Polyphagy and florivory prevail in a leaf-beetle community (Coleoptera: Chrysomelidae) inhabiting the canopy of a tropical lowland rainforest in southern Venezuela

ABSTRACT

Embedded within the interdisciplinary research project ‘Towards an understanding of the structure and function of a Neotropical rainforest ecosystem with special reference to its canopy’ organised by the Austrian Academy of Science, the canopy beetle fauna was surveyed by means of a 42 m tall tower crane. This paper presents results of the chrysomelid beetle fauna observed and collected at canopy trees for 1 year. A total of 1783 adult leaf beetles were collected, representing 117 morphospecies (Bruchinae are not included) including 31 singletons. The most abundant family was Galerucinae sensu stricto with 827 individuals (46% of collection). The most speciose subfamilies were Galerucinae sensu stricto followed by Alticini, Cryptocephalinae and Eumolpinae. Nineteen species collected with at least two individuals were restricted to a single tree species whereas 68 species were found to feed on several canopy host trees. Only a few species fed on leaves; these were in Cassidinae, Cryptocephalinae, Eumolpinae and Galerucinae. Strikingly, most canopy chrysomelids were collected at flowers of canopy trees, although some species fed also on extrafloral nectaries or fruits. Alticini were restricted predominantly to flowers, but Cryptocephalinae, Eumolpinae and Galerucinae revealed broader plasticity in host tissue selection. Insights into beetle seasonality, diurnal/nocturnal activity and intra-canopy migration are provided. Abundant flower-visiting species occurred on their host trees commonly over the entire flowering season, with their abundances often correlated with the number of open flowers. After termination of one tree’s flowering season, many flower-visiting leaf beetles moved to other flowering trees. Certain congeneric species of Galerucinae and Eumolpinae occurred together at their host plants within the same periods.     

Differentiated use of pollen sources by two sympatric species of oil-collecting bees (Hymenoptera: Apidae)

We identified the food niche breadth of two sympatric species of oil-collecting bees, Centris (Heterocentris) analis (Fabricius, 1804) and Centris (Hemisiella) tarsata Smith, 1874, based on pollen analyses of larval food. We tested differences in the use of pollen sources considering the anther type and pollen size of the flowers. The species presented a low similarity in the use of pollen sources and C. analis had a wider niche breadth than C. tarsata. Centris analis mainly used Heteropterys spp. and other flowers with non-poricidal anthers. In contrast, C. tarsata commonly used Solanum lycocarpum A. St.-Hil., as well as other flowers with poricidal anthers. Despite the differences in pollen composition of larval food, both species predominantly used medium-sized pollen grains. Although C. analis and C. tarsata are sympatric species, belonging to the same functional group and presenting an overlap in nesting periods, they used different pollen sources, which suggests the occurrence of food niche partitioning.     

The nesting habits and flower relationships of the bee Melitoma ameghinoi (Holmberg) (Hymenoptera,Apidae), with notes on its taxonomy and distribution

ABSTRACT

The nesting behaviour of Melitoma ameghinoi was studied in the province of Chaco, Argentina. Contrary to other Melitoma species, which are known to nest on banks or other vertical or sloping surfaces, the nests were found on horizontal ground, in extremely hard clay soil. The nests were shallow, with three to four vertical cells. The short turrets pointed upwards for a short stretch and then were strongly curved, with the entrance directed towards the soil surface. The floral relationships of this species were studied by pollen analysis of faeces from cells, a pollen mass, scopal loads of specimens, and direct observation of floral visits. Pollen counts and field observations indicate that M. ameghinoi collects pollen exclusively from Ipomoea species. A compilation of pollen sources for species of Melitoma is presented. All known species, including M. ameghinoi, fall in the category of narrowly oligolectic. A discussion of the taxonomic relationships of the species is presented, and a lectotype is designated.     

