João Carvalho

Disease-mediated bottom-up regulation: An emergent virus affects a keystone prey, and alters the dynamics of trophic webs.

Emergent diseases may alter the structure and functioning of ecosystems by creating new biotic interactions and modifying existing ones, producing cascading processes along trophic webs. Recently, a new variant of the rabbit haemorrhagic disease virus (RHDV2 or RHDVb) arguably caused widespread declines in a keystone prey in Mediterranean ecosystems - the European rabbit (Oryctolagus cuniculus). We quantitatively assess the impact of RHDV2 on natural rabbit populations and in two endangered apex predator populations: the Iberian lynx (Lynx pardinus) and the Spanish Imperial eagle (Aquila adalberti). We found 60–70% declines in rabbit populations, followed by decreases of 65.7% in Iberian lynx and 45.5% in Spanish Imperial eagle fecundities. A revision of the web of trophic interactions among rabbits and their dependent predators suggests that RHDV2 acts as a keystone species, and may steer Mediterranean ecosystems to management-dependent alternative states, dominated by simplified mesopredator communities. This model system stresses the importance of diseases as functional players in the dynamics of trophic webs.

Climate and land‐use drivers of invasion: predicting the expansion of Vespa velutina nigrithorax into the Iberian Peninsula

The yellow‐legged hornet (Vespa velutina nigrithorax) has been identified as a major threat to European entomofauna. Species distribution models have been used to assess its invasiveness risk. No studies were, however, developed specifically for peripheral regions, where unique biodiversity can be threatened by this species. This study aims to address that particular issue by incorporating non‐commonly used drivers and by forecasting regions in Iberian Peninsula where the species has high risk of expansion. Climatic, anthropogenic and land‐use variables were considered. The species potential distribution was assessed using a generalised linear model. Overall, the model predicted the northern regions of the Iberian Peninsula suitable for the species expansion. Only the driest regions at the south are conservatively predicted to not be occupied by the yellow‐legged hornet. Precipitation and temperature have the highest influence in Vespa velutina nigrithorax distribution, with land‐use also playing an important role in its expansion at regional scale. These results highlighted the threat of this species to beekeeping activities. Due to high species richness and endemicity levels, peripheral regions integrated in Biodiversity Hotspots need special attention and control measures.

Following The Trail: Factors Underlying the Sudden Expansion of the Egyptian Mongoose ( Herpestes ichneumon ) in Portugal

Species range-limits are influenced by a combination of several factors. In our study we aimed to unveil the drivers underlying the expansion of the Egyptian mongoose in Portugal, a carnivore that was confined to southern Portugal and largely increased its range during the last three decades. We evaluated the expansion of the species in three periods (1980-1990, 1990-2000 and 2000-2010), by projecting the presence/absence data of the species in each temporal range and proposed four hypotheses to explain this sudden expansion associated to changes in the barrier effects of human infrastructure and topographic features, and in the availability of suitable areas due to climate change or land use. An exploratory analysis was made using Spearman rank correlation, followed by a hierarchical partitioning analysis to select uncorrelated potential explanatory variables associated with the different hypotheses. We then ran Generalized Linear Models (GLM) for every period for each hypothesis and for every combination of hypotheses. Our main findings suggest that dynamic transitions of land-use coupled with temperature and rainfall variations over the decades are the main drivers promoting the mongoose expansion. The geographic barriers and the human infrastructures functioned as barriers for mongoose expansion and have shaped its distribution. The expansion of the Egyptian mongoose across the Portuguese territory was due to a variety of factors. Our results suggest a rapid shift in species range in response to land-use and climate changes, underlining the close link between species ranges and a changing environment.

