ABSTRACT
In several montane forests around the world, epiphytes coexist in mats, sharing the rhizosphere and forming histosol‐type soils rich in nutrients. The role of these epiphytes in the ...formation of canopy soil and the fitness costs that epiphytes face when cohabiting in these mats are unknown.
In a lower montane cloud forest in central Veracruz, Mexico, a 2‐year factorial experiment was carried out with the presence/absence of ramets of Phlebodium areolatum (Polypodiaceae), Tillandsia kirchhoffiana, T. multicaulis and T. punctulata (Bromeliaceae). We examined (i) which epiphyte species contribute to the formation of canopy soil, (ii) the role of epiphyte composition in the soil nutrient composition, and (iii) the fitness costs faced by epiphytes when cohabiting.
Canopy soil formation highest when P. areolatum is present. Soil nutrient content does not change with epiphyte composition, is influenced by the microbiota, and P content decreases with the presence of epiphytes. The fitness costs show that the species compete, decreasing their survival and growth, but the competitive capacity differs between the species.
We conclude that P. areolatum is an ecosystem engineer that promotes the creation of canopy soil but is a poor competitor. The results coincide with the model of succession by facilitation. Canopy soil is a slow‐created component whose nutrient content does not depend on the epiphytic flora. In epiphyte mats, the dominant interactions are competitive, but there is also facilitation.
Canopy soil formation depends on one fern species, and the species compete inside the canopy soil carpets.
Canopy soil (CS) volume reflect epiphyte community maturity, but little is known about the factors that retain CS or species succession within it. Humus fern species (e.g. Phlebodium areolatum) ...appear capable of retaining CS.
In ten Quercus spp. we sampled 987 epiphyte mats to examine the role of the common epiphyte species and crown traits determining CS volume, in order to infer successional stages and identify pioneer and late successional species. Branch traits (height, diameter and slope), CS volume and cover of the epiphyte species were determined for each mat. Nutrient content was determined in CS random samples of 12 epiphyte associations and sizes (one sample from each size quintile).
A total of 60% of the mats lack CS. Cover of P. areolatum was the main variable explaining CS volume, and this species was present in 46.8% of those with CS. Epiphyte composition was highly variable, but pioneer (species appearing in monospecific mats, without CS) and late successional species could be identified. Canopy soil nutrient content was similar among the associations of epiphytes. Magnesium, Ca and pH decreased with CS volume, while P and N increased.
Phlebodium areolatum is associated with high CS volumes and could act as a key species in its retention. Monospecific mats of pioneer species lack CS or have low volumes, while CS is much higher in mats with late successional species, but the mechanisms of CS formation and nutrient retention in response to interactions between epiphyte species remain to be tested.
In a tropical montane forest, the volume of canopy soil (CS) is mainly associated to a fern species (Phlebodium areolatum), suggesting that this species is an ecosystem engineering.
Aim For epiphytic plants trees are habitat units, and tree size determines epiphyte species richness. While growing, trees generate vertical microhabitats that are exploited by epiphytes. One would ...expect to find four different types of relationship between tree size and epiphyte species richness: positive linear (young trees), neutral (old trees), negative (old decaying trees) and positive asymptotic (trees of mixed size class in a mature forest). We tested these relationships in plots of colonizing sweetgum trees in pastureland, isolated remnant trees in pastureland (old oaks) and sweetgum and oaks in a pristine forest. Location The study was carried out in a landscape shaped by the fragmentation of lower montane cloud forest in San Andrés Tlalnelhuayocan (19° 30'56" N and 96° 59'50" W; 1500-1600 m a.s.l.) in central Veracruz, Mexico. Methods We measured the d.b.h. of all oaks and sweetgum trees (d.b.h. ≥ 5 cm) present in pastureland and in three 100 m2plots of a lower montane cloud forest. All trees were climbed and species richness of the epiphytes recorded. Results As expected, colonizer trees in pastureland showed a linear positive relationship. Although we found evidence that remnant oaks in pastureland had a neutral relationship between tree size and epiphyte species richness, the low power of the test did not allow us to make conclusions about the kind of relationship. Mixed size-class pristine forest trees showed a positive linear relationship between tree size and epiphyte species richness instead of a positive asymptotic one. Main conclusions Our results suggest that in the study area epiphyte communities are unsaturated, as the number of species increases with tree size and does not reach a ceiling. This evidence supports the idea that the species-area relationship is not asymptotic. However, the epiphyte community on remnant pastureland oaks may be saturated as epiphyte species richness did not increase with tree size, but a larger sample size is needed to confirm the neutral pattern. Neutral, asymptotic and negative patterns in the relationship between tree size and epiphyte species richness depend on the saturation of the trees by epiphytes. Other studies have suggested tree saturation, but further research is necessary in order to confirm or rule out these patterns.
