Chin J Plan Ecolo ›› 2009, Vol. 33 ›› Issue (5): 901-910.

• Research Articles •

### BET HEDGING IN HETEROMORPHIC ACHENES OF HETERACIA SZOVITSII (ASTERACEAE), A DESERT EPHEMERAL

CHENG Xiao-Jun;TAN Dun-Yan*

1. Xinjiang Key Laboratory of Grassland Resources and Ecology, College of Grassland and Environment Sciences, Xinjiang Agricultural Univer-sity, Ürümqi 830052, China
• Online:2009-09-30 Published:2009-09-30
• Contact: TAN Dun-Yan

Abstract: Aims Heteracia szovitsii is a common ephemeral Asteraceae species that germinates in early spring in the Junggar Desert of China and produces three types of achenes with different morphologies in one infructescence. To better understand how this species is adapted to its desert habitat, we studied 1) the morphological, structural and dispersal characteristics of the three types of achenes and 2) according to the bet-hedging strategy, how heterocarpy spreads the risk of survival in the desert environment.
Methods For the three types of achenes, we recorded number, mass, morphology, surface ornamentation (via scanning electron micrographs), pericarp structure, dispersal distance and landing time in the laboratory and mode of dispersal and its duration in the field.
Important findings Compared with central achenes, the pericarps of peripheral and intermediate achenes were thicker, darker in color, and contained a higher amount of phenolic compounds and more sclerenchyma, which could protect the embryo better and cause the seeds to be more dormant. Embryo mass of peripheral and intermediate achenes was greater than that of central achenes, and thus could produce larger and more competitive seedlings. After maturation, central achenes with pappus dispersed over a wide range, while peripheral and intermediate achenes with no pappus usually dispersed near the mother plant. The different number of heteromorphic achenes could spread the risk of dispersal and settlement for this species. The larger number of central achenes increases chance for their random dispersal, and this is favorable for exploiting a larger geographical range for the population. The lower number of peripheral and intermediate achenes could decrease sibling competition due to dispersal near the mother plant. Formation of heteromorphic achenes is a form of bet hedging that could spread the risk of mortality in the extreme environment of the Junggar Desert. The peripheral and intermediate achenes pre-sumably represent a “low-risk” strategy and the central achenes a “high-risk” strategy in one capitulum. Based on these strategies, H. szovitsii can spread the risk of survival and ensure its reproductive success.