Experimental Investigation of Pathogenic Stress on Phytolith Formation in Wild Gourds (Cucurbita pepo ssp. ovifera var. texana)

Silica phytoliths formed in plant tissues are useful to archaeologists because of their diagnostic value and longevity in ancient deposits.  Paleoecology, site formation processes, plant domestication, and other topics are routinely addressed using phytolith assemblages, especially when macrobotanical remains are not preserved.  However, little research has been conducted to document the effects of common ecological variables on phytolith formation.  Here, we investigate the effects of mosaic virus and bacterial wilt disease on diagnostic scalloped phytoliths in the rind of a wild-type gourd.  We observe no difference between control plants and individuals with mosaic virus.  However, we observe a significant difference between plants with bacterial wilt disease and control plants, with diseased individuals carrying a greater proportion of large-diameter scalloped phytoliths.  This and similar phenomena could potentially confound archaeological interpretations of phytolith assemblages, and the effects of this and other ecological variables should be studied in a diverse range of taxa.