Habitat and flower resource partitioning by an exotic and three native bumble bees in central Hokkaido, Japan

Studies of the interspecific relationships between alien and native pollinator species can help forecast the success of alien species as well as assess the extent of disturbance to native plant-pollinator interactions. We examined the habitat and flower resource occupancy by the invasive introduced bumble bee Bombus terrestris and three dominant native bumble bees in central Hokkaido, northern Japan, in relation to a landscape factor (forest cover ratio) and flower morphology with respect to the proboscis length of bees. Three years of monitoring the invasive boundary of B. terrestris indicated that this species, which dominates open agricultural areas, probably will not invade the forests in which the native species dominate. This habitat partitioning likely followed the displacement of the natives by the invader in open agricultural lands. In forested areas, the native species partitioned flower resources on the basis of the relationship between proboscis length and the lengths of the corolla tubes of flowers. However, in open agricultural areas, both the long- and short-tubed flowers were primarily visited by the exotic short-tongued B. terrestris, which foraged illegitimately (by nectar robbing) on long-tubed flowers (Trifolium pratense L.) and legitimately on short-tubed flowers (T. repens L. and Lavandula angustifolia Mill.). The invasion of B. terrestris into open natural vegetation, in addition to open agricultural areas, has recently been reported in Hokkaido. Even though the exotic and dominant native bumble bees partition their habitat according to landscape factors, the invasive bee has the potential to alter the overall interactions within plant-pollinator systems in the regions of open vegetation on Hokkaido Island.     

Wild bee species increase tomato production and respond differently to surrounding land use in Northern California

Pollination provided by bees enhances the production of many crops. However, the contribution of wild bees remains unmeasured for many crops, and the effects of anthropogenic change on many bee species are unstudied. We experimentally investigated how pollination by wild bees affects tomato production in northern California. We found that wild bees substantially increase the production of field-grown tomato, a crop generally considered self-pollinating. Surveys of the bee community on 14 organic fields that varied in proximity to natural habitat showed that the primary bee visitors, Anthophora urbana Cresson and Bombus vosnesenskii Radoszkowski, were affected differently by land management practices. B. vosnesenskii was found primarily on farms proximate to natural habitats, but neither proximity to natural habitat nor tomato floral abundance, temperature, or year explained variation in the visitation rates of A. urbana. Natural habitat appears to increase B. vosnesenskii populations and should be preserved near farms. Additional research is needed to determine how to maintain A. urbana. Species-specific differences in dependency on natural habitats underscore the importance of considering the natural histories of individual bee species when projecting population trends of pollinators and designing management plans for pollination services. Thus, to maintain an entire bee community, multiple approaches, including maintaining natural habitat, should be implemented.     

Are urban parks refuges for bumble bees Bombus spp. (Hymenoptera: Apidae)?

Declines in bee populations have been documented in several parts of the world. Bees are dependent upon flowering plants for resources, and flowering plants often depend upon bees for pollination services. Bees can therefore serve as indicator species of habitat degradation due to these relationships with flowering plants. This study investigates how the bumble bee community in San Francisco has responded to urbanization and which urban park characteristics are important for the current community’s structure. To answer these questions we sampled bumble bees, in 18 urban parks and two nearby wild parks. We estimated park characteristics and used multiple regression analysis to determine which characteristics predicted bumble bee abundance and species richness. Bumble bee abundance was positively associated with resource availability or proxies of resource availability; “natural area” (areas that contain remnant fragments that have been largely unchanged by human activity) in 2003 and nest site abundance and openness of the surrounding matrix in both 2003 and 2004. Bumble bee species richness was negatively associated with abundance of a dominant species, Bombus vosnesenskii, in 2004. The importance of the surrounding matrix suggests that these parks do not act as islands. Accordingly, area of park did not explain species richness, while abundance of the dominant competitor did. The species that was most influenced by competition, Bombus sitkensis, uses rodent holes as nest sites and is possibly excluded from nest sites by the early emerging B. vosnesenskii, another subterranean nester. The species least influenced by competition, Bombus melanopygus, is able to use both rodent holes and abandoned bird nests as nest sites.     

