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1. Niche theory, neutral theory, and more recently the unifying theory of biodiversity offer alternative views of the structure (or not) of ecological communities. The relative importance of these theories has not been so thoroughly used to explain community assembly processes in phytophagous insects. 2. We studied the mechanisms of community assembly in pine trees phloem feeders, exploring the relative contributions of deterministic and stochastic processes. 3. Temporal and spatial partitioning of wood borers and bark beetles belonging to the pine phloem feeding gild, was assessed through flight traps and pine bolts extracted from felled live Pinus pinaster trees presenting evidence of decline/wilting. 4. We found that deterministic factors explained most cases of coexistence between species, with partitioning in space and time reducing asymmetric competition for resources and intraguild predation, mediated by differences in size. However, in the case of very closely related species with minimum differences in size—in this case three species of Arhopalus—they occupied the same niche in space and time, suggesting that stochastic processes are more likely to maintain co‐occurrence. 5. The present work indicates that both niche and stochastic processes contribute to the assembly of the phloem feeding community. This could be one more example of accordance with the unifying theory of biodiversity. [ABSTRACT FROM AUTHOR]

Algerian populations of Juniperus thurifera are the most restricted in terms of distribution and the least studied among all populations of the entire range of the species in the western Mediterranean region. Although this species is regarded as being of least concern according to the International Union for Conservation of Nature (IUCN), many studies have pointed to the need for its conservation, especially in North Africa, where populations are fragmented and the potential for regeneration is reduced. Understanding the current range of distribution of J. thurifera in Algeria and the environmental factors responsible for this is of key importance for the protection and restoration of these populations. In the present study, a maximum entropy approach (MaxEnt) was used to model the distribution of J. thurifera. Thirty occurrence records were analyzed in combination with climatic, topographic, and anthropogenic predictors at two different spatial resolutions (900 m and 30 m). The best‐performing model included climatic, topographic, and anthropogenic predictors, suggesting that the distribution of the species is influenced by a combination of factors, while the performance of climatic and topographic models was similar. The most important predictors of the occurrence of Algerian J. thurifera are water‐related factors. However, when considering only topographic variables, altitude has a huge impact. Finally, using improved resolution for modeling distribution enhanced the prediction capability of the model (AUC = 0.942). The findings of the present study confirmed the resilience of J. thurifera, and highlighted the tolerance to drought of Algerian populations. [ABSTRACT FROM AUTHOR]

Bursaphelenchus xylophilus, the pinewood nematode and causal agent of pine wilt disease (PWD), is a globally destructive pine pest. PWD is favoured by high temperatures and drought, but B. xylophilus can also persist in symptomless hosts in areas not prone to PWD. We compared seedlings of different Pinus species that were inoculated with B. xylophilus when well‐watered and under moderate temperatures, conditions that favour sublethal infections. We compared isolates of B. xylophilus in south‐west Europe (Portugal) and south‐east USA (Louisiana). P. pinea, P. pinaster, and P. radiata were challenged in both areas with inoculations of local B. xylophilus. P. sylvestris in Portugal and P. palustris in Louisiana were also tested. Seedling mortality was low, as expected, but nematode establishment was common. There were higher nematode densities and more damage in seedlings of P. sylvestris and P. radiata, followed by P. pinaster, with P. pinea and P. palustris proving to be more tolerant. Life history of hosts was a better predictor of resistance to B. xylophilus than geographical origin, even under sublethal conditions. Fast‐growing species (P. radiata and P. pinaster) appeared most likely to be symptomless carriers in areas not prone to the development of PWD. Cold‐adapted species (P. sylvestris) may still be suitable hosts for the pathogen, even at the sublethal conditions of their distribution areas. There were more nematodes per gram of host using nematode isolates from Portugal. Nonetheless, our results opposed the hypothesis that North American pinewood nematodes have such low virulence that they are obligatorily saprophytic. [ABSTRACT FROM AUTHOR]

Different spatial processes are likely to generate variability at different scales. Thus, the explanation of patterns may be facilitated by knowledge about the spatial scales where variation in patterns occurs. In the present study, the link between spatial patterns of the pine processionary moth Thaumetopoea pityocampa Den. & Schiff. (Lepidoptera, Notodontidae) at two different scales, as well as its population dynamics, was assessed., First, the spatial patterns of T. pityocampa population were assessed at the forest stand scale by surveying the distribution of larval colonies within the pine forest, indicative of adult dispersion. Second, egg-laying patterns across individual host-plants, indicative of female oviposition choices, were assessed, as well as their impact on the survival of immature stages., It was found that T. pityocampa presents a gregarious distribution in homogeneous pine forests, over distances of a few dozen metres. At the pine tree scale, females tend to aggregate their egg batches, whereas aggregation increases with population density. Natural enemies such as parasitoids do not appear to play an important role in regulating the population dynamics of the species. At the same time, aggregation in individual hosts leads to increased mortality in the period from hatching to the third instar, which is notable at high population densities., A patchy distribution in the landscape over short distances has a potentially positive effect on population dynamics of the species, avoiding the Allee effect, and allowing for a rapid increase in population, even where initial numbers are low, leading to localized outbreaks. At the same time, increased mortality as a result of egg-batch clumping at high population densities is a potential density-dependent mechanism of population regulation. [ABSTRACT FROM AUTHOR]

1. In pine ecosystems, the role of the larval nests of the Mediterranean defoliator Thaumetopoea pityocampa as shelter of other arthropods, was studied for the first time. In Portugal, Pinus stands which differed in understorey plant diversity and level of attack by T. pityocampa were compared. 2. The arthropod fauna found sheltering inside the nests consisted of 60 species, representing 12 foraging types. Both arthropod richness and abundance were positively correlated with nest size, expressed as larval biomass. Arthropod richness was further positively correlated with understorey plant diversity, while no correlation was detected between arthropod richness and nest density. 3. Spiders accounted for up to 50% of the species richness, while 80% of the individuals collected were either juveniles, or females with brood, implying that T. pityocampa nests are used for overwintering and brood care. Seventy-six per cent of the Araneae were nocturnal ground foragers and specialised cryptic hunters, demonstrating the occurrence of indirect interactions among species belonging to different communities, namely ground vegetation layers and forest pine coppice. 4. It was concluded that, in Mediterranean pine ecosystems, T. pityocampa nests (i) create habitat diversification and contribute to improve overwintering survival of a wide range of arthropod species; (ii) play a functional role in the food web of pine ecosystems, by promoting indirectly mediated interactions among species from different communities; and (iii) do not contribute to create habitat for symtopic phytophagous arthropods, since contrary to literature references for different types of shelters, 98% of the associated species belonged to foraging types other than T. pityocampa. [ABSTRACT FROM AUTHOR]