Population structure and genetic diversity of native and invasive populations of Solanum rostratum (Solanaceae)

Aims: We investigate native and introduced populations of Solanum rostratum, an annual, self-compatible plant that has been introduced around the globe. This study is the first to compare the genetic diversity of Solanum rostratum between native and introduced populations. We aim to (1) determine the level of genetic diversity across the studied regions; (2) explore the likely origins of invasive populations in China; and (3) investigate whether there is the evidence of multiple introductions into China. Methods: We genotyped 329 individuals at 10 microsatellite loci to determine the levels of genetic diversity and to investigate population structure of native and introduced populations of S. rostratum. We studied five populations in each of three regions across two continents: Mexico, the U.S.A. and China. Important Findings: We found the highest genetic diversity among Mexican populations of S. rostratum. Genetic diversity was significantly lower in Chinese and U.S.A. populations, but we found no regional difference in inbreeding coefficients (FIS) or population differentiation (FST). Population structure analyses indicate that Chinese and U.S.A. populations are more closely related to each other than to sampled Mexican populations, revealing that introduced populations in China share an origin with the sampled U.S.A. populations. The distinctiveness between some introduced populations indicates multiple introductions of S. rostratum into China

Map showing the location of the 15 sampled populations of <i>Solanum rostratum</i> used in this study.

<p>Left panel: Mexican (native, green circles) and U.S.A. populations from the U.S.A. (residence time >130 years, blue circles). Right panel: Chinese populations (residence time <31 years, red circles). Details of localities and population codes are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079807#pone-0079807-t001" target="_blank">Table 1</a>.</p

Network diagram of 15 populations of <i>Solanum rostratum</i> in Mexico (green circles), the U.S.A. (blue circles), and China (red circles) calculated in POPULATION GRAPH [32].

<p>The diameter of each sphere is proportional to the amount of heterozygosity in each population. Black lines represent connections (edges) linking two populations.</p

Genotype data-PONE-D-13-20610

This file includes genotype data of the paper, “Population structure and genetic diversity of native and invasive populations of Solanum rostratum (Solanaceae)." We genotyped 329 individuals at 10 microsatellite loci to determine the levels of genetic diversity and to investigate population structure of native and introduced populations of S. rostratum. We studied five populations in each of three regions across two continents: Mexico, the U.S.A. and China

Venn diagram of the distribution of all distinct alleles across loci for the three geographic regions studied: Mexico, the U.S.A. and China.

<p>Overlapping areas (intersections) denote shared alleles between two or three regions.</p

Posterior probability of cluster assignment in nested InStruct analyses of 329 <i>Solanum rostratum</i> individuals genotyped at 10 microsatellite loci across 15 populations in three geographic regions: Mexico, the U.S.A. and China.

<p>Each bar represents a single individual with populations separated by black lines and arranged from North to South within each region. Panel <b>A</b> depicts the uppermost level of population structure across regions. The optimal number of clusters (<i>K*</i> = 2) was calculated using Evanno’s et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079807#B31" target="_blank">31</a>] <i>∆K</i> statistic. For illustration, panel <b>B</b> shows the assignment probabilities for <i>K</i> = 3. Panel <b>C</b> represent two separate analyses of either U.S.A./Chinese or Mexican populations; the optimal number of clusters [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079807#B31" target="_blank">31</a>] in each of these separate analyses was <i>K</i>_US-C<i>*</i> =<i>K</i>_US-C<i>*</i> = 2. Panel <b>D</b>, shows assignment probabilities for <i>K</i> = 3, for each separate analysis.</p

Unweighted pair group method with arithmetic mean (UPGMA) tree depicting the relationships between 15 <i>Solanum rostratum</i> populations from Mexico, the U.S.A. and China.

<p>The tree is based on the standardized genetic distances among populations (Nei's <i>D</i>_<i>S</i>) calculated from a matrix of genotypes at 10 microsatellite loci. The numbers above the nodes represent percentage of bootstrap support (1000 replications). Only bootstrap support above 50% is shown. Population codes as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079807#pone-0079807-t001" target="_blank">Table 1</a>.</p

Impact of different shade coffee management scenarios, on a population of <i>Oncidium poikilostalix</i> (Orchidaceae), in Soconusco, Chiapas, Mexico

<p><b><i>Background</i></b>: Understanding the effect of perturbation, be it natural or anthropogenic, on the demography and dynamics of the plant populations can help conservation management planning.</p> <p><b><i>Aims</i></b>: We assessed the impacts of management of a shade coffee plantation on a population of <i>Oncidium poikilostalix</i> (Orchidaceae).</p> <p><b><i>Methods</i></b>: We studied in a coffee (<i>Coffea arabica</i>) agroecosystem the impact of the current traditional management [T] and two hypothetical epiphyte control management scenarios (intense ‘desmusgue’ [ID] and moderate ‘desmusgue’ [MD]), on the only known Mexican population of <i>O</i>. <i>poikilostalix</i>. Based on 3 years of field demographics data, the population dynamics of the orchid were projected using T, ID and MD scenarios for 20 years into the future.</p> <p><b><i>Results</i></b>: Under the current management T, the population of <i>O. poikilostalix</i> was projected to grow continuously (λ = 1.102). Conversely, under management ID, the loss of individuals would lead to a sustained population decline (λ = 0.843); in the case of MD, the population would decline more slowly with the population growth rate tending towards equilibrium (λ = 0.966).</p> <p><b><i>Conclusions</i></b>: The changes in the management of coffee plantations that have become common throughout the south-east of Mexico represent a threat to the survival of the only population of <i>O. poikilostalix</i> in Mexico, and likely threaten other epiphytic species.</p