The Evolution of Nest Site Specialization and its Macroevolutionary Consequences in Passerine Birds

A long-standing hypothesis in evolutionary biology is that the evolution of resource specialization can lead to an evolutionary dead end, where specialists have low diversification rates and limited ability to evolve into generalists. However, in recent years, advances in comparative methods investigating trait-based differences associated with diversification have enabled more robust tests of this idea and have found mixed support. Here we test the evolutionary dead end hypothesis by estimating net diversification rate differences associated with nest site specialization among 3,224 species of passerine birds. In particular, we test whether the adoption of hole-nesting, a nest site specialization that decreases predation, results in reduced diversification rates relative to nesting outside of holes. Further, we examine whether evolutionary transitions to the specialist hole-nesting state have been more frequent than transitions out of hole-nesting. Using diversification models that accounted for background rate heterogeneity and different extinction rate scenarios, we found that hole-nesting specialization was not associated with diversification rate differences. Furthermore, contrary to the assumption that specialists rarely evolve into generalists, we found that transitions out of hole-nesting occur more frequently than transitions into hole-nesting. These results suggest that interspecific competition may limit adoption of hole-nesting, but that such competition does not result in limited diversification of hole-nesters. In conjunction with other recent studies using robust comparative methods, our results add to growing evidence that evolutionary dead ends are not a typical outcome of resource specialization.

THE ROLE OF TRANSBAIKALIA IN THE FAR EASTERN MACROREGION

The object of the study is the regions of Transbaikalia joined the Far Eastern Federal District, through which the main connecting infrastructure of the macroregion with the main territory of the country passes. The purpose of the paper is to show the position of Transbaikalia in the system of the emerging economic corridor China-Mongolia-Russia as a part of China's foreign policy initiative "One Belt - One Road" by analyzing the impact of foreign investment on its current economic situation. This corridor will facilitate the access of Chinese companies to the resources of Siberia and the Far East, enhancing the resource specialization of the area. At the same time, the geostrategic functions of the Trans-Baikal territory, given to it by the new Spatial Strategy of the Russian Federation, require strengthening its own economic potential through the development and diversification of the local economy and horizontal ties between the subjects of the macroregion.

Resource preferences and the emergence of individual niche specialization within populations

Growing evidence that individuals of many generalist animals behave as resource specialists has attracted research interest for its ecological and evolutionary implications. Although variation in resource preferences is critical for developing a general theory of individual specialization, it remains to be shown whether diverging preferences can arise among individuals sharing a similar environment and whether these are stable enough to be ecologically relevant. We addressed these issues by means of common garden experiments in feral pigeons (Columba livia), a species known to exhibit resource specialization in the wild. Food-choice experiments on wild-caught pigeons and their captive-bred descendants showed that variation in food preferences can easily arise within a population and that this variation may represent a substantial fraction of the population niche. However, a cross-fostering experiment revealed that the genetic and early common-environment components of food preferences were low, reducing their stability and eroding niche variation in the long-term.

A Multiscalar Consideration of the Athabascan Migration

Genetic and linguistic evidence suggests that, after living in the Subarctic for thousands of years, Northern Athabascans began migrating to the American Southwest around 1,000 years ago. Anthropologists have proposed that this partial out-migration and several associated in situ behavioral changes were the result of a massive volcanic eruption that decimated regional caribou herds. However, regional populations appear to increase around the time of these changes, a demographic shift that may have led to increased territoriality, resource stress, and specialization. Building on existing syntheses of cultural dynamics in the region, analyses of excavated materials, and landscape data from Alaska and Yukon, this research shows that the Athabascan transition represented a gradual shift toward resource specialization in both salmon and caribou with an overall increase in diet breadth, indicating a behavioral transition that is more consistent with gradual demographic change. Further, this behavioral shift was already in motion at the time of the volcanic eruption circa 1150 cal BP and suggests that the ultimate migration from the area was the result of demographic pressures. In sum, this research elaborates on the complex dynamics of resilience and adaptation in hunter-gatherer groups and provides a testable model for explaining past migrations.

Ecological mechanisms explaining interactions within plant–hummingbird networks: morphological matching increases towards lower latitudes

Interactions between species are influenced by different ecological mechanisms, such as morphological matching, phenological overlap and species abundances. How these mechanisms explain interaction frequencies across environmental gradients remains poorly understood. Consequently, we also know little about the mechanisms that drive the geographical patterns in network structure, such as complementary specialization and modularity. Here, we use data on morphologies, phenologies and abundances to explain interaction frequencies between hummingbirds and plants at a large geographical scale. For 24 quantitative networks sampled throughout the Americas, we found that the tendency of species to interact with morphologically matching partners contributed to specialized and modular network structures. Morphological matching best explained interaction frequencies in networks found closer to the equator and in areas with low-temperature seasonality. When comparing the three ecological mechanisms within networks, we found that both morphological matching and phenological overlap generally outperformed abundances in the explanation of interaction frequencies. Together, these findings provide insights into the ecological mechanisms that underlie geographical patterns in resource specialization. Notably, our results highlight morphological constraints on interactions as a potential explanation for increasing resource specialization towards lower latitudes.