滇东南南瓜传粉昆虫密度对生境丧失的差异性响应

响应多样性理论认为不同传粉蜂对环境胁迫的响应尺度和过程在时空上存在差异,然而目前尚不清楚我国重要农林生态系统传粉蜂对环境胁迫的响应规律。试验以云南省文山州广南县南瓜农田生态系统为研究对象,根据农田景观中自然半自然生境数量和面积的变化梯度和离自然半自然生境的距离梯度选择南瓜样地,抽样调查南瓜样地内熊蜂密度和蜜蜂密度。解译卫星影像获取土地类型数据,分析熊蜂密度和蜜蜂密度同自然半自然生境面积百分率和耕地面积百分率的相关系数,在最大相关系数对应的空间尺度下探索蜜蜂密度和熊蜂密度对生境丧失的响应规律。研究发现,熊蜂密度随自然半自然生境面积百分率的增加而显著增加,但蜜蜂密度并不受自然半自然生境面积的影响。同时,熊蜂密度随耕地面积百分率的增加而显著下降,但蜜蜂密度不受耕地面积的影响。此外,熊蜂密度随离自然半自然生境的距离增加而显著下降,但蜜蜂密度不受距离作用的影响。由此可见,云南省文山州南瓜传粉熊蜂和蜜蜂多度对生境丧失表现出多样的响应规律。熊蜂和蜜蜂对生境丧失的差异性响应可能是保障该区域南瓜受粉的重要机制。     

Impact of introduced honey bees on native pollination interactions of the endemic Echium wildpretii (Boraginaceae) on Tenerife, Canary Islands

The aim of this study was to investigate effects of introduced honey bees (Apis mellifera) on native pollination interactions of Echium wildpretii ssp. wildpretii in the sub-alpine desert of Tenerife. We selected two study populations, one dominated by honey bees, while the other was visited by many native insects. During peak activity period of insects, nectar was nearly completely depleted in flowers of the first, but not the latter population. Thus, a high abundance of honey bees may have suppressed visitation by native animals due to exploitative competition. Honey bees stayed longer and visited more flowers on the same inflorescence than native bees, thus potentially promoting self-pollination of the plants. Level of seed set and viability was similar in the two study populations. However, we cannot rule out long-term changes in genetic population structure due to changes in gene-flow patterns caused by foraging behaviour of honey bees vs. native flower-visitors.     

Pollination of the invasive exotic shrub Lupinus arboreus (Fabaceae) by introduced bees in Tasmania

Exotic plant invasions threaten ecological communities world-wide. Some species are limited by a lack of suitable pollinators, but the introduction of exotic pollinators can facilitate rapid spread. In Tasmania, where many non-native plants are naturalised, exotic honeybees (Apis mellifera) and bumblebees (Bombus terrestris) have become established. We determined how these species affect the pollination of Lupinus arboreus, an invasive, nitrogen-fixing shrub, which is rarely visited by native pollinators. The proportion of flowers setting seed and the number of ovules fertilised per flower were positively related to the visitation rates of both exotic bee species. There was no effect of bee visitation rates on the proportion of seeds aborted prior to maturity, possibly due to post-fertilisation environmental constraints. We conclude that the spread of B. terrestris may not alter the fecundity of L. arboreus because of the pollination service provided by A. mellifera, and discuss potential interactions between these two bee species.     

Reproductive success and pollinator effectiveness differ in common and rare Persoonia species (Proteaceae)

In plants, understanding the interactions between breeding systems and pollination ecology may enable us to predict the impacts of rarity. We used a comparative approach to test whether rarity is associated with reproductive biology in two closely-related species pairs. This system has been recently altered by changes in fire regimes and the introduction of European honeybees. More than 35% of flowers matured fruits in the common species after natural-pollination compared to <20% of flowers in the rare species. All species were obligate outcrossers in each of the study populations, but only the two rare species were pollen-limited, having significantly lower fruit-set on open-pollinated flowers than those cross-pollinated by hand (mean ± SE; 0.18 ± 0.02 vs. 0.42 ± 0.05; p < 0.001). Native bees (Leioproctus species) and introduced honeybees (Apis mellifera) visited all species. The native bees visited fewer flowers within a plant and moved greater distances between plants while foraging than honeybees, so the native bees are expected to be more effective in promoting outcrossing. While honeybees were the most frequent visitors to flowers of all species, native bees made more visits to common than rare species (0.65 ± 0.20 vs. 0.20 ± 0.09). Our results suggest that the poorer reproductive success in rare Persoonia species is associated with lower pollinator effectiveness, which is exacerbated by frequent fires and introduced honeybees. If this is a causal relationship, this may increase the probability of extinction in populations of these species.     

