Dry Forest Species Research Articles

Antagonistic interaction networks in a native and an exotic legume species in Colombian tropical dry forest

Las interacciones entre plantas y animales desempeñan un papel fundamental en el funcionamiento y la estructura de los ecosistemas. Se espera que las comunidades de insectos asociados a semillas sean muy específicas para cada especie de planta debido a la gran cantidad de barreras físicas y químicas que las semillas imponen a los herbívoros. Además, las especies leguminosas, el taxón vegetal dominante en el bosque seco tropical, ofrecen una gran cantidad de recursos para la especialización de insectos, estructurando comunidades especiliazadas de herbivoros. Sin embargo, la introducción de especies exóticas en este ecosistema puede reducer la diversidad y simplificar las interacciones. Mediante el análisis de redes ecológicas, comparamos la diversidad y estructura de los insectos asociados a las semillas y sus parasitoides entre la especie de leguminosa nativa Pseudosamanea guachapele y la leguminosa exótica e invasora Leucaena leucocephala. También evaluamos las diferencias en la composición química de semillas con el fin de determinar en qué medida ésta podría ayudar a explicar las diferencias en las comunidades de insectos asociadas. El estudio se llevó a cabo en un bosque seco tropical en el departamento de Tolima, Colombia. Encontramos siete especies de escarabajos y ocho especies de parasitoides. Las redes de interacción de insectos de ambas especies de plantas tenían baja conectividad, anidamiento, generalidad y vulnerabilidad. Leucaena leucocephala tuvo la mayor diversidad de escarabajos y parasitoides en comparación con P. guachapele, tal vez porque L. leucocephala produce semillas durante todo el año, mientras que P. guachapele tiene una estacionalidad marcada produciendo frutos sólo durante uno o dos meses del año. Identificamos un total de 26 compuestos en las semillas de los dos huéspedes. Las semillas de P. guachapele, tienen el doble de compuestos que las de L. leucocephala. Entre las principales diferencias entre la composición de las semillas de la planta hospedera se encuentran la composición de ácidos grasos, que ofrecen diferentes fuentes de colesterol para el desarrollo de insectos. Esto puede ayudar a explicar la presencia de especies de consumidores de semillas asociadas a cada planta. Es importante resaltar que las redes descritas aquí pueden cambiar a través del tiempo y los paisajes, haciendo interesante seguir analizando la variación en la riqueza y estructura de dichas redes con el fin de definir hasta qué punto las interacciones encontradas en este estudio se mantienen constantes.

A synopsis of Byttnerieae (Malvaceae, Byttnerioideae) from the Atlantic Forest, with notes on geographical distribution, nomenclature, and conservation

This synopsis presents diagnostic characters and comments on morphological variability, distribution, and conservation of species of Byttnerieae (Malvaceae, Byttnerioideae) from the Atlantic Forest. Byttnerieae is represented by species from two allied genera in this phytogeographic domain: Ayenia L. and Byttneria Loefl. An extensive literature survey along with herbarium collection analyses revealed the occurrence of 20 species in the Atlantic Forest, nine of which are endemic to Brazil. Seven species are restricted to the Southern portion of the Atlantic Forest, i.e., occurring from southern São Paulo state to the state of Santa Catarina, with most records being in Brazil, but some species also occur in Argentina and Paraguay. Beyond the Southern portion of the Atlantic Forest, three species are restricted either to the state of Rio de Janeiro or to Bahia, in Brazil. An identification key focusing on vegetative characters, as well as illustrations and notes on species distribution and conservation, are presented. Nomenclatural comments or updates for some taxa were provided, including: the designation of lectotypes for six names; the amendment of authorship of one name (B. gracilipes); and reassessment of the distribution of A. glabrescens, an endemic species of dry deciduous forests of Bahia whose precise location was unknown.

