Biology subjects

Lancaster, L. T.

Publications and source records attributed to Lancaster, L. T..

5 recordsLinked to original sources

bioRxiv2025

Flexibility in movement strategies of neotropical nectarivorous birds: insights from high-Andean hummingbirds and flowerpiercers

Nectarivorous birds should have flexible movement behaviours in response to the presence of competitors and the spatiotemporal availability of flowering plants, particularly in tropical regions where flower blooms follow patterns of precipitation that are unpredictable across years. While pollinators such as hummingbirds (Trochilidae) have diet breadths that are constrained by trait-matching with flowers, nectar-robbing flowerpiercers are tanagers (Thraupidae) that typically drink nectar from holes they pierce near the flowers base. Consequently, distinct movement patterns for these two bird families would be expected from optimal foraging theory, yet little is known about how tropical nectarivores move in response to fluctuating conditions. We used fine-resolution tracking data from an automated radio telemetry grid to compare movement patterns between hummingbirds and flowerpiercers in high-Andean mountain ecosystems. We obtained an accumulated total of 435,513 location estimates and 452 tracking days from 22 individuals across six different bird species. Our results indicate that hummingbirds exhibit a greater diversity of movement behaviours in comparison to flowerpiercers, with varying space use and recursion patterns that are characteristic of sedentary, commuting/traplining and exploratory strategies, whereas most species of flowerpiercers were classified as central-place foragers. However, daily movement metrics show that there is substantial variation, and hierarchical clustering does not necessarily group together bird families, species, nor even individuals as more similar to each other. Flexibility in daily movement behaviours has seldom been described for neotropical nectarivorous birds in the wild. It emerges as an important trait to adjust behaviour to variable local contexts, and may be adaptive for persistence in challenging mountain ecosystems where weather conditions are harsh and floral resources are seasonal and limited. A better understanding of flexibility in movement behaviour can enhance our predictions about how animals respond to environmental change and anthropogenic pressures.

ecology↗

bioRxiv2024

Tracking small animals in complex landscapes: a comparison of localisation workflows for automated radio telemetry systems

Automated radio telemetry systems (ARTS) have the potential to revolutionise our understanding of animal movement by providing a near-continuous record of individual locations in the wild. However, localisation error in data generated by ARTS can be very high, especially in natural landscapes with complex vegetation structure and topography. This curtails the ecological questions that may be addressed with this technology. Here, we set up an ARTS grid in a valley with heterogeneous vegetation cover in the Colombian high Andes and applied an analytical pipeline to test the effectiveness of localisation methods. We performed calibration trials to simulate animal movement in high-or low-flight, or walking on the ground, and compared workflows with varying decisions related to signal cleaning, selection, smoothing, and interpretation, along with four multilateration approaches. We also quantified the influence of spatial features on the systems accuracy. We tested the grid by deploying tags on two high-altitude hummingbirds, the Great Sapphirewing (Pterophanes cyanopterus) and Bronze-tailed Thornbill (Chalcostigma heteropogon). Results showed large variation in localisation error, ranging from only 0.4-43.4 m from known locations up to 474-1929 m, depending on the localisation method used. The lowest average median error across calibration tracks was 105 m. In particular, we found that the selection of higher radio signal strengths and data smoothing based on the temporal autocorrelation in movement data are useful tools to improve accuracy. Moreover, the variables that significantly influence localisation error include terrain ruggedness, height of movement, vegetation type, and the location of animals inside or outside the grid area. In the case of our study system, thousands of location points were successfully estimated for two hummingbird species that previously lacked movement ecology data. Our case study on hummingbirds suggests ARTS grids can be used to estimate small animals home ranges, associations with vegetation types, and seasonality in occurrence. We present a comparative localisation pipeline, highlighting the variety of possible decisions while processing radio signal data. Overall, this study provides guidance to improve the resolution of location estimates, broadening the application of this tracking technology in the study of the spatial ecology of wild populations.

