I suppose density-dependent reductions in per capita seed production might be an example.
On Thu, Jan 21, 2016 at 5:11 AM, Thomas Rosburg <[email protected]> wrote: > Here’s the question: *Has any population of organisms (humans excluded) > regulated and reduced their population size by lowering their birth rate > instead of increasing their death rate*? And have any slowed their rate > of increase by raising the age at first birth? Most of the examples I know > of natural population control do so by increasing the death rate. > > > Do you mean consciously? Then probably no. But yes for question 1 if > you consider dominance hierarchies where birth rates (matings) decrease > during reduced resource availability. And yes for question 2 if you > consider the example in some small mammals where stress resulting from > reduced resources produces pheromones in older females that delays sexual > maturity in younger females. > > > > Thomas Rosburg, PhD > > Professor and Chair, Department of Biology > > Drake Biodiversity Center and Herbarium > > Drake University, 2507 University Avenue > > Des Moines, IA 50311 > > > > 515.271.2768 > > 515.271.2920 > > cell 515.460.4468 > > Photo - finish of Leadville Silverrush 50 mile ultramarathon, with > daughter Vanessa > > > "Let the rivers run like they always do, its not up to me its not up to > you; When we reach the end, when our time is done; Let us all be still > while the rivers run" Bob Seger, *Let the Rivers Run* on Ride Out > > > ------------------------------ > *From:* Ecological Society of America: grants, jobs, news < > [email protected]> on behalf of Howard S. Neufeld < > [email protected]> > *Sent:* Wednesday, January 20, 2016 8:38 AM > *To:* [email protected] > *Subject:* [ECOLOG-L] Reducing Population Size in Natural Populations of > Organisms - A Question > > > Hi all - I am currently working on an abstract about global climate change > for a regional biology meeting in the southeast, and I wanted to say > something about the control of natural populations of organisms, but I am > not sure if the statement I want to make is true, so I’m asking for some > advice and counsel on this. > > > > Here’s the question: *Has any population of organisms (humans excluded) > regulated and reduced their population size by lowering their birth rate > instead of increasing their death rate*? And have any slowed their rate > of increase by raising the age at first birth? Most of the examples I > know of natural population control do so by increasing the death rate. > > > > Some further comments: If resources get scarce as populations increase in > density then behavioral changes could lead to reductions in the birth rate, > but under resource scarcity I would assume that the death rate would go up > also. I know about density-dependent and density-independent controls on > population growth, but here, I’m looking for explicit examples where > populations decrease birth rate without increasing the death rate. > > > > You may wonder why I’m asking this. It's because I’m wondering if humans > can, in the long-term, reduce their population by lowering the birth rate > without increasing the death rate. Yes, some countries are already on > that path (Japan, for example), but economists and social and political > scientists seem to have a problem with such demographic changes, > particularly in a free-market situation where an aging population, even if > sustainable, is viewed as less competitive and therefore at risk of losing > out (whatever that means) to younger, more dynamic populations. It > suggests to me that ecology and society are fundamentally at odds here, and > that future societies may require paradigm shifts in the way they operate > if humans are to actually create a sustainable society. But that’s > another story. > > > > For now, I’d be really interested to hear explicit examples if anyone has > any. > > > > Thanks. > > Howie Neufeld > > -- > Dr. Howard S. Neufeld, Professor > Director, Southern Appalachian Environmental Research and Education Center > (SAEREC) > Chair, Appalachian Interdisciplinary Atmospheric Research Group (AppalAIR) > > Mailing Address: > Department of Biology > 572 Rivers St. > Appalachian State University > Boone, NC 28608 > Tel: 828-262-2683; Fax 828-262-2127 > > Websites: > Academic: http://biology.appstate.edu/faculty-staff/104 > Personal: http://www.appstate.edu/~neufeldhs/index.html > SAEREC: http://saerec.appstate.edu > AppalAIR: http://appalair.appstate.edu > Fall Colors: > Academic: http://biology.appstate.edu/fall-colors > Facebook: https://www.facebook.com/FallColorGuy > > <http://biology.appstate.edu/faculty-staff/104> > Dr Howard S Neufeld | Department of Biology | Appalachian ... > <http://biology.appstate.edu/faculty-staff/104> > biology.appstate.edu > Our Fall 2015 featured faculty member is Dr. Matt Estep. He specializes in > Evolutionary Genetics and Genomics. His philosophy of teaching and a short > description of ... > > >