The importance of wood density in determining the phenology of tree species in a coastal rain forest

AbstractThe phenology of tree species in tropical dry forests is related to a well‐characterized interaction between functional traits (e.g., wood density) and climatic seasonality (e.g., drought stress), but the existence of these relationships in tropical wet forests is largely unknown. For 12 months, we monitored the vegetative and reproductive phases of 281 individuals of 46 tree species in a coastal rain forest in Northeastern Brazil. We hypothesized that wood density and related tissue water storage would reliably distinguish phenological groups of trees, and that leaf shedding, flushing, and flowering in high wood density species would be closely related to rainfall, due to low tissue water storage capacity in these species. By contrast, we predicted leaf unfolding and flowering of low wood density species would depend exclusively on photoperiod. As predicted, wood density and saturated water content were inversely correlated, and species with either high or low wood density had distinct phenological patterns and levels of synchrony within species. Abiotic variables were not strongly associated with phenological events. Phenophases of leaf unfolding, flowering, and fruiting occurred earlier in low wood density species than in high wood density species, possibly indicating an adaptive strategy for preemptive resource capture.Abstract in Portuguese is available with online material.

Effect of forest fragmentation and disturbance on diversity and structure of woody species in dry Afromontane forests of northern Ethiopia

Anthropogenic disturbance and fragmentation have changed the structure and composition of northern Ethiopian forests. This study was conducted to determine disturbance levels of patches, and examine the effect of anthropogenic disturbance and fragment size on diversity and structural attributes of woody species. A systematic sampling method was used to collect data and 61 nested plots of each 400 m2 were used. The disturbance index was used to assess disturbance intensities. To examine the effects of fragment size and anthropogenic disturbances on woody species diversity and structure, regression analysis was performed. ANOVA was used to examine differences in woody species diversity and structural attributes among fragments. Similarities among patches were assessed by Sorensen’s similarity index. A total of 80 woody species, representing 68 genera and 43 families were recorded. Diversity, evenness, stem density ha−1, and basal area were 2.8 ± 0.47, 0.73 ± 1.10, 1171.21 ± 220.10, and 39.89 ± 17.47 m2 ha−1 respectively. The mean number of species, evenness, and diversity were significantly different among fragments. Diversity, evenness, the mean number of species, and stem density per hectare significantly increased with increasing fragment size. Disturbance intensities varied among fragments. However, the mean basal area, mean seedling, and sapling density per hectare were not significantly affected by patch size and disturbance intensities. Generally, forest fragmentation and anthropogenic disturbance resulted in the reduction of diversity, affect woody species structure, and increased the level of disturbance. Therefore, recognizing the role of small fragments for forest conservation, minimizing further disturbance, and undertaking restoration activities in disturbed patches are strongly needed.

Diversity of Eusocial Bees in Natural and Anthropized Areas of a Tropical Dry Forest in the Parque da Sapucaia (Montes Claros, Minas Gerais, Brazil)

In the present study we inventoried the diversity of eusocial bees (Hymenoptera: Apidae) in preserved and anthropized areas of a tropical dry forest in the Parque da Sapucaia (Montes Claros, Minas Gerais, Brazil). We tested the hypothesis that the diversity of bee species would: 1) be greater in the preserved areas, 2) respond positively to the structure of the vegetation and 3) decrease during the dry season. We sampled eusocial bee species in 18 plots of 10 x 10 m distributed throughout the park, being nine plots in anthropized areas and nine plots in areas with preserved vegetation. In total we recorded 382 individuals and eight species of eusocial bees. The most abundant species was Oxytrigona tataira (Smith) (N = 233) and the most common species was Trigona spinipes (Fabricius) recorded in 72.2% of the plots. As expected, we found that eusocial bee diversity (Shannon diversity) was higher in preserved plots than in anthropized plots. Tree species richness positively affected bee species richness and abundance, while tree abundance positively influenced the bee abundance and tree height positively affected the bee Shannon diversity, corroborating our expectations. On the other hand, we detected no differences in the diversity of eusocial bees between dry and rainy seasons. Our findings suggest that both natural (vegetation structure) and anthropogenic (habitat modification) factors are important predictors of the diversity of eusocial bee species in tropical dry forests.