Insect-mediated pollination in slickspot peppergrass, Lepidium papilliferum L. (Brassicaceae), and its implications for population viability

Field experiments on the pollination biology of slickspot peppergrass, Lepidium papilliferum L. (Brassicaceae), a rare species endemic to microsites in sagebrush-steppe habitat in southwestern Idaho, were conducted at 2 sites from May to July 2001. Site KB contained over 10,000 plants, whereas site WG contained less than 150 plants. Insect exclusion experiments revealed that seed production in L. papilliferum is dependent on insect-mediated pollination; median percent seed set dropped from 70% to 2% when insects were excluded from flowers. A total of 25 insect families from 5 orders visited L. papilliferum flowers: 24 families at KB and 11 families at WG. Only 9 families contained more than trace amounts of pollen on their bodies: Hymenoptera-Anthophoridae, Apidae, Colletidae, Halictidae, Sphecidae, Vespidae; Coleoptera-Cerambycidae, Dermestidae; Diptera-Syrphidae. Insects from these families are likely responsible for pollination of L. papilliferum , although some may be of only minor significance due to their infrequent visits to flowers. Two of the 4 most common and pollen-laden insects found at KB, honey bees ( Apis mellifera ) and colletid bees, were absent or rare at WG. Three other pollen-carrying families present at KB, Sphecidae, Vespidae, and Halictidae, were not found at WG. We raise several possible explanations for this disparity in pollinator communities between sites and discuss the importance of pollinator diversity to the long term viability of L. papilliferum .     

Time-lapse photography reveals the occurrence of unexpected bee-pollination in Calanthe izuinsularis,an endangered orchid endemic to the Izu archipelago

Calanthe izuinsularis is a rare, beautiful and fragrant orchid endemic to the Izu archipelago. Although it is known that mainland populations of closely related Calanthe species are pollinated by medium- to large-sized bees, it is likely that C. izuinsularis has been forced to alter its floral biology to attract alternative pollinators, as large-sized bees are rarely found on the Izu Islands. Indeed, the unusual floral characteristics of C. izuinsularis, which produces pale flowers that emit a strong and fragrant scent during the night, are considered the adaptation to a moth-pollinator syndrome. As expected, our time-lapse photography using a digital camera revealed that the inflorescences of C. izuinsularis were most frequently visited by nocturnal moths such as Noctuidae, Geometridae and Crambidae, which accounted for 50% of all insect visits (in terms of both the number of frames with captured visitors and the number of times visited). However, our study could not provide evidence of a pollinator shift towards moths because none of the moth species was observed with pollinaria. On the other hand, our study found that the pollinaria of C. izuinsularis could become attached to the mesothorax of the small-sized sweat bee Lasioglossum occidens. Therefore, our study suggests that C. izuinsularis is still somewhat dependent on bee pollination, while the orchid has changed its floral colouration and scent. The occurrence of bee-pollination in C. izuinsularis would provide an explanation for how the natural hybridisation between C. aristulifera, C. discolor and C. izuinsularis can occur.     

Reproductive biology, hybridization and flower visitors of rare Sclerocactus taxa in Utah's Uintah Basin

We studied the mating system and flower visitors of 2 threatened species of Sclerocactus (Cactaceae) in the Uintah Basin of eastern Utah—an area undergoing rapid energy development. We found that both S. wetlandicus and S. brevispinus are predominantly outcrossed and are essentially self-incompatible. A third presumptive taxon (undescribed; here called S. wetlandicus -var1) is fully self-compatible but cannot produce seeds unless the flowers are visited by pollinators. We found tentative evidence for pollinator limitation of fruit set in S. brevispinus but not in the other taxa. Pollinators are largely species of native ground-nesting bees in the subfamily Halictinae. These bees are indiscriminate collectors of pollen and nectar from Sclerocactus flowers and other plant species. The well-being of Sclerocactus populations requires that land managers ensure the preservation of halictid bee habitat, which includes both nesting sites and a diversity of floral resources. These bees are also undoubtedly the pollen vectors responsible for the production of hybrids in areas where S. wetlandicus and S. brevispinus meet. We experimentally confirmed that reciprocal crosses between S. wetlandicus and S. brevispinus are indistinguishable from each other or from pure crosses in fruits/flower, seeds/fruit and seed weights. We suggest that hybridization preceded energy development, that it attests to the ongoing process of evolution in the Sclerocactus group, and that it should not be suppressed by anthropogenic activity.     

