A revision of Helictotrichon (Gramineae) in Malesia

In Malesia there are two species of grasses here tentatively included in Helictotrichon Besser (Gramineae): H. sumatrense Ohwi and H. virescens (Nees ex Steud.) Henr. [inch H. asperum (Munro ex Thw.) Bor and H. junghuhnii (Buse) Henr.]. The delimitation and nomenclature of Helictotrichon, Avenastrum Opiz and Avenula (Dum.) Dum. are discussed. It is proposed to lectotypify Helictotrichon with Avena sempervirens Vill. In the matter of automatic typification of superfluous names Art. 7. 11 is in conflict with Artt. 7. 10 and 63. 3; a correction is proposed

Species diversity in a mycophagous insect community : the case of spatial aggregation vs. resource partitioning

1. Previous work has suggested that species diversity in resource-limited insect communities on patchy resources is maintained by spatial aggregation, not by resource partitioning. The most comprehensive test of this claim to date was by Shorrocks & Sevenster (1995), but some of their datasets included only a few resource types, which reduces the likelihood of finding a strong effect of resource partitioning. Also, methods of analysis have since been refined, e.g. to account for patch size. 2. We collected 733 mushroom samples belonging to 66 taxa in a Dutch woodland area. From these mushrooms, 38,891 insects were reared, belonging to 60 taxa of Diptera and Hymenoptera. Drosophilid species and their parasitoids were identified to the species level; other taxa to the family level. We argue that the community is resource limited. 3. Generally, the insects have fairly narrow diets, including only a few of the available mushroom species. The degree of niche overlap varies widely in this community. 4. Within single resource types, co-existence can be explained by intra-specific aggregation over patches alone, in accordance with previous studies. 5. This conclusion remains unchanged for the mycophagous community as a whole: intra-specific aggregation of competitors is a sufficient and necessary mechanism for co-existence in this diverse community, while resource partitioning does not contribute detectably to species diversity. This is the first time that this pattern has been demonstrated in a dataset involving such a large number of resource types. 6. Our conclusions are strongly supported by data manipulations in which we removed or intensified the effect of resource partitioning and spatial aggregation. 7. We argue that this community may be close to saturation, but we emphasize that saturation is a gradual phenomenon in patchy systems. 8. Since differential use of resource types does not reduce competitive interactions among the insects, it seems unlikely that inter-specific competition constitutes the selective pressure favouring specialization