Find research datasets worth reusing

opencc-zeroDec 2010View details →

Data from: Loss of sexual recombination and segregation is associated with increased diversification in evening primroses

The loss of sexual recombination and segregation in asexual organisms has been portrayed as an irreversible process that commits asexually-reproducing lineages to reduced diversification. We test this hypothesis by estimating rates of speciation, extinction, and transition between sexuality and functional asexuality in the evening primroses. Specifically, we estimate these rates using the recently developed BiSSE (Binary State Speciation and Extinction) phylogenetic comparative method, which employs maximum likelihood and Bayesian techniques. We infer that net diversification rates (speciation minus extinction) in functionally asexual evening primrose lineages are roughly eight times faster than diversification rates in sexual lineages, largely due to higher speciation rates in asexual lineages. We further reject the hypothesis that a loss of recombination and segregation is irreversible because the transition rate from functional asexuality to sexuality is significantly greater than zero.and in fact exceeded the reverse rate. These results provide the first empirical evidence in support of the alternative theoretical prediction that asexual populations should instead diversify more rapidly than sexual populations because they are free from the homogenizing effects of sexual recombination and segregation. Although asexual reproduction may often constrain adaptive evolution, our results show that the loss of recombination and segregation need not be an evolutionary dead-end in terms of diversification of lineages.

Data from: Interactive effects of climate change and biodiversity loss on ecosystem functioning

Climate change and biodiversity loss are expected to simultaneously affect ecosystems, however research on how each driver mediates the effect of the other has been limited in scope. The multiple stressor framework emphasizes non-additive effects, but biodiversity may also buffer the effects of climate change, and climate change may alter which mechanisms underlie biodiversity-function relationships. Here, we performed an experiment using tank bromeliad ecosystems to test the various ways that rainfall changes and litter diversity may jointly determine ecological processes. Litter diversity and rainfall changes interactively affected multiple functions, but how depended on the process measured. High litter diversity buffered the effects of altered rainfall on detritivore communities, evidence of insurance against impacts of climate change. Altered rainfall affected the mechanisms by which litter diversity influenced decomposition, reducing the importance of complementary attributes of species ("complementarity effects"), and resulting in an increasing dependence on the maintenance of specific species ("dominance effects"). Finally, altered rainfall conditions prevented litter diversity from fuelling methanogenesis, because such changes in rainfall reduced microbial activity by 58%. Together, these results demonstrate that the effects of climate change and biodiversity loss on ecosystems cannot be understood in isolation and interactions between these stressors can be multifaceted.

opencc-zeroJul 2019View details →

Data from: Loss of cultural song diversity and the convergence of songs in a declining Hawaiian forest bird community

The effects of population decline on culturally transmitted behaviors in animals has rarely been described, but may have major implications to population viability. Learned vocal signals in birds are of critical importance to behaviors associated with reproduction, intrasexual interactions, and group cohesion, and the complexity of vocal signals such as song can serve as an honest signal of an individual's quality as well as the viability of a population. In this study, we examined how rapid population declines recently experienced by Hawaiian honeycreepers on the island of Kaua'i (USA) may have influenced the diversity, complexity, and similarity of learned honeycreeper songs. We analyzed the acoustic characteristics of songs recorded during 3 time periods over a 40-year time frame for three species of declining Kaua'i honeycreepers. We detected a loss of song complexity and diversity over the 40-year time period that paralleled dramatic population declines. Concurrent with the loss of complexity we also found that the acoustic characteristics of the three honeycreepers' songs became more similar to another. To our knowledge, this is the first documentation of convergence of acoustic characteristics among rapidly declining species. The reduction of song complexity and diversity and convergence of songs not only signals a loss of culturally transmitted behaviors in these endemic Hawaiian honeycreepers, but also potential challenges to recovery of these rapidly declining species. Moreover, the present study highlights that there is a "hidden" cost to declining populations beyond just the loss of individuals that is not often considered, the loss of culturally transmitted social behaviors.

