In zoology, a palynivore /pəˈlɪnəvɔːɹ/, meaning "pollen eater" (from Greek παλύνω palunō, "strew, sprinkle", and Latin, vorare, meaning "to devour") is an herbivorous animal which selectively eats the nutrient-rich pollen produced by angiosperms and gymnosperms. Most true palynivores are insects or mites. The category in its strictest application includes most bees, and a few kinds of wasps, as pollen is often the only solid food consumed by all life stages in these insects. However, the category can be extended to include more diverse species. For example, palynivorous mites and thrips typically feed on the liquid content of the pollen grains without actually consuming the exine, or the solid portion of the grain. Additionally, the list is expanded greatly if one takes into consideration species where either the larval or adult stage feeds on pollen, but not both. There are other wasps which are in this category, as well as many beetles, flies, butterflies, and moths. One such example of a bee species that only consumes pollen in its larval stage is the Apis mellifera carnica. There is a vast array of insects that will feed opportunistically on pollen, as will various birds, orb-weaving spiders and other nectarivores.
Pollen, the essential component of the palynivore diet, is a male gametophyte that is formed in the anther, or the male part of the flower. Pollen is needed to fertilize the female part of the flower, or gynoecium, and has a long history of consumption by various species. There is evidence that suggests palynivory dates back to at least the Permian period. It is likely that a coevolution has occurred between plants and palynivores in a form of mutualism, or the process by which two species individually benefit from the activity of the other. For example, palynivores benefit by receiving nutrients from the pollen, and thus the structure of the palynivore eye evolved to better interpret visual cues given by the pollen. Pollen benefits from the animal-plant interaction by being spread as the animal carries it from flower to flower, furthering the reproductive success of its respective flower. Thus, pollen has evolved to be more visually appealing to palynivores, and changed its surface texture to be more readily recognized by palynivore's tactile sensory receptors.
Evolution The earliest evidence of palynivory can be traced back to the Silurian (444 million years ago (Mya) – 419 Mya) and early Devonian (419 Mya – 393 Mya) periods Fossil evidence from these periods suggests that early arthropods, with unspecialized mandibular mouthparts, engaged in spore-feeding behavior. Unlike pollen, spores are asexual reproductive particles produced by primitive organisms such as ferns, fungi, and bacteria. Palynivory, which is thought to have derived from early spore-feeders, emerged much later during the Pennsylvanian era (323 Mya – 299 Mya). Much of the evidence relating to palynivory evolution has been linked to a change in the structure of mandibular mouthparts, allowing for easier pollen collection. Such evidence can be found in Coleoptera (beetles), the most diverse group of palynivores, wherein species have developed mouthparts for pollen collection in addition to the evolution of early mandibular appendages into specialized structures assisting in pollen consumption. Furthermore, modern-day palynivore mouthpart adaptations can also be tied to the evolution of ancient palynivore mouthparts involved in nectar uptake. The beginnings of structures involved in nectar uptake can be found in early, unrelated insect clades. The evolution of these structures occurred in three distinct tracks: sponge-like labellum of flies and caddisflies, siphon structures in butterflies and moths, and glossa in wasps and bees. Within each track, further specialization of these structures has occurred. For example, in wasps and bees, eight variations of mouthpart structures incorporating glossa have been identified. The evolution of various structural and morphological adaptations of present-day palynivores has also been thought to have co-evolved with pollen grains. The abundance and diversity of seed-bearing plant fossils identified from the Late Pennsylvanian suggest greater palynivore evolution and adaptations to the evolving plant fauna. Furthermore, this highlights the co-evolution of this behavior with plant species at the time. Based on the morphological features of fossil remnants of the era, early palynivores are hypothesized to have belonged to the diaphanopterodean, protorthopteran, and hemipteroid taxonomic groups. Following this period, evolution and more specialized adaptations in palynivore mouthparts and pollen or prepollen found in the gut of fossilized insects showed convergence into three major lineages: Orthoptera (grasshoppers, crickets, and locusts), Coleoptera, Diptera (flies), and Hymenoptera (wasps, sawflies, bees, and ants). Currently, almost all palynivores are in five insect orders believed to have come about during the early Mesozoic period (248 Mya - 65 Mya): Coleoptera, Diptera, Thysanoptera (thrips), Hymenoptera, and Lepidoptera (butterflies and moths).
Adaptations of palynivores Numerous species of insects (bees, wasps, ants, beetles, flies, butterflies, moths), mites, spiders, and birds consume pollen as a food source. To more efficiently collect pollen, palynivores have evolved various adaptations in their body parts and behavior. These adaptations include specialized mouthparts, hair, digestive systems, and patterns of reproduction and foraging. Although all palynivores eat pollen, they do so to varying degrees and ways, so consequently their adaptations also differ. Bees and ants, for example, are insects that place different amounts of emphasis on pollen in their diets.
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