Coadaptation Of Flowers And Their Visitors In Changbai Mountain Region

In the long course of evolution, flowers and insects produced a sophisticated and subtle relation of mutual adaptation. The structure of flower becomes increasingly complex, the flowers clustered, the color of flower becomes increasingly bright, has nectary, pollen and fragrance, toward the direction of more conducive to attract insects. And, accordingly, morphology and living habits of insects have also changed, towards the direction of collecting nectar and pollination. This study considered the mutual adaptation between the main nectar plants and flower-visiting insects in Changbai Mountain Region through the floral features, including flower structure, color, pollen morphology, odor, and insects'characteristics, including the external morphology of insects, such as the mouthpart, portability foot powder; the morphology and structure of alimentary canal, and the type, number and distribution of antennal sensilla. This study not only helps on the rare nectar plants and ecosystem protection, but also for the development of new insect attractant, and provides a theoretical basis for insect pollination in the field of facilities agriculture. The main methods used in this study and the findings are as follows:(1) A total of 452 species of flower-visiting insects in Changbai Mountain Region were collected, indentified and literature searched, which belonging to 10 orders,74 families and 283 genera.(2) The major visitors of Compositae flowers were Hymenoptera insects, Diptera insects, and Lepidoptera butterflies; the major visitors of Rosaceae flowers were Hymenoptera bumblebees, Lepidoptera butterflies and Coleoptera flower longhorn beetles; the major visitors of Ranunculaceae flowers, Legumes flowers and Labiatae flowers were Hymenoptera insects; the major flower-visiting insects of Hyacinth and Caryophyllaceae were Lepidoptera butterflies; the major visitors of Umbelliferae flowers were Hymenoptera bumblebees, Coleoptera flower longhorn beetles; the major visitors of Polygonum flowers, Poppy flowers, Geraniaceae flowers were Hymenoptera and Diptera insects; the major visitors of Valerianaceae flowers were Diptera insects; the major visitors of Onagraceae flowers were Hymenoptera and Lepidoptera butterflies.(3) Bumblebees prefered panicle, raceme and cyme, and mainly visited flowers with corolla type of radial symmetry and bilateral symmetry. In the sight of flower color, bumblebees visited colorful flowers, often yellow or blue-purple. Lepturinae visited larger–shaped flowers, mainly panicles, umbel, cyme and corymb. Lepturinae feed on pollen and petal, so they visited flowers with a large number of stamens and pollen, and often lack nectar. Lepturinae visited flowers mainly with corolla type of radial symmetry, and the shape of flowers were rotating, altar-like, rather than tubular or lipped. In the sight of flower color, Lepturinae often visited white, pale yellow flowers, rarely with red or purple because of lacking color vision. Syrphidae like to visit Asteraceae and Umbelliferae plants. In the sight of Inflorescence types, Syrphidae prefered capitulum and umbel. Because of their long beak tube, they can visit the tube-shaped flowers, taking the honey from the base of flower. Syrphidae had stronger ability in the choice of colors, they prefered to visit white and yellow flowers. Butterflies prefered the flower with capitulum and raceme, and tend to visit the brightly-colored flowers.(4) In this study, the pollen morphology of the main nectar plants in Changbai Mountain region were observed using scanning electron microscopy, and the relationship between pollen morphology and main flower-visiting insects were analyzed. The results showed that Bombus and Lepturinae perfered prolate, larger pollen (P/E values are greater than 1.14) with three–hole groove and reticulate surface. Syrphidae and butterflies were not strict with pollen morphology.(5) The composition of ethanol extracts from 11 major nectar plants in Changbai Mountain area were analyzed using gas chromatography-mass spectrometer and compared in this study. The results showed that it didn't had signifiant different among the components of ethanol extract from Asteraceae, Rosaceae, Umbelliferae, Onagraceae and legumes. The main substance were acids, followed by ketones and esters. The ethanol extracts from 11 major nectar plants were all containing 1 - hydroxy -2 - acetone, acetic acid, formic acid, cis - 9, 12 - octadecadienoic acid and phenol. These five kinds of component had a similar proportional relationship, among them, 1 - hydroxy - 2 - acetone, cis - 9, 12 - octadecadienoic acid accounted for about 20%, acetic acid accounted for about 40%, formic acid and phenol were about 10%, respectively. Presumably, these components have a lure on the attraction of flower-visiting insects. But, if it is produced by the mixture or by on of these substance is need to be further study.(6) The adaptation on the external morphological feature of insects for visiting flower:①Bumblebees: more sturdy; with hairs, casued a large number of pollen stickied in the process of visiting; chewing-lapping mouthparts, longer tongue, making them take nectar from flowers with deep corolla; wide hind tarsus, with smooth surface and long-hairs around the end, forming pollen baskets; had wide hind coxal and tibia, with neatly arranged brushes in the inner surface, making them carry large amounts of pollen.②Lepturinae: front of the head tend to elongate, sometimes forming a beak-like protuberances, and a number of bristles and the rounded prominent part in the upper lips (suitable for lick nectary); usually have larger compound eyes and many small eyes, so that beetles can successfully search for the host plants; wings well developed and often color; antennae relatively long, usually silk or jagged, mostly located in the head rather than side, which makes beetles adapt to regular flights, and provides the possibility for beetles to carry pollen to a wide range.③Syrphidae: can adhere pollen through the body hairs; Licking mouthparts can secrete saliva diluted slurry in order to absorb the nectar; Tarsus with chemical receptors which sensitive to the sugar.④Butterflies: Siphoning mouthpa are good at feeding nectar; have more developed feet, which grasp to the flowers, and can adhere a large number of pollen; Developed vision, tend to visit brightly–colored flowers. The study on the characteristic of insects which suitable for visiting flowers will be conductive to tap the new pollinators.(7) Alimentary canal of Bombus, Lepturinae, Syrphidae and butterflies are all composed of foregut, midgut and hindgut. For Bombus, honey sac was obvious, with vertical and horizontal folds on its wall, and larger to accommodate honey. Midgut thick, inner wall formed by a number of longitudinal ridges, in which there were many processes that can increase the intestinal surface area, and helping in the intestinal secretion of digestive juice and nutrient absorption. Lepturinae insect feed on pollen and flower petals, the inner wall of its crops and midgut's inner formed a number of milky blind sac. Syrphidae insects and butterflies feed on nectar and other liquid food, its crop wall and intestinal wall rather than smooth, playing a major role in absorption.(8) Sensilla trichodea (A, B, C/ D), sensilla basiconica (A, B), sensilla coeloconica, sensilla placodea and Bohm's bristles were differentiated according to their size and shape on the antennae of Bombus; Sensilla trichodea (Ⅰ,Ⅱ,Ⅲ), sensilla chaetica (Ⅰ,Ⅱ,Ⅲ,Ⅳ), sensilla basiconica (Ⅰ,Ⅱ,Ⅲ) and Bohm's bristles were observed on the antennae of Lepturinae; Sensilla trichodea (Ⅰ,Ⅱ) and microtrichia were on the antennae of Syrphidae; And sensilla trichodea (A, B), sensilla squamiformia and sensilla stellate were on the antennae of butterflies. There were sensilla trichodea inferred as one important receptor on all this four insect groups, which play an important role in the habitat of flower-visiting insects. Besides, each group had its own type of sensilla. Of the close relationship between flower–visiting insects and plants in view, in order to clarify the function of the olfactory receptors of different kinds of insects, the further study on the antennal cell electrophysiological are needed.