Data from: Scaling up effects of measures mitigating pollinator loss from local- to landscape-level population responses

1. Declining pollinator populations have caused concern about consequences for food production, and have initiated an increasing number of initiatives that aim to mitigate pollinator loss through enhancement of floral resources. Studies evaluating effects of mitigation measures generally demonstrate positive responses of pollinators to floral resource enhancement. However, it remains unclear whether this represents landscape-level population effects or results from a spatial redistribution of individuals from otherwise unaffected populations. 2. Here we present a method for estimating landscape-level population effects using data from commonly used standardized pollinator transect surveys. The approach links local density responses of pollinators in both mitigation sites and surrounding landscape elements to the area these habitats occupy in mitigation landscapes as well as control landscapes to obtain landscape-level population estimates. 3. We demonstrate the method using data from a two-year study examining the effects of experimental wildflower enhancements on wild bumble bees and solitary bees in Dutch agricultural landscapes. The results show that conclusions based on local responses may differ significantly from those based on landscape-level responses. 4. Wildflower enhancements significantly enhanced landscape-level abundance of both bumble bees and solitary bees. Bumble bees showed a pronounced positive local density response in mitigation sites and the surrounding landscape that was in line with significant landscape-level increases in abundance. However, solitary bees showed no local response to mitigation sites, and the landscape-level increases in abundance only became apparent when the area of bee habitat was taken into account. 5. Incorporating the area of both newly created and pre-existing pollinator habitats into effect estimates accounts for density-dependent processes such as dilution, spill-over and local concentration of individuals. It therefore results in more reliable estimates of the response to mitigation measures of pollinators, as well as other mobile arthropod groups that are often being surveyed using transect surveys.

Data from: Multiple stressors and the potential for synergistic loss of New England salt marshes

Climate change and other anthropogenic stressors are converging on coastal ecosystems worldwide. Understanding how these stressors interact to affect ecosystem structure and function has immediate implications for coastal planning, however few studies quantify stressor interactions. We examined past and potential future interactions between two leading stressors on New England salt marshes: sea-level rise and marsh crab (Sesarma reticulatum) grazing driven low marsh die-off. Geospatial analyses reveal that crab-driven die-off has led to an order of magnitude more marsh loss than sea-level rise between 2005 and 2013. However, field transplant experimental results suggest that sea-level rise will facilitate crab expansion into higher elevation marsh platforms by inundating and gradually softening now-tough high marsh peat, exposing large areas to crab-driven die-off. Taking interactive effects of marsh softening and concomitant overgrazing into account, we estimate that even modest levels of sea-level rise will lead to levels of salt marsh habitat loss that are 3x greater than the additive effects of sea-level rise and crab-driven die-off would predict. These findings highlight the importance of multiple stressor studies in enhancing mechanistic understanding of ecosystem vulnerabilities to future stress scenarios and encourage managers to focus on ameliorating local stressors to break detrimental synergisms, reduce future ecosystem loss, and enhance ecosystem resilience to global change.

Data from: Habitat fragmentation, not habitat loss, drives the prevalence of blood parasites in a Caribbean passerine

Habitat destruction due to human land-use activities is well recognized as a central threat to biodiversity. However, there is still debate about the relative influence of its two components, habitat loss and habitat fragmentation, mostly because few studies have been able to disentangle their respective effects. We studied mechanisms by which habitat destruction might influence the prevalence of vector-transmitted haemosporidian blood parasites of the genera Plasmodium and Haemoproteus the Lesser Antillean Bullfinch, Loxigilla noctis, on the Caribbean islands of Guadeloupe and Martinique . Starting from a large set of environmental descriptors (including metrics reflecting habitat loss, habitat fragmentation and landscape heterogeneity; as well as other variables not linked to habitat destruction, such as climatic conditions), we used PLS regression analyses to determine which variables were driving parasite prevalence on the islands. Our results showed that variables related to forest destruction were much more influential than other factors for all parasites analyzed on both islands. Remarkably, the effects documented were almost exclusively due to forest fragmentation, as opposed to habitat loss. This positive effect of forest fragmentation on blood parasite prevalence is proposed to happen through its effects on insect vectors and/or host biology. Increased understanding of the role of habitat fragmentation as a driver of parasitic diseases can help anticipate future effects and limit the risk of emergence and proliferation of wildlife pathogenic outbreaks and zoonosis through informed landscape planning.

