How far do Asian forest hornbills disperse seeds? Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Rohit Naniwadekar, Akanksha Rathore, Ushma Shukla, Saniya Chaplod, Aparajita Datta Abstract Biotic seed dispersal of plants is a complex phenomenon that is influenced by multiple seed disperser species with implications for plant fitness and range expansions. While inter-species variation has been well-studied, the importance of incorporating intraspecific variation in seed dispersal is increasingly being acknowledged. We compared seed dispersal patterns of breeding and non-breeding great hornbills Buceros bicornis and a breeding wreathed hornbill Rhyticeros undulatus by combining data on fruiting tree visitations, gut passage time and movement data from tagged hornbills. Seed dispersal probability at nest trees (by breeding males) was low (<12%) suggesting that males scatter-disperse seeds, unlike breeding females that deposit seeds below nest trees. Median seed dispersal distance of great hornbills was 294 m and 254 m in the breeding and non-breeding season respectively, and, the distribution tail was shorter for breeding birds (2.5 km) than non-breeding birds (13 km). The median and maximum seed dispersal distance by the wreathed hornbill was 1.35 km and 11 km respectively. This study highlights intraspecific variation in seed dispersal patterns across sexes and breeding and non-breeding male hornbills and potential variation between two hornbill species. This is the first study that estimates long-distance seed dispersal by Asian hornbills.

Tree abundance, richness, and phylogenetic diversity along an elevation gradient in the tropical forest of Diaoluo Mountain in Hainan, China Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Zhi-Xin Zhu, Mir Muhammad Nizamani, Sunil Kumar Sahu, Anusha Kunasingam, Hua-Feng Wang Abstract Taxonomic and phylogenetic diversity within forest communities are influenced by many factors, but our understanding concerning diversity patterns along elevational gradients is still unclear. Though there are many studies on diversity patterns such as phylogenetic diversity (PD), there are only handful describing how altitude affects these diversity patterns, especially in the tropical forest areas of China. It has been assumed that increases in elevation can lead to gradual decreases in abundance, richness, and phylogenetic diversity. Here, we assessed these parameters in fifteen 50 × 50 m plots across various elevations (281 m–1175 m) at Diaoluo Mountain of the Hainan tropical forest in the years 2010 and 2015. Regressions between tree richness, PD, and environmental variables (climate and soil variables) were conducted to uncover the potential drivers of tree richness and PD. We found that the tree abundance, richness, and phylogenetic diversity first increased with increasing elevation, then reached maximum values at intermediate elevations, and finally decreased at the highest elevations. Tree species composition was mainly shaped by elevation (p = 0.001 < 0.005), suggesting that intermediate elevations result in an environmental screening effect due to the abundance of energy and moisture resources (i.e., high temperature and humidity), which is typical of tropical forests. We speculate that the intermediate elevations and historical disturbances shape the available species pool. Overall, our research revealed the diversity patterns of the Diaolu Mountain plants along the elevation, providing the basis for future plant protection planning, such as protecting plant species, maintaining plant habitats, and coordinating plant management in the area.

The absence of keystone indigenous trees inhibits bird recovery up to a decade after invasive tree removal from riparian habitats Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): J.R. Mangachena, S. Geerts Abstract When invasive alien trees are removed, ecosystems are usually left to “self-repair”. Little is known about the extent of recovery or whether plant and animal taxa respond in a similar way. In most cases, the absence of a historical condition makes it difficult to measure restoration success and a flexible approach is usually followed using practical target communities. We explored these issues by sampling bird and plant assemblages after the removal of invasive trees, using a chronosequence (space-for-time substitution) approach. We used the Berg River, one of the most invaded riparian systems in the Cape Floristic Region of South Africa, as a case study. Study sites – cleared of Eucalyptus camaldulensis in 2005, 2007, 2008 and 2014 – were sampled in 2014 and compared to invaded and near-pristine areas. In total, 27 native plant species (four trees, six shrubs, seven forbs, four graminoids, four geophytes and two vines) and 26 alien plant species (four trees, three shrubs, twelve forbs and seven graminoids) from 50 genera and 31 families were recorded across all sites and years. Cleared sites had significantly more native plant species than invaded sites, but this was similar to near-pristine sites. Cleared sites had the highest plant species richness, driven by significantly more alien species, but canopy cover was significantly lower than in invaded or near-pristine sites. In total, 2049 birds from 52 species were recorded across all sites and years. A decade after clearing, bird species richness, abundance and community composition are different to near-pristine sites. This is due to the lower abundance and diversity of trees in cleared sites, which could be important as habitat or a food source for birds in an agricultural landscape. From a bird perspective, we support the approach of selectively clearing invasive trees over time to allow native trees to recover through succession. We highlight the importance of monitoring fauna to evaluate recovery after invasive alien plant clearing and to guide further management interventions.

