The relationship between flowers and their pollinators is a fascinating example of co-evolution. Flowers have evolved unique shapes, colors, scents and patterns specifically to attract certain pollinating insects and animals. One such example is the relationship between certain flowers and the hummingbird moth. Hummingbird moths are active, day-flying moths that feed on nectar from flowers using their long proboscis which allows them to reach deep into tubular flowers. They get their name from the fact that they can hover in front of flowers much like hummingbirds while they feed. Some flowers have evolved specific traits to attract these busy pollinators. One key feature that flowers utilize to draw in hummingbird moths is color, especially shades of red, orange and pink.
The Importance of Flower Pollination
Before diving into the details of how flowers attract hummingbird moths, it helps to understand why flower pollination is so important. Pollination is a key step in the reproductive process of flowering plants. Pollen grains from the anthers, or male reproductive organs, of a flower must come into contact with the stigma, the female reproductive organ, in order for fertilization to occur. Once a pollen grain reaches a stigma, it germinates and grows pollen tubes down the style into the ovules, allowing fertilization to take place. This fertilization produces seeds that will mature and later be dispersed to propagate the next generation. Without pollination, seeds and fruit cannot form. While some plants are pollinated by wind or water, the majority rely on animal pollinators like birds, bees, butterflies, bats and many other creatures. These mobile animals provide a more direct and efficient transfer of pollen between flowers as they travel from plant to plant seeking food in the form of nectar and pollen. Flowers and their pollinators have coevolved specialized morphological and behavioral adaptations over time to maximize the mutual benefits of the relationship. Understanding pollination ecology provides key insights into the biology of both the flowers and their pollinators.
Flower Adaptations for Attracting Hummingbird Moths
There are several key characteristics that certain flowers have developed to specially appeal to hummingbird moths and improve their chances of pollination by these creatures:
Color
Hummingbird moths are particularly attracted to flowers in shades of red, orange and pink. These flowers stand out visually against green foliage which helps them catch the attention of the day-flying moths. Some examples of red flowers pollinated by hummingbird moths include bee balm, columbines, fuchsias, penstemons, and sages. The moths see these warm-colored flowers well and will seek them out. In contrast, flowers specializing in nighttime moth pollination often evolve pale or white flowers since those colors show up better in dim light. The red color preference of hummingbird moths also overlaps with that of their namesakes, the hummingbirds, and the two unrelated creatures end up competing for some of the same tubed blossoms during the day.
Flower Shape
Flowers adapted to hummingbird moth pollination frequently have long, tubular shapes which match the moths’ exceptionally long proboscis (tongue). Some have even evolved into a curved tube shape which follows the shape of the moth as it hovers overhead to feed on the nectar contained deep within the specialized flower shapes. Examples of some flowers with this coevolved long, tubular shape include coral honeysuckle, trumpet vine, and certain passionflowers. The match between flower tube depth/curve and moth proboscis length and curve improves the efficiency of nectar feeding which benefits both the moth and flower.
Abundant Nectar
To power their hovering flight and active lifestyle, hummingbird moths need plenty of high-energy nectar. Flowers that rely on these moths for pollination produce large volumes of sugary, high-calorie nectar as a nutritious reward. This, in turn, gets the moths to visit the flowers more frequently to collect this plentiful food source, increasing pollination in the process. The nectar is stored deep down in a tubular corolla so that the moth has to come into close contact with the flower’s reproductive organs in order to access it, allowing pollen transfer. Bright red fuchsias are classic examples of flowers that produce copious nectar.
Fragrance
Some flowers specially adapted to hummingbird moth pollination also produce a strong, sweet scent. Fragrance provides an additional floral cue that helps the moths locate suitable nectar sources. Night-blooming flowers tend to be the most fragrant since scent is a more useful attractant in darkness, but some daylight bloomers adapted to hummingbird moths also produce mild to strong aromas. Jasmine and nicotiana flowers, for example, open their flowers towards evening when hummingbird moths are most active and emit fragrance to help guide the moths in.
Visible Anthers and Stigma
To increase the chances of pollen transfer, some flowers adapted to hummingbird moth pollination have evolved prominent reproductive structures. Brightly colored or exaggerated anthers and stigma increase the chances that the moth will inadvertently contact these organs and either deposit or pick up pollen grains. Penstemons, for example, often have large, protruding anthers in addition to tubular blossoms which brush up against the moth’s body as it feeds on the nectar inside, facilitating pollination.
Characteristics of Hummingbird Moths
To understand why certain floral adaptations appeal to hummingbird moths, it helps to look at some key characteristics of the moths themselves:
Daytime Activity
Unlike most moths which fly at night, hummingbird moths are most actively seeking nectar during the day. This is why flowers specially adapted to their pollination tend to evolve bright, visible colors and fragrances detectable in daylight rather than pale night bloomers. The moths have good daylight vision and are drawn to colorful tubular flowers.