Maximum foraging ranges in solitary bees: only few individuals have the capability to cover long foraging distances

To preserve populations of endangered bee species, sound knowledge of their maximum foraging distance between nest and host plants is crucial. Previous investigations predicted maximum foraging distances of 100-200 m for small bee species and up to 1100 m for very large species based on mainly indirect methods. The present study applied a new and direct approach to experimentally investigate maximum foraging distances in solitary bees. One endangered and two common species of different body sizes, all of which restrict pollen foraging to a single plant genus, were established in a landscape lacking their specific host plants. Females were forced to collect pollen on potted host plants that were successively placed in increasing distance from fixed nesting stands. The maximum foraging distance recorded for the small Hylaeus punctulatissimus was 1100 m, for the medium sized Chelostoma rapunculi 1275 m and for the large Hoplitis adunca 1400 m, indicating that maximum foraging distances at species level have been underestimated. However, the capability to use resources on such a large spatial scale applied only to a small percentage of individuals as 50% of the females of H. punctulatissimus and H. adunca did not forage at distances longer than 100-225 m and 300 m, respectively. This finding suggests that a close neighbourhood of nesting and foraging habitat within few hundred meters is crucial to maintain populations of these species, and that threshold distances at which half of the population discontinues foraging are a more meaningful parameter for conservation practice than the species specific maximum foraging distances.     

Are roads and railroads barriers to bumblebee movement in a temperate suburban conservation area?

We investigated how habitat fragmentation affects the movement of marked bumblebees between plant patches in a temperate conservation area in metropolitan Boston, Massachusetts. Our study was conducted on populations of sweet pepperbush (Clethra alnifolia L. f.) separated by a road and natural woodland, and buttonbush (Cephalanthus occidentalis L.) separated by a railroad. Bumblebees showed high site fidelity and only rarely crossed roads or railroads. When bees captured at one sweet pepperbush population were moved across a road to a new sweet pepperbush population and released, they returned to their original site, some within 20 min of their capture. When all inflorescences were removed from one sweet pepperbush patch, most bees moved to another sweet pepperbush population on the same side of the road. The results show that while bumblebees have the ability to cross a road and railroad, these human structures may restrict bumblebee movement and act to fragment plant populations because of the innate site fidelity displayed by foraging bees. Moreover, marked bees were almost never observed to move between populations unless they were displaced, or forced to seek additional forage sites.     

The abundance and efficacy of Rhizobium leguminosarum bv. viciae in cultivated soils of the eastern Canadian prairie

For optimum production, the use of commercial rhizobial inoculant on pea (Pisum sativum L.) at seeding is necessary in the absence of compatible rhizobial strains or when rhizobial soil populations are low or symbiotically ineffective. Multiple site experiments were conducted to characterize the abundance and effectiveness of resident populations of Rhizobium leguminosarum bv. viciae (Rlv) in eastern Canadian prairie soils. A survey of 20 sites across a broad geographical range of southern Manitoba was carried out in 1998 and was followed by more intensive study of five of the sites in 1999 and 2000. Appreciable nodulation of uninoculated pea was observed at all sites which had previously grown inoculated pea. However, uninoculated pea grown at two sites, which had not previously grown pea, had negligible nodulation. Likewise, wild Lathyrus sp. and Vicia sp. plants collected from uncultivated areas adjacent to agricultural sites were poorly nodulated. In the more intensively studied sites, there was a tendency towards higher nodulation in pea plants receiving commercial inoculant containing Rlv strain PBC108 across all site-years (e.g., 4.7% in nodulation and 22% in nodule mass), but the effect was significant at only 2 of 10 site-years. Despite a relatively high range of soil pH (6-8), regression analysis indicated that decreasing soil pH resulted in lower nodulation rates. Likewise, electrical conductivity (EC) was correlated to nodulation levels, however the effect of EC was likely more indicative of the influence of soil texture and organic matter than salinity. As with nodulation, commercial inoculation tended to increase above-ground dry matter (DM) and fixed-N (estimated by the difference method) at the early pod-filling stage, but again the effects were significant at only 2 of 10 site-years. Specifically, above-ground DM and fixed-N levels were up to 29 and 51% greater, respectively, in inoculated compared to non-inoculated treatments at these sites. Addition of N-fertilizer at a rate of 100 kg N ha⁻¹ decreased nodulation at almost all site-years (by as much as 70% at one site), but rarely resulted in increases in above-ground DM compared to inoculated plots. The study indicates for the first time that populations of infective, and generally effective strains of Rlv occur broadly in agricultural soils across the eastern Canadian prairie, but that there is a tendency for increased symbiotic efficiency with the use of commercial inoculant.     