Most plants that inhabit ant-gardens (AGs) are cultivated by the ants. Some orchids occur in AGs; however, it is not known whether their seeds are dispersed by AG ants because most orchid seeds are ...tiny and dispersed by wind. We performed in situ seed removal experiments, in which we simultaneously provided Azteca gnava ants with seeds of three AG orchid species and three other AG epiphyte species (Bromeliaceae, Cactaceae and Gesneriaceae), as well as the non-AG orchid Catasetum integerrimum. The seeds most removed were those of the bromeliad Aechmea tillandsioides and the gesneriad Codonanthe uleana, while seeds of AG orchids Coryanthes picturata, Epidendrum flexuosum and Epidendrum pachyrachis were less removed. The non-AG orchid was not removed. Removal values were positively correlated with the frequency of the AG epiphytes in the AGs, and seeds of AG orchids were larger than those of non-AG orchids, which should favour myrmecochory. Our data show that Azt. gnava ants discriminate and preferentially remove seeds of the AG epiphytes. We report for the first time the removal of AG orchid seeds by AG ants in Neotropical AGs.
Symptoms of depressive disorders such as anhedonia and despair can be a product of an aberrant adaptation to stress conditions. Chronic unpredictable stress model (CUS) can generate an increase in ...the activity of the hypothalamic-pituitary-adrenal axis (HPA) and induce a reduction of neurotrophin signaling and the proliferation of neural progenitors in the adult dentate gyrus, together with increased oxidative stress. Levels of the endocannabinoid anandamide (AEA) seem to affect these depression-by-stress-related features and could be modulated by fatty acid amide hydrolase (FAAH). We aimed to evaluate the effects of FAAH inhibitor, URB597, on depressive-like behavior and neural proliferation of mice subjected to a model of CUS. URB597 was administered intraperitoneally at a dose of 0.2 mg/kg for 14 days after CUS. Depressive-like behaviors, anhedonia, and despair were evaluated in the splash and forced swimming tests, respectively. Alterations at the HPA axis level were analyzed using the relative weight of adrenal glands and serum corticosterone levels. Oxidative stress and brain-derived neurotrophic factor (BDNF) were also evaluated. Fluorescence immunohistochemistry tests were performed for the immunoreactivity of BrdU and Sox2 colabeling for comparison of neural precursors. The administration of URB597 was able to reverse the depressive-like behavior generated in mice after the model. Likewise, other physiological responses associated with CUS were reduced in the treated group, among them, increase in the relative weight of the adrenal glands, increased oxidative stress, and decreased BDNF and number of neural precursors. Most of these auspicious responses to enzyme inhibitor administration were blocked by employing a cannabinoid receptor antagonist. In conclusion, the chronic inhibition of FAAH generated an antidepressant effect, promoting neural progenitor proliferation and BDNF expression, while reducing adrenal gland weight and oxidative stress in mice under the CUS model.
