Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).

A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the bree...

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Main Authors: D T Tyler Flockhart, Tara G Martin, D Ryan Norris
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2012-01-01
Series:PLoS ONE
Online Access:http://europepmc.org/articles/PMC3440312?pdf=render
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author D T Tyler Flockhart
Tara G Martin
D Ryan Norris
author_facet D T Tyler Flockhart
Tara G Martin
D Ryan Norris
author_sort D T Tyler Flockhart
collection DOAJ
description A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism.
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spelling doaj.art-03cc14ef9d344a99a3a4542fd6c404882022-12-22T00:50:40ZengPublic Library of Science (PLoS)PLoS ONE1932-62032012-01-0179e4508010.1371/journal.pone.0045080Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).D T Tyler FlockhartTara G MartinD Ryan NorrisA central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism.http://europepmc.org/articles/PMC3440312?pdf=render
spellingShingle D T Tyler Flockhart
Tara G Martin
D Ryan Norris
Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).
PLoS ONE
title Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).
title_full Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).
title_fullStr Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).
title_full_unstemmed Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).
title_short Experimental examination of intraspecific density-dependent competition during the breeding period in monarch butterflies (Danaus plexippus).
title_sort experimental examination of intraspecific density dependent competition during the breeding period in monarch butterflies danaus plexippus
url http://europepmc.org/articles/PMC3440312?pdf=render
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AT taragmartin experimentalexaminationofintraspecificdensitydependentcompetitionduringthebreedingperiodinmonarchbutterfliesdanausplexippus
AT dryannorris experimentalexaminationofintraspecificdensitydependentcompetitionduringthebreedingperiodinmonarchbutterfliesdanausplexippus