Adaptation to Substrate in Rock Outcrop Plants: Interior Highlands Talinum (Portulacaceae)

Abstract

Talinum calycinum Engelm. (Portulacaceae) and T. parviflorum Nutt. are small succulent-leaved perennial herbs of very shallow soils of rock outcrops in the Interior Highlands (Ozarks and Quachitas), United States. The first species has been considered substrate indifferent, occurring on a variety of outcrops but only rarely on limestone; the second also occurs on a variety of outcrops, but not on limestone. Populations of T. parviflorum from sandstone outcrops grown experimentally on native and alien soils grew as well on shale outcrop soils as on their own native sandstone soils, but when grown on calcareous outcrop soils showed abnormal coloration (yellow-green, with much red pigment), high mortality, and extremely poor total growth. In T. calycinum also, all populations, regardless of origin (sandstone, shale, granite, syenite, limestone), grew well on all noncalcareous soils, but growth was extremely poor on calcareous soils. Talinum calycinum thus is not substrate indifferent but, in fact, its growth...