Lianas have more acquisitive traits than trees in a dry but not in a wet forest

Abstract Lianas are increasing in relative abundance and biomass in many tropical forests. We tested the hypothesis that lianas conform to the fast and acquisitive end of the continuum of plant strategies, allowing lianas to acquire resources faster than trees. We assessed functional traits representative of the leaf (LES) and wood economics spectrum (WES), including plant hydraulics, in 16 liana and 16 tree species in the canopy of two tropical forests at the extremes of the climatic and geological gradient across the Isthmus of Panama. For both forests, we observed a trade‐off between the construction of more productive leaves with rapid turnover and expensive leaves with slower turnover. We also found trait variation associated with wood and hydraulic traits. These two axes were orthogonal, suggesting that trade‐offs at the leaf and stem, including plant hydraulics, operate independently. For the dry forest, lianas had cheaper and more efficient leaves than trees. For the wet forest, lianas and trees overlapped in leaf and stem characteristics. Moreover, the duration of green foliage highly explained the variation between dry forest species, reflecting different adaptations to drought. In the wet forest, fast‐growing species benefited from a higher return on investments of leaf vascular tissues than slow‐growing species and they had a higher capacity to transport water through the leaf. A higher capacity to construct more productive leaves and display leaves with lower costs may favour lianas over trees in light interception, photosynthetic rates, and growth under high light and nutrient availability in dry forests. Synthesis. Lianas in a dry tropical forest had a more acquisitive strategy than trees, characterized by more productive leaves and more efficient display for light interception. In dry environments, lianas appear to benefit from high‐light and nutrient‐rich soils and thus take advantage of higher resource conditions compared to trees. By contrast, in a wet tropical forest, lianas and trees overlapped in leaf and stem characteristics and lianas were not more acquisitive than trees. In wet environments, low light availability and nutrient‐poor soils in a context of low water limitation may constrain variation in resource acquisition strategies between lianas and trees.

Dynamic seed zones to guide climate-smart seed sourcing for tropical dry forest restoration in Colombia

Tree-based forest landscape restoration interventions require knowledge on the suitability and origin of seed sources and planting material. A common recommendation is to select locally sourced material based on the assumption that it is well adapted to local environmental conditions and to avoid introduction of maladapted genes. However, faced with accelerating climate change, it may be prudent to supplement local provenances with ‘climate-matched’ provenances, i.e. where current climate conditions are similar to those anticipated in the future at the planting site. Restoration practitioners usually do not have access to the necessary information to implement such climate-smart seed sourcing. Here, we combine genetic data of 11 socio-economically important tree species of the tropical dry forests of Colombia with spatial environmental data to inform the delineation of dynamic seed zones for the restoration of this highly threatened ecosystem. Analysis of Molecular Variance (AMOVA) indicates significant population genetic differentiation within all 11 species. We fitted linear mixed effects models to evaluate if the genetic distance between trees was mainly related to geographic distance (i.e. isolation by distance; IBD), environmental distance (i.e. isolation by environment; IBE), or both. Observed scales of genetic differentiation were best explained by the model including both geographic and environmental distance (IBD + IBE) for 6 out of 11 species, and by the IBE model for the remaining species, suggesting that the observed differentiation is at least partly driven by adaptive processes. Aiming at capturing as much as possible of the observed genetic differentiation, we propose a set of 36 provisional seed zones that are applicable across species and dynamic under climate change, based on the clustering of environmental data and geographical coordinates. We project these seed zones to future climate conditions using five general circulation models and two emission scenarios, and discuss how they can be used to implement different climate-smart seed sourcing strategies in a pragmatic way. The seed zone maps are made available in a user-friendly online tool.

Identification of spectral features in the longwave infrared (LWIR) spectra of leaves for the discrimination of tropical dry forest tree species

With the emergence of longwave hyperspectral imaging systems, studies are revealing the potential of these data for discriminating tree species. However, few studies have applied statistical methods of band selection to select and characterize features at the species level that can then be used for improved classification. A dataset of leaf spectra was recently collected in-situ from twenty-six tree species in a Costa Rican tropical dry forest. The spectra of the species present overall low contrast and a range in spectral shapes, with some species displaying spectral similarity. This motivates our study to explore the performance of band selection tools to help identify key spectral features for the classification of these species.The bands selected using an ensemble of multiple methods improved the Logistic Regression classification performance by 3% in comparison to a result without band selection. The multiple methods encompassed the random forest, minimum redundancy maximum relevance and n-dimensional spectral solid angle methods. Bands selected by the ensemble methods agree well with the features previously identified based on expert knowledge and can be understood in the context of leaf constitutional compounds and related spectral features. The longwave hyperspectral bands or features identified in this study can potentially assist the future image mapping of tree species at large scales. The ensemble strategy is recommended for the band analysis of vegetation for its highest accuracy and stability.

