Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

Increased nutrient supply can have drastic effects on natural ecosystems, especially in naturally nutrient-poor ones such as most tropical rainforests. Many studies have focused on the reaction of trees to fertilization, but little is known about herbaceous plants. Ferns are a particularly common group in tropical forests, spanning all vegetation types and zones. Here, we assess how seven years of moderate addition of nitrogen (N), phosphorus (P), and N+P along an elevational gradient (1000–3000 m) have impacted richness and composition of fern and lycophyte assemblages in tropical montane rain forests growing on naturally nutrient deficient soils in the Ecuadorian Andes. We found that fertilization does not affect overall species richness, but that there were strong differences in species abundances (~60% of species), both negative and positive, that were apparently related to the systematic affiliations and ecological properties of the affected species. These diverse responses of ferns to fertilization provide insight into the sensitivity and complexity of the relationships of nutrient availability and community composition in tropical forests.

Abstract:

Background: The impact of selective thinning on forest diversity has been extensively studied in temperate and boreal regions. However, in the tropics, knowledge is still poor regarding the impacts of this silvicultural treatment on functional diversity, especially in tropical mountain forests, which are considered to be highly biodiverse ecosystems and also endangered by human activities. By evaluating the changes on functional diversity by using different indicators, hypothesizing that selective thinning significantly affects (directly or indirectly) tropical mountain forests, this work promotes sustainable ecosystem use. Methods: A total of 52 permanent plots of 2500 m2 each were installed in a primary mountain forest in the San Francisco Biological Reserve to assess the impact of this silvicultural treatment. Selective thinning can be defined as a controlled process, in which trees that compete with ecologically and/or valuable timber species are progressively removed to stimulate the development of profitable ones, called potential crop trees (PCT). In doing so, the best specimens remain in the forest stand until their final harvest. After PCT selection, 30 plots were chosen for the intervention, while 22 plots served as control plots. The thinning intensity fluctuated between 4 and 56 trees ha−1 (average 18.8 ± 12.1 stems ha−1). Functional Diversity (FD) indices, including the community weighted mean (CWM), were determined based on six traits using the FD package implemented in R software. The difference between initial and final conditions of functional richness (FRic), functional divergence (FDiv), functional evenness (FEve), functional dispersion (FDis), and Rao quadratic entropy (RaoQ) was modeled using linear mixed models (LMM). As fixed factors, we used all the predictors inherent to structural and ecological forest conditions before and after the selective thinning and as a random variable, we used the membership to nested sampling units. Results: Functional Richness (FRic) showed significant changes after selective thinning, the other indexes (FEve, FDis, FDiv, RaoQ) were only influenced by predictors related to ecological conditions and characteristics of the community.

Abstract:

Projected climate warming will potentially cause profound modifications of ecosystems worldwide, including large redistribution of biodiversity. Among the ecosystems that react most sensitive to climatic changes are tropical mountain rain forests. An essential step to conserve these ecosystems is to study the response of their biodiversity to changing climate conditions. For this purpose elevational gradients are particular suitable. Furthermore, it is important to consider a topographical gradient because of the rugged mountainous study area. Species richness, the commonly used measure for biodiversity, only describes parts of biodiversity. Therefore, it is crucial to additionally study phylogenetic and functional diversity to detect impacts of climate change on ecosystem functions. Hence, the aim of the study was to investigate the influence of an elevational and a topographical gradient on species richness, phylogenetic diversity (PD) and functional composition of two traits, specific leaf area (SLA) and wood specific gravity (WSG), taking tree communities as example. Additionally, I measured the phylogenetic signal of the traits to expose if they are conserved or convergent. By the combination of PD and trait based methods community assembly patterns were detected and furthermore, it was tested if PD mirrors the functional diversity. The results showed no change in rarefied species richness with elevation. In contrast, PD increased from low to mid elevation and decreased from mid to high elevation. The topographical gradient also had an influence on PD. The functional composition of SLA and WSG changed with elevation and partly with topographic position. While SLA values decreased from low to high elevation and were lower on the upper slopes at mid and high elevation, WSG values at high elevation were overall high with a lower range but did not change with topographic position. Both traits appeared to be convergent. Considering the detected trait convergence, it is likely that competitive interactions shape the community at low elevation whereas at high elevation environmental filtering probably is the main assembly process. Furthermore, filtering effects on the upper slope at mid elevation could be exposed. The functional composition of SLA and WSG indicated biotic filters, like competition for light, at low elevation and abiotic stress filters at high elevation. Moreover, a filtering effect of the topographical gradient on SLA on the upper slope at mid and high elevation was detected. Overall, the PD uncovered more facets of the biodiversity than species richness. However, the addition of trait based methods is important to confirm assembly patterns detected by PD and to detect further underlying processes.

