DOI: 10.5061/dryad.b60v7
title: Data from: Impacts of worker density in colony-level aggression, expansion, and survival of the acacia-ant Crematogaster mimosae

description: Experimental studies assessing the impact of demographic changes on
 aggression and inter-group competitive outcomes in communities of social
 species are rare. This gap in our knowledge is important, not only because
 social species are foundational elements of many terrestrial ecosystems,
 but because interference competition among social groups often involves
 decision-like processes influenced by demographic and environmental
 contexts. In East Africa, the symbiotic ant Crematogaster mimosae is a
 co-dominant competitor that engages in high-mortality, intra- and
 interspecific battles for sole possession of host trees. We manipulated
 worker density on C. mimosae Acacia host trees, and the colony's
 opportunity to expand onto neighboring trees to identify how these factors
 influenced colony-level aggression, expansion success, and longer-term
 survivorship. Worker density on focal trees was increased through
 translocation of domatia-bearing branches, and was decreased using partial
 tree fumigations. We examined impacts of density manipulations on
 aggression and immediate expansion success under two different risk
 scenarios. We tied focal trees to either an experimentally emptied-tree
 (low-risk treatment), or to a C. nigriceps-occupied tree (high-risk
 treatment). Expansion success onto emptied neighbor trees was 100% for
 controls and increased-density colonies, but only 50% for
 decreased-density colonies, despite the fact that host trees are a
 limiting resource in this system. Success expanding onto trees occupied by
 a heterospecific competitor reached 36%, 40%, and 79% in decreased,
 control, and increased-density trees, respectively. Our results show that
 changes in worker density due to disturbances or inter-group battles have
 the potential to disrupt competitive hierarchies. Worker density
 manipulations also affected longer-term colony persistence. Behavioral and
 genetic data revealed that 12 months after expansions 100% of the
 decreased-density colonies, and 25% of control and increased-density
 colonies, had been supplanted by neighboring opportunistic conspecifics.
 Intraspecific aggression may have lower costs in C. mimosae because
 aggressive colonies can incorporate workers or queens from defeated
 competitors. The unexpectedly high frequency of conflicts between
 conspecific C. mimosae, in combination with behaviors decreasing the cost
 of intraspecific competition relative to interspecific conflict, may
 create opportunities for the survival of subordinate competitors in this
 ant–plant system.
description: Ruiz_Guajardo_MRC_DensManip.csvThis file contains data from experimental manipulations of worker density, aggression, and survival of focal experimental trees of the co-dominant symbiotic Crematogaster mimosae ant. All colonies are located at Mpala Research Centre, Laikipia in Kenya. For an explanation of the acronyms used for denote each variable measured, and a description of each of them please refer to the ReadMe file entitled: Ruiz-Guajardo_MRC_DensManip_VariablesRuiz_Guajardo_MRC_NonFocalSurv.csvThis file contains data from non-focal tree survivorship, that was used to examine how our experimental manipulations of Crematogaster mimosae worker density in focal selected trees affected the survival probability of the rest of the experimental colony. For an explanation of the variable acronyms, and a description of each measurement please refer to the ReadMe file entitled: Ruiz-Guajardo_MRC_NonFocalSurv_VariablesMainAnal_Fig_Ruiz-Guajardo_MRC_DensManipRCodeThis file contains annotated code used to construct the 4 Figures showed in the MS, as well as a general guide to the main data analyses performed. It is intended as a guide only and does not contain all code for every model and analyses performed, but will allow the reader to follow the general flow of the analyses made. We are happy to provide answers to questions or further details that may arise from using the code.RCode_MainAnalyses_Figures_Ruiz-Guajardo_MRC_DensManips.r