Heat shock effects on germination and seed survival of five woody species from the Chaco region

In tropical dry forests, fire is a common disturbance and seed traits may drive regeneration of plant populations during these events. In this study, we aimed to (i) investigate whether the seed coat and/or fruit endocarp impose physical dormancy, (ii) check whether physical dormancy confers seed tolerance to heat shocks and (iii) verify whether heat shocks break physical dormancy among woody species. Seeds were collected from five native species of dry forests occurring within the Argentine Chaco: Aspidosperma quebracho-blanco, Sarcomphalus mistol, Schinopsis lorentzii, Prosopis nigra and Vachellia aroma. Initial seed viability was checked by the tetrazolium test before treatments. Heat shocks of 80, 110, 140, and 170 °C simulating a fire event were applied to the seeds for five minutes. Controls consisted of untreated seeds subjected or not to scarification. After heat shock treatments, the seeds were incubated in a germination chamber set at 30 °C under a photoperiod of 12 h (white light). After 35 days, non-germinated seeds were scarified, and after more 55 days the remaining seeds were checked for their final viability. Seed coat does not arrest germination in seeds of A. quebracho-blanco and showed germination after heat shock of 80 °C. Seeds of S. mistol present a fruit wall-imposed dormancy, but barely tolerated heat shock of 80 °C. S. lorentzii present seed dormancy, but not imposed by the seed coat since scarification was ineffective to promote germination; its seeds do not tolerate heat shock. Seeds of P. nigra present endocarp-imposed dormancy, and they germinate after heat shock of 80 °C. Seeds of V. aroma present coat-imposed physical dormancy, and they tolerate heat shock of 80 and 110 °C, but these treatments did not alleviate dormancy. Seed viability among non-germinated seeds after heat shocks were close to zero, revealing a low tolerance to high temperatures. Overall, seed coats did not protect seeds from the damaging effects of heat shock, and heat shock treatments did not break coat- or endocarp-imposed dormancy among the selected species. The heat sensitivity presented by the diaspores suggests that frequent wildfires may reduce their recruitment rates, compromising the maintenance of genetic diversity and the current distribution of their natural populations over the Chaco region.

Preliminary assessment of the conservation status of timber species in the threatened piedmont dry forest of northwestern Argentina

The piedmont dry forest of northwestern Argentina has been under intensive and unplanned forest logging focused on 12 tree species, without any attempts having been made to ensure their regeneration or long-term conservation. In this study, we assessed the conservation status of these timber species in the piedmont dry forest of northwestern Argentina and compared our results with the IUCN assessment. We considered an inadequate conservation status if the species: (1) occurred in less than 50 % of the sampled plots, (2) had a density of large trees (more than 40 cm DBH) lower than one in. ha−1, or (3) had a density of saplings (more than 30 cm in height and less than 9.9 cm in DBH) lower than 30 in. ha−1. Our results showed an inadequate conservation status for eight of the 12 studied timber tree species. Additionally, only seven species were previously assessed and categorized on the IUCN Red List, with our categorization agreeing with only four of them. The data provided in this work can serve as a baseline to monitor the population trends of these species; information can also help to prioritize conservation efforts, which is essential considering the high number of tree species that have potential extinction risk in the short-term.

VARIACIÓN DEL NÚMERO DE SEMILLAS EN FRUTOS DE 156 ESPECIES LEÑOSAS DEL ECUADOR

The functional study seeds traits allows us to increase our knowledge about the morphology and reproductive biology in tropical environments. However, seeds traits in forest plants have been poorly evaluated. The objective of this work was to determine the variation in seeds number per fruit in 156 woody species distributed in different habitats of Ecuador. For that, between five and ten fruits were collected from five individuals per species. The seeds number obtained in the fruits was extracted and quantified and it was related to the fruit type, habit, and species. The results showed that the species present from one to more than 400 seeds per fruit. However, the tendency of 57% of woody species is to produce less than 10 seeds per fruit. This trait showed a greater range of variation in the amount of seeds per fruit between the wet and dry forest species. However, there is not significant differences they were evidenced with the fruit type and species habit.

Evidence for the Pleistocene Arc Hypothesis from genome-wide SNPs in a Neotropical dry forest specialist, the Rufous-fronted Thornbird (Furnariidae: Phacellodomus rufifrons).

