The individual basis of plant diversity.

The simple trait space of germination The concepts can be illustrated for the primary step of germination, which is commonly governed by conservative relations between time and temperature. Data collected and supplied by the Unit of Comparative Plant Ecology, Sheffield were used to construct a space of time, temperature and % germination for a range of species. In a preliminary survey2, the weeds and other wild plants examined displayed rate-temperature curves similar to those found many times previously with crops. In principle therefore, a wide range of cultivated and wild species could be examined by a similar analysis. A deeper re-analysis of the data revealed time-temperature trait maps (Fig. 1) that are highly characteristic of a species or population. The contrasting Saxifraga tridactylites and Brachypodium pinnatum represent extremes in the flora, each differing in the time to first germination, the amount of non-germination indicated by the grey shelves in the maps, the temperature at which seeds do and do not germinate, and many other features, especially the spread of trait values within the population at any temperature or time. In contrast, the grass weed Anisantha sterilis (= Bromus sterilis) displays a very wide map, germinating near to 100% over much of the ranges of temperature and time.