Bromus sitchensis in Belgium (and do we still have genuine B. carinatus?)

Bromus section Ceratochloa is a taxonomically complex assemblage of several different closely related taxa, all of New World origin. Especially Bromus carinatus and its relatives are notoriously difficult in terms of identification: some authors tend to accept a single variable species, others are convinced that several species merit species rank. The current account of Bromus carinatus on this website (see: http://alienplantsbelgium.be/content/bromus-carinatus-0) accepts, pending further research, one species but indicates that several forms occur/have occurred and that probably more than one species is involved.
In the past months the Belgian collections of the Bromus carinatus-aggregate have been studied more thoroughly. A full account will be published in a future issue of Dumortiera (autumn 2012). However, for now, it seems appropriate to draw the attention to the fact that most (all?) currently known Belgian populations seem to pertain to a different species, Bromus sitchensis. This species is depicted here. It has very long (> 8 cm) lowermost inflorescence branches that are drooping soon after flowering begins, longer spikelets (usually at least 35 mm long, excl. the awns), wider leaves (at least 10 mm wide), longer ligules (up to 4 mm long), etc. Other distinguishing features (palea length, rachilla length, etc.) should be critically assessed but seem less reliable. Genuine Bromus carinatus, in contrast, has much shorter lowermost inflorescence branches (these are stiffly erect), shorter spikelets, narrow leaves and shorter ligules.
All plants currently found in Brussels seem to pertain to Bromus sitchensis. Other populations seen in 2012 (Gent, Zwevegem) also belong with Bromus sitchensis.
Belgian botanists are encouraged to collect Bromus carinatus s.l. and send a pressed specimen to the author at: Filip Verloove, Nationale Plantentuin van België, Domein van Bouchout, B-1860 Meise. They may also communicate localities (whenever possible accompanied by photos) to: filip.verloove@br.fgov.be.
Filip Verloove June 2012

Bromus sitchensis, Gent (Muide), foot of wall, May 2012, F. Verloove Bromus sitchensis, Gent (Muide), foot of wall, May 2012, F. Verloove
Bromus sitchensis, Zwevegem, by former railway track, June 2012, F. Verloove Bromus sitchensis, Gent (Muide), foot of wall, May 2012, F. Verloove

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