Evolution of germination strategy in the invasive speciesUlex europaeus

Abstract

Aims. The study of the adaptive potential of the germination patterns of invading species enables us to identify some traits linked with their capacity to colonize new sites, and to better understand their area of distribution. The aim of the present study is to determine the germination pattern of Ulex europaeus, a cosmopolitan invasive species, in relation to temperature and to explore its potential evolution in a tropical invaded region since its introduction from Europe. Methods. We studied the germination pattern of U. europaeus (the common gorse) to test both physical dormancy and germination capacity within the range of temperatures found in the native and invasive regions. To comprehend its germination pattern and its evolution, the rate and the speed of germination, as well as the percentage of seeds that mold during the experiment, have been compared between a native habitat, France and a habitat to which it has been introduced, the tropical island of La Reunion. Important findings. The results show that the gorse seeds possess a very high power of germination, the ability to germinate under a wide range of temperatures and confirm the physical dormancy of the seeds (caused by seed coat impermeability).The decrease in germination from 25ºC upwards, coupled with an increase in the rate of moulding help to explain its restricted distribution at altitude in tropical environments. For scarified seeds, we have not detected any difference between the two regions, neither in the percentage of germinated seeds, nor in the percentage of mould seeds. However, seeds from Réunion germinate faster at 20ºC than seeds from France. For unscarified seeds … and a greater number of seeds from Réunion are able to germinate without scarification (10-60 % for Reunion vs 0-10 % for France). These results suggest that whilst preserving the advantages of the native habitat, in Réunion gorse develops a strategy which favours the rapid occupation of new sites.

Differential germination strategies of native and introduced populations of the invasive species Plantago virginica

“…Kudoh et al (2007) found that Japanese (introduced) populations of Cardamine hirsuta exhibited stronger initial dormancy and more persistent seed banks than European (native) populations, both of which can increase the probability of survival in the novel range. An opposite pattern of seed dormancy was reported for introduced populations of Ulex europaeus which showed less physical dormancy, perhaps selected by decreased seed predation in the introduced range (Udo et al 2017).…”

“…In contrast, the earliest part of the life cycle, germination, has received relatively little attention. (Udo et al 2017;Gioria and Pyšek 2017).…”

Germination and Seedling Growth of Water Primroses: A Cross Experiment between Two Invaded Ranges with Contrasting Climates

“…Further investigation would be needed in order to control the maternal effects between these populations, by growing plants from seeds for two generations under the same environmental conditions ( Fenster and Galloway, 2000 ). Future research comparing germination dynamics of seeds of the two water primroses from their native range, tested in native and exotic range conditions, could yield valuable information about the evolution of germination capacity ( Hierro et al, 2009 ; Gioria and Pyšek, 2017 ; Udo et al, 2017 ).…”

Cold stratification, temperature, light, GA3, and KNO3 effects on seed germination of Primula beesiana from Yunnan, China

“…Estimates of time ( t g , days) taken for cumulative germination to reach different percentiles (g) for successive increments of 5% germination were interpolated from the germination progress curves ( Covell et al., 1986 ). Germination rate (1/ t 25 ) was plotted as a function of temperature and regressed using a linear model ( Udo et al., 2017 ), to estimate the base temperature ( T b ) below which germination rate was equal to zero. The slope of the linear regression line corresponded to the reciprocal of the thermal-time requirement at suboptimal temperatures ( θ 25 ).…”