Mosquitoes can change their feeding behaviours based on past experiences, such as shifting from biting animals to biting humans or avoiding defensive hosts (Wolff & Riffell 2018
Hummingbirds utilize visual cues to locate flowers, but little is known about the role olfaction plays in nectar foraging despite observations that hummingbirds avoid resources occupied by certain insects. We investigated the behavioral responses of both wild and captive hummingbirds to olfactory cues of hymenopteran floral visitors, including native wood ants (
Recent reviews reveal that avian olfaction is not just limited to vultures and a few taxa. We demonstrate that a very charismatic group, hummingbirds, avoid defensive and aggregatory chemical cues from insects present at nectar resources. Olfactory cues can provide critical information about the presence and potential threat of insect floral visitors. This study raises new questions about the underrated importance of olfaction in avian foraging and specifically, hummingbird foraging.
- NSF-PAR ID:
- 10305205
- Publisher / Repository:
- Springer Science + Business Media
- Date Published:
- Journal Name:
- Behavioral Ecology and Sociobiology
- Volume:
- 75
- Issue:
- 9
- ISSN:
- 0340-5443
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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J. Exp. Biol. 221 , jeb157131. (doi:10.1242/jeb.157131 )). Dopamine is a critical neuromodulator for insects, allowing flexibility in their feeding preferences, but its role in the primary olfactory centre, the antennal lobe (AL), remains unclear (Vinaugeret al. 2018Curr. Biol. 28 , 333–344.e8. (doi:10.1016/j.cub.2017.12.015 )). It is also unknown whether mosquitoes can learn some odours and not others, or whether different species learn the same odour cues. We assayed aversive olfactory learning in four mosquito species with different host preferences, and found that they differentially learn odours salient to their preferred host. Mosquitoes that prefer humans learned odours found in mammalian skin, but not a flower odour, and a nectar-feeding species only learned a floral odour. Comparing the brains of these four species revealed significantly different innervation patterns in the AL by dopaminergic neurons. Calcium imaging in theAedes aegypti AL and three-dimensional image analyses of dopaminergic innervation show that glomeruli tuned to learnable odours have significantly higher dopaminergic innervation. Changes in dopamine expression in the insect AL may be an evolutionary mechanism to adapt olfactory learning circuitry without changing brain structure and confer to mosquitoes an ability to adapt to new hosts. -
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ABSTRACT Hummingbirds, a highly diverse avian family, are specialized vertebrate pollinators that feed upon carbohydrate-rich nectar to fuel their fast metabolism while consuming invertebrates to obtain protein. Previous work has found that morphologically diverse hummingbird communities exhibit higher diet specialization on floral resources than morphologically similar hummingbird communities. Due to the difficulties of studying avian diets, we have little understanding whether hummingbirds show similar patterns with their invertebrate prey. Here, we use DNA metabarcoding to analyze floral and invertebrate diets of 3 species of sympatric North American hummingbirds. We collected fecal samples from 89 Anna’s (Calypte anna), 39 Black-chinned (Archilochus alexandri), and 29 Calliope (Selasphorus calliope) hummingbirds in urban and rural localities as well as across an elevational gradient from sea level to 2,500 meters above sea level in California, USA. We found hummingbirds showed high dietary overlap in both invertebrate and plant resources, with few invertebrate and plant families common to most individuals and many families found in only a few individuals. Chironomidae was the most common invertebrate family across all species, and Rosaceae and Orobanchaceae were the most common plant families. Anna’s Hummingbirds had significantly higher invertebrate diet diversity than Black-chinned Hummingbirds when found at the same sites, but we found no difference in plant diet diversity among any of the 3 species. Hummingbirds in urban sites had higher plant diet diversity than in rural sites, but we found no effect of elevation on dietary richness. Our study shows how DNA metabarcoding can be used to non-invasively investigate previously unknown life-histories of well-studied birds, lending insight to community structure, function, and evolution.
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Abstract Floral microbes, including bacteria and fungi, alter nectar quality, thus changing pollinator visitation. Conversely, pollinator visitation can change the floral microbial community.
Most studies on dispersal of floral microbes have focused on bees, ants or hummingbirds, yet Lepidoptera are important pollinators.
