
NSF Org: |
DMS Division Of Mathematical Sciences |
Recipient: |
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Initial Amendment Date: | August 30, 2014 |
Latest Amendment Date: | August 30, 2014 |
Award Number: | 1407564 |
Award Instrument: | Standard Grant |
Program Manager: |
Junping Wang
jwang@nsf.gov (703)292-4488 DMS Division Of Mathematical Sciences MPS Directorate for Mathematical and Physical Sciences |
Start Date: | September 1, 2014 |
End Date: | August 31, 2020 (Estimated) |
Total Intended Award Amount: | $300,000.00 |
Total Awarded Amount to Date: | $300,000.00 |
Funds Obligated to Date: |
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History of Investigator: |
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Recipient Sponsored Research Office: |
845 N PARK AVE RM 538 TUCSON AZ US 85721 (520)626-6000 |
Sponsor Congressional District: |
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Primary Place of Performance: |
617 N. Santa Rita Ave Tucson AZ US 85721-0089 |
Primary Place of
Performance Congressional District: |
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Unique Entity Identifier (UEI): |
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Parent UEI: |
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NSF Program(s): |
POP & COMMUNITY ECOL PROG, MATHEMATICAL BIOLOGY, MSPA-INTERDISCIPLINARY |
Primary Program Source: |
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Program Reference Code(s): |
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Program Element Code(s): |
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Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.049 |
ABSTRACT
Higher temperatures associated with climate change can cause changes in marine food webs, resulting in a diminished food supply for top consumers. In response, these consumer species must change strategies and behaviors in order to adapt. One change that has been observed in numerous species is an increase in cannibalism. Another is the timing of reproductive activities. Such changes can in turn lead to a cascade of changes throughout an ecosystem, affecting survival of individual species and the well-being of the entire system. El Niño events mimic some features of long-term climate change on short time scales, allowing for tests of some climate-related hypotheses in marine systems. This project will examine the impact of climate-change-related food shortages on organisms both theoretically, using mathematical models, and empirically, at a large colony of seabirds that function as an important indicator species. The work will provide cross-disciplinary training in mathematical biology for undergraduate, masters, and Ph.D. students. The project emphasizes training undergraduates and members from underrepresented groups. Undergraduate students will be involved at every stage of the research process, from data collection and analysis to joint authorship of peer-reviewed publications. The investigators engage the general public and wildlife managers through public lectures and interviews, and by working with biologists and managers from the U.S. Fish and Wildlife Service. The results of this work have important implications for the management of natural populations responding to climate change.
In previous work the investigators demonstrated (1) a strong positive association between rising sea surface temperatures (SSTs) and increased egg cannibalism in glaucous-winged gulls (Larus glaucescens), which are important indicators of marine environmental quality; and (2) the existence of every-other-day ovulation synchrony in glaucous-winged gulls, with the degree of synchronization proportional to colony density. Proof-of-concept mathematical models suggest that the two traits may be co-adaptive, and that, in general, rising SSTs may initiate a cascade of changes in life history strategies in colonial seabirds. The objectives of this study are to (1) develop and analyze general mathematical models for exploring the interaction of SSTs, reduced environmental food availability, cannibalism, and reproductive synchrony in terms of population and adaptive dynamic responses to changes in food availability; (2) field test, in a specific system, predictions associated with two general hypotheses suggested by the mathematical models, namely, that cannibalism is an adaptive response to decreased food supply, which can be a consequence of increased SST, and that reproductive synchrony is an adaptive response to cannibalism; and (3) train undergraduate, master's, and Ph.D. students in interdisciplinary STEM research involving mathematical modeling and field research, intentionally emphasizing the training of underrepresented groups.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This Award # 1407564 (PI J. M. Cushing) was a collaborative with Award # 1407040 (co-PI?s S.M. Henson and J. Hayward). It was a highly interdisciplinary project that observed and modeled marine animal behavior at a remote ecological site located on Protection Island, WA, which is a wildlife refuge administered by the U.S. Fish and Wildlife Service.
The main focus was the glaucous-winged gull, which is considered an indicator of ecological health in that region and which breeds by the tens of thousands on the island every spring and early summer. J. Hayward, the lead ecologists on the team, together with numerous graduate and undergraduate students collected an immense amount of data on many aspects of gull behavior: mating, feeding, preening, etc. and rigorously correlated these behaviors with a large number of environmental variables, including ambient air temperature, humidity, sea surface temperature, tidal patterns, length of day, etc. Using this data, the modeling team (lead by S. M. Henson and J. M. Cushing) devised both statistical models and deterministic models that describe the dynamics of these behaviors over the course of a breeding season as well as between seasons. The goal was to not just to describe the data (fit the models) but make predictions for the next season and to validate the predictive capability of the models. This project had to goals: to better understand gull behavior and to show that mathematical models can be predictive. During the first years of the project, we were highly successful in this effort, as we demonstrated the ability of the models to predict, after one season, precise behavioral characteristics within the colony that were validated by observations the next season.
During the course of this multi-year project interesting out-of-the-ordinary phenomena were observed that correlated with the occurrence of el Ni?o years, when sea surface temperatures rise dramatically. Since there has been a steady increase in sea surface temperature since (at least) the middle of last century, these el Ni?o events and the accompanying changes in gull behavior serve as a kind of natural experiment for the future of the gull colonies as sea surface temperature continue to rise in the future. The two most striking behavior changes observed during el Ni?o year was a significant occurrence of egg cannibalism (to nearly 50% of eggs layed) and egg-laying synchronization by females (who lay one egg, on average, every other day). Egg cannibalism can be explained by reduced environmental food resources due to increase sea temperature (which drives fish and zooplankton to deeper depths and different locations) and the fact that eggs are highly nutritious for an adult gull (50% daily nutritional requirements). The egg-laying synchrony is hypothesized to be the classic ecological strategy of a prey saturation to overwhelm predators and thus is a strategy used by individual females to protect their own eggs (cannibals are mostly males). But given the background of steady climate warming, can these behavioral changes and responses, which might well provide population survival in the short term, provide a survival strategy in the long term? A major project for the modeling team was to investigate these hypotheses by means of ?proof-of-concept? models (as opposed to details, models designed specifically for gulls). Our modeling methodology and analysis showed that, under the right circumstances (mainly a high enough benefit to a cannibal?s survival probability from cannibalistic resources) the answer is yes: a cannibalistic population can survive in the long run in a degraded environment when a non-cannibalistic population would not. However, this conclusion comes with two important caveats: population numbers must be kept at a suitably high level and there is a ?tipping? point for the environmental resource at which, if exceeded, will cause a sudden catastrophic extinction of the population. Our models were also modified to include adaptation by Darwinian principles in order to show that evolution can indeed select for increased cannibalism in degraded environments (whereas it selects for decreased cannibalism in improved environments).
The models we developed have a high level of generality (they are not specific to gulls or any other specific species) and therefore these conclusions contribute to the general theory of life history strategies. From a mathematical point of view, the project made original contributions to bifurcation theory. It did this because available theorems and analytic methods did not apply to some of the models and required the development and proof of new theorems. Post-doctoral collaborators and graduate students contributed significantly to this effort (resulting in two Ph.D. dissertations).
Last Modified: 09/12/2020
Modified by: Jim M Cushing
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