Repellency of insecticides and the effect of thiacloprid on bumble bee colony development in red clover (Trifolium pratense L.) seed crops

The study intended to compare repellency of three insecticides on bumble bees and honey bees in Norwegian red clover (Trifolium pratense L.) seed crops, and to examine effects of thiacloprid on bumble bee colony development in the field. The repellency study was carried out in a large-scale field trial in SE Norway in 2013. On average for observations during the first week after spraying, 17 and 40% less honey bees (P?=?.03) and 26 and 20% less bumble bees (P?=?.36) were observed on plots sprayed with the pyrethroids lambda-cyhalothrin and alpha-cypermethrin, respectively, than on unsprayed control plots. No pollinator repellency was found on plots sprayed with the neonicotinoid thiacloprid. Compared with unsprayed control the seed yield increases were 22% on plots sprayed with thiacloprid vs. 12–13% on plots sprayed with pyrethroids (P?=?.10). Follow-up studies in 2014–2016 focused on the effect of thiacloprid on bumble bee colony development in commercially reared nests of Bombus terrestris placed into red clover seed crops at the start of flowering. Unsprayed control crops were compared with crops sprayed either at the bud stage or when 18–44% of flower heads were in full bloom. Chemical analyses of adult bumble bees showed that thiacloprid was taken up in bees when crops were sprayed during flowering, but not detected when crops were sprayed at the bud stage. The bumble bees in late-sprayed crops also developed weaker colonies than in unsprayed crops. Dead bees with a high internal concentration of thiacloprid were found in one crop sprayed during the night at 35% flowering. This shows that thiacloprid is not bee-safe if sprayed after anthesis and that spraying has to be conducted at the bud stage to reduce its contamination of nectar and pollen.     

The genetic diversity of Rhizobium leguminosarum bv. viciae in cultivated soils of the eastern Canadian prairie

Soil populations of Rhizobium leguminosarum bv. viciae (Rlv) that are infective and symbiotically effective on pea (Pisum sativum L.) have recently been shown to be quite widespread in agricultural soils of the eastern Canadian prairie. Here we report on studies carried out to assess the genetic diversity amongst these endemic Rlv strains and to attempt to determine if the endemic strains arose from previously used commercial rhizobial inoculants. Isolates of Rlv were collected from nodules of uninoculated pea plants from 20 sites across southern Manitoba and analyzed by plasmid profiling and PCR-RFLP of the 16S-23S rDNA internally transcribed spacer (ITS) region. Of 214 field isolates analyzed, 67 different plasmid profiles were identified, indicating a relatively high degree of variability among the isolates. Plasmid profiling of isolates from proximal nodules (near the base of the stem) and distal nodules (on lateral roots further from the root crown) from individual plants from one site suggested that the endemic strains were quite competitive relative to a commercial inoculant, occupying 78% of the proximal nodules and 96% of the distal nodules. PCR-RFLP of the 16S-23S rDNA ITS also suggested a relatively high degree of genetic variability among the field isolates. Analysis of the PCR-RFLP patterns of 15 selected isolates by UPGMA indicated two clusters of three field isolates each, with simple matching coefficients (SMCs) ≥0.95. However, to group all field isolates together, the SMC has to be reduced to 0.70. Regarding the origin of the endemic Rlv strains, there were few occurrences of the plasmid profiles of field isolates being identical to the profiles of inoculant Rlv strains commonly used in the region. Likewise, the plasmid profiles of isolates from nodules of wild Lathyrus plants located near some of the sites were all different from those of the field isolates. However, comparison of PCR-RFLP patterns suggested an influence of some inoculant strains on the chromosomal composition of some of the field isolates with SMCs of ≥0.92. Overall, plasmid profiles and PCR-RFLP patterns of the isolates from endemic Rlv populations from across southern Manitoba indicate a relatively high degree of genetic diversity among both plasmid and chromosomal components of endemic strains, but also suggest some influence of chromosomal information from previously used inoculant strains on the endemic soil strains.     

