Miguel Porto

Complex size-dependent habitat associations in potamodromous fish species

Knowledge of the distribution of species life stages at multiple spatial scales is fundamental to both a proper assessment of species management and conservation programmes and the ability to predict the consequences of human disturbances for river systems. The habitat requirements of three native cyprinid species—the Iberian barbel Barbus bocagei Steindachner, the Iberian straight-mouth nase Pseudochondrostoma polylepis (Steindachner), and the Northern straight-mouth nase Pseudochondrostoma duriense (Coelho)—were examined at 174 undisturbed or minimally disturbed sites in 8 river catchments across western Iberia, by modelling occurrence and counts of species life stages at two spatial scales—large (regional) and instream (local)—using hurdle models. All the life stages of the barbel showed a negative association with upstream high-gradient river reaches, whereas juvenile P. duriense favoured such areas. Stream width and openness were negatively related with the occurrence of juvenile and small adult barbel, but not with large adults. Juvenile nase, on the other hand, were found to be mainly confined to fast-flowing habitats with high instream cover and coarser substrata. Advanced life stages of the barbel were mainly associated with the “pure” regional and shared components, whereas the purely local attributes accounted for much of the model variation among nases, in particular juveniles, and juvenile barbel. The results of this study are useful for setting or refining management goals, and highlight the need to separately consider life stages when performing conservation-related studies of species distribution.

Optimization of Landscape Services under Uncoordinated Management by Multiple Landowners

Landscapes are often patchworks of private properties, where composition and configuration patterns result from cumulative effects of the actions of multiple landowners. Securing the delivery of services in such multi-ownership landscapes is challenging, because it is difficult to assure tight compliance to spatially explicit management rules at the level of individual properties, which may hinder the conservation of critical landscape features. To deal with these constraints, a multi-objective simulation-optimization procedure was developed to select non-spatial management regimes that best meet landscape-level objectives, while accounting for uncoordinated and uncertain response of individual landowners to management rules. Optimization approximates the non-dominated Pareto frontier, combining a multi-objective genetic algorithm and a simulator that forecasts trends in landscape pattern as a function of management rules implemented annually by individual landowners. The procedure was demonstrated with a case study for the optimum scheduling of fuel treatments in cork oak forest landscapes, involving six objectives related to reducing management costs (1), reducing fire risk (3), and protecting biodiversity associated with mid- and late-successional understories (2). There was a trade-off between cost, fire risk and biodiversity objectives, that could be minimized by selecting management regimes involving ca. 60% of landowners clearing the understory at short intervals (around 5 years), and the remaining managing at long intervals (ca. 75 years) or not managing. The optimal management regimes produces a mosaic landscape dominated by stands with herbaceous and low shrub understories, but also with a satisfactory representation of old understories, that was favorable in terms of both fire risk and biodiversity. The simulation-optimization procedure presented can be extended to incorporate a wide range of landscape dynamic processes, management rules and quantifiable objectives. It may thus be adapted to other socio-ecological systems, particularly where specific patterns of landscape heterogeneity are to be maintained despite imperfect management by multiple landowners.

Habitat patchiness affects distribution and microhabitat use of endangered Mira chub Squalius torgalensis (Actinopterygii, Cypriniformes)

We hypothesized that distribution and microhabitat use by imperilled chub Squalius torgalensis in the Torgal stream, Portugal, during low flows, were related to spatial patchiness in physical resources and shifts in ontogenetic preferences. We mapped fish abundance and sampled microhabitat use and availability via snorkelling. We used the coefficient of dispersion in abundance, and spatial autocorrelation analyses to characterize chub distribution, and Hurdle models to relate chub presence and abundance to habitat characteristics. We showed that chub displayed an aggregated distribution, apparently in association with patchily distributed and autocorrelated physical resources, such as debris, roots and aquatic vegetation. Microhabitat use generally was unrelated to velocity, and ontogenetic differences in microhabitat use were not substantial. Nevertheless, sometimes small chub preferred low-velocity patches with coarse substrata, debris and roots, whereas large chub preferred deeper patches with roots and aquatic vegetation. Results suggest that, in low flow conditions, chub respond to resource patchiness by congregating in favourable microhabitats, and that maintenance of mosaics of patches with variable substrata, cover and depth may be important for the persistence of fish in Mediterranean streams.

Using beta diversity to inform agricultural policies and conservation actions on Mediterranean farmland

Summary Spatial variation in species composition (β-diversity) is an important component of farmland biodiversity, which together with local richness (α-diversity) drives the number of species in a region (γ-diversity). However, β-diversity is seldom used to inform conservation, due to limited understanding of its responses to agricultural management, and lack of clear links between β-diversity changes and conservation outcomes. We explored the value of β-diversity to guide conservation on farmland, by quantifying the contribution of bird α- and β-diversity to γ-diversity variation in low- and high-intensity Mediterranean farmland, before (1995–1997) and after (2010–2012) the Common Agricultural Policy reform of 2003. We further related β-diversity to landscape heterogeneity, and assessed the conservation significance of β-diversity changes. In 1995–1997, bird diversity was highest in low-intensity farmland, where it further increased in 2010–2012 due to a strong positive contribution of α-diversity to γ-diversity. In high-intensity farmland, diversity converged over time to much the same values of low-intensity farmland, with strong positive contributions of both α- and β-diversity. These patterns were largely consistent for total, farmland and species of European conservation concern assemblages, and less so for steppe birds. Beta diversity increased with landscape heterogeneity, particularly related to spatial gradients from agricultural to natural habitats in low-intensity farmland, and from annual to permanent crops (olive groves) in high-intensity farmland. The first gradient was associated with the replacement of steppe birds of high conservation concern by more generalist species, while the second was associated with the replacement between species with lower or higher affinity for woodland and shrubland habitats. Synthesis and applications. In low-intensity farmland, spatial variation in species composition (β-diversity) was largely stable over time, reflecting a positive conservation outcome related to persistence of landscape heterogeneity patterns required by endangered steppe bird species. In contrast, β-diversity in high-intensity farmland was favoured by increases in landscape heterogeneity driven by olive grove expansion, contributing to enhancement of total bird diversity. Overall, our results stress the value of β-diversity to understand impacts of agricultural policies and conservation actions, but also highlight the need to evaluate β-diversity changes against specific conservation goals.