We asked (a) where are microbes present on the butterfly body, (b) do butterflies transfer microbes while foraging, and (c) how does butterfly foraging affect microbial abundance on different floret structures.
The tarsi and proboscis had significantly more microbes than the thorax in wild‐caught
Glaucopsyche lygdamus (Lepidoptera: Lycaenidae) andSpeyeria mormonia (Lepidoptera: Nymphalidae).Glaucopsyche lygdamus , a smaller‐bodied species, had fewer microbes thanS. mormonia. As a marker for microbes, we used a bacterium (
Rhodococcus fascians, near NCBI Y11196) isolated from aS. mormonia that was foraging for nectar, and examined its dispersal byG. lygdamus andS. mormonia visiting florets ofPyrrocoma crocea (Asteraceae). Microbial dispersal among florets correlated positively with bacterial abundance in the donor floret. Dispersal also depended on butterfly species, age, and bacterial load carried by the butterfly.Recipient florets had less bacteria than donor florets. The nectaries had more bacteria than the anthers or the stigmas, while anthers and stigmas did not differ from each other. There was no differential transmission among floral organs.
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Abstract Background and Aims Floral volatiles, visual traits and rewards mediate attraction and defence in plant–pollinator and plant–herbivore interactions, but these floral traits might be altered by global warming through direct effects of temperature or longer-term impacts on plant resources. We examined the effect of warming on floral and leaf volatile emissions, floral morphology, plant height, nectar production, and oviposition by seed predators.
Methods We used open-top chambers that warmed plants in the field by +2–3 °C on average (+6–11 °C increase in daily maxima) for 2–4 weeks across 1–3 years at three sites in Colorado, USA. Volatiles were sampled from two closely related species of subalpine Ipomopsis with different pollinators: Ipomopsis aggregata ssp. aggregata, visited mainly by hummingbirds, and Ipomopsis tenuituba ssp. tenuituba, often visited by hawkmoths.
Key Results Although warming had no detected effects on leaf volatiles, the daytime floral volatiles of both I. aggregata and I. tenuituba responded in subtle ways to warming, with impacts that depended on the species, site and year. In addition to the long-term effect of warming, temperature at the time of sampling independently affected the floral volatile emissions of I. aggregata during the day and I. tenuituba at night. Warming had little effect on floral morphology for either species and it had no effect on nectar concentration, maximum inflorescence height or flower redness in I. aggregata. However, warming increased nectar production in I. aggregata by 41 %, a response that would attract more hummingbird visits, and it reduced oviposition by fly seed predators by ≥72 %.
Conclusions Our results suggest that floral traits can show different levels of plasticity to temperature changes in subalpine environments, with potential effects on animal behaviours that help or hinder plant reproduction. They also illustrate the need for more long-term field warming studies, as shown by responses of floral volatiles in different ways to weeks of warming vs. temperature at the time of sampling.
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Abstract Phenotypic intermediacy is an indicator of putative hybrid origin and has provided the main clues to discovering hybrid plants in nature.
Mandevilla pentlandiana andM. laxa (Apocynaceae ) are sister species with clear differences in floral phenotype and associated pollinator guilds: diurnal Hymenoptera and nocturnal hawkmoths, respectively. The presence of individuals with intermediate phenotypes in a wild population raises questions about the roles of visual and olfactory signals (i.e . corolla morphology and floral fragrances) as barriers to interbreeding, and how the breakdown of floral isolation occurs.We examined phenotypic variation in a mixed
Mandevilla population, analysing the chemical composition of floral fragrances, characterising floral shape through geometric morphometrics and assessing individual grouping through taxonomically relevant traits and an unsupervised learning algorithm. We quantified the visitation frequencies of floral visitors and tracked their foraging movements using pollen analogues.The presence of morphologically intermediate individuals and pollen analogue movement suggested extensive hybridisation between
M. laxa andM. pentlandiana , along with asymmetrical rates of backcrossing between these putative hybrids andM. laxa . Floral volatiles from putative hybrid individuals showed a transgressive phenotype, with additional compounds not emitted by either parental species.Our results suggest the presence of a hybrid swarm between sympatric
M. pentlandiana andM. laxa and indicate that initial hybridisation events between these parental species are rare, but once they occur, visits between putative hybrids andM. laxa are common and facilitate continued introgression.
