Sex-driven neighborhood effects on herbivory in the dioecious Mediterranean palm Chamaerops humilis L

Although it is well recognized that the strength of plant-herbivore interactions can vary with the plant sex, the distance, and the density of conspecific neighbors, no study has yet assessed their combined influence. Here, we filled this knowledge gap by focusing on the dioecious palm Chamaerops humilis L., and its two main herbivores, the invasive moth Paysandisia archon Burmeister and the feral goat Capra hircus L. We evaluated levels and spatial patterns of herbivory, as well as those of plant size and number of inflorescences in two palm populations in Mallorca (Balearic Islands, Spain). Our spatial point pattern analyses revealed that palms not affected by moth herbivory or goat florivory were spatially aggregated, goats fed more strongly upon inflorescences in palms with more neighbors, but they consumed more leaves in isolated palms. Interestingly, we could reveal for the first time that plant sex is a key plant trait modulating neighborhood effects. For instance, whereas aggregated female palms experienced lower intensity of goat florivory than isolated ones, male palms showed the opposite pattern. Palm size and number of inflorescences also showed sex-related differences, suggesting that sexual dimorphism is a key driver of the observed neighborhood effects on herbivory. Our study highlights the importance of considering relevant plant traits such as sex when investigating plant neighborhood effects, calling for further research to fully understand the dynamics governing plant-herbivore interactions in dioecious systems.

Aspects of molar form and dietary proclivities of African colobines

This study investigates aspects of molar form in three African colobine species: Colobus polykomos, Colobus angolensis, and Piliocolobus badius. Our samples of C. polykomos and P. badius are from the Taï Forest, Ivory Coast; our sample of C. angolensis is from Diani, Kenya. To the extent that protective layers surrounding seeds are hard, we predicted that molar features related to hard-object feeding would be more pronounced in Colobus than they are Piliocolobus, as seed-eating generally occurs at higher frequencies in species of the former. We further predicted that among the colobines we studied, these features would be most pronounced in Taï Forest C. polykomos, which feeds on Pentaclethra macrophylla seeds encased within hard and tough seed pods. We compared overall enamel thickness, enamel thickness distribution, absolute crown strength, cusp tip geometry, and flare among molar samples. Sample sizes per species and molar type varied per comparison. We predicted differences in all variables except overall enamel thickness, which we expected would be invariant among colobines as a result of selection for thin enamel in these folivorous species. Of the variables we examined, only molar flare differed significantly between Colobus and Piliocolobus. Our findings suggest that molar flare, an ancient feature of cercopithecoid molars, was retained in Colobus but not in Piliocolobus, perhaps as a result of differences in the seed-eating proclivities of the two genera. Contrary to predictions, none of the aspects of molar form we investigated tracked current dietary differences in seed-eating between the two Colobus species. Finally, we explored the possibility that molar flare and absolute crown strength, when analyzed together, might afford greater differentiation among these colobine species. A multivariate t test of molar flare and absolute crown strength differentiated C. polykomos and P. badius, possibly reflecting known niche divergence between these two sympatric Taï Forest species.

Masticatory and ingestive effort in Procolobus verus, a small-bodied African colobine

The olive colobus (Procolobus verus) is the smallest extant colobine. Based on the axiom that folivory is associated with larger body mass, the olive colobus is expected to be less folivorous than its sister taxon Piliocolobus badius, but previous studies show that the opposite is true. Here we test the hypothesis that masticatory and ingestive effort in the olive colobus is greater due to allometric factors related to bite force scaling and throughput of ingested foods. We analyzed oral processing data collected on olive colobus in the Taï Forest, Ivory Coast, between May 2016 and May 2018. We compare these with previously published data on P. badius and Colobus polykomos from Taï. In terms of overall feeding effort, olive colobus invest more effort (i.e., chewing cycles) than the larger colobines. When contrasts are restricted to commonly consumed foods, this greater energetic investment is not consistently observed. Ingestion of young leaves is associated with a reduced number of masticatory cycles in all three colobine species. A slightly elevated average effort in the olive colobus during young leaf feeding suggests this food source is more challenging in smaller monkeys, but mature leaf processing effort is generally the same among Taï colobines. Thus, for olive colobus, leaf ductility may be more problematic than leaf toughness in terms of masticatory effort. While there may be an allometric cost to being a small colobine, food selectivity is an important mitigating factor.

