Genetic diversity of the narrow endemicAllium aaseae(Alliaceae)

Abstract

Low levels of genetic variability are common for a number of geographically restricted plants: these data are consistent with theoretical expectations that small populations should be genetically depauperate. However, in some species, high levels of variability have been found in rare species. Allium aaseae is a rare, narrow endemic in the foothills of the Boise Front of southwestern Idaho. Genetic variation in the rare endemic A. aaseae, and nearby populations of the more common species, A. simillimum, was examined with randomly amplified polymorphic DNA (RAPD) data. Eight populations of A. aaseae and six populations of A. simillimum (three near the range of A. aaseae, and three distant populations) of 25 individuals each were examined for this analysis. Genetic diversity as determined with RAPD markers of both species examined in this study is largely found within and not among populations. Levels of genetic diversity are high, especially for a narrow endemic species such as A. aaseae. Proportion of RAPD loci polymorphic was high in both species, although slightly higher in the more common A. simillimum. Because these higher levels of genetic variability run counter to theory, alternative explanations beyond population size must be invoked to explain the levels of genetic diversity found in this study. Possible explanations are (1) A. aaseae is only recently derived from A. simillimum, (2) hybridization between A. aaseae and A. simillimum is occurring, (3) multiple origins of A. aaseae, (4) populations of A. simillimum included in the analysis are all A. aaseae, (5) A. aaseae and A. simillimum are conspecific, and (6) an artifact of RAPD data.

Patterns of genetic and phenotypic variation inIris hayneiandI. atrofusca(Irissect.Oncocyclus = the royal irises) along an ecogeographical gradient in Israel and the West Bank

“…In summary, the level of within‐population RAPD diversity maintained by haynei / atrofusca is somewhat surprising, particularly if one considers their narrow geographical distribution. However, unexpectedly high levels of RAPD diversity have also been reported in the allogamous Allium aaseae , another monocot species with life history and geographical traits similar to the Iris taxa studied here ( H = 0.274, P % = 0.522–0.672; Smith & Pham 1996). A similar pattern is seen in other nonmonocot species restricted in range (e.g.…”

Genetic differentiation in silicicolous Echinospartum (Leguminosae) indicated by allozyme variability

“…van Treuren et al 1991), small populations and geographically restricted taxa should exhibit low levels of polymorphism and genetic variability due to mainly genetic drift, inbreeding, and restricted gene¯ow. However, E. algibicum showed only relatively lower levels of genetic diversity than the widespread E. ibericum, and can not be considered to be genetically depauperate, coinciding with the results in many other studies dealing with genetic variability in endangered restricted species (Gottlieb 1974, Linhart and Premoli 1993, Lewis and Crawford 1995, Purdy and Bayer 1996, Shapcott and Playford 1996, Smith and Pham 1996, Godt and Hamrick 1998b, Neel and Ellstrand 2001. Factors such as hybridisation, multiple origins, the maintenance of genetic diversity in refuge populations, and recent speciation from a widespread species may in¯uence genetic diversity in small populations (Karron et al 1988).…”

Genetic diversity and structure of natural populations ofPlathymenia reticulata(Mimosoideae), a tropical tree from the Brazilian Cerrado

“…The fact that no DNA sequence information is known about this species is one of the main reasons that have motivated the choice of the RAPD technique to develop this study. There are many studies using RAPD markers that estimate gene frequencies p and q from the square root of the frequency of null homozygotes (q 2 ), assuming therefore that the populations are in Hardy–Weinberg equilibrium (Smith & Pham 1996; Aagaard et al . 1998; Morden & Loeffler 1999).…”