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opencc-zeroJul 2020View details →

Data from: Occupancy patterns and upper range limits of lowland Bornean birds along an elevational gradient

Aim: The traditional view of species' distributions is that they are less abundant near the edges of their ranges and more abundant toward the center. Testing this pattern is difficult because of the complexity of distributions across wide geographical areas. An alternative strategy, however, is to measure species' distributional patterns along elevational gradients. We applied this strategy to examine whether lowland forest birds are indeed less common near their upper range limits on a Bornean mountain, and tested co-occurrence patterns among species for potential causes of attenuation, including signatures of habitat selection and competition at the periphery of their ranges. Location: Mt. Mulu, Borneo Taxon: Rain forest birds Methods: We surveyed lowland forest birds on Mt. Mulu (2,376 m), classified their elevation-occupancy distributions using Huisman – Olff – Fresco (HOF) models, and examined co-occurrence patterns of species pairs for signatures of shared habitat patches and interspecific competition. Results: For 39 of 50 common species, occupancy was highest at sea level then gradually declined near their upper range edges, in keeping with a 'rare periphery' hypothesis. With respect to habitat selection, lowland species do not appear to cluster together at sites of patchy similar habitat near their upper range limits; neither are most lowland species segregated from potential montane competitors where ranges overlap. Main conclusions: High relative abundance at sea level implies that species inhabit 'truncated niches' and are not currently near the limits of their fundamental niche, unless unknown critical response thresholds exist. However, indirect effects of increasing temperature predicted under climate change scenarios could still influence lower range limits of lowland species indirectly by altering habitat, precipitation regimes, and competitive interactions. The lack of non-random co-occurrence patterns implies that patchy habitat and simple pairwise species interactions are unlikely to be responsible for upper range limits in most species; diffuse competition across diverse rain forest bird communities could still play a role.

opencc-zeroNov 2020View details →

Data from: Biotic interactions help explain variation in elevational range limits of birds among Bornean mountains

Aim Physiological tolerances and biotic interactions along habitat gradients are thought to influence species occurrence. Distributional differences caused by such forces are particularly noticeable on tropical mountains, where high species turnover along elevational gradients occurs over relatively short distances and elevational distributions of particular species can shift among mountains. Such shifts are interpreted as evidence of the importance of spatial variation in interspecific competition and habitat or climatic gradients. To assess the relative importance of competition and compression of habitat and climatic zones in setting range limits, we examined differences in elevational ranges of forest bird species among four Bornean mountains with distinct features. Location Bornean mountains Kinabalu, Mulu, Pueh and Topap Oso. Taxon Rain forest bird communities along elevational gradients. Methods We surveyed the elevational ranges of rain forest birds on four mountains in Borneo to test which environmental variables—habitat zone compression or presence of likely competitors—best predicted differences in elevational ranges of species among mountains. For this purpose, we used two complementary tests: a comparison of elevational range limits between pairs of mountains, and linear mixed models with naïve occupancy as the response variable. Results We found that lowland species occur higher in elevation on two small mountains compared to Mt. Mulu. This result is inconsistent with the expectation that distributions of habitats are elevationally compressed on small mountains, but is consistent with the hypothesis that a reduction in competition (likely diffuse) on short mountains, which largely lack montane specialist species, allows lowland species to occur higher in elevation. The relative influence of competition changes with elevation, and the correlation between lower range limits of montane species and the distribution of their competitors was weaker than in lowland species. Main conclusions These findings provide support for the importance of biotic interactions in setting elevational range limits of tropical bird species, although abiotic gradients explain the majority of distribution patterns. Thus, models predicting range shifts under climate change scenarios must include not only climatic variables, as is currently most common, but also information on potentially resulting changes in species interactions, especially for lowland species.

opencc-zeroDec 2023View details →

The role of tropical rainfall in driving range dynamics for a long-distance migratory bird

