Gaining insight into the assimilated diet of small bear populations by stable isotope analysis

Apennine brown bears (Ursus arctos marsicanus) survive in an isolated and critically endangered population, and their food habits have been studied using traditional scat analysis. To complement current dietary knowledge, we applied Stable Isotope Analysis (SIA) to non-invasively collected bear hairs that had been individually recognized through multilocus genotyping. We analysed carbon (δ13C) and nitrogen (δ15N) stable isotopes of hair sections and bear key foods in a Bayesian mixing models framework to reconstruct the assimilated diet on a seasonal basis and to assess gender and management status effects. In total, we analysed 34 different seasonal bear key foods and 35 hair samples belonging to 27 different bears (16 females and 11 males) collected during a population survey in 2014. Most bears showed wide δ15N and δ13C ranges and individual differences in seasonal isotopic patterns. Vegetable matter (herbs, fleshy fruits and hard mast) represented the major component of the assimilated diet across the dietary seasons, whereas vegetable crops were rarely and C4 plants (i.e., corn) never consumed. We confirmed an overall low consumption of large mammals by Apennine bears consistently between sexes, with highest values in spring followed by early summer but null in the other seasons. We also confirmed that consumption of fleshy fruits peaked in late summer, when wild predominated over cultivated fleshy fruits, even though the latter tended to be consumed in higher proportion in autumn. Male bears had higher δ 15N values than females in spring and autumn. Our findings also hint at additional differences in the assimilated diet between sexes, with females likely consuming more herbs during spring, ants during early summer, and hard mast during fall compared to males. In addition, although effect sizes were small and credibility intervals overlapped considerably, management bears on average were 0.9‰ lower in δ 13C and 2.9‰ higher in δ 15N compared to non-management bears, with differences in isotopic values between the two bear categories peaking in autumn. While non-management bears consumed more herbs, wild fleshy fruits, and hard mast, management bears tended to consume higher proportions of cultivated fruits, ants, and large mammals, possibly including livestock. Although multi-year sampling and larger sample sizes are needed to support our findings, our application confirms that SIA can effectively integrate previous knowledge and be efficiently conducted using samples non-invasively collected during population surveys.

The role of the brown bear Ursus arctos as a legitimate megafaunal seed disperser

Megafaunal frugivores can consume large amounts of fruits whose seeds may be dispersed over long distances, thus, affecting plant regeneration processes and ecosystem functioning. We investigated the role of brown bears (Ursus arctos) as legitimate megafaunal seed dispersers. We assessed the quantity component of seed dispersal by brown bears across its entire distribution based on information about both the relative frequency of occurrence and species composition of fleshy fruits in the diet of brown bears extracted from the literature. We assessed the quality component of seed dispersal based on germination experiments for 11 fleshy-fruited plant species common in temperate and boreal regions and frequently eaten by brown bears. Across its distribution, fleshy fruits, on average, represented 24% of the bear food items and 26% of the total volume consumed. Brown bears consumed seeds from at least 101 fleshy-fruited plant species belonging to 24 families and 42 genera, of which Rubus (Rosaceae) and Vaccinium (Ericaceae) were most commonly eaten. Brown bears inhabiting Mediterranean forests relied the most on fleshy fruits and consumed the largest number of species per study area. Seeds ingested by bears germinated at higher percentages than those from whole fruits, and at similar percentages than manually depulped seeds. We conclude that brown bears are legitimate seed dispersers as they consume large quantities of seeds that remain viable after gut passage. The decline of these megafaunal frugivores may compromise seed dispersal services and plant regeneration processes.

Seed dispersal in Neuwiedia singapureana: novel evidence for avian endozoochory in the earliest diverging clade in Orchidaceae

Background Seed dispersal allows plants to colonize new habitats that has an significant influence on plant distribution and population dynamics. Orchids produce numerous tiny seeds without endosperm, which are considered to be mainly wind-dispersed. Here, we report avian seed dispersal for an early diverging orchid species, Neuwiedia singapureana, which produces fleshy fruits with hard seed coats in the understory of tropical forests. Results Neuwiedia singapureana produced fleshy fruits that turned red in autumn, and birds were confirmed to be the primary seed dispersers. As compared to its sister species, N. veratrifolia with dehiscent capsular fruits, embryos of N. singapureana were larger and enclosed by thickened and lignified seed coats. After passing through the digestive tracts of birds, the seeds still stayed alive, and the walls of seed coat contained several cracks. The germination percentage increased significantly for digested seeds as compared with seeds from intact fruits. Conclusion The thickened and lignified seed coat may protect seeds as they passed through the digestive tracts of birds. Taken together with a recent report of insect-mediated seed dispersal system in the subfamily Apostasioideae, the animal-mediated seed dispersal may be an adaptive mechanism promoting the success of colonization in dark understory habitats.

