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Hydrocotyle sibthorpioides (Apiaceae) new for Texas and notes on introduced species
Abstract
Hydrocotyle sibthorpioides (Apiaceae) is reported as new to the Texas flora. Introduced species in the East Texas flora, as well as noxious plants and invasive exotics (including four particularly problematic species (Cuscuta japonica, Orobanche ramosa, Solanum viarum, and Triadica sebifera) are discussed.
Spatial patchiness and temporal variability in water availability are common in nature under global climate change, which can remarkably influence adaptive responses of clonal plants, i.e. clonal integration (translocating resources between connected ramets). However, little is known about the effects of spatial patchiness and temporal heterogeneity in water on growth and clonal integration between congeneric invasive and native Hydrocotyle species. In a greenhouse experiment, we subjected severed or no severed (intact) fragments of Hydrocotyle vulgaris, a highly invasive species in China, and its co-existing, native congener H. sibthorpioides to different spatial patchiness (homogeneous and patchy) and temporal interval (low and high interval) in water supply. Clonal integration had significant positive effects on growth of both species. In the homogeneous water conditions, clonal integration greatly improved the growth in fragments of both species under low interval in water. However, in the patchy water conditions, clonal integration significantly increased growth in both ramets and fragments of H. vulgaris under high interval in water. Therefore, spatial patchiness and temporal interval in water altered the effects of clonal integration of both species, especially for H. vulgaris. The adaptation of H. vulgaris might lead to invasive growth and potential spread under the global water variability.
Solanum viarum, Tropical Soda-Apple (Solanaceae), is an aggressive weed from South America. Since it is known from the southern U.S., including Louisiana, it has been watched for in Texas. A population has now been confirmed and vouchered from Jasper County, Texas. Other populations probably exist.
The floating fern Salvinia molesta D.S. Mitchell is recorded for the first time from South America. Its distribution there appears to be limited to southern Brazil.