Sex-biased severity of sarcoptic mange at the same biological cost in a sexually dimorphic ungulate

BackgroundIn sexually dimorphic species, male susceptibility to parasite infection and mortality is frequently higher than in females. The Iberian ibex (Capra pyrenaica) is a sexually dimorphic mountain ungulate endemic to the Iberian Peninsula commonly affected by sarcoptic mange, a chronic catabolic skin disease caused by Sarcoptes scabiei. Since 1992, sarcoptic mange affects the Iberian ibex population of the Sierra Nevada Natural Space (SNNS). This study aims at exploring whether mange severity, in terms of prevalence and its effects on body condition, is male-biased in Iberian ibex.FindingsOne thousand and seventy-one adult Iberian ibexes (439 females and 632 males) were randomly shot-harvested in the SNNS from May 1995 to February 2008. Sarcoptic mange stage was classified as healthy, mildly infected or severely infected. Sex-biased prevalence of severe mange was evaluated by a Chi-square test whereas the interaction between mange severity and sex on body condition was assessed by additive models. Among scabietic individuals, the prevalence of severely affected males was 1.29 times higher than in females. On the other hand, both sexes were not able to take profit of a higher availability of seasonal food resources when sarcoptic, particularly in the severe stages.ConclusionsSarcoptic mange severity is male-biased in Iberian ibex, though not mange effects on body condition. Behavioural, immunological and physiological characteristics of males may contribute to this partial sex-biased susceptibility to sarcoptic mange.

Urban wild boars prefer fragmented areas with food resources near natural corridors

Wild boar populations are expanding throughout the world and intruding into periurban and urban areas. In the last years, wild boar has colonized several European cities, including our study area, the city of Barcelona. It is required to identify the main factors driving wild boar into urban areas prior to establish management measures. We built Boosted Regression Trees (BRT) using 3148 wild boar presences registered in the urban area of Barcelona from 2010 to 2014 to identify the variables correlated with these presences. The variables analysed included proxies for distance to source population, urban food resources, climate and urban habitat structure. Wild boars enter the urban area from close natural habitat using corridors such as streams, preferably in fragmented urban environment, looking for food such as urban green areas or dry pet food from cat colonies. Wild boar presence is higher in spring possibly due to the births of piglets and the dispersion of yearlings during that season, and also when natural resources in the Mediterranean habitat fail to satisfy the nutritional requirements of the wild boar population during the summer season. Management measures derived from this study are currently being applied in the city of Barcelona, including vegetation clearings in the wild boar entrance areas and an awareness campaign aimed at reducing the anthropogenic food availability for wild boars. The methodology used can be applied to other cities with wild boar or even other wildlife species issues. The comparison between the factors attracting wild boars into different urban areas would be helpful to understand the global phenomenon.

Expansion and Current Status of Roe Deer (Capreolus capreolus) at the Edge of Its Distribution in Portugal

The European roe deer (Capreolus capreolus) is the most abundant and widespread cervid species in Europe. Despite being the subject of extensive research elsewhere, knowledge of the roe deer in Portugal is scarce. Here we review and summarize the available information on its distribution in Portugal, with the emphasis on: (i) historical distribution, (ii) current distribution and abundance, and (iii) main conservation/management problems. The roe deer is native to Portugal and its populations always persisted in a few patches to the north of the Douro river until the 1990s, when a series of reintroduction programmes restored this species to central and south Portugal. Currently, a natural expansion of the original and reintroduced populations is taking place. The roe deer is present and well established in mountain ranges in north Portugal and is naturally expanding its range towards the border with Spain (west-central Portugal). A number of threats to the species such as potential interspecific competition with the red deer and livestock, along with inadequate management, human disturbances (both roads and human settlements) and climate change have been identified. It is therefore imperative to identify research and monitoring gaps, and finally to draw conclusions under a holistic framework. This will ensure that informed decisions concerning the roe deer management are made at the national level, taking into account that changes in land use occur continuously, possibly affecting the deer abundance.