The Physiological and Molecular Mechanism of Abscisic Acid in Regulation of Fleshy Fruit Ripening

The ripening of fleshy fruits is coupled with the degradation of both chlorophyll and cell walls, as well as changes in the metabolism of phenylpropanoids, flavonoids, starch/sucrose, and carotenoids. These processes are controlled by phytohormones and other factors, including abscisic acid (ABA), ethylene, auxin, polyamines, sugar, and reactive oxygen species. The ripening of climacteric fruits is controlled by ethylene and non-climacteric fruit ripening is regulated mainly by ABA. Also, ABA and ethylene may interact in both types of fruit ripening. ABA concentrations in fleshy fruits are regulated in response to developmental and environmental cues and are controlled by the relative rates of ABA biosynthesis and catabolism, the former mainly via 9-cis-epoxycarotenoid dioxygenases (NCEDs) and β-glucosidases and the latter via ABA 8'-hydroxylases (CYP707As) and β-glycosyltransferases. In strawberry fruit ripening, ABA is perceived via at least two receptors, Pyrabactin resistance (PYR)/PYR-like (PYL) and putative abscisic acid receptor (ABAR), which are linked separately to the conserved signaling pathway ABA-FaPYR1-FaABIl-FaSnRK2 and the novel signaling pathway ABA-FaABAR-FaRIPK1-FaABI4. Downstream signaling components include important transcription factors, such as AREB (ABA responsive element binding protein)/ABF (ABRE binding factors ABA responsive factor), ethylene response factor (ERF), and V-myb Myeloblastosis viral oncogene homolog (MYB), as well as ripening-related genes. Finally, a comprehensive model of ABA linked to ethylene, sugar, polyamines, auxin and reactive oxygen species in the regulation of strawberry fruit ripening is proposed. Next, new integrated mechanisms, including two ABA signaling pathways, ABA and ethylene signaling pathways, and ABA/ethylene to other phytohormones are interesting and important research topics in ripening, especially in non-climacteric fruits.

Correlations between morphological fruit types, fruit and seed colors, and functional groups

The associations between morphological fruit types, fruit and seed colors, and functional plant traits: life forms, epiphytism, physiology, nutritional relationships, fruit phenology, and successional stage, were determined for 1,139 plant species from contrasting plant communities. Texture and dehiscence were closely related. Dehiscence is largely associated with dry tissues; indehiscence, however, is an attribute of both dry and fleshy fruits. The number of morphological fruit types was 28 or 55 for Gray's and Spjut's classifications, respectively. Fruits were predominantly dark in color (brown, purple-black, black or green), whilst seeds had both dark and light colors (brown, beige, or black). The most representative associations were mainly found between the more abundant fruit types and the colors most common. Asymmetries in the level of specialization, whereby less common fruit and seed colors tended to be associated with the most common fruit types, were also found. Fleshy fruits showed more variation as regards their coloration, and only drupes and berries showed a tendency towards a specific color: purple-black. The relationships among fruit type and color, seed color, and functional plant traits revealed the following trends: trees produced both fleshy and dry fruits; shrubs produced fleshy fruits; and herbaceous species, dry fruits. Woody species tended to have dark or bright colors, depending on their seed dispersal mechanisms and phylogenetic relations. Epiphytes were associated with dry-dehiscent fruits and brown seeds, and parasitic-hemiparasitic species had predominantly fleshy-indehiscent fruits. Pioneer species were more likely to have dry fruits, whereas fleshy fruits tended to be more frequent in late successional stage species. The C4 species, mostly herbs, had mainly one-seeded dry fruits, but multi-seeded fruits in succulent-CAM species showed morphologically diverse fruit types. Unripe and ripe fruits showed seasonal changes, especially during the rainy-dry transition period for the most abundant morphological fruit types, dry fruits during the dry period and fleshy fruited species was positively associated with the rainy season. All these trends are discussed with regard to their environmental significance and the relationships between fruit morphology, colors and functional groups. .

Buddleja madagascariensis (smokebush).

B. madagascariensis is a shrub native to Madagascar that has been introduced outside its native range as an ornamental and hedge plant (USDA-ARS, 2016). This species has escaped from cultivation and once naturalized it behaves as an aggressive invader principally in ruderal and heavily disturbed areas (Starr et al., 2003; GISD, 2016). Its rapid growth enables it to form dense impenetrable thickets that outcompete and displace native vegetation. In addition to its aggressive growth, this species produces fleshy fruits with numerous seeds that can be easily dispersed by birds and other animals. While seeds are not produced in some areas, the ability of this species to regenerate from stem fragments allows dispersal to distant locations as stem fragments can be carried by animals (i.e., birds and livestock), humans, vehicles, and waterways (Starr et al., 2003; Norman, 2012; GISD, 2016; Weeds of Australia, 2016). Currently it has been listed as invasive in Bermuda, South Africa, St Helena, New Zealand, New Caledonia, Hawaii and Australia (MacKee, 1994; Wagner et al., 1999; Kairo et al., 2003; Henderson, 2007; GISD, 2016; PIER, 2016; Weeds of Australia, 2016).