The ascomycete Geosmithia morbida and the walnut twig beetle Pityophthorus juglandis are associated with thousand cankers disease of Juglans (walnut) and Pterocarya (wingnut). The disease was first reported in the western United States (USA) on several Juglans species, but has been found more recently in the eastern USA in the native range of the highly susceptible Juglans nigra. We performed a comprehensive population genetic study of 209 G. morbida isolates collected from Juglans and Pterocarya from 17 geographic regions distributed across 12 U.S. states. The study was based on sequence typing of 27 single nucleotide polymorphisms from three genomic regions and genotyping with ten microsatellite primer pairs. Using multilocus sequence-typing data, 197 G. morbida isolates were placed into one of 57 haplotypes. In some instances, multiple haplotypes were recovered from isolates collected on the same tree. Twenty-four of the haplotypes (42%) were recovered from more than one isolate; the two most frequently occurring haplotypes (H02 and H03) represented 36% of all isolates. These two haplotypes were abundant in California, but were not recovered from Arizona or New Mexico. G. morbida population structure was best explained by four genetically distinct groups that clustered into three geographic regions. Most of the haplotypes isolated from the native range of J. major (Arizona and New Mexico) were found in those states only or present in distinct genetic clusters. There was no evidence of sexual reproduction or genetic recombination in any population. The scattered distribution of the genetic clusters indicated that G. morbida was likely disseminated to different regions at several times and from several sources. The large number of haplotypes observed and the genetic complexity of G. morbida indicate that it evolved in association with at least one Juglans spp. and the walnut twig beetle long before the first reports of the disease.

A variety of factors can affect the biodiversity of tropical mammal communities, but their relative importance and directionality remain uncertain. Previous global investigations of mammal functional diversity have relied on range maps instead of observational data to determine community composition. We test the effects of species pools, habitat heterogeneity, primary productivity and human disturbance on the functional diversity (dispersion and richness) of mammal communities using the largest standardized tropical forest camera trap monitoring system, the Tropical Ecology Assessment and Monitoring (TEAM) Network. We use occupancy values derived from the camera trap data to calculate occupancy-weighted functional diversity and use Bayesian generalized linear regression to determine the effects of multiple predictors. Mammal community functional dispersion increased with primary productivity, while functional richness decreased with human-induced local extinctions and was significantly lower in Madagascar than other tropical regions. The significant positive relationship between functional dispersion and productivity was evident only when functional dispersion was weighted by species' occupancies. Thus, observational data from standardized monitoring can reveal the drivers of mammal communities in ways that are not readily apparent from range map-based studies. The positive association between occupancy-weighted functional dispersion of tropical forest mammal communities and primary productivity suggests that unique functional traits may be more beneficial in more productive ecosystems and may allow species to persist at higher abundances.

While plant-animal interactions occur fundamentally at the individual level, the bulk of research examining the mechanisms that drive interaction patterns has focused on species or population levels. In seed-dispersal mutualisms between frugivores and plants, little is known about the role of space and individual-level variation among plants in structuring patterns of frugivory and seed dispersal in a plant community. Here we use a zoocentric approach to examine how space and variation between individual plants affect movement and visitation by frugivores foraging on individual fruiting plants. To do this, we used a spatially explicit network approach informed by observations of the movement and foraging of a frugivorous lemur species Eulemur rubriventer among individual plants in a diverse plant community in Madagascar. The resulting hierarchical networks show a few individual plants receiving the bulk of the interactions, demonstrating that a generalist frugivore species could act as an individual-plant specialist within a plant community. The few individual plants that dominated interactions with lemurs shaped the modular spatial structure of frugivory interactions in the community and facilitated visitation to near neighbors. This interaction structure was primarily driven by extrinsic factors, as lemur movements among plants were significantly influenced by the individual plant's spatial position and the fruiting plant richness in its immediate neighborhood. Individual plants in central spatial locations with large fruit crops received the most visits. The observed inequality in the interactions of a generalist frugivore within a highly diverse plant community highlights the importance of considering individual-level variation for essential ecosystem processes such as seed dispersal.

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