[MUSIC] Most alpine plants survive for multiple years. In fact, cushions can live for hundreds of years. Perennials, plants that persist for more than two years, are better adapted to alpine environments than annuals which complete their entire life cycle in one year and then die. [SOUND] In extreme environments with short growing seasons, unfavorable conditions that diminish the likelihood of successful reproduction are pretty common. If annuals fail to reproduce they could be lost entirely from a region. In contrast, perennials can persist through tough years and reproduce when conditions are more favorable. Alpine plants often reproduce asexually too. Sexual reproduction is challenging in alpine environments because of the density and diversity of pollinators is low and the viability of seeds is strongly influenced by environmental conditions. A more reliable strategy to cope with this variation is vegetative reproduction, a process by which new plants grow from parts of parent plants. In alpine plants asexual reproduction is commonly achieved using rhizomes which are modified underground stems that extend away from the plant and grow new shoots. The advantage of this strategy is that a plant can survive and reproduce even if harsh conditions prevent sexual reproduction. Alpine plants that reproduce sexually tend to rely on insect pollination and have developed specialized traits to attract these pollinators. Despite being low-lying and small, alpine plants are known for their spectacular floral displays. Their disproportionately large and strongly scented flowers function to attract pollinators that are relatively rarer in cold alpine regions. Clusters of flowers together on cushion forming plants also attract a greater number of pollinators. Then they would have if they grew more separately. Because of the short growing season at high elevations, most alpine flowering plants bloom within a few weeks following the snow melt. This allows them more time to attract pollinators but pollinator activity is reduced early in the season due to cold conditions. As a result, plants have adaptations that create warm micro-climates around their flowers. For example, darker flowers trap more heat than lighter colored flowers. Many alpine plants also have flowers that are cup shaped, which focuses solar radiation towards the center of the flower. Increasing the temperature inside of the flower relative to the surrounding air. Flowers of mountain avens, or Dryas octopetala, are heliotropic, following the sun as it moves across the sky. The petals reflect sunlight onto the pistils inside the flower warming them by up to seven degrees Celsius compared to the surrounding air temperature. Insects sometimes seek refuge in the warmth of the flowers, which increases opportunities for pollination. This warming also maintains stable temperature in flowers which can accelerate development of the sexually reproductive organs in flowers and facilitate fertilization and seed development. For example, solar tracking enhances pollen germination by up to 44% in the Snow Buttercup, Ranunculus adoneus, a common alpine species in the central Rocky Mountains. Different flower shapes and colors are also important for attracting specific types of pollinators. Flowers and pollinators form a mutualistic association. Plants benefit pollinators by providing nectars food and in turn, pollinators transfer pollen between plants to facilitate their reproduction. Specific species of plants and pollinators often have exclusive relationships due to specialized adaptations that have evolved through a process called co-evolution in which two or more species reciprocally affect each others evolution. Trait specialization benefits pollinators by reducing competition for nectar. And benefits plants by increasing the chance that pollinators will visit other plants of the same species to successfully pollinate them. On the other hand, opting for a generalist strategy may be less risky in mountain environments, where the possibility of one specialist species failing in a given year may be quite high. Therefore, some plants have traits that make them more generally attractive to a wide range of pollinators. The most important pollinators in mountain ecosystems, bumblebees and flies, employ very different pollination strategies. Bumblebees are specialist pollinators that preferentially visit plants with adaptations that match their morphology. While flies are generalist pollinators that visit a wider variety of unspecialized plants. Here to discuss some of these alpine pollination strategies is University of Virginia ecologist, Jessamyn Manson. >> Bee pollinators perceive blue, green, violet, and yellow, and prefer to visit flowers that are brightly colored, particularly blue and yellow flowers. These flowers often have nectar guides, lines and patterns that can only be seen under ultraviolet light, which direct bees towards the nectar and pollen in the flowers. Bird pollinators like humming birds also are of excellent color vision. But they can't see any ultraviolet range. However, unlike bees, birds can see the color red and they have a preference for bright-red flowers. In contrast, flies have limited color vision and are attracted to white flowers. Because fly pollinators do a poor job of distinguishing between colors, there's no advantage for fly pollinator flowers to invest in their limited resources in producing colorful floral displays. Moths are nocturnal pollinators and moth pollinated flowers are therefore almost exclusively white. However, moths usually find their flowers using scent. Flower scent is also important for bees and flies although they have very different preferences. While bees are attracted to sweet smelling flowers, flies prefer flowers that smells like rotting meat. Birds have a very poor sense of smell, and bird-pollinated flowers tend to be scentless. To form an exclusive relationship with a certain type of pollinator, flowers have adaptations that make their nectar or pollen inaccessible to other pollinators. For example, the nectar of sun bee pollinated flowers is often located at the bottom of a long tube. The high dexterity of bees allows them to manipulate flower parts to access the nectar while their long tongues allow them to extract that nectar. In contrast the nectar of generalist flowers is easier to access because it needs to be available to a wide variety of pollinators. Therefore there is no advantage to having a long tongue if you're a generalist pollinator. It's beneficial for flowers to provide large amounts of nectar to bees to increase their chances of being pollinated. Because of the low temperatures, larger body bees, such as bumblebees, are more common in the alpine. >> Mountains clearly provide some of the world's most spectacular landscapes and host an amazing diversity of species and habitat types. Within just a few 100 meters of elevation on a mountain slope, you can travel through ecosystems and plant communities that are otherwise separated by many hundreds of kilometers of latitude between the equator and the poles. Plants living in mountain environments have many adaptations for growing and reproducing under these often extreme conditions. In the following lesson, we'll look at some of the unique adaptations of animals living in mountain environments. This brings us to the end of the lesson. Because we weren't as focused on geography, we wont be returning to your mountain world this time. But Laura Redmond is standing by with a tech tip on camping gear that you wont want to miss. Good luck on your end of lesson Quiz, too. And we'll see you next time when we'll be talking about the adaptations of animals.
