BAILEY, C. DONOVAN* AND JEFF J. DOYLE. L.H. Bailey Hortorium, Cornell University, 462 Mann Library, Ithaca, NY 14853. - SPECIES BOUNDARIES IN SPHAEROCARDAMUM (BRASSICACEAE): INTEGRATING MULTIPLE DATA SOURCES.
As currently circumscribed, Sphaerocardamum (Brassicaceae)
contains eight species that are endemic to limestone soils of Mexico’s
Chihuahuan desert. Populations of Sphaerocardamum are small,
scattered, and difficult to find, which has resulted in poor
representation of the genus in herbaria. Previous authors have
considered the current species limits relatively tentative and the
present project was developed to address the species boundaries within
the genus as part of a systematic study of Sphaerocardamum and
its relatives. Field studies were conducted to obtain new material
from known localities as well as from regions of the Chihuahaun desert
from which Sphaerocardamum had not been previously collected.
Data from crossing studies, DNA sequences (chloroplast trnL
intron - trnL/F spacer, nrDNA ITS, and pistillata intron
1), flow cytometry, meiotic chromosome counts, and morphology were
generated to address these problems. The results suggest that the
genus should be reduced from eight species to a maximum of four and
that some interspecific gene flow may have occurred. The results
identify that these are diploid taxa with genome sizes ranging from
0.35-0.42 pg/2C. The genome sizes match species boundaries based on
morphological and molecular data.
Key words: Cruciferae, Cytology, Cytometry, Genome, Molecular, Sphaerocardamum