Biology subjects

Jankowski, J. E.

Publications and source records attributed to Jankowski, J. E..

3 recordsLinked to original sources

bioRxiv2025

Selective sweeps and the role of divergent and parallel selection in Amazonian and Andean bird diversification

Both divergent and parallel selection can contribute to evolutionary change, yet their relative contributions to adaptation and speciation are poorly understood, especially during environmental change. We quantified selective sweep signatures and divergence times in Amazonian avian sister species pairs that either differ in elevation and are expected to have experienced strong divergent selection; or occur in similar lowland habitats and are expected to have experienced strong parallel selection. We found that elevational differentiation resulted in a greater accumulation of selective sweep signatures over the five-million-year timespan covered by our dataset, supporting the importance of divergent selection. Nevertheless, lowland-restricted species pairs accumulated more selective sweeps over the most recent two million years, suggesting that parallel selection, driven by major Pleistocene glacial cycles, produced faster evolutionary change than divergent selection in elevationally differentiated species pairs. Our results highlight parallel selection as an important driver of adaptation and evolution, especially during environmental instability.

zoology↗

bioRxiv2021

Plant-pollinator Specialization: Origin and measurement of curvature

A feature of biodiversity is the abundance of curves displayed by organs and organisms. Curvature is a widespread, convergent trait that has important ecological and evolutionary implications. In pollination ecology, the curvature of flowers and pollinator mouthparts (e.g. hummingbird bills) along the dorsiventral plane has been associated with specialization, competition, and species co-existence. Six methods have historically been used to measure curvature in pollination systems; we provide a solution to this inconsistency by defining curvature using well-established concepts from differential geometry. Intuitively, curvature is the degree to which a line is not straight, but more formally, it is the rate at which the tangent of a curve changes direction with respect to arc length. Here, we establish a protocol wherein a line is fitted against landmarks placed on an image of a curved organ or organism, then curvature is computed at many points along the fitted line and the sum taken. The protocol is demonstrated by studying the development of nectar spur curvature in the flowering plant genus Epimedium (Berberidaceae). By clarifying the definition of curvature, our aim is to make the language of comparative morphology more precise and broadly applicable to capture other curved structures in nature.

ecology↗

bioRxiv2019

A meta-analysis of global avian survival across species and latitude

Tropical birds are purported to be longer lived than temperate species of similar size, but it has not been shown whether avian survival rates covary with a latitudinal gradient worldwide. Here, we perform a global-scale meta-analysis to investigate the extent of the latitudinal survival gradient. We modeled survival as a function of latitude for the separate northern and southern hemispheres, and considered phylogenetic relationships and extrinsic (climate) and intrinsic (life history) predictors hypothesized to moderate these effects. Using a database of 1,004 estimates from 246 studies of avian survival, we demonstrate that in general a latitudinal survival gradient exists in the northern hemisphere, is dampened or absent for southern hemisphere species, and that survival rates of passerine birds largely account for these trends. We found no indication that the extrinsic climate factors were better predictors of survival than latitude alone, but including species intrinsic traits improved model predictions. Notably, species with smaller clutch size and larger body mass showed higher survival. Our results illustrate that while some tropical birds may be longer lived than their temperate counterparts, the shape of the latitude-survival gradient differs by geographic region and is strongly influenced by species intrinsic traits.

ecology↗