Experimental evidence for an intraspecific Janzen-Connell effect mediated by soil biota.

The negative effect of soil pathogens on seedling survival varies considerably among conspecific individuals, but the underlying mechanisms are largely unknown. For variation between heterospecifics, a common explanation is the Janzen-Connell effect: negative density dependence in survival due to specialized pathogens aggregating on common hosts. We test whether an intraspecific Janzen-Connell effect exists, i.e., whether the survival chances of one population's seedlings surrounded by a different conspecific population increase with genetic difference, spatial distance, and trait dissimilarity between them. In a shade-house experiment, we grew seedlings of five populations of each of two subtropical tree species (Castanopsis fissa and Canarium album) for which we measured genetic distance using intersimple sequence repeat (ISSR) analysis and eight common traits/characters, and we treated them with soil material or soil biota filtrate collected from different populations. We found that the relative survival rate increased with increasing dissimilarity measured by spatial distance, genetic distance, and trait differences between the seedling and the population around which the soil was collected. This effect disappeared after soil sterilization. Our results provide evidence that genetic variation, trait similarity, and spatial distance can explain intraspecific variation in plant-soil biotic interactions and suggest that limiting similarity also occurs at the intraspecific level.

New Meliolaceae from the Brazilian Atlantic forest 1. Species on hosts in the families Asteraceae, Burseraceae, Euphorbiaceae, Fabaceae and Sapindaceae.

Five new species, two new varieties and three newly reported taxa belonging to the Meliolaceae were collected in fragments of Atlantic forest from Minas Gerais, Brazil, in association with native plants and are described and illustrated herein. The newly described species are Appendiculella eupatorii, Meliola cassiae-ferrugineae, M. mutisiae, M. peruiferae, M. vernaliae. The new varieties are M. garugae var. protii and M. paullinifolii var. rubiginosae. These taxa are reported in Brazil for the first time: Asteridiella cyclopoda, A. entebbeensis var. codiaei and Meliola pazschkeana var. macropoda. We studied other species belonging in Meliolaceae collected on hosts belonging to the Asteraceae, Burseraceae, Euphorbiaceae, Fabaceae (Caesalpinioideae and Papilionoideae) and Sapindaceae in Brazil.

Phylogenetic relationship of Marasmius mbalmayoensis sp. nov. to the tropical African Marasmius bekolacongoli complex based on nuc-LSU rDNA sequences.

Marasmius mbalmayoensis (Basidiomycotina, Marasmiaceae) growing on decayed leaves of Canarium schweinfurthii in the Mbalmayo Forest Reserve, Cameroon, is described. The species is remarkable due to the large basidiomata with shallow orange yellow umbilicus, long central stipe accompanied by similar long rhizomorphs on thickened basal mycelium and large lacrymiform to sigmoid basidiospores. The coarsely plicate pilei with lilac, violet to dark violaceous tints, and large distant adnate lamellae are reminiscent macroscopically of the tropical African species M. bekolacongoli. The phylogenetic relationship among M. mbalmayoensis and M. bekolacongoli was assessed, extended to other species of sects. Globulares and Sicci based on DNA sequences. Phylogenetic analysis based on nuc-LSU rDNA sequence data of selected Marasmiaceae taxa confirmed the placement of M. mbalmayoensis within the Marasmius spp. and its phylogenetic separation from M. bekolacongoli. Amyloflagellula inflata, which a BLAST analysis closely related to M. mbalmayoensis, clustered in the same clade with M. mbalmayoensis and M. bekolacongoli. The findings also indicated the complexity of M. bekolacongoli.