Flora-On: Occurrence data of the vascular flora of mainland Portugal

Abstract The Flora-On dataset currently includes 253,310 occurrence records for the class Embryopsidae (vascular plants), comprising data collated via the platform http://flora-on.pt/ relating to observation records of vascular plants across mainland Portugal. Observations are uploaded directly to the database primarily by experienced botanists and naturalists, typically on a weekly basis, and consist of geo-referenced data points for species (or infraspecific taxa) along with their date of observation and phenological state. The Flora-On project aims to compile and make publicly accessible chorological, ecological, morphological and photographic information for the entire vascular flora of Portugal. The project’s website offers powerful query and visualization capabilities, of which we highlight the probabilistic bioclimatic and phenological queries which operate based on the empirical density distributions of species in those variables. Flora-On was created and continues to be maintained by volunteers who are Associate members of Sociedade Portuguesa de Botânica (Botanical Society of Portugal). Given its focus on research-grade and current data, the Flora-On project represents a significant contribution to the knowledge of the present distribution and status of the Portuguese flora.

Local and regional-scale factors drive xerophytic shrub community dynamics on Mediterranean stabilized dunes

AimsThe aim of this study was to analyse the main drivers of compositional and distributional changes of xerophytic shrub communities at different spatial scales. We also assess whether the ecological dynamics of these communities comply with the Clementsian and/or Gleasonian paradigms of community assembly.MethodsWe study the influence of environmental variables and human impacts at different scales on three xerophytic scrub communities growing on inland sand dunes. In 70 plots we sampled shrub cover, herb presence, soil characteristics and human disturbance. PCA and NMS were used to describe environmental and species variations. The effects of main drivers were assessed through Mantel tests, taking spatial structure into account. GAMs were used to model the scrub dynamics across environmental gradients.ResultsWe found that local and regional environmental factors drive the patchy distribution of the xerophytic scrub communities. The gradient found from Stauracanthus genistoides to Ulex australis-dominated communities depends on nutrient availability, probably through species interactions, namely facilitation and competition. In turn, the gradient from S. genistoides to Juniperus navicularis-dominated communities follows an aridity gradient associated with human disturbance, namely agriculture.ConclusionsWe propose that the three studied scrub communities are the extremes of two successions. The S. genistoides to U. australis-dominated communities’ succession is driven by local edaphic factors, following Clementsian principles while the S. genistoides to Juniperus navicularis-dominated communities’ succession responds to local—disturbance—and regional—aridity—processes, following both Clementsian and Gleasonian principles. This implies that only dynamic management approaches directed to ensure a natural functioning of this landscape can be successful for their long-time preservation.

Mismatches between habitat preferences and risk avoidance for birds in intensive Mediterranean farmland

Land use intensification may create habitats that organisms perceive as suitable, but where reproduction or survival is insufficient to maintain self-sustaining populations. Such conditions may qualify as ecological traps, but their existence is often hard to prove. Here, we provide a practical framework to evaluate a potential ecological trap resulting from mismatch between habitat preferences and predation risk, focusing on ground-nesting farmland birds of conservation concern. The framework is based on species-specific associations with safe or unsafe habitat types (i.e. field and landscape types with high or low nest survival), and the occurrence of risk avoidance (i.e. negative responses to predator abundances or to nest failure rates after controlling for habitat effects). Bird densities were far more influenced by field characteristics than landscape context. Corn bunting and fan-tailed warbler were associated with tall swards (safe habitats), and did not show risk avoidance. Tawny pipit and and Galerida larks were associated with short swards (unsafe habitats), with the former avoiding fields with high nest predation rates, and the later avoiding high mongoose abundances. Short-toed lark was associated with fields with short swards and low nest trampling rates. Results suggest that short-toed lark may be the most vulnerable to ecological trapping, because it nests on unsafe habitats and did not show predation risk avoidance. Our approach provides a practical first step to infer vulnerability to a potential ecological trap, though further research is needed to confirm this effect. Management actions increasing nest survival in short sward fields will likely favour grassland bird conservation in intensive Mediterranean farmland.

Influence of moonlight on nightjars’ vocal activity: a guideline for nightjar surveys in Europe

Abstract Strictly nocturnal or crepuscular habits on birds are restricted to a very limited number of species such as nightjars. Physiological skills of these species combined with ecological and behavioural adaptations provide them the ability to colonise a less competitive niche. Nightjars’ nocturnal ecological adaptations have been largely neglected on bird survey methods, which can bias the obtained results. Here, we studied the factors affecting vocal activity of two nightjar species, red-necked nightjar Caprimulgus ruficollis and European nightjar C. europaeus in a Mediterranean area of southern Portugal by modelling observed vocal activity of both species as a function of astronomic variables, particularly moon phase and day of the year. Red-necked nightjar vocal behaviour was positively associated with brighter moon phases and springtime, whereas European nightjar was only influenced by the season, being more active in the summer. This reveals the importance of light conditions on vocal activity of the former species. We suggest that specifically designed field surveys for these species should be preferentially conducted during brighter nights, when the lunar cycle is close to full moon. Furthermore, positive contacts with birds are maximized from late spring to early summer, at least for the red-necked nightjar.