Gut microbiota of frugo-folivorous sifakas across environments

Background

Captive animals, compared to their wild counterparts, generally harbor imbalanced gut microbiota owing, in part, to their altered diets. This imbalance is particularly striking for folivores that fundamentally rely on gut microbiota for digestion, yet rarely receive sufficient dietary fiber in captivity. We examine the critically endangered Coquerel’s sifaka (Propithecus coquereli), an anatomically specialized, rather than facultative, folivore that consumes a seasonal frugo-folivorous diet in the wild, but is provisioned predominantly with seasonal foliage and orchard vegetables in captivity. Using amplicon and metagenomic sequencing applied to fecal samples collected from two wild and one captive population (each comprising multiple groups), we clarify how dietary variation underlies the perturbational effect of captivity on the structure and function of this species’ gut microbiota.

Results

The gut microbiota of wild sifakas varied by study population, most notably in community evenness and in the abundance of diet-associated microbes from Prevotellaeceae and Lachnospiraceae. Nevertheless, the differences among wild subjects were minor compared to those evident between wild and captive sifakas: Unusually, the consortia of captive sifakas were the most diverse, but lacked representation of endemic Bacteroidetes and metagenomic capacity for essential amino-acid biosynthesis. Instead, they were enriched for complex fiber metabolizers from the Firmicutes phylum, for archaeal methanogens, and for several metabolic pathways putatively linked to plant fiber and secondary compound metabolism.

Conclusions

The relatively minor differences in gut microbial structure and function between wild sifaka populations likely reflect regional and/or temporal environmental variability, whereas the major differences observed in captive conspecifics, including the loss of endemic microbes, but gain in low-abundance taxa, likely reflect imbalanced or unstable consortia. Indeed, community perturbation may not necessarily entail decreased community diversity. Moreover, signatures of greater fiber degradation indicate that captive sifakas consume a more fibrous diet compared to their wild counterparts. These results do not mirror those typically reported for folivores and herbivores, suggesting that the direction and strength of captivity-induced ‘dysbiosis’ may not be universal across species with similar feeding strategies. We propose that tailored, species-specific dietary interventions in captivity, aimed at better approximating naturally foraged diets, could functionally ‘rewild’ gut microbiota and facilitate successful management of diverse species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00093-5.

A systematic review of the direct and indirect effects of herbivory on plant reproduction mediated by pollination

BACKGROUND

Plant reproduction is influenced by the net outcome of plant-herbivore and plant-pollinator interactions. While both herbivore impacts and pollinator impacts on plant reproduction have been widely studied, few studies examine them in concert.

METHODOLOGY

Here, we review the contemporary literature that examines the net outcomes of herbivory and pollination on plant reproduction and the impacts of herbivores on pollination through damage to shared host plants using systematic review tools. The direct or indirect effects of herbivores on floral tissue and reported mechanisms were compiled including the taxonomic breadth of herbivores, plants and pollinators.

RESULTS

A total of 4,304 studies were examined producing 59 relevant studies for synthesis that reported both pollinator and herbivore measures. A total of 49% of studies examined the impact of direct damage to floral tissue through partial florivory while 36% of studies also examined the impact of vegetative damage on pollination through folivory, root herbivory, and stem damage. Only three studies examined the effects of both direct and indirect damage to pollination outcomes within the same study.

CONCLUSIONS

It is not unreasonable to assume that plants often sustain simultaneous forms of damage to different tissues and that the net effects can be assessed through differences in reproductive output. Further research that controls for other relative drivers of reproductive output but examines more than one pathway of damage simultaneously will inform our understanding of the mechanistic relevance of herbivore impacts on pollination and also highlight interactions between herbivores and pollinators through plants. It is clear that herbivory can impact plant fitness through pollination; however, the relative importance of direct and indirect damage to floral tissue on plant reproduction is still largely unknown.