Tropical montane cloud forest is one of the most threatened ecosystems, in central Veracruz, Mexico. Within this ecosystem, terrestrial orchids are strongly dependent on forest conditions and may be ...sensitive to environmental change. We applied field surveys of abiotic and biotic factors associated with the presence of the terrestrial orchid Cyclopogon luteo‐albus and combined this with correlative niche modeling approaches to evaluate its potential distribution under two different environmental sets and two different extents. Layers of environmental information were obtained from Landsat imagery and interpolated bioclimatic and soil property layers. Existing species records were used as training data by sampling five forest fragments in central Veracruz, utilizing herbarium and global biodiversity information facility databases. The resulting predictions were tested by sampling at 15 sites of potential distribution. The model predicted the presence of C. luteo‐albus with a reliability of 80%. The most important variables of models derived from interpolated layers coincide with site‐relevant parameters suggesting the utility of these tools to further explore species suitabilities at larger geographic extents. Potential distribution mapping is an important tool to identify key areas for conservation and priority areas for future studies of species and partially resolves the lack of records of many orchid species.
Several plants of the Fabaceae family have been assessed regarding their high nutritional value and anthelmintic properties. The ovicidal effect of the hydroalcoholic extract (Bm-HAE) and ...subfractions from the aerial parts of Brongniartia montalvoana (Fabaceae) against a mixed strain of gastrointestinal nematodes (GIN) (Haemonchus spp., Trichostrongylus spp. and Oesophagostomum spp.) resistant to albendazole sulfoxide, ivermectin and levamisole was evaluated by the egg hatch test (EHT). The Bm-HAE was subjected to liquid-liquid chemical separation with ethyl acetate giving two fractions, an aqueous (Bm-Aq) and an organic (Bm-EtOAct). The purification of the bioactive fraction (Bm-EtOAct) through chromatographic separation resulted in four bioactive subfractions (BmR6, BmR7, BmR8 and BmR10). The treatments were designed as follows: Bm-HAE at 800, 1,500, 3,000 and 6,000 μg/mL, and Bm-Aq, Bm-EtOAct and subfractions (BmR6, BmR7, BmR8 and BmR10) at 100, 200, 400 and 800 μg/mL. Two properly negative controls (distilled water and 2% methanol) and thiabendazole (100 μg/mL) as a positive control were used for each bioassay. The chemical identification of the extract, fractions and subfractions was performed through chromatographic processes like open column chromatography, thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC-PDA). Additionally, the GIN eggs exposed to the bioactive compounds were observed through confocal laser scanning microscopy (CLSM). The Bm-HAE showed 99.5% egg hatching inhibition (EHI) at 6,000 μg/mL with a lethal concentration (LC50) of 1110 μg/mL. The Bm-EtOAc fraction displayed 99.1% EHI at 800 μg/mL with LC50 = 180 μg/mL. The ovicidal activity of the four subfractions was similar at 800 μg/mL: BmR6 (92% EHI); BmR7 (100% EHI); BmR8 (97.8%); and BmR10 (99.1%). The HPLC-PDA analysis of the bioactive subfractions allowed identification of p-coumaric acid, ferulic acid and coumarin derivatives as major compounds. The CLSM analysis allowed observation of morphological alterations in unhatched larvae caused by bioactive compounds present in the Bm-EtOAc and BmR10. In addition, the flavonoids eriodyctiol, luteolin and cynaroside were described for the first time for B. montalvoana.
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•Brongniartia montalvoana showed ovicidal activity against multi-drug resistant GIN.•The morphology of unhatched larvae was strongly affected by the organic fraction.•Coumarins, ferulic acid and p-coumaric acid were detected in active subfractions.•Three flavonoids were described for the first time for B. montalvoana.•Colocalization between compounds and larvae fluorescence was observed.
