Hymenopus heteromorphus Benth. Sothers and Prance

Kirmse, Susan & Chaboo, Caroline S, 2020, Flowers are essential to maintain high beetle diversity (Coleoptera) in a Neotropical rainforest canopy, Journal of Natural History 54 (25 - 26), pp. 1661-1696 : 1669

Target tree Hymenopus heteromorphus Benth. Sothers and Prance

(Chrysobalanaceae)

This paper targets beetle visitors to flowers of Hymenopus heteromorphus (Benth.) Sothers and Prance (Chrysobalanaceae) . This tree species was chosen to compare its flowervisiting beetles to our previous study, Kirmse and Chaboo (2019), of two other Chrysobalanaceae tree species in the plot, Licania hebantha Mart. ex Hook. f. and Moquilea subarachnophylla (Cuatrec.) Sothers and Prance , that attracted extrafloral nectary-visiting beetles. To test hypothesis 2, we compared the beetle assemblages associated with different food resources of these confamilial tree species.

Hymenopus (Benth.) Sothers and Prance is a Neotropical genus with 28 species which are distributed from Central America ( Costa Rica and Panama), Trinidad and Tobago to northern South America ( Colombia, Venezuela, the Guianas, Ecuador, Bolivia, Peru and in Brasil mainly the Amazonian region) ( Sothers et al. 2016). Hymenopus heteromorphus is morphologically variable and widespread and occurs in five varieties through Central and South America ( Sothers et al. 2016). Our single investigated tree, #970, belongs to the variety heteromorphus which grows in Trinidad, from Colombia, Venezuela and the Guianas through Brasil southwards to Peru and Bolivia ( Sothers et al. 2016). This specific variety is commonest in periodically flooded forest, but it occurs elsewhere ( Sothers et al. 2016). The whitish/yellowish flowers are tiny, ~ 2 mm wide and length is ~ 3 mm, with a flat cup-like shape ( Figure 2 (a)). The flowers are arranged in racemose panicles. Flowers have a weak sweet odour. The hermaphrodite flowers are actinomorphic to zygomorphic. A disc is present ( Prance and Sothers 2009).

Nine tree specimens of H. heteromorphus with a DBH of ≥ 10 cm grew inside the crane plot. One specimen of H. heteromorphus (ID tag #970; Figure 2 (a)) and its flower visitors were monitored during one flowering season, 25 February to 16 March 1999 (20 days). The beetles were hand-collected throughout the flowering season during the day and the night. In addition, one window trap was placed within the tree crown to provide semiquantitative data. This tree #970 had a height of 22 m and belonged to the middle to lower upper canopy; its crown diameter was about 4 m. Flower buds were found on this tree at the end of February. The first flowers were open on 3 March. On 5 March, the tree was full in bloom; by 9 March, the zenith of open flowers was already passed. From 12 March onwards, only a few open flowers were remaining on this tree specimen. According to Wesenberg (2004), this tree flowered usually once a year between the end of January and start of April. We estimated the amount of flowers on this single tree #970 was approximately 100,000 in the flowering season of 1999. For this evaluation, the number of flowers was counted on an average twig and then calculated for branches and the entire crown.

Figures

Figure 2. Small white flowers of the generalist pollination syndrome in a lowland rainforest canopy, Venezuela. (a) Flowers of Hymenopus heteromorphus (Benth.) Sothers and Prance var. heteromorphus (Chrysobalanaceae), March 1999. (b) Macraspis festiva Burmeister (Scarabaeidae) mating on flowering Matayba guianensis Aubl. (Sapindaceae), September 1997.