Effects of Above- and Below-Ground Interactions of Plants on Growth of Tree Seedlings in Low-Elevation Tropical Rainforests on Hainan Island, China

Understanding the effects of above- and below-ground interactions on seedling growth is pivotal for identifying the key drivers of secondary forest succession. However, it is still unclear whether the effects of above- and below-ground interactions of plants are consistent for seedling growth of deciduous and evergreen species. There are two types of broadleaved forests (i.e., tropical lowland rainforest and tropical deciduous monsoon rainforest) in the low-elevation (<800 m) areas of Hainan Island in China. Here, 32 seedling transplanting plots (1 × 1 m2) were established in the tropical lowland rainforest and the tropical deciduous monsoon rainforest, respectively. Four treatments (each with 16 replicates) were carried out to reduce above- and below-ground interactions of plants in the low-elevation forests: removal of vegetation (R), root trenching (T), removal of vegetation and root trenching (R + T), and no vegetation removal or trenching (as the control) (C). Seedlings of four deciduous species and four evergreen species were planted to observe their performance in the experiments. The relative growth rates (RGR) of the seedlings were measured to distinguish the relative effects of above- and below-ground interactions. The photosynthetically active radiation (PAR) was measured as a proxy for above-ground interaction and the root biomass was used as a proxy for below-ground interaction. The relationships between seedling RGR and PAR/root biomass were examined. Results showed that: (1) R and R+T treatments significantly increased the seedlings RGR, but T treatment had no effect on the RGR; (2) the growth rates of deciduous species were greater than those of the evergreen species; and (3) seedling growth rates were increased with more PAR. Our study suggests that above-ground vegetation removal had a stronger effect than trenching on the growth and assembly of tree seedlings in the low-elevation tropical rainforests.

Description and biology of two new egg parasitoid species, Trichogramma chagres and T. soberania (Hymenoptera: Trichogrammatidae) reared from eggs of Heliconiini butterflies (Lepidoptera: Nymphalidae: Heliconiinae) collected in Panama

Two new minute egg parasitoid wasp species belonging to the genus Trichogramma (Hymenoptera: Trichogrammatidae), T. chagres sp. nov. and T. soberania sp. nov., were found in a tropical lowland rainforest in Panama, Central America. In this paper, we describe, illustrate and discuss the biology, morphological and molecular characterization of the two new Trichogramma wasp species. Both species were collected from eggs of passion vine butterflies, Agraulis vanillae vanillae (Lepidoptera: Nymphalidae: Heliconiinae) and unidentified Heliconiini species, laid on different Passiflora species (Malpighiales: Passifloraceae). A female T. soberania sp. nov. wasp was noted on the wings of a female Heliconius hecale melicerta butterfly caught in the wild. This suggests that this species may occasionally hitch a ride on adult female butterflies to find suitable host eggs. Our study adds two more species identifications to the scarce record of Trichogramma wasps from the widespread Heliconiini butterflies in Central America.

Phylogeny of the climber genus Haumania (Marantaceae) endemic to the tropical lowland rainforest in Central Africa

The genus Haumania (Marantaceae) consists of three described species of perennial climbers endemic to the tropical lowland rainforest in Central Africa. To unravel their phylogenetic relationship to each other, we used variation among DNA sequences of two nuclear ribosomal (nr) and four plastid (p) markers in five to seven accessions per species sampled across their respective distribution range. Maximum parsimony and Bayesian analyses were applied. All datasets and analyses corroborated the monophyly of the genus. Within the genus, individuals of the species H. danckelmaniana and H. leonardiana were each monophyletic. Individuals of H. liebrechtsiana, however, were paraphyletic. They clustered into two distinct geographic clades (Gabon and Democratic Republic of Congo), with the Gabonese clade being most closely related to the individuals of H. danckelmaniana. The latter might be due to introgression in areas of distributional overlap between these two species, as shown in earlier phylogeographic studies. A recent hybridisation event between H. danckelmaniana and H. liebrechtsiana is documented here in a single individual by incongruence in the nr and p dataset. Overall, the study provides support for H. leonardiana being sister to all other species of this genus. To confirm the absence of hybridisation in H. leonardiana further sampling is proposed in the respective areas of distributional overlap with its sister species.