Chromosome counts in section Simiolus of the genus Mimulus (Scrophulariaceae). XI. M. glabratus complex (cont.)

Chromosome numbers were ascertained from aceto-carmine squash preparations for members of the Mimulus glabratus complex that had been little studied previously. Representative populations of M. glabratus var. fremontii from Chihuahua, Durango, and Baja California Sur were found to have «=15 chromosomes. Populations from Colombia, the disjunct South American range of M. glabratus var. glabratus, have n = 3 1 chromosomes. Populations from Peru of M. andicolus and M. pilosiusculus have n 46. An intergrading population between M. glabratus var. glabratus (n = 3 1) and M. andicolus ( n 46) was found at Pasto on the southern border of Colombia. This cytological study is an integral part of our long-range, experimental studies on the evolution of species in Mimulus (Vickery 1950, 1964, 1978). The chromosome counts here reported are for populations of the M. glabratus complex of related speciesM glabratus H.B.K, (and its varieties), M. andicolus H.B.K., and M. pilosiusculus H.B.K. Not only do these counts help provide baseline data for the larger project, but they are of intrinsic interest for a better understanding of this highly polymorphic and plastic complex. Materials and Methods The study populations sampled areas of the Western Hemisphere range of the complex that had been little studied previously (McArthur et al. 1972, Vickery 1978), although they represent some of the main taxa comprising the complex (Table 1). Cultures of 20 to 30 plants of each population were grown in the University of Utah greenhouse. The chromosome counts were obtained from aceto-carmine squash preparations of pollen mother cells as before (Mia et al. 1964, McArthur et al. 1972). Twenty or more cells were studied from five or more plants of the culture of each population. Representative cells were recorded with sketches, camera lucida drawings or photographs (Fig. 1). Madrono, Vol. 32, No. 2, pp. 91-94, 26 April 1985 This content downloaded from 157.55.39.4 on Sat, 10 Sep 2016 05:18:19 UTC All use subject to http://about.jstor.org/terms