Predicting how the range dynamics of migratory species will respond to climate change requires a mechanistic understanding of the factors that operate across the annual cycle to control the distribution and abundance of a species. Here we use multiple lines of evidence to reveal that environmental conditions during the nonbreeding season influence range dynamics across the lifecycle of a migratory songbird, the American redstart (Setophaga ruticilla). Using long-term data from the nonbreeding grounds and breeding origin estimated from stable hydrogen isotopes in tail feathers, we found that the relationship between nonbreeding season survival and migration distance is mediated by precipitation, but only during dry years. A long-term drying trend throughout the Caribbean is associated with higher mortality for individuals from the northern portion of the species' breeding range, resulting in an approximate 500 km southward shift in breeding origins of this Jamaican population over the past 30 years. This shift in connectivity is mirrored by changes in the redstarts breeding distribution of abundance. These results demonstrate that the climatic effects on demographic processes originating during the tropical nonbreeding season is actively shaping range dynamics in a migratory bird.

Fig. 5 in Ethological Aspects Of Biodiversity Within And Between Phylloscopus Species: Behavioral Variation Among Birds From The Centre And Periphery Of Breeding Ranges

Fig. 5. Ratio of males of different statuses from the number of all the males tried to occupy territories in the study area in 2007 – 2014.

Fig. 6 in Ethological Aspects Of Biodiversity Within And Between Phylloscopus Species: Behavioral Variation Among Birds From The Centre And Periphery Of Breeding Ranges

Fig. 6. Change of places of singing (1, 2, etc.) during a season in Wood Warblers. Examples for some different controlled males are indicated by the lines of different types (2007 – 2014).

Fig. 1 in Ethological Aspects Of Biodiversity Within And Between Phylloscopus Species: Behavioral Variation Among Birds From The Centre And Periphery Of Breeding Ranges

Fig. 1. Population densities of the Leaf Warblers in the study area at different stages of reproductive seasons of 2007 – 2014.

Fig. 2 in Ethological Aspects Of Biodiversity Within And Between Phylloscopus Species: Behavioral Variation Among Birds From The Centre And Periphery Of Breeding Ranges

Fig. 2. The overlapping of projections of Chiffchaff territories ('maximum-territories' according to the point mapping method) and the real segregating of the territorial rooms in space: a scheme.

opencc-zeroJun 2023View details →

Blood variation implicates respiratory limits on elevational ranges of Andean birds

The extent to which species ranges reflect intrinsic physiological tolerances is a major, unsolved question in evolutionary ecology. To date, consensus has been hindered by the limited tractability of experimental approaches across most of the tree of life. Here, we apply a macrophysiological approach to understand how hematological traits related to oxygen transport shape elevational ranges in a tropical biodiversity hotspot. Along Andean elevational gradients, we measured traits that affect blood oxygen-carrying capacity—total and cellular hemoglobin concentration and hematocrit—for 2,355 individuals of 136 bird species. We used these data to evaluate the influence of hematological traits on elevational ranges. First, we asked whether the sensitivity of hematological traits to elevation is predictive of elevational range breadth. Second, we asked whether variance in hematological traits changed as a function of distance to the nearest elevational range limit. We found that the correlation between hematological sensitivity and elevational range breadth was slightly positive, consistent with a facilitative role for sensitivity in elevational range expansion. We further found reduced local variation in hematological traits near elevational range limits and at high elevations, patterns consistent with intensified natural selection, reduced effective population size, or compensatory changes in other cardiorespiratory traits. Our findings suggest that constraints on hematological sensitivity and local genetic adaptation to oxygen availability promote the evolution of the narrow elevational ranges that underpin tropical montane biodiversity.

opencc-by-4.0Jul 2023View details →

The evolution of local co-occurrence in birds in relation to latitude, degree of sympatry, and range symmetry

This study analyzes a large sample of occurrence records (7,834,063 checklists from the eBird project) of 887 passerine bird species distributed globally. Under the assumption that speciation and trait divergence rates are faster in temperate areas and that trait divergence does promote local secondary contact of newly evolved species, the expectaction is that local co-occurrence increases with latitude.Syntopy increased from the Southern to Northern Hemisphere and was positively related to sympatry and range symmetry.