ecology↗

bioRxiv2022

Population demography maintains biogeographic boundaries

Global biodiversity is organized into biogeographic regions that comprise distinct biotas. The contemporary factors maintaining differences in species composition between biogeographic regions are poorly understood. Given the evidence that populations with sufficient genetic variation can adapt to fill new habitats, it is surprising that we do not see more homogenization of species assemblages among regions. Theory suggests that the expansion of populations across biogeographic transition zones could be limited by environmental gradients that affect population demography in ways that could limit adaptive capacity, but this has not been empirically explored. Using three independently curated data sets describing continental patterns of mammalian demography and population genetics, we show that populations closer to biogeographic transition zones have lower effective population sizes and genetic diversity, and are more genetically differentiated. These patterns are consistent with reduced adaptive capacity near biogeographic transition zones. The consistency of these patterns across mammalian species suggests they are stable, predictable, and generalizable in their contribution to long-term limits on expansion and homogenization of biodiversity across biogeographic transition zones. Understanding the contemporary processes acting on populations that maintain differences in the composition of regional biotas is crucial for our basic understanding of the current and future organization of global biodiversity. The importance of contemporary, population-level processes on the maintenance of global biogeographic regions suggests that biogeographic boundaries are susceptible to environmental perturbation associated with human-caused global change.

ecology↗

bioRxiv2021

Epigenetic Control of Temperature-Dependent Female Reproductive Life History Trade-Offs in Seed Beetles, Callosobruchus maculatus

Many species are threatened by climate change and must rapidly respond to survive changing environments. Epigenetic modifications, such as DNA methylation, can facilitate plastic responses by regulating gene expression in response to environmental cues. Understanding epigenetic responses is therefore essential for predicting species ability to rapidly adapt in the context of global environmental change. Here, we investigated the functional significance of DNA methylation on temperature-dependent life history in seed beetles, Callosobruchus maculatus. We assessed changes in DNA methyltransferase (Dnmt1 and Dnmt2) expression levels under ambient conditions and thermal stress, and reproductive performance following artificially-induced epimutation via 3-aminobenzamide (3AB) and Zebularine (Zeb), at a range of ambient and warmer temperatures over two generations. We found that Dnmt1 and Dnmt2 were greatly expressed in females, throughout the body, and exhibited temperature-dependence; in contrast, Dnmt expression was minimal in males. Epimutation led to shifts in female reproductive life history trade-off allocation, and differentially altered thermal optima of fecundity and offspring viability. This study revealed the optimal allocation strategy among these fitness components is temperature-dependent, and trade-offs become increasingly difficult to resolve epigenetically under more extreme warming. Results suggest that epigenetic mechanisms are strongly implicated in, and perhaps limiting of, invertebrate life history responses to temperature change. Further investigation will reveal targeted DNA methylation patterns and specific loci associated with temperature-dependent life history trade-offs in seed beetles and other invertebrates.

evolutionary biology↗

bioRxiv2021

Fauxcurrence: simulating multi-species occurrences for null models in species distribution modelling and biogeography

Defining appropriate null expectations for species distribution hypotheses is important because sampling bias and spatial autocorrelation can produce realistic, but ecologically meaningless, geographic patterns. Generating null species occurrences with similar spatial structure to observed data can help overcome these problems, but existing methods focus on single or pairs of species and do not incorporate between-species spatial structure that may occlude comparative biogeographic analyses. Here, we describe an algorithm for generating randomised species occurrence points that mimic the within- and between-species spatial structure of real datasets and implement it in a new R package - fauxcurrence. The algorithm can be implemented on any geographic domain for any number of species, limited only by computing power. To demonstrate its utility, we apply the algorithm to two common analysis-types: testing the fit of species distribution models (SDMs) and evaluating niche-overlap. The method works well on all tested datasets within reasonable timescales. We found that many SDMs, despite a good fit to the data, were not significantly better than null expectations and identified only two cases (out of a possible 32) of significantly higher niche divergence than expected by chance. The package is user-friendly, flexible and has many potential applications beyond those tested here, such as joint SDM evaluation and species co-occurrence analysis, spanning the areas of ecology, evolutionary biology and biogeography.

ecology↗