Capsella

Capsella as a genus is stereotyped by one of its three members: the tetraploid shepherd's purse (C. bursa pastoris L. Medic), which is an extremely common species of disturbed, and especially arable, farmed land. Despite its prevalence, Capsella has one fact in common with the other ca. 300 species of wild plants to be found on arable farmland. The fact is that we know embarrassingly little about its ecology and biology. Even the most basic and fundamental information is lacking for many common species and even whole genera (see Hawes et al. Oikos 109:521-534, 2005 and Moss Wild Plant Res 48:389-393, 2007). This situation persists despite Capsella's immense potential as a model species for production ecosystems. Capsella, like many wild plant species, is given the label weed, inferring that the group is a burden. With the exception of the last sentence, I avoid completely the use of this unscientific term in this article and encourage use of the term wild plant in its place. Of all the wild species, only a very small fraction, and only in certain circumstances, are pernicious to crops. Wild plants, such as Capsella, are especially important producers, as they are one of the main resource providers for the food web, and underpin the resilience of ecosystem services. We should understand the ecology of wild plants, such as Capsella, if we are to manage environment and food security. Firstly, wild plants must be acknowledged as the essential component of ecosystems, and therefore, worthy of the effort and expense of focused and sustained research. Secondly, we must understand the scientific basis of wild plant ecology. The first point demands no empirical research, but a deep realization that the concept is a cornerstone upon which effective research policies may be directed. The second point is also challenging, as there are thousands of wild species. However, the biology of Capsella is presented and discussed here in detail to justify its importance as a suitable model species with special relevance in situ.