Do plants adjust their sex allocation and secondary sexual morphology in response to their neighbours?
OBJECTIVE
Changes in the sex allocation (i.e. in pollen versus seed production) of hermaphroditic plants often occur in response to the environment. In some homosporous ferns, gametophytes choose their gender in response to chemical cues sent by neighbours, such that spores develop as male gametophytes if they perceive a female or hermaphrodite nearby. Here it is considered whether a similar process might occur in the androdioecious angiosperm species Mercurialis annua, in which males co-occur with hermaphrodites; previous work on a Spanish population of M. annua found that individuals were more likely to develop as males at high density.


METHODS
Using a novel approach to treat plants with leachate from pots containing males or hermaphrodites of M. annua, the hypothesis that individuals assess their mating opportunities, and adjust their sex expression accordingly, was tested through an exchange of chemical cues through the soil.


RESULTS
For the population under study, from Morocco, no evidence was found for soil-signal-dependent sex expression: neither sex ratios nor sex allocation differed among experimental treatments.


CONCLUSIONS
The results imply either that the Moroccan population under study behaves differently from that previously studied in Spain (pointing to potential geographical variation in plasticity for sex expression), or that our method failed to capture the signals used by M. annua for adjustment of sex expression.
Department of Ecology and Evolution, Le Biophore, UNIL-SORGE, University of Lausanne, Switzerland. julia.sanchezvilas@gmail.com
Julia Sánchez
JS
Vilas
John R
JR
Pannell
D018533:Biomass; D004777:Environment; D019665:Euphorbiaceae / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*; D009018:Morocco; D010641:Phenotype; D053147:Plant Exudates / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development / Q000502:physiology; D011058:Pollen / Q000737:chemistry / Q000254:growth & development / Q000502:physiology; D012098:Reproduction; D036226:Seedlings / Q000737:chemistry / Q000254:growth & development / Q000502:physiology; D012639:Seeds / Q000737:chemistry / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction
D053147:Plant Exudates