South American dry forests have a complex and poorly understood biogeographic history. Based on the fragmented distribution of many Neotropical dry forest species, it has been suggested that this biome was more widely distributed and contiguous under drier climate conditions in the Pleistocene. To test this scenario, known as the Pleistocene Arc Hypothesis, we studied the phylogeography of the Rufous-fronted Thornbird (Phacellodomus rufifrons), a widespread dry forest bird with a disjunct distribution closely matching that of the biome itself. We sequenced mtDNA and used ddRADseq to sample 7,167 genome-wide single-nucleotide polymorphisms from 74 P.rufifrons individuals across its range. We found low genetic differentiation over two prominent geographic breaks - particularly across a 1,000km gap between populations in Bolivia and Northern Peru. Using demographic analyses of the joint site frequency spectrum, we found evidence of recent divergence without subsequent gene flow across those breaks. By contrast, parapatric morphologically distinct populations in northeastern Brazil show high genetic divergence with evidence of recent gene flow. These results, in combination with our paleoclimate species distribution modelling, support the idea that currently disjunct patches of dry forest were more connected in the recent past, probably during the Middle and Late Pleistocene. This notion fits the major predictions of the Pleistocene Arc Hypothesis and illustrates the importance of comprehensive genomic and geographic sampling for examining biogeographic and evolutionary questions in complex ecosystems like Neotropical dry forests.

Climate-growth relationships for Aspidosperma tomentosum Mart. in South American tropical dry forests

The precise demarcation and cross-dating of tree rings in Aspidosperma tomentosum Mart., a valuable timber species in the tropical dry forests of South America, were used to develop the first well-replicated chronology covering the period 1843–2015. A. tomentosum Mart. tree growth is strongly regulated by soil water availability prior to and during the current growing season. In the context of increased drought severity due to climate change, determining of climate influences on A. tomentosum Mart. radial growth is necessary to establish appropriate guidelines for the management, conservation and restoration of this species, currently affected by extreme weather events, extensive fires and deforestation in the Chiquitania forests, Bolivia. Tropical forest ecosystems play a critical role in the functioning of the Earth; thus, a better understanding of the influences of climate on tree growth is needed to estimate changes in forest productivity and consequently in carbon sink variations at regional and global scales. In the context of global environmental changes, our study aimed at using the growth rings of A. tomentosum Mart. to establish the relationships between radial growth and climatic variations. The anatomical characterization of the wood elements facilitated the precise annual band delimitation and the rejection of samples with false rings and growth anomalies. A tree-ring chronology was developed using traditional dendrochronological methods and the relationships with climate determined using correlation functions. The chronology is based on 20 individuals and covers the period 1843–2015. Tree-ring statistics indicate an important common signal in growth variations between trees (R-bar = 0.31, EPS = 0.90). Interannual variations in A. tomentosum Mart. are directly related to total annual precipitation (r = 0.76) and inversely to mean annual temperature (r = − 0.44). These relationships are similar to those documented for other commercial species (Centrolobium microchaete, Schinopsis brasiliensis) from tropical dry forests in South America, suggesting a consistent climatic influence on tree growth at a regional scale. The strong dependence of tree growth on climate variability is a major concern, as climate change scenarios for tropical dry forests in South America predict an increase in the frequency and intensity of droughts, which in turn would reduce the A. tomentosum Mart. growth during the twenty-first century.

Environmental filtering both indirectly and directly drives the Dry Tropical Forest species composition and functional composition

AbstractSoil is a relevant driver of taxonomic, functional and phylogenetic composition at local scales. However, the mechanisms by which the soil act in these components or how these components interact with each other are not elucidated. Herein, we propose to understand the role of soil (environmental filtering) on the turnover of taxonomic and phylogenetic components and their role in determining the functional composition of Seasonally Dry Tropical Forest (SDTF) communities. We sampled all the arboreal individuals with Diameter at Breast Height equal to or higher than 3 cm and collected soil variables of 25 units from five SDTF fragments located in the Brazilian Caatinga Domain. These data enabled us to obtain the taxonomic, functional and phylogenetic composition of each plot, which were then analyzed by Structural Equation Models jointly with the soil variables. Our results suggest that the soil conditions select specific phylogenetic lineages from a regional species pool according to the adaptive potential, which affects the distribution and abundance of species (taxonomic composition). However, it was not possible to establish a direct relationship between the phylogenetic composition and the taxonomic composition, possibly due to the use of labile functional traits in the analysis. We also found that soil acts directly on the functional composition, leading to a differential success of individuals which would represent a direct and indirect effect of taxonomic composition on the functional composition. Thus, we found community aspects result from different ecological mechanisms which act in a continuous and progressive way between functional, phylogenetic and taxonomic composition.