Data from: Brood-tending males in a biparental fish suffer high paternity losses but rarely cuckold

Extra-pair paternity within socially monogamous mating systems is well-studied in birds and mammals but rather neglected in other animal taxa. In fishes, social monogamy has evolved several times but few studies have investigated the extent to which pair-bonded male fish lose fertilizations to cuckolders and gain extra-pair fertilizations themselves. We address this gap and present genetic paternity data collected from a wild population of Variabilichromis moorii, a socially monogamous African cichlid with biparental care of offspring. We show that brood-tending, pair-bonded males suffer exceptionally high paternity losses, siring only 63% of the offspring produced by their female partners on average. The number of cuckolders per brood ranged up to nine and yet, surprisingly, brood-tending males in the population were rarely the culprits. Brood-tending males sired very few extra-pair offspring, despite breeding in close proximity to one another. While unpaired males were largely responsible for the cuckoldry, pair-bonded males still enjoyed higher fertilization success than individual unpaired males. We discuss these results in the context of ecological and phenotypic constraints on cuckoldry and the fitness payoffs of alternative male tactics. Our study provides new insights into how pair-bonded males handle the trade-off between securing within-pair and extra-pair reproduction.

opencc-zeroDec 2015View details →

Data from: Loss of genetic diversity and increased embryonic mortality in non-native lizard populations

Many populations are small and isolated with limited genetic variation and high risk of mating with close relatives. Inbreeding depression is suspected to contribute to extinction of wild populations, but the historical and demographic factors that contribute to reduced population viability are often difficult to tease apart. Replicated introduction events in non-native species can offer insights into this problem because they allow us to study how genetic variation and inbreeding depression are affected by demographic events (e.g. bottlenecks), genetic admixture and the extent and duration of isolation. Using detailed knowledge about the introduction history of 21 non-native populations of the wall lizard Podarcis muralis in England, we show greater loss of genetic diversity (estimated from microsatellite loci) in older populations and in populations from native regions of high diversity. Loss of genetic diversity was accompanied by higher embryonic mortality in non-native populations, suggesting that introduced populations are sufficiently inbred to jeopardize long-term viability. However, there was no statistical correlation between population-level genetic diversity and average embryonic mortality. Similarly, at the individual level, there was no correlation between female heterozygosity and clutch size, infertility or hatching success, or between embryo heterozygosity and mortality. We discuss these results in the context of human-mediated introductions and how the history of introductions can play a fundamental role in influencing individual and population fitness in non-native species.

opencc-zeroDec 2015View details →

Data from: Selective logging in tropical forests decreases the robustness of liana-tree interaction networks to the loss of host tree species

Selective logging is one of the major drivers of tropical forest degradation, causing important shifts in species composition. Whether such changes modify interactions between species and the networks in which they are embedded remain fundamental questions to assess the 'health' and ecosystem functionality of logged forests. We focus on interactions between lianas and their tree hosts within primary and selectively logged forests in the biodiversity hotspot of Malaysian Borneo. We found that lianas were more abundant, had higher species richness and different species compositions in logged than in primary forests. Logged forests showed heavier liana loads disparately affecting slow-growth tree species, which could exacerbate the loss of timber value and carbon storage already associated to logging. Moreover, simulation scenarios of host tree local species loss indicated that logging might decrease the robustness of liana-tree interaction networks if heavily infested trees (i.e. the most connected ones) are more likely to disappear. This effect is partially mitigated in the short term by the colonization of host trees by a greater diversity of liana species within logged forests, yet this might not compensate for the loss of preferred tree hosts in the long term. As a consequence, species interaction networks may show a lagged response to disturbance, which may trigger sudden collapses in species richness and ecosystem function in response to additional disturbances, representing a new type of "extinction debt".

Data from: Transient negative biochar effects on plant growth are strongest after microbial species loss

Biochar has been explored as an organic amendment to improve soil quality and benefit plant growth. The overall positive effects of biochar on crop yields are generally attributed to abiotic changes, while the alternative causal pathway via changes in soil biota is unexplored. We compared plant growth effects of legumes in sterile soil inoculated with dilutions of soil and soil microbial suspensions to determine the direct effects of biochar-induced changes in soil biota on plant growth. Suspensions and soil were from soil amended with biochar and soil without biochar. By comparing consecutive plant growth phases on the same inoculated soils, we also determined the temporal effects of soil biota from biochar-amended and control soils. Biota from biochar-amended soil was less beneficial for Medicago sativa growth, especially with small amounts of inocula. Flowering was delayed in the presence of biota from biochar plots. Inoculum with either soil or soil suspension gave similar results for plant biomass, indicating that microorganisms play a major role. Vicia villosa growth did not respond to the various inocula, even though the inoculum quantity strongly affected nematode community composition and protozoan abundance. In a later growing phase the negative effect of biochar-associated biota on Medicago growth mostly disappeared, which leads to the conclusion that the benefits of biochar application via abiotic changes may outweigh the negative effects of biochar on soil biota.

