Showing papers by "Daniel Sol published in 2018"

Risk-taking behavior, urbanization and the pace of life in birds

Abstract: Despite growing appreciation of the importance of considering a pace-of-life syndrome (POLS) perspective to understand how animals interact with their environment, studies relating behavior to life history under altered environmental conditions are still rare. By means of a comparative analysis of flight initiation distances (i.e., the distance at which an animal takes flight when a human being is approaching) across > 300 bird species distributed worldwide, we document here the existence of a POLS predicted by theory where slow-lived species tend to be more risk-averse than fast-lived species. This syndrome largely emerges from the influence of body mass, and is highly dependent on the environmental context. Accordingly, the POLS structure vanishes in urbanized environments due to slow-lived species adjusting their flight distances based on the perception of risk. While it is unclear whether changes in POLS reflect plastic and/or evolutionary adjustments, our findings highlight the need to integrate behavior into life history theory to fully understand how animals tolerate human-induced environmental changes. Animals can often respond to changing environmental conditions by adjusting their behavior. However, the degree to which different species can modify their behavior depends on their life history strategy and on the environmental context. Species-specific perception of risk is a conspicuous example of adjustable behavior tightly associated with life history strategy. While there is a general tendency of higher risk aversion in rural than city-dwelling birds, it is dependent on the species’ life history strategy. Slow-lived species are more prone to adjust their flight initiation distances based on the perception of risk, allowing humans to approach closer in urban than rural environments. Behavior must therefore be taken into account together with life history to reliably assess species’ vulnerability at the face of ongoing environmental change.

Predictable evolution towards larger brains in birds colonizing oceanic islands

Abstract: Theory and evidence suggest that some selective pressures are more common on islands than in adjacent mainland habitats, leading evolution to follow predictable trends. The existence of predictable evolutionary trends has nonetheless been difficult to demonstrate, mainly because of the challenge of separating in situ evolution from sorting processes derived from colonization events. Here we use brain size measurements of >1900 avian species to reveal the existence of one such trend: increased brain size in island dwellers. Based on sister-taxa comparisons and phylogenetic ancestral trait estimations, we show that species living on islands have relatively larger brains than their mainland relatives and that these differences mainly reflect in situ evolution rather than varying colonization success. Our findings reinforce the view that in some instances evolution may be predictable, and yield insight into why some animals evolve larger brains despite substantial energetic and developmental costs.

Are Urban Vertebrates City Specialists, Artificial Habitat Exploiters, or Environmental Generalists?

Abstract: Although urbanization is a major threat to biodiversity, some species are able to thrive in cities. This might be because they have specific adaptations to urban conditions, because they are able to cope with artificial habitats in general or because they are generalists that can live in a wide range of conditions. We use the latest version of the IUCN database to distinguish these possibilities in 25,985 species of the four classes of terrestrial vertebrates with the help of phylogenetically controlled methods. We first compare species occurrence in cities with that of the five other artificial habitats recognized by the IUCN and use principal components analyses to ask which of these most resembles cities. We then test whether urban species have a wider habitat breadth than species occurring in other, non-urban, artificial habitats, as well as species that occur only in natural habitats. Our results suggest that the proportion of terrestrial vertebrates that occur in urban environments is small and that, among the species that do occur in cities, the great majority also occur in other artificial habitats. Our data also show that the presence of terrestrial vertebrates in urban habitats is skewed in favor of habitat generalists. In birds and mammals, species occurrence in urban areas is most similar to that of rural gardens, while in reptiles and amphibians, urban areas most resemble pasture and arable land. Our study suggests that cities are likely not unique, as is often thought, and may resemble other types of artificial environments, which urban exploiters can adapt to because of their wide habitat breadth.

Bees use anthropogenic habitats despite strong natural habitat preferences

Abstract: Habitat loss and alteration is widely considered one of the main drivers of the current loss of pollinator diversity. Unfortunately, we still lack a comprehensive analysis of habitat importance, use and preference for major groups of pollinators. Here, we address this gap analysing a large dataset of 15,762 bee specimens (more than 400 species) across northeast USA. We found that natural habitats sustain the highest bee diversity, with many species strongly depending on such habitats. By characterizing habitat use and preference for the 45 most abundant species, we also show that many bee species can use human-altered habitats despite exhibiting strong and clear preferences for forested habitats. However, only a few species appear to do well when the habitat has been drastically modified. We conclude that although altered environments may harbor a substantial number of species, preserving natural areas is still essential to guarantee the conservation of bee biodiversity.

Do public-private partnership enabling laws increase private investment in infrastructure?

Abstract: Rising use of public-private partnerships, or PPPs, is an important development in U.S. infrastructure delivery. PPPs are detailed contracts between a public-sector infrastructure project sponsor and a private-sector provider that bundle delivery services. PPPs represent a middle ground between pure-public project delivery and complete privatization. As of 2016, thirty-five U.S. states had enacted PPP enabling laws. That legislation defines the broad institutional framework surrounding a PPP agreement. It addresses such questions as the mixing of public- and private-sector funds, the treatment of unsolicited PPP proposals, and need for prior legislative approval of PPP contracts, among other key issues. We provide the first thorough empirical assessment of the impact of PPP enabling laws on a state’s utilization of private investment. We analyze the overall effect of having a PPP enabling law while controlling for a variety of factors, including the state’s indebtedness, its broad political disposition, union membership, per-capita income, and other variables. We then assess the impact of thirteen individual PPP enabling-law provisions. We develop an expertinformed weighted index reflecting the degree to which a state’s law is encouraging or discouraging of private investment. We find that more favorable PPP enabling laws increase private investment: when our favorability index increases by one-tenth, the proportion of infrastructure investment delivered via PPP in a state increases by 0.5-0.6. We find that PPP enabling-law provisions allowing unsolicited proposals and the comingling of public and private funds are particularly important in attracting private investment.