Rasgos funcionales de la madera de tres bosques en Colombia: Bosque Seco, Andino y Alto-Andino

This research analyzed twelve (12) wood functional traits in 144 species of three forests in Colombia. The traits were classified according to their incidence in the functions of storage, support and conduction in the xylem. The conduction relations in the three forests suggest that when the pores diameter is big, its density decrease, and at the same time the pits diameter increase, as a strategy to guarantee exchange between vessels. The tracheid length is related to the fibers length and the pores diameter, because the tracheids fulfill both functions: conduction and support. Tracheids are only in the Andean and High Andean Forest species. The species of the High Andean Forest have long and wide rays allowing greater storage capacity and horizontal conduction. In the Andean Forest species, the fibers length and tracheids length were higher. The Dry forest species had the highest wood densities, however, the values of fiber length and thickness fiber were the lowest, reducing their support capacity. Six functional plant types (TFPs) are established and described from the evaluated traits.

Novelties in Brazilian Waltheria L. (Byttnerioideae, Malvaceae): two new species and one re-establishment

This work validates two Waltheria species endemic to campo rupestre with complete descriptions, illustrations, updated geographical distributions and comments on taxonomic affinities. Waltheria biribiriensis and Waltheria terminans are restricted to the Southern Espinhaço Province in eastern South America, occurring on mountain tops where campo rupestre vegetation prevails. Furthermore, Waltheria brachypetala, a species of dry deciduous forests in Brazil that was long considered as conspecific with W. ferruginea due to its shrubby lifeform and similar indumentum, is re-established based on differences of phyllotaxy, blade shape and inflorescence type. The first occurrence records of W. brachypetala in the state of Paraíba are also provided, as well as the first record in the Atlantic Forest domain. Lastly, a lectotype is designated for W. ferruginea.

Post-fire resprouting capacity of seasonally dry forest species – Two quantitative indices

Qualitative measures of resprouting capacity often fail to capture inter- and intra-species variation, whereas available quantitative methods can be complex and time-consuming, hindering broad-scale comparative studies. Here, we propose two quantitative indices that can be applied in a standard way in different regions. We sampled 1046 plants of 20 dominant species (6 shrubs, 7 trees and 7 tree/shrubs) from the seasonally dry forests of the arid Chaco, central-western Argentina. Sampling was conducted in burned field sites one growing season after fire. For each sampled plant we measured the diameter of the main burned trunk (MTD) and main resprout (MRD), and the number of burned trunks (TN) and resprouts (RN); we then built estimated composite diameters for trunks and resprouts (ECTD and ECRD) and we calculated two alternative Resprouting Capacity Indices: RCI 1 (ECRD/ECTD); and RCI 2 (MRD/MTD). The indices were validated against a measure of Resprouting Vigour (RV) that included detailed measurement of all trunks and resprouts for a subset of sampled plants. In all cases, variables indicative of fire severity were measured and included in the analyses. The RCIs and RV were highly related, both at the species and growth form levels. Fire severity had no significant effect on these relationships, but growth form affected RCI 2. All species were capable of resprouting, showing considerable inter-species variation for the two proposed RCIs. Species rank differed considerably between RCIs and survival-only estimations. RCI 1 was higher in tree/shrubs (i.e. species regarded as trees or shrubs) and trees than in shrubs. All species showed decreasing resprouting capacity with increasing ECTD. Our results support the use of the proposed RCIs as a robust tool to assess resprouting capacity, providing more details than survival-based assessments. Choosing one or the other implies a trade-off between accuracy and simplicity, and may depend on the scale and objective of the study, and resprouting patterns of studied species. Species, growth form and individual plant size are relevant in explaining post-fire resprouting capacity and survival.