The diet and feeding behavior of the black-and-white colobus (Colobus guereza) in the Kalinzu Forest, Uganda

One of the goals for primate feeding ecology is to understand the factors that affect inter- and intra-specific variations. Therefore, a detailed description of basic feeding ecology in as many populations as possible is necessary and warrants further understanding. The black-and-white colobus (Colobus guereza) or guereza is widely distributed in Africa and is one of the well-studied colobines in terms of their feeding; they demonstrate considerable variation in their diets in response to local conditions. We studied the diet of a group of guerezas in the Kalinzu Forest, Uganda, for over 30 consecutive months using behavioral observation (4308 h in total), phenology, and vegetation surveys. A total of 31 plant species were consumed by the study group. This study group was predominantly folivorous; the majority of their feeding time was involved in feeding on young leaves (87%). However, during certain times of the year, fruits and seeds accounted for 45% of monthly feeding time. Young leaves of Celtis durandii were by far the most important food, which constituted 58% of the total feeding records. There was a significant increase in the consumption of fruits and flowers once young leaf availability was low, but their consumption of fruits did not significantly increase even when fruit availability was high. Their monthly dietary diversity increased as the number of available plants with young leaves declined, suggesting that much of the dietary diversity in the study group may be attributable to the young leaf portion of their diet. Our findings may help contribute to a better understanding of the dietary adaptations and feeding ecology of guerezas in response to local environmental conditions.

Settling on leaves or flowers: herbivore feeding site determines the outcome of indirect interactions between herbivores and pollinators

Herbivore attack can alter plant interactions with pollinators, ranging from reduced to enhanced pollinator visitation. The direction and strength of effects of herbivory on pollinator visitation could be contingent on the type of plant tissue or organ attacked by herbivores, but this has seldom been tested experimentally. We investigated the effect of variation in feeding site of herbivorous insects on the visitation by insect pollinators on flowering Brassica nigra plants. We placed herbivores on either leaves or flowers, and recorded the responses of two pollinator species when visiting flowers. Our results show that variation in herbivore feeding site has profound impact on the outcome of herbivore–pollinator interactions. Herbivores feeding on flowers had consistent positive effects on pollinator visitation, whereas herbivores feeding on leaves did not. Herbivores themselves preferred to feed on flowers, and mostly performed best on flowers. We conclude that herbivore feeding site choice can profoundly affect herbivore–pollinator interactions and feeding site thereby makes for an important herbivore trait that can determine the linkage between antagonistic and mutualistic networks.

Does Oxygen Stable Isotope Composition in Primates Vary as a Function of Vertical Stratification or Folivorous Behaviour?

Stable isotopes of oxygen often vary within a community of primates. For example, folivorous monkeys that forage in the upper reaches of the forest canopy tend to evince high δ18O values, whereas those that prefer the understory tend to have lower δ18O values. Given that leaves also have high δ18O values, particularly higher in the canopy, there is uncertainty as to which behavioural variable - vertical stratification or folivory - is the primary determinant of variation in δ18O values. Here, we explore further δ18O values from the Taï Forest monkeys (n = 7 species; n = 33 individuals) by examining the interaction between diet and vertical stratification, thereby allowing us to differentiate the effects of each covariate. We found that δ18O values varied as a function of mean canopy height, but not folivory, resolving uncertainty about the primary cause of δ18O variation. This outcome revolves largely, but not entirely, on the behaviours of Procolobus verus, a highly folivorous but understory forager. Relatively elevated values in Cercopithecus diana, a frugivorous but middle-to-high canopy forager, raises the possibility that plant reproductive tissues (e.g., fruits, flowers) may be increasingly sensitive to evaporative fractionation at higher forest canopy levels. Overall, our results further affirm the value of using δ18O values to estimate the vertical behaviour of primate species in a fossil assemblage.