opencc-zeroDec 2015View details →

Data from: Molecular evolution of anthocyanin pigmentation genes following losses of flower color

Background: Phenotypic transitions, such as trait gain or loss, are predicted to carry evolutionary consequences for the genes that control their development. For example, trait losses can result in molecular decay of the pathways underlying the trait. Focusing on the Iochrominae clade (Solanaceae), we examine how repeated losses of floral anthocyanin pigmentation associated with flower color transitions have affected the molecular evolution of three anthocyanin pathway genes (Chi, F3h, and Dfr). Results: We recovered intact coding regions for the three genes in all of the lineages that have lost floral pigmentation, suggesting that molecular decay is not associated with these flower color transitions. However, two of the three genes (Chi, F3h) show significantly elevated dN/dS ratios in lineages without floral pigmentation. Maximum likelihood analyses suggest that this increase is due to relaxed constraint on anthocyanin genes in the unpigmented lineages as opposed to positive selection. Despite the increase, the values for dN/dS in both pigmented and unpigmented lineages were consistent overall with purifying selection acting on these loci. Conclusions: The broad conservation of anthocyanin pathway genes across lineages with and without floral anthocyanins is consistent with the growing consensus that losses of pigmentation are largely achieved by changes in gene expression as opposed to structural mutations. Moreover, this conservation maintains the potential for regain of flower color, and indicates that evolutionary losses of floral pigmentation may be readily reversible.

opencc-zeroJun 2019View details →

Data from: Larger genomes linked to slower development and loss of late-developing traits

Genome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel dataset with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear. We established that genome size is negatively correlated with development rate across 90 anuran species and found that genome size evolution is correlated with evolutionary loss of the middle ear bone (columella) among 241 species (224 eared and 17 earless). We further tested whether the development of the tympanic middle ear could be constrained by large cell sizes and small body sizes during key stages of tympanic middle ear development (metamorphosis). Together, our evidence suggests that larger genomes, slower development rate, and smaller body sizes at metamorphosis may contribute to the loss of the anuran tympanic middle ear. We conclude that increases in anuran genome size, although less drastic than in salamanders, may affect development of late-forming traits.

Data from: Forest loss in protected areas and intact forest landscapes: a global analysis

In spite of the high importance of forests, global forest loss has remained alarmingly high during the last decades. Forest loss at a global scale has been unveiled with increasingly finer spatial resolution, but the forest extent and loss in protected areas (PAs) and in large intact forest landscapes (IFLs) have not so far been systematically assessed. Moreover, the impact of protection on preserving the IFLs is not well understood. In this study we conducted a consistent assessment of the global forest loss in PAs and IFLs over the period 2000–2012. We used recently published global remote sensing based spatial forest cover change data, being a uniform and consistent dataset over space and time, together with global datasets on PAs' and IFLs' locations. Our analyses revealed that on a global scale 3% of the protected forest, 2.5% of the intact forest, and 1.5% of the protected intact forest were lost during the study period. These forest loss rates are relatively high compared to global total forest loss of 5% for the same time period. The variation in forest losses and in protection effect was large among geographical regions and countries. In some regions the loss in protected forests exceeded 5% (e.g. in Australia and Oceania, and North America) and the relative forest loss was higher inside protected areas than outside those areas (e.g. in Mongolia and parts of Africa, Central Asia, and Europe). At the same time, protection was found to prevent forest loss in several countries (e.g. in South America and Southeast Asia). Globally, high area-weighted forest loss rates of protected and intact forests were associated with high gross domestic product and in the case of protected forests also with high proportions of agricultural land. Our findings reinforce the need for improved understanding of the reasons for the high forest losses in PAs and IFLs and strategies to prevent further losses.

opencc-zeroJun 2019View details →

Data from: Loss of functional connectivity in migration networks induces population decline in migratory birds

