Fred Ruhe
Well-known member
Katherine Marriott, Donald R. Prothero & Kristin Watmore, 2022
How did Northern Harriers (Circus hudsonius) from La Brea Tar Pits respond to climate change during the last glacial-interglacial cycle?
in Lucas et al., 2022, Fossil Record 8. New Mexico Museum of Natural History and Science Bulletin 90: 303-308
https://www.researchgate.net/publication/362680627_How_did_Northern_Harriers_Circus_hudsonius_from_La_Brea_Tar_Pits_respond_to_climate_change_during_the_last_glacial-interglacial_cycle
Abstract
Changing environmental pressures are associated with expected minor morphological changes in bird populations over just a few generations. This was first documented in Charles Darwin’s studies on Galápagos finches. However, microevolutionary changes in the shape of limbs are not associated with climate, and usually another factor is the cause for the new adaptation, such as predation or competition for a food source. The Rancho La Brea (RLB) tar pits preserve an exceptional quantity of bird fossils in extraordinary resolution spanning the interval from 37 ka to 9 ka. The quantity and quality of bird fossils at RLB makes it suitable for time-series studies on microevolution. All RLB birds studied so far do not exhibit any change in body size or limb proportions through the last glacial maximum about 18,000-20,000 years ago, when the southern California chaparral was replaced by snowy coniferous forests. Birds, like most multicellular organisms, exhibit evolutionary stasis throughout most of their lineage. Stasis is overwhelmingly independent of climatic shifts. To further test this conclusion, we
measured leg bones of Circus hudsonius, the Northern Harrier. We found complete stasis in specimens ranging from 37 ka to 9 ka, a period which encompasses both the peak glacial interval (20-18 ka) and the end of the last ice age (11.7 ka).
Enjoy,
Fred
How did Northern Harriers (Circus hudsonius) from La Brea Tar Pits respond to climate change during the last glacial-interglacial cycle?
in Lucas et al., 2022, Fossil Record 8. New Mexico Museum of Natural History and Science Bulletin 90: 303-308
https://www.researchgate.net/publication/362680627_How_did_Northern_Harriers_Circus_hudsonius_from_La_Brea_Tar_Pits_respond_to_climate_change_during_the_last_glacial-interglacial_cycle
Abstract
Changing environmental pressures are associated with expected minor morphological changes in bird populations over just a few generations. This was first documented in Charles Darwin’s studies on Galápagos finches. However, microevolutionary changes in the shape of limbs are not associated with climate, and usually another factor is the cause for the new adaptation, such as predation or competition for a food source. The Rancho La Brea (RLB) tar pits preserve an exceptional quantity of bird fossils in extraordinary resolution spanning the interval from 37 ka to 9 ka. The quantity and quality of bird fossils at RLB makes it suitable for time-series studies on microevolution. All RLB birds studied so far do not exhibit any change in body size or limb proportions through the last glacial maximum about 18,000-20,000 years ago, when the southern California chaparral was replaced by snowy coniferous forests. Birds, like most multicellular organisms, exhibit evolutionary stasis throughout most of their lineage. Stasis is overwhelmingly independent of climatic shifts. To further test this conclusion, we
measured leg bones of Circus hudsonius, the Northern Harrier. We found complete stasis in specimens ranging from 37 ka to 9 ka, a period which encompasses both the peak glacial interval (20-18 ka) and the end of the last ice age (11.7 ka).
Enjoy,
Fred