Questions: Ant-gardens (AGs) involve a close association between epiphytes and ants with concurrent mutualistic interactions including protection, dispersal and nutrition; however, little is known ...about the spatial structure patterns that determine their establishment and formation. Our main questions were: (1) do AGs have a particular pattern of vertical distribution on their host trees; (2) does a process of succession of epiphytes occur during development of AGs; and (3) are epiphytes segregated in AGs? Location: Anthropic landscape in southeast Mexico. Methods: We studied AGs built by Azteca gnava ants. We examined their vertical distribution on host trees as well as the diversity, composition and reproductive status of vascular epiphytes associated with the lower, middle and upper zones of small, medium and large AGs. Results: A total of 859 AGs and 10 871 epiphytes, belonging to 26 different species, were recorded. We found that AGs are primarily (75%) located within tree crowns, and that the diversity and composition of epiphytes vary among AG sizes and among AG zones. We infer that the epiphytes that first become established in AGs are the bromeliad Aechmea tillandsioides and the gesneriad Codonanthe uleana, followed by the orchid Epidendrum flexuosum and the cactus Epiphyllum phyllanthus; these species were recorded, either individually or in cooccurrence, in 74% of the AGs examined. The species Ae. tillandsioides, Coryanthes picturata and Epid. flexuosum were most frequent in the upper AG zone, while Epid. pachyrachis was most frequent in the middle AG zone. Conclusions: Our results show that AGs have distinct vertical distribution patterns on their tree hosts and that the establishment of epiphytes in AGs is successive and segregated, suggesting spatial and temporal optimization in the establishment and development of these complex mutualistic systems.
Abstract
Aims
Habitat loss and fragmentation are the main threats to biodiversity in tropical forests. Agroecosystems such as shaded cocoa plantations (SCP) provide refuge for tropical forest biota. ...However, it is poorly known whether the interspecific ecological interactions are also maintained in these transformed habitats. We evaluated the diversity, reproductive status and photosynthetic metabolism (CAM or C3) of the epiphytic orchid community, and their interactions with host trees (phorophytes) in SCP compared to tropical rainforest (TRF).
Methods
In southeastern Mexico, three sites each in TRF and SCP were studied, with four 400 m2 plots established at each site to record all orchids and their phorophytes. We determined the reproductive (adult) or non-reproductive (juvenile) status of each orchid individual in relation to the presence or absence, respectively, of flowers/fruits (or remnants), and assigned the photosynthetic pathway of each orchid species based in literature. We used true diversity and ecological networks approaches to analyze orchid diversity and orchid–phorophyte interactions, respectively.
Important Findings
In total, 607 individuals belonging to 47 orchid species were recorded. Orchid diversity was higher in TRF (19 effective species) than in SCP (11 effective species) and only seven species were shared between the two habitats. CAM orchid species were more frequent in SCP (53%) than in TRF (14%). At the community level the proportion of non-reproductive and reproductive orchid species and the nested structure and specialization level of the TRF orchid–phorophyte network were maintained in SCP. However, only a subset of TRF epiphytic orchids remains in SCP, highlighting the importance of protecting TRF. Despite this difference, shaded agroecosystems such as SCP can maintain some of the diversity and functions of natural forests, since the SCP epiphytic orchid community, mainly composed of CAM species, and its phorophytes constitute a nested interaction network, which would confer robustness to disturbances.
Habitat isolation is one of the most important factors endangering the biodiversity, but little research has been done with vascular epiphytes. In order to understand the effect of isolation on the ...epiphyte community, we studied epiphyte diversity on three plots in a forest fragment, two riparian forest fragments, and in isolated pastureland trees. We found 118 vascular epiphyte species. On forest plots, both epiphyte richness per tree (Stree) and species turnover rate within trees (βtree) registered the highest values, although the lowest Stree diversity was also found there; additionally inside the forest were host species with clearly different epiphyte community. Stree and βtree diversities of riparian fragments behaved similarly to those of the forest. Isolated trees had the second highest Stree diversity, although their βtree diversity was the lowest. In the forest plots were both, the highest and lowest expected accumulated richness (α diversity); on riparian fragments it was intermediate, and the second lowest α diversity was registered for isolated trees. Species turnover rate among plots (β) was high and was associated with both, isolation and a distance gradient from permanent water sources. The epiphyte community on isolated trees was clearly different to the other habitats. Results suggest that deforestation eliminated dry areas and specific hosts that were important for the maintenance of epiphyte species richness. In pastureland trees the epiphyte βtree diversity diminished, suggesting a simplification of the environment for epiphytes and causing a low α diversity.
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