Influence of fruit dispersal on genotypic diversity and migration rates of a clonal cactus from the Chihuahuan Desert

Abstract

The diverse offspring of clonal species differ in their dispersability, influencing genotypic diversity and clonal structure. Here, we determined dispersal patterns and their impact on genetic structure in Opuntia microdasys, a self‐incompatible cactus with three dispersal units (one sexual and two clonal). We analyzed dispersal, using experiments at three populations, and assessed multilocus genotypes (ISSR markers) of all individuals in 10 clumps per population with known reproductive origin (sexual or clonal). Genotype of all samples, population structure, and migration between clumps and populations were assessed with GenAlEx and GenoDive, assuming higher genotypic diversity and migration when sexual reproduction is more frequent. We determined the most likely number of genetic clusters with STRUCTURE and geneland. Dispersal differed among populations; primary dispersal occurred at short distances and was farthest on steep slopes, and dispersal distance increased after secondary dispersal. Clumps had 116 different multilocus genotypes in three spatially explicit genetic clusters. We detected genetic structure at small scale, genotypic diversity among clumps varied between populations; diversity decreased while clonal dominance increased, and the most variation occurred among clumps. Genetic structure was moderate, suggesting gene flow by seed dispersal allows slight differentiation among population at large scales. Genetic diversity within clumps was the lowest because dispersal of clonal propagules was limited and caused genotypic dominance at local scale. However, the combined dispersal pattern of sexual and clonal dispersal units is fine‐tuned by environmental factors, generating a range of genetic diversity among clusters and populations. This pattern suggests that genetic structure of clonal plants is more dynamic than thought, and dispersal of different types of offspring affects genetic structure at many scales.

Variability in mating strategies in a widespread cactus in the Chihuahuan Desert

“…Another cause could be related to mate availability, defined as the probability that a randomly chosen individual was compatible with another individual from the same population (Byers and Meagher 1992, Fischer et al 2003, Clark‐Tapia et al 2006). In our study we used pollen from at least five donor plants but, considering that Opuntia species are known to have short‐distance dispersion of sexual and clonal offspring (Carrillo‐Ángeles et al 2011, García‐Morales et al 2018), we cannot rule out that the pollen donors selected for our pollination treatments were clones or closely related individuals. Additionally, solitary bees tend to fly within a radius of 150–600 m from their nests (Gathmann and Tscharntke 2002).…”

Conservation genetics of the protected candy barrel cactus Echinocactus platyacanthus in the Chihuahuan Desert Region

“…Amplifications were carried out by duplicates in a 10 µl PCR reaction containing 1 µl of 10X DreamTaq™, 0.2 µl of dNTPs (10 µM each), 0.5 µl of primer (10 µM), 0.062 µl of DreamTaq™ and nuclease free water. Ten random ISSR primers, developed by the University of British Columbia (UBC), were screened given that they have been used in other cacti studies (Bustamante et al, 2016;García-Morales et al, 2018;Valadez-Moctezuma et al, 2015), and 4 of them were selected based on the amount of information they provided and their reproducibility. ISSR primer names and sequences with their corresponding annealing temperatures are as follow (UBC name, primer sequence and annealing temperature): UBC-879, (CTTCA)3, 43˚ C; UBC-868, (GAA)6, 43˚ C; UBC-840, (GA)8 CT, 50˚ C and UBC-814, (CT)8 A, 50˚ C. PCR conditions for the ISSRs were an initial denaturation cycle of 94° C for 1.5 minutes followed by 40 cycles of 94 °C for 40 seconds, the corresponding annealing temperatures for 40 seconds and 72 °C of extension for 1.5 minutes with a final cycle of 72 °C for 7 minutes to end reactions holding samples at 4 °C for 10 minutes.…”