. The ecological implications of priming in desiccation sensitive seeds are discussed in this study.
Grasses are recognized as a critical regeneration barrier in tropical pastures, yet the effects of rodents and rodent–grass interactions are not well understood. As selective foragers, rodents could ...shape tree communities, moderating biodiversity in regenerating tropical landscapes. We utilized a fully crossed two-way factorial design to examine the effect that grasses, rodents, and their interaction had on tree seedling establishment in pasture habitat. We followed two separate tree cohorts for 1 year each within the experimental framework. Multiple cohorts were used to better represent successional tree species variation and responses. Trees species were characterized by a gradient of seed masses and as pioneer or persistent successional type. Both cohort seedlings were altered when rodents were present compared to control treatments. In Cohort 1, rodents adversely affected seedlings of persistent tree species only in the absence of grass. In Cohort 2, seedlings of persistent tree species were decimated by rodents in the absence or presence of grass. In both cohorts, seedlings of persistent species established better in grass treatments, while seedlings of pioneer tree species were strongly suppressed. Tree species seed mass positively correlated with seedling establishment across all treatments except no grass–rodent treatments. Strong suppression of tree seedlings by rodents (
Sigmodon toltecus
) is a novel result in tropical land recently released from agriculture. One implication is that selective foraging by rodents on large-seeded persistent tree species may be facilitated by the removal of grass. Another implication is that temporary rodent control in pastures may permit higher establishment of deep-forest persistent species.
Dung beetles are secondary seed dispersers, incidentally moving many of the seeds defecated by mammals vertically (seed burial) and/or horizontally as they process and relocate dung. Although several ...studies have quantified this ecological function of dung beetles, very few have followed seed fate until seedling establishment, and most of these have focused on the effects of seed burial. We know very little about the effects of horizontal seed movement by dung beetles, though it is generally assumed that it will affect plant recruitment positively through diminishing seed clumping. The objective of our study was to assess the effects of dung beetle activity on the spatial distribution of seeds and seedlings, and on the probability of seedling establishment. In a tropical rainforest in Mexico we carried out two complementary field experiments for each of two tree species (Bursera simaruba and Poulsenia armata), using seeds experimentally imbedded in pig dung and recording their fate and spatial location over time. For both species, dung beetle activity reduced the spatial clumping of seeds and seedlings; however, it did not increase the probability of seedling establishment. We discuss the context- and species-specificity of the combined effects of horizontal and vertical dispersal of seeds by dung beetles, and the need to quantify long-term seedling fates to more accurately determine the effects of seed movement by dung beetles on plant recruitment.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background: Lianas are an important woody component of tropical rain forests. We described and compared the composition, structure, and diversity of the liana community in one of the northernmost ...neotropical rain forests.
Question: How much does this liana community differ in attributes with global patterns documented in other tropical and subtropical rain forests?
Study site and dates: Los Tuxtlas Tropical Biology Station, Veracruz, Mexico. 2015-2018.
Methods: We censused all lianas ≥ 1 cm in diameter in a 1-ha plot and determined dominant families and species, diametric distribution, and diversity of order q .
Results: We recorded 396 liana stems, 42 species, and 20 families. Basal area was 6619.2 cm2. Order 1 and 2 diversity was 21.9 and 13.4, respectively. Apocynaceae, Bignoniaceae, Celastraceae, and Malpighiaceae accounted for about 60 % of abundance and basal area, and 45.2 % of species richness. The 10 most abundant species included more than 60 % of stems and basal area.
Conclusions: Species richness, abundance, and basal area were low compared with other tropical and subtropical sites worldwide. It was noteworthy the coincidence of some dominant species and families across the Neotropics and the absence of Fabaceae among the most important families. Latitudinal location and some key climatic factors such annual average rainfall and dry season length may explain, in part, our findings.
Background and Research Aims
Forest loss and fragmentation have a negative impact on large-sized predators and prey, whose populations are reduced or extirpated locally. We explored the ...spatiotemporal coexistence of the mesopredators (< 15 kg) coyote, ocelot, and white-nosed coati, with their potential prey (< 15 kg) Mexican agouti, lowland paca, and collared peccary in a defaunated rainforest.
Methods
We used two-species occupancy-detection models between mesopredators and their potential prey, overlap index of circular models, and latency time measurements to evaluate temporal and spatial segregation and habitat use of species.
Results
Presence of ocelot and coyote was influenced by an increase in the detectability and occupancy of the Mexican agouti. Among most mesopredator–prey species pairs, the correlation for both the capture rates at camera-trap stations and the 1-hr intervals were mainly moderate or low. Some mesopredator–prey species pairs showed low or inverse correlations suggesting species avoidance. The Mexican agouti exhibited a significant negative correlation with the presence of mesopredators. The coyote and ocelot showed a positive correlation with their use of low use trails by people.
Conclusions
Spatiotemporal tolerance was observed among mesopredator omnivores and prey herbivores. High temporal overlap of ocelots and potential prey (lowland paca) was observed compared to other tropical forests holding large-sized predators, suggesting behavioral shifts for increasing mesopredator–prey encounters. Furthermore, mesopredator coexistence was mediated by a displacement in the temporal peaks of activity and spatial segregation among species.
Implications for Conservation
Defaunated tropical forests need protection to ensure the conservation of remaining species and their ecological interactions.
Background and Research
One noteworthy element found throughout the tropical anthropogenic mosaic is the live fence, which is established within agricultural matrices and its structure within the ...landscape retains ecological processes, but few are recognized as elements of biological and cultural conservation.