A mixed pollination system in Penstemon pseudospectabilis M. E. Jones (Scrophulariaceae)

A population of Penstemon pseudospectabilis M. E. Jones (Scrophulariaceae) on Cave Creek in Cochise County, Arizona, was used in an experimental test of reproductive fitness with three caging treatments: all flying pollinators excluded, hummingbirds excluded, and no exclusion. Twenty plants were chosen and three shoots on each used in the experiment. The flowers were 25.6 (s.d. = 1.5) mm long, the end diameter was 8.5 (s.d. = 1.0) mm, the tube opening was 6.5 (s.d. = 1.0) mm, and the greatest diameter, 75% distal from the receptacle, was 10.1 (s.d. = 0.8) mm (N= 59). Floral nectar contained 11.7% (s.d. = 2.9%) fructose, 13.8% (s.d. = 2.7%) glucose, and 74.5% (s.d. = 5.4%) sucrose (N = 74). There was some evidence, significant only for fructose, that nectar-sugar composition varies between morning and evening. Larger floral dimensions were correlated with lower sucrose and higher hexoses. Casual observation showed Xylocopa sp., small bees, flies, and hummingbirds to be visitors. There was no sign of nectar robbing. Five percent of flowers set seed with all pollen vectors excluded, 44% with hummingbirds excluded, and 63%with no exclusion. Seed set per fruit was 2 with all excluded, 23 with hummingbirds excluded, and 46 with no exclusion. Mean seed set on pollinated flowers was 60, with a range of 2 to 192. Multiple linear regression showed the fraction of fruit setting seed when hummingbirds were excluded to be related to larger flower diameters and shorter flowers. With no pollinator exclusion, fruits setting seed were related to larger diameters and nectar fructose. For seeds per fruit, multiple regression gave similar, but less clear, results. We conclude that P. pseudospectabilis is pollinated by both bees and hummingbirds, with other pollinators not to be excluded as possible contributors. We found no hard evidence of selective forces currently at work.     

Scale length/wing length correlation in Lepidoptera (Insecta)

Significant positive correlation between wing length and scale length was found in a broad sample of lepidopteran taxa. No breakdown of the correlation was observed in the lowest wing size range. The best fit is a non-linear (power) curve. The minimum individual scale length observed was 40 µm (in a nepticulid), while the maximum was close to 500 µm (in a castniid; there are literature records of even larger scales in this family). Scale size variation probably reflects variation in the size of scale-forming trichogen cells. The latter, in turn, may at least partly reflect difference in genome size, such as has long been known to be the case with the cells that form, respectively, the cover and ground scales in some higher moths.     

Pollination experiments in the Mimulus cardinalis--M. lewisii complex

Experimental sets of Mimulus cardinalis and M. lewisii plants were (1) exposed to pollinators and (2) shielded from pollinators at study sties in Red Butte Canyon and Big Cottonwood Canyon, Wasatch Mountains, Utah. The exposed plants produced 1,535 seedlings and the shielded plants only 1. Clearly, seed production is dependent upon cross-pollination. A few syrphid flies were observed visiting the flowers but no hummingbirds or bumble bees, although the latter two have been reported as the main pollinators of M. cardinalis and M. lewisii , respectively. No interspecific hybrids were produced even though the species are fully interfertile, indicating that pollinators are faithful to their species or that different parts of their bodies pick up and carry pollen to the two different species.     

Remarkable waxing, waning, and wandering of populations of Mimulus guttatus : an unexpected example of global warming

Experimental sets of Mimulus cardinalis and M. lewisii plants were (1) exposed to pollinators and (2) shielded from pollinators at study sties in Red Butte Canyon and Big Cottonwood Canyon, Wasatch Mountains, Utah. The exposed plants produced 1,535 seedlings and the shielded plants only 1. Clearly, seed production is dependent upon cross-pollination. A few syrphid flies were observed visiting the flowers but no hummingbirds or bumble bees, although the latter two have been reported as the main pollinators of M. cardinalis and M. lewisii , respectively. No interspecific hybrids were produced even though the species are fully interfertile, indicating that pollinators are faithful to their species or that different parts of their bodies pick up and carry pollen to the two different species.     