Commercialized European bumblebee can cause pollination disturbance: An experiment on seven native plant species in Japan

Non-native pollinator species are now widely utilized to facilitate pollination of agricultural crops. Evaluation of the ecological risk of alien pollinators is necessary because they could have a large impact on native ecosystems through disturbing native plant-pollinator interactions. We conducted a greenhouse experiment to examine the impact of the non-native commercialized European bumblebees, Bombus terrestris, on the pollination success of seven Japanese bumblebee-pollinated plant species. Plants were exposed to three groups of bumblebees: native bumblebee(s) only (NATIVE treatment); the alien bee only (ALIEN) and a mix of the two (MIX). ALIEN treatment had negative effects on fruitset and/or fruit quality of five plants, including self-incompatible and compatible, herb and woody, and queen- and worker-pollinated species. The negative effects were caused by a decrease in legitimate flower visitation due to (1) physical inaccessibility to nectary in deep-corolla flowers by the alien bee with insufficient tongue length and, (2) biased flower preference between short-corolla flowers. Fruitset tended to decrease drastically for the self-incompatible species while fruit quality decreased moderately for the self-compatible species. Effects of MIX were not intermediate between NATIVE and ALIEN in most plant species, and caused pollination success to vary in an unpredictable manner amongst plant species, probably due to interaction between native and alien bees. This non-linear relationship between plants’ pollination success and the relative density of the alien suggests that the alien bee can disturb pollination of a plant species even when only representing a small fraction of the total pollinator community.     

Decline of bumble bees (Bombus) in the North American Midwest

Declines in many bumble bee species have been documented in Europe raising several ecological and economic concerns. The nature and extent of bumble bee decline in North America is poorly understood due mainly to a lack of baseline and long-term data. Museum collections provide excellent sources of information on past and current species distributions, which can be used to infer changes in the composition of insect communities. Using the Illinois Natural History Survey’s electronic database of Hymenoptera and a recent biodiversity survey of historically sampled localities, we were able to examine changes in the richness and distribution of the bumble bee fauna of Illinois over the last century. We found that bumble bee species richness declined substantially during the middle of the century (1940-1960). Four species were locally extirpated: Bombus borealis, Bombus ternarius, Bombus terricola and Bombus variabilis. The ranges of Bombus affinis, Bombus fraternus, Bombus pensylvanicus and Bombus vagans have also decreased in Illinois. Our analyses also indicated that current bumble bee diversity is highest in northern Illinois, where conservation efforts would be most productive. Our study demonstrates that half of the bumble bee species found historically in Illinois have been locally extirpated or have suffered declines, supporting observations of broader declines in North America. Major declines in the bumble bee fauna coincided with large-scale agricultural intensification in Illinois between 1940 and 1960. Attempts to conserve bumble bees in Illinois should involve wildlife-friendly approaches to agriculture, such as increasing agricultural land set-asides and hedgerows, and employing integrated pest management.     

Effects of marine reef National Parks on fishery CPUE in coastal Kenya

The role of marine protected areas in conserving fish stocks and their potential influence on adjacent fisheries was studied at Malindi and Watamu Marine National Parks, Kenya (established in 1968). For most species catch per unit effort (CPUE) in traditional Dema traps fished across park boundaries was higher within the parks (up to an order of magnitude). However, a few species (e.g., the seagrass parrotfish, Leptoscarus vaigensis and the whitespotted rabbitfish, Siganus sutor, WSR) had higher seasonal CPUE outside the parks. Potential spillover of fishes from the parks to adjacent fished areas was tested with a logistic “decay” model of density gradients (CPUE) across park borders from fringing and patch reefs. A steep decay in CPUE off the Malindi patch reef suggested little spillover of most species. However, greater spillover was suggested off fringing reefs. Species differences were evident. The two most important commercial species showed different density gradients. Species diversity declined more abruptly off the fringing reefs. We conclude that although spillover of most species from the parks is limited, the most important commercial species exhibits significant spillover to adjacent fisheries and the Parks likely comprise important nursery and growth areas for other species.     