Methods
In this study, we have researched plant diversity and anthropic management of live fences in five sites surrounded by contrasting vegetation references: Tropical evergreen forest; tropical deciduous forest; cloud forest; and pine–oak and pine forests. We recorded the type of management by interviews with peasants. We established thirty 2 × 50 m transects within each site and sampled two strata: trees and saplings. Also, we documented seed dispersal mechanism, life form, local use, and origin of each species. Importance Value Index and diversity metrics were estimated for each site.
Results
253 plant species were registered (181 genera/74 families). While fences associated with the tropical deciduous forest showed the greatest species richness (109 species), the pine forest fences showed the lowest richness (21 species). Zoochory was the main type of seed dispersal mechanism.
Conclusions
Independent to the site and the altitude, the configuration of living fences is structured by three processes: the selection of the initial trees, the availability of the arrival of zoochory species, and the tolerance of the owners for the plant species.
Implications for Conservation
Based on our results, live fences can be considered important tools for landscape management in Mexico.
While some studies have shown that ants that visit extrafloral nectaries may defend their host plants against potential herbivores, recent researches have shown that such ant-plant mutualism may be ...broken in some cases. For example, the presence of ants on plants could also drive away pollinators and seed dispersers. However, it is not yet known what mechanisms could favor that ant presence on plants does not affect other mutualistic interactions involving plants. In this work, we performed a series of field experiments to test the hypothesis that the presence of ants on EFNs located at the base of the inflorescences of Vigna luteola (Fabaceae) may have a negative effect on floral visitors but not on potential pollinators in a Mexican coastal sand dune. In general, we found that the presence of ants on the plants decreased the rate of flower visitation. However, we observed that the time of visitation of the effective pollinators the bee (Pseudocentron) sp. on the flowers was less compared to that of other floral visitors. This strategy may allow that ants cannot aggressively scare away the effective pollinators. In summary, we show that the effective pollinators of V. luteola present strategies that allow them to visit the flowers without being aggressively attacked by the ants that visit the extrafloral nectaries (EFNs). Therefore, the presence of ants on plants could have a dual function: protecting plants against potential herbivores as well as, filtering flowers against nectar thieves.
To design conservation strategies, the extent of plant richness of tropical forests needs to be characterized in terms of their seed longevity. In this study, we examined the potential seed ...longevity, that is, storage ex situ, of species from south-eastern Mexico: Chamaedorea glaucifolia, Cymbopetalum baillonii, Magnolia mexicana, Nectandra coriacea, and Ternstroemia tepezapote. Immediately after collection, seeds were stored at different temperatures (≤23℃). We evaluated seed germination after different storage durations. Seed water content (WC) was determined for each period. Seed desiccation sensitivity was determined as WC50, which is the WC at which the initial seed viability decreases to 50%; further, the time required to reach WC50 was also determined. Subsequently, we analyzed the relations between seed functional traits with other morphological and functional traits, along with the weather characteristics of their respective habitat. All of the studied species had short-lived seeds; they exhibited desiccation sensitivity after storage with differences across the species. Additionally, C. baillonii exhibited differences in seed desiccation sensitivity across 2 years of seed collection. Interaction was observed between storage time and storage temperature: Seeds exhibited less deterioration at 15℃ in C. glaucifolia and C. baillonii and at 5℃ in M. mexicana and N. coriacea. Seed storage behavior is discussed in this article. Finally, a relationship determined between germination traits, and seed WC, embryo size, endosperm amount, and rain and temperature patterns in the month of seed dispersal explained the limited longevity of the studied species.
•Scientists using field stations work almost in isolation from the social contexts.•It is urgent to conduct research based on local people' needs and interests.•Local rural people are willing to have ...more interactions with scientists.•A linkage technician at each station can enhance communication with local communities.
Tropical ecosystems have been transformed at alarming rates provoking their transformation mainly into agricultural and pasturelands for cattle. This has drastically modified landscapes, the provision of ecosystem services, and thus human livelihoods. As a response to the need to preserve and study tropical forests, the National Autonomous University of Mexico created two research field stations around 50 years ago. Los Tuxtlas Tropical Biology Station located in a tropical rain forest on the southern coast of the Gulf of Mexico, and the Chamela Biological Station established in a tropical dry forest on the central Pacific coast. A significant amount of research has been conducted in both areas although one question that arises pertains to the impact these stations have had on the areas in which they are located. The aim of this paper is to analyze the scientific production of the research field stations and their relation to local information needs and interests, as well as to document local people's perspectives regarding their presence in their regions. Research methods included interviews and surveys with local communities, as well as analysis of the stations' databases. Although our results are preliminary, they show that from the identification of information needs and interests of local communities at each site (52 and 28 respectively), around 40% were not covered by existing knowledge. Furthermore, those fully or partially covered would need to be transformed into products accessible to rural communities. In both sites, local people expressed an interest in the work of the stations and particularly, they acknowledge possible benefits for their regions. If the goal is to reverse the degradation of ecosystems and mitigate environmental problems, field stations can no longer work in isolation but become agents of social transformation. It is necessary to revise how biological, ecological, and socio-ecological knowledge can be shared with people so that it is meaningful and useful for them. A linkage process between scientific institutions and local people should be strengthened in order for scientific knowledge to have a local impact on the long-term maintenance of tropical socioecological systems.
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