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Nest relocation and excavation in the Florida harvester ant, Pogonomyrmex badius.

Tschinkel WR - PLoS ONE (2014)

Bottom Line: Relocation is probably intrinsic to the life history of this species, and the causes of relocation remain obscure--the architecture of old and new nests was very similar, and neither the forest canopy nor the density or size of neighbors was correlated with relocation.Colonies moving more than once in two years lost more size than those moving less often, suggesting that moving may bear a fitness cost.Colony relocation is a dramatic and consistent feature of the life history of the Florida harvester ant, inviting inquiry into its proximal and ultimate causes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America.

ABSTRACT
The Florida harvester ant (Pogonomyrmex badius) excavates deep nests in the sandy soils of the Gulf and Atlantic coastal plains. Nest relocations of over 400 colonies in a north Florida coastal plains pine forest were tracked and mapped from 2010 to 2013. Individual colonies varied from one move in two years to four times a year, averaging about one per year. Almost all moves occurred between May and November peaking in July when more than 1% of the colonies moved per day. Move directions were random, and averaged 4 m, with few moves exceeding 10 m. Distance moved was not related to colony size. Over multiple moves, paths were random walks around the original nest location. Relocation is probably intrinsic to the life history of this species, and the causes of relocation remain obscure--the architecture of old and new nests was very similar, and neither the forest canopy nor the density or size of neighbors was correlated with relocation. Monitoring entire relocations (nā€Š=ā€Š20) showed that they were usually completed in 4 to 6 days. Moves were diurnal, peaking in the mornings and afternoons dipping during mid-day, and ceasing before sundown. Workers excavated the new nest continuously during the daytime throughout the move and beyond. A minority of workers carried seeds, charcoal and brood, with seeds being by far the most common burden. The proportion of burdened workers increased throughout the move. Measured from year to year, small colonies gained size and large ones lost it. Colonies moving more than once in two years lost more size than those moving less often, suggesting that moving may bear a fitness cost. Colony relocation is a dramatic and consistent feature of the life history of the Florida harvester ant, inviting inquiry into its proximal and ultimate causes.

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Average normalized activity by time of day (in 2-hr blocks) in four sampled months of 2013.The grey zone shows the mean range of trail temperature by time of day. The ordinate shows activity as proportion of the observed total. Peak activity occurs early and late in the day in June, but shifts to mid-day by August and October.
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pone-0112981-g016: Average normalized activity by time of day (in 2-hr blocks) in four sampled months of 2013.The grey zone shows the mean range of trail temperature by time of day. The ordinate shows activity as proportion of the observed total. Peak activity occurs early and late in the day in June, but shifts to mid-day by August and October.

Mentions: The large differences among colonies in the rates of worker, brood, seed, callows and charcoal movement suggest that normalizing the data as fraction of the total observed items or ants moved during 2-hr time blocks between 8:30 a.m. and 8:30 p.m. would put colonies of different sizes and rates on the same scale. Fig. 16 presents such data for the daily movement activity over the season atop the mean trail temperature range. June temperatures were high much of the day, probably because the weather was very sunny. Between June and October, peak temperatures occurred later in the day. Across the season, the fraction of items and ants moved during each 2-hr period changed dramatically. Worker traffic to and from the new nest showed a distinct mid-day decrease in June and July. August's greater cloudiness and more frequent rain reduced the maximum temperatures, reducing early morning activity, allowing a greater proportion of movement mid-day, and moving the lull to early afternoon. By October, mornings remained cool longer and maximum temperatures occurred later in the day, reducing early morning activity and creating a large peak in traffic during late morning and mid-day. Across months, evenness of traffic throughout the day decreased after July, with a sharper, larger peak occurring during late morning, and decreased activity after mid-day.


Nest relocation and excavation in the Florida harvester ant, Pogonomyrmex badius.

Tschinkel WR - PLoS ONE (2014)

Average normalized activity by time of day (in 2-hr blocks) in four sampled months of 2013.The grey zone shows the mean range of trail temperature by time of day. The ordinate shows activity as proportion of the observed total. Peak activity occurs early and late in the day in June, but shifts to mid-day by August and October.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4237378&req=5

pone-0112981-g016: Average normalized activity by time of day (in 2-hr blocks) in four sampled months of 2013.The grey zone shows the mean range of trail temperature by time of day. The ordinate shows activity as proportion of the observed total. Peak activity occurs early and late in the day in June, but shifts to mid-day by August and October.
Mentions: The large differences among colonies in the rates of worker, brood, seed, callows and charcoal movement suggest that normalizing the data as fraction of the total observed items or ants moved during 2-hr time blocks between 8:30 a.m. and 8:30 p.m. would put colonies of different sizes and rates on the same scale. Fig. 16 presents such data for the daily movement activity over the season atop the mean trail temperature range. June temperatures were high much of the day, probably because the weather was very sunny. Between June and October, peak temperatures occurred later in the day. Across the season, the fraction of items and ants moved during each 2-hr period changed dramatically. Worker traffic to and from the new nest showed a distinct mid-day decrease in June and July. August's greater cloudiness and more frequent rain reduced the maximum temperatures, reducing early morning activity, allowing a greater proportion of movement mid-day, and moving the lull to early afternoon. By October, mornings remained cool longer and maximum temperatures occurred later in the day, reducing early morning activity and creating a large peak in traffic during late morning and mid-day. Across months, evenness of traffic throughout the day decreased after July, with a sharper, larger peak occurring during late morning, and decreased activity after mid-day.

Bottom Line: Relocation is probably intrinsic to the life history of this species, and the causes of relocation remain obscure--the architecture of old and new nests was very similar, and neither the forest canopy nor the density or size of neighbors was correlated with relocation.Colonies moving more than once in two years lost more size than those moving less often, suggesting that moving may bear a fitness cost.Colony relocation is a dramatic and consistent feature of the life history of the Florida harvester ant, inviting inquiry into its proximal and ultimate causes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America.

ABSTRACT
The Florida harvester ant (Pogonomyrmex badius) excavates deep nests in the sandy soils of the Gulf and Atlantic coastal plains. Nest relocations of over 400 colonies in a north Florida coastal plains pine forest were tracked and mapped from 2010 to 2013. Individual colonies varied from one move in two years to four times a year, averaging about one per year. Almost all moves occurred between May and November peaking in July when more than 1% of the colonies moved per day. Move directions were random, and averaged 4 m, with few moves exceeding 10 m. Distance moved was not related to colony size. Over multiple moves, paths were random walks around the original nest location. Relocation is probably intrinsic to the life history of this species, and the causes of relocation remain obscure--the architecture of old and new nests was very similar, and neither the forest canopy nor the density or size of neighbors was correlated with relocation. Monitoring entire relocations (nā€Š=ā€Š20) showed that they were usually completed in 4 to 6 days. Moves were diurnal, peaking in the mornings and afternoons dipping during mid-day, and ceasing before sundown. Workers excavated the new nest continuously during the daytime throughout the move and beyond. A minority of workers carried seeds, charcoal and brood, with seeds being by far the most common burden. The proportion of burdened workers increased throughout the move. Measured from year to year, small colonies gained size and large ones lost it. Colonies moving more than once in two years lost more size than those moving less often, suggesting that moving may bear a fitness cost. Colony relocation is a dramatic and consistent feature of the life history of the Florida harvester ant, inviting inquiry into its proximal and ultimate causes.

Show MeSH