Leroy et al. 2012 (Article) ant-garden

Ant species identity mediates reproductive traits and allocation in an ant-garden bromeliad

Author(s):—C. Leroy, B. Corbara, L. Pelozuelo, J. Carrias, A. Dejean & R. Céréghino

Publication:—Annals of Botany 109: 145-152. (2012)

Abstract:—- Background and Aims Determining the sources of variation in floral morphology is crucial to understanding themechanisms underlying Angiosperm evolution. The selection of floral and reproductive traits is influenced by theplant’s abiotic environment, florivores and pollinators. However, evidence that variations in floral traits resultfrom mutualistic interactions with insects other than pollinators is lacking in the published literature and hasrarely been investigated. We aimed to determine whether the association with either Camponotus femoratus or Pachycondyla goeldii (both involved in seed dispersal and plant protection) mediates the reproductive traitsand allocation of Aechmea mertensii , an obligatory ant-garden tank-bromeliad, differently.
- Methods Floral and reproductive traits were compared between the two A. mertensii ant-gardens. The nitrogenflux from the ants to the bromeliads was investigated through experimental enrichments with stableisotopes ( 15 N).
- Key Results Camponotus femoratus -associated bromeliads produced inflorescences up to four times longer thandid P. goeldii -associated bromeliads. Also, the numbers of flowers and fruits were close to four times higher, andthe number of seeds and their mass per fruit were close to 1.5 times higher in C. femoratus than in P. goeldii -associated bromeliads. Furthermore, the 15 N-enrichment experiment showed that C. femoratus -associatedbromeliads received more nitrogen from ants than did P. goeldii -associated bromeliads, with subsequent positiverepercussions on floral development. Greater benefits were conferred to A. mertensii by the association with C. femoratus compared with P. goeldii ants.
- Conclusions We show for the first time that mutualistic associations with ants can result in an enhancedreproductive allocation for the bromeliad A. mertensii . Nevertheless, the strength and direction of the selectionof floral and fruit traits change based on the ant species and were not related to light exposure. The differentactivities and ecological preferences of the ants may play a contrasting role in shaping plant evolution andspeciation.

Keywords:—Aechmea mertensii , Camponotus femoratus , bromeliad, Bromeliaceae, d 15 N, floral traits, fruit-set,mutualistic ants, Pachycondyla goeldii , reproductive allocation, stable isotopes.