Molecular markers and a sequence deletion in intron 2 of the putative partial homologue of LEAFY reveal geographical structure to genetic diversity in the acutely threatened legume genus Clianthus

Clianthus is an acutely threatened, bird-pollinated genus endemic to New Zealand, represented in the wild by only one population of C. puniceus and 11 populations of C. maximus, each with very few individuals (typically <10 per population). A limited number of named Clianthus cultivars of indeterminate origin are commonly grown as ornamentals. Genomic DNA from individual Clianthus plants was extracted for genetic diversity analysis using a range of molecular markers, including amplified fragment length polymorphism (AFLP). Data were analysed by the unweighted pair-group method with arithmetic averaging (UPGMA), the generation of Neighbor-Joining trees, and analyses of molecular variance (AMOVA). Genetic distance between wild populations of C. maximus was highly correlated with geographical distance between populations. Sequencing of intron 2 of a putative partial homologue of the floral meristem identity gene LEAFY (CmLFY) revealed a 7 bp deletion that was exhibited homozygously in the more northern populations of C. maximus, and in all individuals tested from the sole population of C. puniceus. This deletion was not exhibited in more southern populations of C. maximus. Further, one geographically intermediate population contained some plants that were heterozygous for the deletion. Parallel analyses of cultivated Clianthus genotypes, more than half of which were also homozygous for the 7 bp deletion, showed that these were not representative of the broad, but threatened, diversity remaining in the wild. It is argued that wild populations of C. maximus are unlikely to have arisen from the escape of plants from cultivation. Conservation effort should focus on the protection and study of the extant plants in these wild populations, rather than on the introduction of disturbance regimes to uncover potential seed banks.     

Reproductive biology of three sympatric endangered plants endemic to Florida scrub

We investigated the reproductive biology of three plants endemic to rosemary scrub habitats on the Lake Wales Ridge of Florida, USA. We used hand-pollination experiments and observations of flowers and their insect visitors to determine their mating systems and pollination. Fruit or seed set after self pollination was 94, 97, and 8% of fruit or seed set after cross pollination in Eryngium cuneifolium (Apiaceae), Hypericum cumulicola (Hypericaceae), and Liatris ohlingerae (Asteraceae) respectively, indicating that the first two are self-compatible and the last is obligately outcrossing. All three depend on insects for seed production (4-7% fruit or seed set without insects). Diverse insects visit flowers of E. cuneifolium (101 species recorded), whereas L. ohlingerae is visited predominantly by butterflies and H. cumulicola by one genus of bees (Dialictus, Halictidae). Our data indicate pollinator visitation does not currently limit seed production in E. cuneifolium or H. cumulicola, but does in L. ohlingerae. Despite the features they share (habit, habitat, disturbance regime), we found unique aspects of these species' reproductive biology yielding unique risks to population viability. We suggest that multispecies recovery plans must consider several aspects of the biology of species with superficial similarities to be successful.     

Plantations of Convallaria majalis L. as a threat to the natural stands of the species: Genetic variability of the cultivated plants and natural populations

The level of polymorphism, genetic variability and relatedness of Convallaria majalis-populations (species native in Poland, under partial legal protection) obtained from three Polish regions and from commercial producers (Polish and Dutch) were studied. In addition the differences between the cultivated plants and those occurring in natural stands were analyzed. Each region was represented by at least 20 populations among which half were collected in natural stands and half from cultivation sites (botanical gardens, private gardens and cemeteries), and compared with samples obtained directly from commercial producers. Seven primer pairs used for AFLP profiling amplified 466 scoreable DNA fragments that were used for multidimensional scaling and clustering. The above analyses make it possible to clearly distinguish among individuals and revealed groups of populations according to their geographic origin. Samples from populations collected in natural stands and cultivated in the same region did not differ from each other significantly.These results suggested that cultivated plants were probably obtained directly from the natural stand and the influence of plant cultures on natural populations was rather small.     

Patterns of gastrointestinal bacterial exchange between chimpanzees and humans involved in research and tourism in western Uganda

Ecological overlap may increase the risks of microbial exchange between humans and wild non-human primates. Escherichia coli bacteria were collected from chimpanzees and humans in Kibale National Park, western Uganda, in May and June 2004, in order to examine whether interaction between humans and apes in the wild might affect gastrointestinal bacterial communities in the two species. Chimpanzees harbored bacteria genetically more similar to those of humans employed in chimpanzee-directed research and tourism than to those of humans from a local village. Most humans (81.6%) and 4.4% of chimpanzees harbored at least one isolate resistant to locally available antibiotics. In isolates from both humans and chimpanzees, resistance was higher to five of these antibiotics than to Ceftiofur, an antibiotic not available in the region. These data indicate that humans and apes interacting in the wild can share genetically and phenotypically similar gastrointestinal bacteria, presumably originating from common environmental sources. Strategies to limit transmission of pathogens between humans and primates, whether that transmission is direct or indirect, would benefit both human health and primate conservation.