Jointed cactus Opuntia aurantiaca modifies soil nutrient concentrations, grass species assemblage and biomass yield in a savanna rangeland Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Sarah Kawanza, Hilton G.T. Ndagurwa, Rayfield J. Chateya, Justice Muvengwi Abstract Biological invasions are currently recognized as a major threat to biodiversity and ecosystem function worldwide, but invasion studies in savanna rangelands are limited. Therefore, we studied the soil properties and grass species abundance, diversity and biomass yield in Opuntia aurantiaca uninvaded, recently-invaded (<30 years ago) and historically-invaded (>30 years) sites in a savanna rangeland, Zimbabwe. Soil nutrient concentrations significantly differed between sites, with nutrient-rich soils in Opuntia-invaded sites. The soil nutrient content in invaded sites was greater by a factor of up to 7 for N, 44 for P and 3.4 for Ca. However, soil pH did not differ between sites (p > 0.05), with slightly acidic soils in all sites. Grass species abundance declined while species evenness increased with time since Opuntia invasion. Further, grass species height and biomass yield in the uninvaded sites were greater than those in the recently-invaded and historically-invaded sites. We also observed a shift in above and belowground biomass allocation in grass species suggesting shifts in plastic allocations with invasion. Overall, redundancy analysis showed a significant negative effect of O. aurantiaca density on the abundance, species richness, species diversity and biomass yield of grass species. In contrast, species evenness and dominance were positively correlated with O. aurantiaca density. In conclusion, despite the positive effects of invasion on soil nutrient concentrations, the findings are worrisome as grass abundance, height and biomass yield are negatively affected. Consequently, rangeland productivity might also be curtailed, indicating the need to manage and eradicate O. aurantiaca given a considerable amount of comparable rangeland that can be affected.

Habitat traits that increase the probability of occupancy of migratory birds in an urban ecological reserve Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): J. Jaime Zúñiga-Vega, Israel Solano-Zavaleta, M. Fernanda Sáenz-Escobar, Gonzalo A. Ramírez-Cruz Abstract Several migratory bird species spend the winter in highly disturbed regions in the tropics. Green areas within cities may be used as wintering grounds and, given the documented population declines of migratory birds, knowledge about the habitat traits that promote the arrival of migratory birds in such fragmented ecosystems is highly necessary. Here, we examined the landscape traits that increased the probability of presence of five migratory species in an ecological reserve immersed within Mexico City. We monitored these species during three consecutive winters and used multiple-season occupancy models (which account for our imperfect detection of these species in the field) to find the particular habitat traits that promote their presence in this urban reserve. Contrary to our expectation, we found that all five species prefer habitat traits associated with the urban areas that surround the core conservation areas of the reserve. We conclude that the heterogeneity of these urban areas (a mixture of areas where exotic trees are abundant and open green areas with minimal tree or shrub cover) promotes the arrival of migratory species with distinct ecological needs.

Community responses to fine-scale environmental conditions: Ferns alpha and beta diversity along Brazilian Atlantic forest remnants Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Lucas Erickson Nascimento da Costa, Xavier Arnan, Rafael de Paiva Farias, Iva Carneiro Leão Barros Abstract Understanding how local environmental factors affect communities and compositional patterns are crucial to biodiversity conservation, especially in environments that were severally affected by anthropic actions. We analyzed the effects of fine-scale local environmental conditions on alpha and beta diversity of fern communities in three Atlantic forest areas and investigated the mechanisms underlying fern community responses. We sampled ferns and collected local environmental variables in 22 plots in three Atlantic forest areas and used multi-model inferences to identify the relationship between community diversity and composition and local environmental factors. We also applied multivariate analyses to verify whether community composition is constrained by local environmental factors. Finally, we analyzed beta-diversity (dissimilarity in species composition) patterns between and within forest areas and identified the contribution of turnover and nestedness to observed beta-diversity patterns. At the local scale, fern diversity was positively and strongly affected by fine-scale variations in nutrient availability and negatively influenced by soil acidity. Meanwhile, changes in community composition were also related to fine-scale variations in nutrient availability and soil rock coverage. Beta-diversity within forest areas (local scale) was as high as between forest areas (regional scale), a pattern that was virtually driven by species turnover at both scales of analysis. Our results highlight a prominent role of environmental filtering in regulating fine-scale local fern community diversity and composition, to such an extent that fine-scale local variation in species composition is as high as between spatially and climatically distant forest areas.

Does road-edge affect liana community structure and liana-host interactions in evergreen rainforests in Ghana? Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Bismark Ofosu-Bamfo, Patrick Addo-Fordjour, Ebenezer J.D. Belford Abstract Though lianas can respond to human disturbance and forest fragmentation, the effects of forest edge on liana community are poorly documented. This study therefore investigated the effects of road-edge on liana community structure and liana-host interactions in two evergreen rainforests in Ghana (Ankasa Conservation Area, Cape Three Points Forest Reserve). Lianas and their hosts were identified and counted in twenty-four 50 m × 50 m plots in each rainforest. The plots were evenly distributed in edge (0–50 m), interior (200 m) and deep-interior (400 m) sites. The edge site of Cape Three Points Forest Reserve supported significantly higher liana diversity, but there was no edge effect on liana diversity in Ankasa Conservation Area. There were no significant edge effects on liana species composition, abundance, and basal area in both evergreen rainforests. However, there was evidence of strong edge effects on the abundance of some individual liana species. In all the three sites of the two evergreen rainforests, liana species showed random species co-occurrence pattern, with no nested structure in liana-tree interaction network. Although forest edge had weak effects on liana community, some species had increased abundance, compensating the loss of individuals of other species at the edge. Overall, the idiosyncratic edge effect on liana species populations can blur the effects on liana community.

