Seedling Survivorship of the Beach Morning Glory, Ipomoea pes-caprae (Convolvulaceae)

Abstract

Factors influencing seedling survivorship in the beach morning glory, Ipomoea pes-caprae (L.) Roth, were studied near Townsville, Queensland, Australia. Censuses of recently germinated seedlings revealed an 83% mortality rate over a period of 11 weeks. Seedlings that died occurred significantly further above high-tide line than did seedlings that were still alive at the end of the study. Although distance to the nearest neighbouring plants did not influence the probability of survival, more seedlings survived if their nearest neighbours were monocots than if they were conspecifics. The probability of survival was greater for seedlings which were closer to neighbouring seedlings of I. pes-caprae, but distance to the nearest adult I. pes-caprae did not affect survival. There was 100% mortality of seedlings that were naturally buried by sand. A field experiment manipulated levels of insect herbivory and sand burial, and showed that herbivory caused a seven-fold increase in mortality rate. Although sand burial also increased mortality, this effect was not significant. Overall, seedling mortality appeared to be influenced by both abiotic factors (location on beach, sand burial) and biotic factors (seedling density, neighbour type and herbivory).