No evolutionary change in the mating system of Solanum rostratum (Solanaceae) during its invasion in China

Abstract

The mating system of flowering plants plays a key role during the process of invasion. Evolution from outcrossing to selfing can allow rapid regeneration of a population after long-distance dispersal by providing reproductive assurance. Solanum rostratum is a self-compatible annual herb that exhibits a high level of outcrossing in its native populations. However, the mating system of invasive populations of S. rostratum has never been assessed. Here, we investigated the mating system based on 11 microsatellite loci and explored ecological factors that may influence the outcrossing rate among 10 invasive populations of S. rostratum in China. We found that the mean outcrossing rate was 0.69 ± 0.12 (range 0.49 to 0.83) with multiple paternity within progeny arrays (average effective number of sires = 7.86), which suggests a mixed mating system dominated by outcrossing. Combined with the uniformly high outcrossing rate (0.70 ± 0.03) previously reported in its native range, these results indicate that there has been no evolutionary shift in mating system during the invasion in China by S. rostratum. There were no relationships between outcrossing and population size, population density, altitude, latitude or longitude. Furthermore, high outcrossing of S. rostratum in China may be facilitated by enantiostyly and heteranthery.

Figure 1

Multilocus outcrossing rates (t _m) with 95% confidence intervals of 1000 bootstrap estimates from ten Chinese populations of Solanum rostratum. The dashed line shows the average outcrossing rate across all populations (${\overline{t}}_{\mathrm{m}}$ = 0.69 ± 0.12). Populations are listed according to the longitude. Population names as those in Table 1.

Figure 2

The average multilocus outcrossing rate (t _m) across Chinese populations and Mexican populations of Solanum rostratum. The t _m of Mexican populations was reported by Vallejo-Marίn.

Figure 3

Geographical distribution of ten populations of Solanum rostratum sampled from North China. (a): ten Chinese sampling populations of Solanum rostratum, the dot between YQ and YG represents there populations located in Hebei province (WSL, NZ, SLZ). (b): details with enlarged scale for the six populations located in Hebei province (WSL, NZ, SLZ) and Beijing (MY, YQ, TZ). Population names are provided in Table 1. This figure was produced using ArcGIS software version 10.1 (http://www.esrichina.com.cn/softwareproduct/ArcGIS/).