Dispersal syndrome influences the match between seed rain and soil seed bank of woody species in a Neotropical dry forest

AbstractAimsPlant recruitment may occur immediately after seed dispersal from the mother plant, or be delayed through the formation of soil seed banks. These strategies are known to be mediated by adaptations of seed dispersal and reproductive phenology, which if analyzed together can provide valuable information about the regeneration strategies of species. We explored whether dispersal syndrome and/or seed dispersal phenology control the similarity between standing vegetation, seed rain and soil seed bank in a seasonally dry tropical forest (SDTF) in Southern Ecuador.LocationArenillas Ecological Reserve, Southwestern Ecuador, the biogeographic region of Pacific Coastal Ecuador.MethodsWe recorded standing vegetation of woody species in a 9‐ha permanent plot and sampled soil seed bank from 265 cores of 0.06 m2. Additionally, we sampled seed rain from 265 seed traps of 0.64 m2 for one year. We evaluated similarity in species composition, species richness, and abundance between the three components for all species and for each dispersal syndrome.ResultsThe community we studied showed a high similarity in species composition between components. The similarity was influenced by dispersal syndrome and the seed dispersal phenology. Similarity between seed rain and standing vegetation was high in species that dispersed in the rainy season, such as zoochorous species, while for autochorous species, compared with the other dispersal syndromes it was higher between seed bank and standing vegetation.ConclusionsIn our SDTF, dispersal phenology seemed to influence whether seeds had direct germination or entered the soil seed bank and influenced the match between seed rain and soil seed bank, suggesting different regeneration strategies related to dispersal ability.

Effects of grass competition on tree seedlings growth under different light and nutrient availability conditions in tropical dry forests in India

AbstractThe interactive effects of light, nutrient availability and grass competition on seedlings of four tropical dry forest tree species, namely, Indian jujube (Ziziphus mauritiana), arjun (Terminalia arjuna), gum arabic (Acacia nilotica) and catechu (Acacia catechu), were evaluated in an experimental study at Banaras Hindu University, Varanasi, India. Full‐ and reduced‐ (20% of the full) sunlight, no‐nutrient and nutrient supplementation, and presence of grass and no‐grass conditions were taken in a split‐plot design to observe the effects on the plant growth and leaf nutrient parameters. We observed a significant interaction between light and nutrient availability on total dry weight and relative growth rate for the tree seedlings of all the species. Seedling growth was lower in presence of grass under full sunlight condition with/without nutrient addition, and also under reduced sunlight condition with nutrient addition. However, leaf‐N and ‐P concentration showed slight increase following nutrient addition across the species and light conditions. All the species responded positively to nutrient addition irrespective of light and grass conditions. Our study further indicates that nutrient addition under reduced light condition in tropical dry forests may be a possible strategy to ameliorate the negative impact of grasses on tree seedling growth. Overall, a better understanding of tree seedling establishment in the presence of grasses is of utmost importance for the development of management plans that may improve the diversity of tree species in tropical dry forests.

Thermal ecophysiology of a native and an invasive gecko species in a tropical dry forest of Mexico.

For ectotherms, thermal physiology plays a fundamental role in the establishment and success of invasive species in novel areas and, ultimately, in their ecological interactions with native species. Invasive species are assumed to have a greater ability to exploit the thermal environment, higher acclimation capacities, a wider thermal tolerance range, and better relative performance under a range of thermal conditions. Here we compare the thermal ecophysiology of two species that occur in sympatry in a tropical dry forest of the Pacific coast of Mexico, the microendemic species Benedetti's Leaf-toed Gecko (Phyllodactylus benedettii) and the invasive Common House Gecko (Hemidactylus frenatus). We characterized their patterns of thermoregulation, thermoregulatory efficiency, thermal tolerances, and thermal sensitivity of locomotor performance. In addition, we included morphological variables and an index of body condition to evaluate their effects on the thermal sensitivity of locomotor performance in these species. Although the two species had similar selected temperatures and thermal tolerances, they contrasted in their thermoregulatory strategies and thermal sensitivity of locomotor performance. Hemidactylus frenatus had a higher performance than the native species, P. benedettii, which would represent an ecological advantage for the former species. Nevertheless, we suggest that given the spatial and temporal limitations in habitat use of the two species, the probability of agonistic interactions between them is reduced. We recommend exploring additional biotic attributes, such as competition, behavior and niche overlap in order assess the role of alternative factors favoring the success of invasive species.