Pollination needs of arrowleaf balsamroot, Balsamorhiza sagittata (Heliantheae: Asteraceae)

Arrowleaf balsamroot, Balsamorhiza sagittata (Pursh) Nutt, is a common, sometimes dominant, longlived forb that flowers early in spring from the foothills to upper-montane areas of the northern Rocky Mountains and Intermountain West. Public land managers desire its seed for rangeland rehabilitation. Through manual pollination field trials, the species was found to have a mixed pollination system. It is primarily xenogamous (46% of ovules yielded plump achenes) but partially self-compatible (31% of achenes were plump). Unvisited flower heads formed virtually no mature achenes; only plump achenes contained seeds with endosperm. Freely visited flower heads in 2 populations produced as many achenes as manual outcross pollinations of flower heads, suggesting that seed production was not pollinator limited. Two species of Osmia bees rely mostly on Balsamorhiza and its close relative, Wyethia , for pollen. At least 165 females per hectare will need to be stocked to achieve thorough flower visitation in cultivated seed production fields.     

Bee visitors of sweetvetch, Hedysarum boreale boreale (Leguminosae), and their pollen-collecting activities

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The native bee fauna visiting and pollinating a population of sweetvetch in Grand Teton National Park was surveyed. The papilionaceous flowers were exploited by 37 bee species, most of which had long mouthparts. Most species collected pollen as well as nectar. Bees foraged most heavily in early afternoon when pollen was most abundant. However, there was no indication that bee species were competing for limited pollen resources: there was no difference among three time periods in percent sweetvetch pollen carried in the scopal pollen loads of bees nor was there any evidence that some species were displacing the foraging times of others. The advantages of developing a native species as a commercial pollinator of sweetvetch are discussed and several potential candidates are mentioned.     

Revision of the Neotropical genus Yagra Oiticica (Lepidoptera: Castniidae)

The Castniidae, or butterfly moths, are characteristically colourful diurnal moths, distributed throughout the tropics except in Africa. The Neotropical representatives forage almost exclusively on monocotyledonous plants and many species are crop pests with more than 60% of the Neotropical castniids found or endemic in Brazil. Research studies that focus on taxonomy, systematics, and morphology of this group are scarce. In this study, Yagra Oiticica, a small genus restricted to south-eastern South America, is revised and the diagnostic morphological characters of male and female genitalia are illustrated. This research is part of long-term study on the Castniidae for future phylogenetic analysis.     

Comparative floral biology of Penstemon eatonii and Penstemon cyananthus in central Utah: a preliminary study

A comparison of the floral visitors of two closely related plant species, Penstemon cyananthus and P. eatonii suggests that flower shape and color may affect the number and type of pollinators, and the ability of the plant to set fruit. Penstemon cyananthus, which is most attractive to hymenopteran visitors, has a blue flower, large in diameter, that is positioned as a convenient “landing pad.” Although many types of insects visit the flower, the transport of pollen directly to flowers of another individual of the same species is somewhat inefficient, since fruiting success is low (66.7 percent). The tubular red flowers of P. eatonii are narrow and droop downward from the stem. The nectar is accessible to a specific and well-adapted visitor, the hummingbird. This less promiscuous, bird-pollinated species sets fruit more successfully (82.4 percent) than P. cyananthus.     

Individual and geographical variation in the stridulatory file of Omocestus viridulus (L.) (Orthoptera: Acrididae)

Summary

Samples of male specimens of Omocestus viridulus from 14 European countries were used to study the individual and geographical variation in the characters associated with the stridulatory file. Significant overall variation between the samples was demonstrated for the length of file, average density of pegs, length of hind femur and ratio of file length to hind femur length.

This variation was found to be significantly correlated with several environmental factors, particularly annual range of temperature and amount of precipitation. These factors were considered to be good indicators of continentality, specimens from more continental regions having longer hind femora and longer files with a lower density of pegs. File length was found to be inversely correlated with amount of precipitation even when considered as a proportion of the hind femur. Number of pegs was also found to be inversely correlated with precipitation. In showing that femur length and file length increase and density decreases with continentality, the results agree with those of my previous study (Pitkin, 1976), in which British samples were found to have shorter femora and shorter files with a greater density of pegs than German samples.