Migratory birds rely on a habitat network along their migration routes by temporarily occupying stopover sites between breeding and non-breeding grounds. Removal or degradation of stopover sites in a network might impede movement, and thereby reduce migration success and survival. The extent to which the breakdown of migration networks, due to changes in land use, impacts the population sizes of migratory birds is poorly understood. We measured the functional connectivity of migration networks of waterfowl species that migrate over the East Asian-Australasian Flyway from 1992-2015. We analysed the relationship between changes in non-breeding population sizes and changes in functional connectivity, while taking into account other commonly-considered species traits, using a Phylogenetic Linear Mixed Model. We found that population sizes significantly declined with a reduction in the functional connectivity of migration networks; no other predictor variables were important. We conclude that the current decrease in functional connectivity, due to habitat loss and degradation in migration networks, can negatively and crucially impact population sizes of migratory birds. Our findings provide new insights into the underlying mechanisms that affect population trends of migratory birds under environmental changes. Establishment of international agreements leading to the creation of systematic conservation networks associated with migratory species' distributions and stopover sites may safeguard migratory bird populations.

Data from: A decline in molluscan carbonate production driven by the loss of vegetated habitats encoded in the Holocene sedimentary record of the Gulf of Trieste

Carbonate sediments in non-vegetated habitats on the NE Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because (1) monitoring of ecosystems prior to the 20th century was scarce and (2) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand-dwelling Gouldia minima and opportunistic Corbula gibba are time-averaged to > 1,000 years and C. gibba shells are older by >2,000 years than shells of co-occurring G. minima. This age difference is driven by temporally disjunct production of two species coupled with decimeter-scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again in the 20th century. In contrast, one of the major contributors to carbonate sands, Gouldia minima, increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. G. minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top-core increments but are rare alive. Although G. minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live-dead mismatch reflects the difference between highstand baseline communities (with soft-bottom vegetated zones and hard-bottom Arca beds) and present-day oligophotic communities with organic-loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the seafloor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats.

opencc-zeroDec 2018View details →

Data from: Testing the hypothesis of loss of defences on islands across a wide latitudinal gradient of Periploca laevigata populations

PREMISE OF THE STUDY: We tested a hypothesis that predicts loss of chemical defences on island plant populations (LCDIH) as an evolutionary response to limited herbivore pressures. METHODS: Using a common garden approach, we grew 16 populations (N = 286 seedlings) of Periploca laevigata, a Mediterranean shrub for which previous studies suggested tannin-mediated responses to animal browsing. Our experimental setting represented a wide latitudinal gradient (37-15ºN) encompassing three island systems, virtually free of large herbivores, and three mainland areas. Putative chemical defences were estimated from tannin-protein precipitation assays, and inducible responses in growth and chemical traits were assessed between seasons and by subjecting plants to a pruning treatment. KEY RESULTS: We failed to find support for the LCDIH, since island populations (Canary Islands, Cape Verde) displayed increasingly higher constitutive levels of tannins at lower latitudes. Seasonality, but not experimental pruning, induced variation in levels of tannins in a consistent pattern across populations. Thus, net differences in leaf tannin concentration remained similar among geographical areas regardless of the factor considered, with latitude being the best explanatory factor for this trait over seasonal growth patterns. CONCLUSIONS: Geographical variation in total tannin pools appears to be mediated by factors other than herbivore pressure in P. laevigata. We hypothesize that abiotic correlates of latitude not considered in our study have promoted high constitutive levels of leaf tannins across Macaronesian populations, which ultimately may explain the pattern of seasonal variation and latitudinal increase from Mediterranean to subtropical Cape Verde populations. In compliance with data protection regulations, please contact the publication office if you would like to have your personal information removed from the database.

Data from: Privatisation rescues essential function following loss of cooperation

A single cheating mutant can lead to the invasion and eventual eradication of cooperation from a population. Consequently, cheat invasion is often considered equal to extinction in empirical and theoretical studies of cooperator-cheat dynamics. But does cheat invasion necessarily equate extinction in nature? By following the social dynamics of iron metabolism in Pseudomonas aeruginosa during cystic fibrosis lung infection, we observed that individuals evolved to replace cooperation with a 'private' behaviour. Phenotypic assays showed that cooperative iron acquisition frequently was upregulated early in infection, which, however, increased the risk of cheat invasion. With whole-genome sequencing we showed that if, and only if, cooperative iron acquisition is lost from the population, a private system was upregulated. The benefit of upregulation depended on iron availability. These findings highlight the importance of social dynamics of natural populations and emphasizes the potential impact of past social interaction on the evolution of private traits.