Roe deer reintroduction in central Portugal: a tool for Iberian wolf conservation

Species reintroduction is an increasingly important tool for species recovery programs and habitat restoration initiatives worldwide. Roe deer Capreolus capreolus (Linnaeus, 1758) densities are very low in central west Portugal (the Freita, Arada, and Montemuro mountains). This area is inhabited by the endangered Iberian wolf Canis lupus signatus Cabrera, 1907, whose numbers have dramatically decreased since the 20th century. An important step in a roe deer reintroduction program is to establish suitable reintroduction sites. The aim of the study was to identify such sites in central Portugal. An Analytical Hierarchy Process (AHP) in combination with a GIS was applied to develop a habitat suitability model, which integrated empirical models and expert knowledge. The variables used in the model included land use, hydrographic network, asphalted roads, population/villages, and relief. Three reintroduction sites suitable for roe deer were identified as potential habitats for their future natural expansion. Those sites were considered as preliminary ones. Finally, future goals and actions are discussed in relation to the promotion of the ecological and social conditions that would favour the survival of roe deer and Iberian wolf in central Portugal.

Stationarity of the inter-event power-law distributions

A number of human activities exhibit a bursty pattern, namely periods of very high activity that are followed by rest periods. Records of these processes generate time series of events whose inter-event times follow a probability distribution that displays a fat tail. The grounds for such phenomenon are not yet clearly understood. In the present work we use the freely available Wikipedia’s editing records to unravel some features of this phenomenon. We show that even though the probability to start editing is conditioned by the circadian 24 hour cycle, the conditional probability for the time interval between successive edits at a given time of the day is independent from the latter. We confirm our findings with the activity of posting on the social network Twitter. Our results suggest that there is an intrinsic humankind scheduling pattern: after overcoming the encumbrance of starting an activity, there is a robust distribution of new related actions, which does not depend on the time of day at which the activity started.

Favourableness and connectivity of a Western Iberian landscape for the reintroduction of the iconic Iberian ibex Capra pyrenaica

Traditional land use practices declined throughout many of Europes rural landscapes during the 20th century. Rewilding (i.e. restoring ecosystem functioning with minimal human intervention) is being pursued in many areas, and restocking or reintroduction of key species is often part of the rewilding strategy. Such programmes require ecological information about the target areas but this is not always available. Using the example of the Iberian ibex Capra pyrenaica within the Rewilding Europe framework we address the following questions: (1) Are there areas in Western Iberia that are environmentally favourable for reintroduction of the species? (2) If so, are these areas well connected with each other? (3) Which of these areas favour the establishment and expansion of a viable population of Iberian ibex in a reintroduction programme? We modelled environmental favourableness for the species in the Iberian Peninsula using a logistic regression with a forward–backward stepwise procedure, and assessed landscape connectivity using a graph analytical approach after downscaling the model to the Western Iberia region. Our results indicate that several habitat patches in the study area present favourable environmental conditions for reintroduction of the Iberian ibex. Overall, most of the habitat connectivity was concentrated in northern and central patches. We highlight the potential and practical application of the analytical protocol used, for successful integration of species distribution modelling and landscape connectivity in the design of broad-scale reintroduction and recovery programmes.

Sex and season explain spleen weight variation in the Egyptian mongoose

Abstract The Egyptian mongoose (Herpestes ichneumon Linnaeus, 1758) is a medium-sized carnivore that experienced remarkable geographic expansion over the last 3 decades in the Iberian Peninsula. In this study, we investigated the association of species-related and abiotic factors with spleen weight (as a proxy for immunocompetence) in the species. We assessed the relationship of body condition, sex, age, season, and environmental conditions with spleen weight established for 508 hunted specimens. Our results indicate that the effects of sex and season outweigh those of all other variables, including body condition. Spleen weight is higher in males than in females, and heavier spleens are more likely to be found in spring, coinciding with the highest period of investment in reproduction due to mating, gestation, birth, and lactation. Coupled with the absence of an effect of body condition, our findings suggest that spleen weight variation in this species is mostly influenced by life-history traits linked to reproduction, rather than overall energy availability, winter immunoenhancement, or energy partitioning effects, and prompt further research focusing on this topic.