New hominoid fossils from Moroto II, Uganda and their bearing on the taxonomic and adaptive status of Morotopithecus bishopi

The early Miocene site of Moroto II, Uganda has yielded some of the oldest known hominoid fossils. A new partial mandible (UMP MORII 03'551) is notable for its long tooth row and large, narrow M₂ with well-developed cristids - a morphological combination previously unknown for large bodied catarrhines of the Early Miocene and suggesting folivory. The tooth proportions are compatible with belonging to the same taxon as the maxilla UMP 62-11, the holotype of Morotopithecus bishopi; likewise, the long tooth row and vertical planum of UMP MORII 03'551 suggest that it may represent the same taxon as mandible(s) UMP 66-01 and UMP 62-10. Canine size strongly suggests UMP MORII 03'551 is a female. Comparisons of the tooth crown morphology and tooth row proportions, relative enamel thickness, enamel-dentine junction morphology, long-period line periodicity, and dental wear patterns support significant morphological, developmental, and inferred dietary differentiation, and therefore generic-level distinctiveness, among Afropithecus, Morotopithecus and the Proconsul clade. An isolated M₁ (UMP MORII 03'559) is morphologically dissimilar, and much smaller than the actual or inferred size of molars in UMP MORII 03'551, UMP 66-01 and UMP 62-10, supporting the presence of two hominoid taxa at Moroto II, M. bishopi and a smaller bodied proconsulid. Given the high level of body mass dimorphism inferred for Morotopithecus and other early Miocene catarrhines, the known postcrania from Moroto II could be attributable to either taxon. However, UMP MORII 03'551 and the femora UMP MORII 94'80 derive from the same stratigraphic interval, while the isolated M₁ was deposited later, increasing the likelihood that the mandible and femora are from the same individual. These new fossils expand our understanding of the taxonomic and adaptive diversity of early Miocene catarrhines.

Consumption of leaves by Platyrrhinus lineatus (Chiroptera, Stenodermatinae): are these bats primarily frugivorous or broadly phytophagous?

Until now, the consumption of leaves by bats has been considered rare or sporadic, even among the herbivorous families Pteropodidae and Phyllostomidae. Among the phyllostomids there are reports of folivory in the genera Artibeus and Platyrrhinus, based on opportunistic observations. Here, we conducted behavioural sampling using camera-trapping in the roost of a colony of Platyrrhinus lineatus already known to consume leaves during the dry and wet seasons, in order to investigate the frequency of leaf consumption, as well as eventual seasonal differences. We observed feeding activity in 80.5% of sampling nights, where fruit was present in 90.3% and leaves at 80.6%, with no significant differences between the consumption of items. When analyzing video recordings, we observed feeding activity in 22.2% of the samples, in which the consumption of fruits was significantly more frequent than the consumption of leaves. We also observed seasonal variation, with the consumption of leaves being significantly higher than that of fruits during the dry season, whereas in the rainy season, fruits were consumed significantly more frequently. Fruits and leaves were consumed in equal proportions during the night, with no differences between the early and late night. Our findings show that the consumption of leaves by herbivorous bats may be more widespread than previously thought. Leaves may often be a regular food item rather than a fallback.

Are the metabolomic responses to folivory of closely related plant species linked to macroevolutionary and plant-folivore coevolutionary processes?

The debate whether the coevolution of plants and insects or macroevolutionary processes (phylogeny) is the main driver determining the arsenal of molecular defensive compounds of plants remains unresolved. Attacks by herbivorous insects affect not only the composition of defensive compounds in plants but also the entire metabolome. Metabolomes are the final products of genotypes and are constrained by macroevolutionary processes, so closely related species should have similar metabolomic compositions and may respond in similar ways to attacks by folivores. We analyzed the elemental compositions and metabolomes of needles from three closely related Pinus species with distant coevolutionary histories with the caterpillar of the processionary moth respond similarly to its attack. All pines had different metabolomes and metabolic responses to herbivorous attack. The metabolomic variation among the species and the responses to folivory reflected their macroevolutionary relationships, with P. pinaster having the most divergent metabolome. The concentrations of terpenes were in the attacked trees supporting the hypothesis that herbivores avoid plant individuals with higher concentrations. Our results suggest that macroevolutionary history plays important roles in the metabolomic responses of these pine species to folivory, but plant-insect coevolution probably constrains those responses. Combinations of different evolutionary factors and trade-offs are likely responsible for the different responses of each species to folivory, which is not necessarily exclusively linked to plant-insect coevolution.

