October 21, 2021

5:00pm 1100 TLSB

EcoEvoPub Seminar Series
Department of Ecology and Evolutionary Biology, UCLA

" Graduate Student Presentations "

Ben Tonelli

Department of Ecology and Evolutionary Biology, UCLA, Tingley Lab

“Geomagnetic disturbance associated with vagrancy in migratory landbirds”

Occurrences of rare, out-of-place birds, known as “accidentals” or “vagrants,” have long captivated birdwatchers and puzzled ornithologists. Although vagrants have been noted by observers for centuries, little is known about the underlying processes driving this phenomenon. One hypothesis is that vagrancy may result from disorientation due to a lack of reliable navigational information. One source of navigational information used by landbirds is the Earth’s magnetic field, which birds sense using specialized magnetoreceptor structures. Here, we investigated whether disruption to the Earth’s magnetic field is associated with vagrancy among terrestrial landbirds. Using a dataset of over 2,000,000 captures of 150 bird species over 60 years, we found a strong cross-species association between disruption in the Earth’s magnetic field and avian vagrancy. These results provide strong support for a previously unknown mechanism underlying avian vagrancy, and could help predict periodic population declines and range shifts in the future.

 

Xiaohui Guo

Department of Ecology and Evolutionary Biology, UCLA, Pinter-Wollman Lab

“Brood:worker ratios determine metabolic scaling of seed harvester ant colonies during ontogeny”

The negative allometric scaling of metabolic rate with mass has been demonstrated in many species of social insects, but the proximate mechanisms remain unclear. System composition theory suggests that the variation in heterogeneous metabolic components can contribute to the allometric scaling of metabolism in organisms and social insect colonies, but how system composition affects the metabolism of social insect colonies remains unclear. To understand how social insect colonies achieve hypometric scaling of metabolism, we repeatedly measured the metabolic rate and mass of 25 seed-harvester ant colonies and their sub-components (brood and mature ants) during ontogenetic growth over 3.5 years. We found the metabolic rate did not scale with mass in a universal power-law, but rather was better explained by the segmented regression model, with isometric scaling (b=1) below the break point (0.31g colony mass), and hypometric scaling (b=0.9) in larger colonies. Brood have much lower metabolic rates than adults, and colonies with higher ratios of brood:workers had higher metabolic rates and activity of workers, presumably due to the increased effort of rearing brood. Changing brood:worker ratios explain changing scaling of metabolic rate of colonies during ontogeny, and provide at least a partial explanation of hypometric scaling of metabolism in P. californicus colonies.