Abstract:

Natural ecosystems across the globe are already modified in their structure and composition. This often leads to a decline of biodiversity which can in turn affect important ecological functions. Species richness as a measure of biodiversity ignores almost 89% of the overall diversity and many traits of species show a phylogenetic signal. Therefore, phylodiversity is often a better indicator of functional processes than species richness. To better understand changes in ecosystem functionality it is thus essential to study and compare taxonomic and phylogenetic diversity patterns across environmental gradients such as elevation. In this study I therefore analyse the effects of elevation and soil parameters on the taxonomic and phylogenetic diversity of tree communities in an Andean mountain rainforest in southern Ecuador. 427 tree species were recorded on 54 plots at three elevation levels at 1000, 2000 and 3000 m, with phyloalpha diversities ranging between -1.91 and 2.20. There was no distinct pattern of over- or underdispersed phyloalpha diversities along the gradient. Elevation affected both the alpha taxonomic and phylogenetic tree species diversity: While taxonomic diversity declined along the elevation gradient, phyloalpha diversity showed a humped relationship with highest phylodiversity values at mid-elevations. I assume environmental filtering to reduce the taxonomic diversity at high elevation. Simultaneously, I suppose the occurrence of facilitator species to enable a nevertheless phylogenetic diverse tree community to persist at high elevations. At low elevations my findings indicate neutral or stochastic processes to shape the phyloalpha dispersion. Elevation had the strongest direct effect on the phyloalpha diversities. Moreover, it influenced soil parameters which explained an additional amount of the phyloalpha diversities. The pattern of phylobeta diversity supported the idea of facilitator species at high elevations and revealed two phylogenetic distantly related tree communities to exist at low and high elevation levels. The ranges of both species sets overlap at mid elevations where phylodiversities are most diverse, corresponding to a mid-domain effect at the phylogenetic scale. Drawing conclusions from phylodiversity to functional traits suggests an ecosystem with a high functional trait space along the gradient with a peak at mid-elevations. Altogether, the analysis of phylodiversity patterns revealed a much more complex picture of the diversity distribution than taxonomic diversity. Furthermore, phylodiversity permitted to find the evolutionary biotic and abiotic processes which shaped the diversity structure.

Abstract:

The moth genus Eois Hu¨ bner (Lepidoptera: Geometridae: Larentiinae) comprises 254 validly described species, 211 of them (83%) occurring in the Neotropical region, 12% in the Asian-Australian region, and 5% in Africa. A checklist of Neotropical Eois is provided and some taxonomic changes are made. Aplogompha noctilaria (Schaus) is excluded from the genus, and Eois bermellada (Dognin) and Eois fragilis (Warren) are transferred to the genus. Further changes include Eois cellulata (Prout) stat. rev., Eois ambarilla (Dognin) stat. rev., and Eois telegraphica Prout stat. rev. By far, the majority of Eois species (82%) were described between 1891 and 1920; approximately half of all species by just two authors. Within the Neotropical region, the majority of species (55%) were described from the tropical Andes (Colombia, Ecuador, Peru, and Bolivia), followed by Central America and the Caribbean (28%), and the rest of South America (17%). Large regions such as the Amazon basin, eastern South America, but also northern Peru are heavily underrepresented. Regional diversity studies provide evidence that the wet tropical Andes are the diversity hotspot of Eois. From a forested elevational gradient (1,020Ð2,670 m above sea level) in southeastern Ecuador, 154 morphospecies are currently known, with only 12% of them described. Regional species richness in Central America is lower (Costa Rica, 66 observed morphospecies along a gradient from 40 to 2,730 m; 29% described). Total richness of the genus is estimated to be 1,000 species in the Neotropical region. If the low proportions of described species only partly recur in other groups of Neotropical geometrid moths, their number may exceed 19,000 species. A taxonomic revision of Eois will be a prerequisite for comparison of ecological data from different regions.

Abstract:

Forest fragmentation can negatively affect tropical epiphyte diversity, but the processes leading to such impoverishment are insufficiently understood. Due to a lack of experimental studies, the relative influence of dispersal constraints vs. growth conditions remains particularly controversial. This paper addresses the fate of late juvenile and adult vascular epiphytes in response to severe forest disturbance in montane southern Ecuador. Plant growth and survival on trunks and lower branches of isolated remnant trees was studied for the first three years following clear-cutting. Overall epiphyte mortality was substantially increased on remnant trees (72% over 3 years) relative to undisturbed forest (11%). Mortality on remnant trees was higher during the first year (52%) than during the second (20%) and third year (26%). Pteridophytes and dicots suffered higher losses than monocots. Plants surviving on remnant trees generally showed a marked negative growth regarding maximum leaf length, whereas the annual increment in leaf number varied more strongly among taxa (families). The present study provides the first field-experimental evidence for the adverse effects of forest disturbance on the performance of later, well-established life stages of vascular epiphytes. The results suggest that growth conditions may often be a more important predictor of epiphyte diversity in disturbed habitats than dispersal constraints. Similar plant responses can be expected to occur along forest edges. Therefore, the retention of scattered green trees, narrow strips or small fragments of forest are unlikely to be sufficient management tools for the conservation of epiphyte diversity in tropical landscapes.

Abstract:

Aneura pinguis (Aneuraceae) is a cosmopolitan thalloid liverwort that shows a specific mycorrhiza-like interaction with basidiomycetes. To date, tropical specimens have not been studied in great depth. Samples of A. pinguis were collected from 48 individuals in one plot in South Ecuador and 54 individuals in five European countries. Light and transmission electron microscopy and molecular analyses based on nuclear rDNA coding for the ribosomal large subunit (nucLSU) and from the 5.8s-ITS2 regions were carried out to identify the associated mycobionts and to study their phylogenetic relationships. Microscopic and ultrastructural investigations of the fungal colonisation showed a high congruence between the European and the Ecuadorian sites and confirmed previous results. Tulasnellales are the only mycobionts that could be detected from ultrastructural characters with certainty. Molecular phylogenetic analysis indicated the presence of tulasnelloid fungi from at least 13 distinct clades. The composition of the communities of tulasnelloid fungi in A. pinguis differs between Ecuador and Europe. The diversity of tulasnelloid fungal partners was much higher at the Ecuadorian site.