Similar local, but different systemic, metabolomic responses of closely related pine subspecies to folivory by caterpillars of the processionary moth

Plants respond locally and systemically to herbivore attack. Most of the research conducted on plant-herbivore relationships at element and molecular levels have focused on the elemental composition or/and certain molecular compounds or specific families of defence metabolites showing that herbivores tend to select plant individuals or species with higher nutrient concentrations and avoid those with higher levels of defence compounds. We performed stoichiometric and metabolomics, both local and systemic, analyses in two subspecies of Pinus sylvestris under attack from caterpillars of the pine processionary moth, an important pest in the Mediterranean Basin. Both pine subspecies responded locally to folivory mainly by increasing relative concentrations of terpenes and some phenolics. Systemic responses differed between pine subspecies, and most of the metabolites presented intermediate concentrations between those of the affected parts and unattacked trees. Our results support the hypothesis that foliar nutrient concentrations are not a key factor for plant selection by adult female processionary moths for oviposition, since folivory was not associated with any of the elements analysed. Phenolic compounds generally did not increase in the attacked trees, questioning the suggestion of induction of phenolics following folivory attack and the anti-feeding properties of phenolics. Herbivory attack produced a general systemic shift in pines, in both primary and secondary metabolism, which was less intense and chemically different from the local responses. Local pine responses were similar between pine subspecies, while systemic responses were more distant.

Rapid estimation of the oxidative activities of individual phenolics in crude plant extracts

Previous studies of purified phenolic compounds have revealed that some phenolics, especially ellagitannins, can autoxidise under alkaline conditions, which predominate in the midgut of lepidopteran larvae. To facilitate screening for the pro-oxidant activities of all types of phenolic compounds from crude plant extracts, we developed a method that combined our recent spectrophotometric bioactivity method with an additional chromatographic step via UPLC-DAD-MS. This method allowed us to estimate the total pro-oxidant capacities of crude extracts from 12 plant species and to identify the individual phenolic compounds that were responsible for the detected activities. It was found that the pro-oxidant capacities of the plant species (i.e., the concentrations of the easily-oxidised phenolics) varied from 0 to 57 mg/g dry wt, representing from 0% to 46% of the total phenolics from different species. UPLC-DAD-MS analysis revealed that most flavonol and flavone glycosides were only slightly affected by alkaline conditions, thus indicating their low pro-oxidant activity. Interestingly, myricetin-type compounds differed from the other flavonoids, as their concentrations decreased strongly due to alkaline incubation. The same effect was detected for hydrolysable tannins and prodelphinidins, suggesting that a pyrogallol sub-structure could be a key structural component that partially explains their easy oxidation at high pH. Other types of phenolic compounds, such as hydroxycinnamic acids, were relatively active, as well. These findings demonstrate that this method displays the potential to identify most of the active and inactive pro-oxidant phenolic compounds in various plant species.

Daily feeding rhythm in proboscis monkeys: a preliminary comparison with other non-human primates

In non-human primates, the daily feeding rhythm, i.e., temporal fluctuation in feeding activity across the day, has been described but has rarely received much analytical interpretation, though it may play a crucial part in understanding the adaptive significance of primate foraging strategies. This study is the first to describe the detailed daily feeding rhythm in proboscis monkeys (Nasalis larvatus) based on data collected from both riverbank and inland habitats. From May 2005 to May 2006, data on feeding behavior in a group of proboscis monkeys consisting of an alpha-male, six adult females and immatures was collected via continuous focal animal sampling technique in a forest along the Menanggul River, Sabah, Malaysia. In both the male and females, the highest peak of feeding activity was in the late afternoon at 15:00-17:00, i.e., shortly before sleeping. The differences in the feeding rhythm among the seasons appeared to reflect the time spent eating fruit and/or the availability of fruit; clearer feeding peaks were detected when the monkeys spent a relevant amount of time eating fruit, but no clear peak was detected when fruit eating was less frequent. The daily feeding rhythm was not strongly influenced by daily temperature fluctuations. When comparing the daily feeding rhythm of proboscis monkeys to that of other primates, one of the most common temporal patterns detected across primates was a feeding peak in the late afternoon, although it was impossible to demonstrate this statistically because of methodological differences among studies.