Data from: Wild birds respond to flockmate loss by increasing their social network associations to others

Understanding the consequences of losing individuals from wild populations is a current and pressing issue, yet how such loss influences the social behaviour of the remaining animals is largely unexplored. Through combining the automated tracking of winter flocks of over 500 wild great tits (Parus major) with removal experiments, we assessed how individuals' social network positions responded to the loss of their social associates. We found that the extent of flockmate loss that individuals experienced correlated positively with subsequent increases in the number of their social associations, the average strength of their bonds and their overall connectedness within the social network (defined as summed edge weights). Increased social connectivity was not driven by general disturbance or changes in foraging behaviour, but by modifications to fine-scale social network connections in response to losing their associates. Therefore, the reduction in social connectedness expected by individual loss may be mitigated by increases in social associations between remaining individuals. Given that these findings demonstrate rapid adjustment of social network associations in response to the loss of previous social ties, future research should examine the generality of the compensatory adjustment of social relations in ways that maintain the structure of social organization.

Data from: Spending limited resources on de-extinction could lead to net biodiversity loss

There is contentious debate surrounding the merits of de-extinction as a biodiversity conservation tool. Here, we use extant analogues to predict conservation actions for potential de-extinction candidate species from New Zealand and the Australian state of New South Wales, and use a prioritization protocol to predict the impacts of reintroducing and maintaining populations of these species on conservation of extant threatened species. Even using the optimistic assumptions that resurrection of species is externally sponsored, and that actions for resurrected species can share costs with extant analogue species, public funding for conservation of resurrected species would lead to fewer extant species that could be conserved, suggesting net biodiversity loss. If full costs of establishment and maintenance for resurrected species populations were publicly funded, there could be substantial sacrifices in extant species conservation. If conservation of resurrected species populations could be fully externally sponsored, there could be benefits to extant threatened species. However, such benefits would be outweighed by opportunity costs, assuming such discretionary money could directly fund conservation of extant species. Potential sacrifices in conservation of extant species should be a crucial consideration in deciding whether to invest in de-extinction or focus our efforts on extant species.

Data from: Large mammal declines and the incipient loss of mammal-bird mutualisms in an African savanna ecosystem

Over the past half-century, large mammal populations have declined substantially throughout East Africa, mainly due to habitat loss and unsustainable direct exploitation. While it has been acknowledged that the loss of large mammals can have direct and cascading effects on community composition and ecosystem characteristics, limited quantitative work has been done on how declines of large herbivore populations impacts the abundance of mutualistic symbionts. Using a space-for-time observational approach, we quantified the large mammal community alongside the densities, host preferences and behaviors of mutualistic red-billed oxpeckers (Buphagus erythrorhynchus), and yellow-billed oxpeckers (Buphagus africanus) in northern Tanzania. At the landscape scale, mammal community composition was substantially less diverse in highly human-dominated areas when compared with more protected areas, with an observed complete loss of large wild mammal species in two study areas. Mirroring this trend, oxpecker densities were lowest in the least protected areas, and highest in fully protected areas. Using resource selection functions implemented via generalized linear models at different scales, we found that oxpeckers (1) were predominantly (67% of red-billed oxpeckers; 70% of yellow-billed oxpeckers) feeding on larger (between 500kg and 1500kg) ungulate host species within the mammal community, (2) usually preferred feeding on larger individuals (adults and males) within a specific host species population, and (3) preferred hosts that were more tolerant of their presence. In particular, cattle were especially intolerant of oxpecker presence and were relatively effective in displacing oxpeckers. We found little evidence that oxpecker feeding was parasitic across all host species; wound feeding was only observed on giraffe, comprising 6% and 4% of feeding behavior in red-billed and yellow-billed oxpeckers respectively. Thus, a loss of large-bodied and oxpecker tolerant host species is a likely explanation for declines of oxpecker populations in human dominated landscapes, which may have further cascading effects.