Fine-scale population structure analysis in Armadillidium vulgare (Isopoda: Oniscidea) reveals strong female philopatry Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Sylvine Durand, Frédéric Grandjean, Isabelle Giraud, Richard Cordaux, Sophie Beltran-Bech, Nicolas Bech Abstract In the last decades, dispersal studies have benefited from the use of molecular markers for detecting patterns differing between categories of individuals and have highlighted sex-biased dispersal in several species. To explain this phenomenon, several hypotheses implying mating systems, intrasexual competition or sex-related handicaps have been proposed. In this context, we investigated sex-biased dispersal in Armadillidium vulgare, a terrestrial isopod with a promiscuous mating system. As a proxy for effective dispersal, we performed a fine-scale investigation of the spatial genetic structure in males and females, using individuals originating from five sampling points located within 70 m of each other. Based on microsatellite markers and spatial autocorrelation analyses, our results revealed that while males did not present a significant genetic structure at this geographic scale, females were significantly and genetically more similar to each other when they were collected in the same sampling point. As females invest more parental care than males in A. vulgare, but also because this species is promiscuous and males experience a high intrasexual competition, our results meet the predictions of most classical hypotheses for sex-biased dispersal. We suggest that widening dispersal studies to other isopods or crustaceans, differing in their ecology or mating system and displaying varying levels of parental care, might shed light on the processes underlying the evolution of sex-biased dispersal.

Manmade structures are used by an invasive species to colonize new territory across a fragmented landscape Publication date: November 2019 Source: Acta Oecologica, Volume 101 Author(s): Iulian Gherghel, Riley Tedrow Abstract Anthropogenic activity often results in habitat fragmentation that can negatively impact biodiversity by destroying viable habitat and reducing the connectivity of the landscape. Anthropogenic features (such as rail ways) can also have the opposite effect, facilitating the expansion of certain species. Here we demonstrate such a case, wherein anthropogenic activity and structures facilitate the dispersal of a species whose capacity for territorial expansion is limited in the natural environment. Using habitat suitability and connectivity models, we show that the Common Wall Lizard (Podarcis muralis) most likely prefers railways as a means to disperse into new habitats and/or maintain population connectivity across a fragmented habitat (i.e. from their southern populations, moving north along rail way tracks to colonize new suitable habitats). Furthermore, we predict the route and location of future colonization events based on availability of viable habitats and corridors to them. The potential impact of this invasion is estimated to be relatively low.

Living with aliens: Suboptimal ecological condition in semiaquatic snakes inhabiting a hot spot of allodiversity Publication date: October 2019 Source: Acta Oecologica, Volume 100 Author(s): Luca Stellati, Nicolò Borgianni, Alessandra M. Bissattini, Vincenzo Buono, Phillip J. Haubrock, Paride Balzani, Elena Tricarico, Alberto F. Inghilesi, Lorenzo Tancioni, Marco Martinoli, Luca Luiselli, Leonardo Vignoli Abstract The presence of alien species can embody a form of disturbance for natural communities and the concomitant presence of alien species at different levels within the trophic chain may compromise ecosystem functionality. We studied the ecology of two species of snake (Natrix tessellata and N. natrix) in a system of five ponds with a high number of alien species at a Mediterranean area in central Italy. We evaluated the potential perturbations to ecological traits of snakes due to the presence of alien species, including their body size, population density, and food habits. We compared the studied populations' body size to that estimated in conspecific populations studied elsewhere, including populations at close distance from the study site. Distance sampling and Capture-Mark-Recapture techniques were used to calculate the population density. Diet was estimated using stomach contents and stable isotope ratios (δ15N and δ13C), using Bayesian stable isotope mixing models to estimate the contribution of food sources and species' isotopic niche spaces. Few prey items were found in the stomach contents of either species, with Ameiurus melas as the main prey. Based on isotope niche analyses, N. tessellata diet consisted of only alien species, and N. natrix diet mostly relied on alien species (>80%). Stomach contents revealed high overlap between the two species, although isotopes showed a random resource use (i.e. low isotopic niche space overlap). Overall, we caught a low number of individuals, indicating small population sizes. Moreover, snakes at the study site were comparatively smaller in size than most other populations found in the literature and almost all the recorded individuals were in very poor condition or injured by ingested alien prey. We suggest that the presence of rich allodiversity has negatively affected the snakes’ fitness by decreasing their foraging performance, increasing their risk of being preyed upon, or through other mechanisms.