Clonal diversity and distribution in Stenocereus eruca (Cactaceae), a narrow endemic cactus of the Sonoran Desert

Abstract

Stenocereus eruca (Cactaceae), a prostrate cactus endemic to the Sonoran Desert, is thought to be highly clonal. We examined its clonal diversity and distribution: (1) at the population level, in four distinct populations along its distribution range; and (2) at a micro scale level, within a single population. Our objective was to evaluate the importance of sexual versus clonal recruitment through the use of RAPD markers. Contrary to previous field observations, clonal diversity was relatively high across the distribution range. This finding suggests that sexual recruitment is an important regeneration mechanism. The proportions of distinguishable genotypes (G/N = 0.83) and genotypic diversity (D = 0.987) were greater than in other clonal cacti, suggesting that clonal propagation is not the major regeneration mechanism. Autocorrelation analyses revealed a spatial genetic structure that may be the result of restricted gene flow (via pollen or seeds) and clonal propagation. A molecular variance analysis (AMOVA) indicated that most of the variation (66.3%) was found within and not across populations. Future studies on pollen and seed dispersal are needed to understand the role of the clonal habit in the mating system of S. eruca.

Reproductive Consequences of Clonal Growth in Stenocereus eruca, a Rare Clonal Cactus of the Sonoran Desert

“…Charpentier, 2002). The evidence on clonal diversity indicates that populations of S. eruca are multiclonal (Clark-Tapia et al, 2005a;Molina-Freaner and Clark-Tapia, 2005). Thus, although it is a narrow endemic species where population size might restrict mate availability (Byers and Meagher, 1992), actual levels of clonal diversity suggest that the number of mating types is not restricted.…”

“…The procedure for the collection, preservation and genetic analysis of the samples using Random Amplified Polymorphic DNA (RAPDs) was the same used in a previous study of clonal diversity (Clark-Tapia et al, 2005a). The genetic similarity between pairs of ramets (pollen donor and receptor) was evaluated by counting the number of shared bands (from a total of 44 loci) among the amplification products with six RAPDs primers.…”

Genetic Diversity and Geographic Differentiation in the Threatened Species Dysosma pleiantha in China as Revealed by ISSR Analysis

“…Qiu et al (2005) speculated that sexual reproduction is likely more important than clonal reproduction in D. pleiantha; however, only one D. pleiantha population was included in a previous isozyme analysis. Again, a problem with the application of enzyme electrophoresis for clonal identification and detecting genetic variation is the low number of polymorphic loci available in many studies (Ellstrand and Roose 1987;Qiu et al 2005;Clark-Tapia et al 2005). DNA type markers are able to detect the genetic variation beyond coding loci and to provide broader information on the amount of genetic variation and the genetic divergence among populations.…”

Effects of spring drought on carbon sequestration, evapotranspiration and water use efficiency in the songnen meadow steppe in northeast China

“…Besides through clonal propagation, many perennial plants give rise to new individuals through sexual reproduction (Clark-Tapia et al, 2005). Spring drought before anthesis induced a decrease in the number of florets per spike (47Ð2 š 2Ð1 florets m 2 in 2007 compared to 66Ð1 š 3Ð4 florets m 2 in 2008), as well as an increased floret sterility.…”