Compared to their temperate-nesting relatives, tropical songbirds grow slow and raise few chicks per nest. Why they do this, when high rates of nest predation in the tropics make the odds of successfully fledging even one chick low, has long been a mystery.
New research from Dr. Tom Martin (OBE, Wildlife Biology, and USGS Montana Co-op Wildlife Research Unit), published in Science August 28, finds the answer in life-history theory. Drawing on years of growth and mortality data from multiple field sites and numerous species, Dr. Martin shows tropical parents are laying fewer eggs to allow greater provisioning of each chick to facilitate faster wing growth, which improves their flight ability to escape predators after leaving the nest. In contrast, higher rates of adult mortality in the temperate zone place a lower premium on the quality of any individual chick, so the same resources are better split among more offspring. Read more about this breakthrough in understanding global patterns of bird variation on the Guardian's GrrlScientist blog and at ScienceDaily.
Slow flight is inefficient, but inevitable during take-off and landing. How (and even whether) birds make the most of their wingbeats during this important stage of flight has long been in question. A new study by OBE grad student Kristin Crandell and advisor Bret Tobalske of the UM Flight Lab used high-tech visualization of air flow around wings to show that some slow-flight upstrokes generate important force. The research article was featured on the cover of the August 2015 issue of the Journal of Experimental Biology.
Hybrids between species are often unfit, but can nonetheless lead to exchange of genetic material from one species to another. Two new papers from DBS researchers address shed light on why, and with what consequences, genetic material flows across species boundaries. In a recent opinion article in Trends in Ecology & Evolution, OBE Associate Professor Winsor Lowe and DBS colleagues argue that elevated dispersal distances in hybrids between native cutthroat trout and introduced rainbow trout account for the rapid spread of damaging rainbow trout genes through Northern Rockies cutthroat. Read more about DBS research into the causes and consequences of trout hybridization in this NPR story.
In the longer term, however, hybridization may leave little but harmless genomic footprints behind. In the September 2015 cover article of the journal Evolution, OBE Assistant Professor Jeff Good and colleagues showed that some populations of the yellow-pine chipmunk long ago swapped their mitochondrial genomes for those of another species. Intriguingly, this ancient mixing left little or no mark on the rest of the introgresssed chipmunks' genomes, suggesting that new genome-scale approaches may uncover cryptic hybridization in many more species and that evolutionary analyses based only mitochondrial markers may often lead researchers astray.