Long Proboscis
Hummingbird moths have an extraordinarily long proboscis, or tubular mouthpart that functions like a straw, allowing them to feed on nectar tucked deeply inside long, narrow flower tubes. Matching corolla tube lengths with moth tongue lengths promotes more efficient feeding.
Hovering Flight
The moths are called hummingbird moths because they share the specialized ability to hover in front of flowers. Their wings beat in a figure-8 pattern that allows them to maintain position while feeding on nectar. This hovering keeps them in close contact with the flower reproductive organs, aiding pollination.
High Energy Requirements
Hovering flight requires a lot of energy, so the moths need a diet rich in sugars from nectar. Flowers that produce abundant, calorie-dense nectar attract more visits from hungry hummingbird moths. Both parties benefit from the huge nectar rewards offered by specialized flowers.
Examples of Flowers Adapted to Hummingbird Moth Pollination
Here are some specific examples of flowers which exhibit adaptations making them attractive and useful for hummingbird moth pollinators:
Fuchsias
Many species of popular ornamental fuchsias in the genus Fuchsia produce their flowers in shades of red and purple which strongly attract hummingbird moths. Their long, tubular, downward-hanging corollas perfectly match the shape of the hovering moths. Abundant nectar inside provides a rich reward.
Columbines
Columbines are flowers in the genus Aquilegia. Their elegant, colorful blossoms have backwards-facing, tubular nectar spurs which require a moth or bird with a long tongue or beak to access the nectar. The petals are red, yellow, or blue which stand out. Colubmines are frequent targets of foraging hummingbird moths.
Sages
Salvias like pineapple sage and scarlet sage have red, tubular flowers protruding from dark bracts which provide an eye-catching display. The red tubes hold abundant nectar to attract hummingbird moths. Salvia flowers are specifically adapted for pollination by hummingbirds and hummingbird moths.
Penstemons
Penstemons, in the plantain family, often produce bright red tubular blossoms with highly visible white or yellow stamen. As hummingbird moths hover at the flowers to drink nectar, the protruding stamen brush up against their bodies, coating them with pollen.
Passionflowers
Exotic passionflowers in the genus Passaflora have intricate, showy blossoms with a central fringelike corona of colorful filaments and a tubular nectary structure. These provide nectar inside and a perch for moths to land on while feeding. Passionflowers tend to open in the evenings when hummingbird moths are active.
Trumpet Creeper
Trumpet creepers are vining plants in the genus Campsis. They have long clusters of orange-red, trumpet shaped flowers which perfectly match hummingbird moth morphology. The curved tubular blossoms follow the curve of the moth body as it feeds while hovering.
Bee Balm
Bee balm (Monarda sp.) has flowers clustered into dense, showy heads. The individual tubular flowers are often bright red, providing a visual signal to attract hummingbird moths from a distance. Nectar fills the inside of each little tube.
Advantages of Specialized Flowers for Hummingbird Moths
There are several advantages to flowers which are specially adapted for pollination by hummingbird moths:
– More efficient pollination since the moths consistently come into contact with reproductive parts
– Reduced nectar robbing by inefficient pollinators
– Promotion of outcrossing instead of self-pollination
– Increased seed and fruit production from successful pollination events
– Enhanced attractiveness to a consistent pollinator leading to reproductive success
– Coevolutionary partnership results in matched morphological adaptations
By shaping specific aspects like color, shape, scent and nectar volume for hummingbird moth appeal, the flowers can essentially ensure the moths will visit them and provide reliable pollination services. This is mutually beneficial to both the plants and the moths.
Advantages of Specialized Flowers for Hummingbird Moths
There are several advantages to flowers which are specially adapted for pollination by hummingbird moths:
– More efficient pollination since the moths consistently come into contact with reproductive parts
– Reduced nectar robbing by inefficient pollinators
– Promotion of outcrossing instead of self-pollination
– Increased seed and fruit production from successful pollination events
– Enhanced attractiveness to a consistent pollinator leading to reproductive success
– Coevolutionary partnership results in matched morphological adaptations
By shaping specific aspects like color, shape, scent and nectar volume for hummingbird moth appeal, the flowers can essentially ensure the moths will visit them and provide reliable pollination services. This is mutually beneficial to both the plants and the moths.
Conclusion
The relationship between hummingbird moths and certain flowers beautifully demonstrates the concept of specialized coevolution between plants and pollinators. Flowers pollinated by hummingbird moths tend to share some key features that attract the moths including bright red, orange or pink coloration; long, curved, tubular corollas; abundant sugary nectar; pronounced fragrance; and prominently displayed reproductive organs. These traits match up with the characteristics and needs of the day-active moths including their vision, proboscis length, hovering flight, and high energy requirements. By evolving to attract, provide for, and utilize hummingbird moths specifically, these flowers improve their chances of productive pollination while providing the moths with reliable nectar sources. The reciprocity between the flowers and the moths drives the continued evolution and maintenance of amazing adaptations like extremely long proboscis and corolla tubes. Understanding these intimate ecological relationships provides insight into the way evolution shapes both plants and pollinators to maximize reproductive success through specialization.
