A-1 



MONITORING SILENE SPALDINGII ON 

 WILD HORSE ISLAND: 1988 PROGRESS REPORT 



Introduction and Methods 



On August 18, 1986, two permanent transects were established 

 on Wild Horse Island in order to monitor a population of Silene 

 spaldinqii and begin to gather data on the life history of this 

 rare plant (see Lesica, 1986 for details on the location of the 

 transects). On August 2, 1988, Bernie Hall and I reread these 

 transects following methods outlined in Lesica (1987). Codes 

 used in recording life history data are as follows: 



S Seedling Only a basal rosette present 



J Juvenile A non-reproductive individual with only 



sterile stems 



I Inflorescence Records the number of flowering stems per 



mature individual 



S Sterile Records the number of sterile stems per 



mature individual 



P Predated Records the number of flowers suffering 



predation 



A Aborted Records the number of unpredated flowers that 



did not produce a mature fruit 



F Fruit Records the number of flowers that produced a 



mature fruit recognized by the presence of a 

 large, swollen ovary 



Results and Discussion 



Fecundity data for the two years are presented in Table 1. 

 The number of plants in the transects decreased by 1/3 from 1986 

 to 1988. In addition, the total number of flowers and fruits 

 produced also declined dramatically. Part of this decline is due 

 to the presence of fewer mature plants, and part is due to a 

 decrease in the number of flowers produced by individual plants. 

 The mean rate of abortion stayed approximately the same. 



A comparison of individual plant performance between the 

 two years are presented in Table 2. Thirteen plants present in 

 1986 could not be located in 1988, and four plants not recorded 

 in 1986 were present in 1988. As measured by flower and fruit 

 production, all plants decreased in vigor. 



Much of the decline in plant vigor indicated by these 