The present study, while establishing that the stridulatory file varies geographically, does not deny its usefulness as a taxonomic tool, particularly when it is used in combination with other characters. When stridulatory characters are used on their own, individual and geographical variability within the species must clearly be taken into account.     

Ontogenetic and habitat-related changes in diet of late larval and juvenile suckers (Catostomidae) in Upper Klamath Lake, Oregon

We describe ontogenetic patterns in the diets of shortnose and Lost River suckers (15.8–92.8 mm standard length) from Upper Klamath Lake in summer 1999. Both species made a transition from surface and planktonic prey to benthic prey at about 20–30 mm standard length, corresponding to the approximate size of the juvenile morphological transition. Surface prey was dominated by adult chironomids and undigestable pollen, while benthic prey was dominated by larval chironomids, chydorids, and ostracods. In the 15–20-mm size class, pollen made up >75% of food particles in 68% of specimens, and only 2 specimens in this size class lacked any pollen grains. A better understanding of the prey selection process in larval suckers is needed to determine the importance of this potential source of starvation. The planktonic prey eaten during the surface-to-benthic feeding transition were widely distributed in the lake, suggesting that larvae use emergent vegetation primarily as a refuge from predators. On a numerical basis, crustaceans and larval chironomids contributed most to the diets of larger juveniles. In specimens >40 mm, shortnose suckers ate more Tanytarsini and Lost River suckers ate more chironomid pupae and chydorids. In specimens >40 mm there was a strong habitat-related difference in diet: specimens collected in offshore samples ate more chironomid larvae and pupae, harpacticoid copepods, and chydorids, whereas onshore specimens ate more cyclopoid copepods and invertebrate eggs. The transition from onshore to offshore habitat appears to occur over a broad size range of about 40–90 mm.     

Observations on the tube-building behaviour of the marine amphipod Cymadusa filosa Savigny (Crustacea: Ampithoidae)

The study reports on the tube-building behaviour of the corophioidean amphipod, Cymadusa filosa Savigny on two algae, Sargassum binderi Sonder and Ulva lactuca Linnaeus, based on experimental protocols using specimens in aquaria and in petri dishes. Cymadusa filosa was observed to construct open-ended, uniform diameter cylindrical tubes using amphipod silk, to bind together faecal pellets, detritus and fronds of Sargassum binderi or Ulva lactuca. Detailed studies of tube-building behaviour were carried out in petri dishes containing Ulva lactuca, using isolated specimens (5–13 mm in size) of different sexes for a period of one and a half months. Both males and females constructed tubes, and an average of four tubes were built by adults in 15 days. Females with young in the brood pouch did not construct new tubes following juvenile release. Juveniles were observed to build tubes using detritus and faecal material only within hours of being released from the brood pouch. The tubes of juveniles were either built on the walls of their mother's tubes or on an algal mass put together by the mother. There was a highly significant positive correlation between body length and tube length in males and females. There was no significant difference in the rate of tube length increase relative to body size between males and females, between males less than or more than 10 mm, or between females of less than or more than 10 mm. Tube-sharing was also observed between males and females.     

Adult butterfly feeding–nectar flower associations: constraints of taxonomic affiliation,butterfly, and nectar flower morphology

Butterfly–flower morphological interrelationships were investigated for 108 butterfly species and 20 plants at Nagpur, India. Distinct clusters of higher taxa (families) are disclosed for butterfly morphology and significant morphological and taxonomic associations occur in nectar exploitation. Flower corolla depth generally restricts exploitation by butterflies in relation to proboscis length and butterflies with high wing load indices bias their feeding to plants with massed flowers. However, important exceptions emerge; also, a substantial number of butterflies feed on plants with massed flowers though their proboscises are of marginal length for corolla depths. These butterfly species are significantly smaller, lighter, with lower wing loading and shorter proboscis indices than species which easily access the same flowering plant species. It is suggested that small size and short proboscises could give them a competitive advantage (increased rate of nectar uptake) for exploiting nectar in such situations. The significance of the findings for conservation is discussed.     

Seed production in Gentiana newberryi (Gentianaceae)

Experimental manipulations and observations in one population of Gentiana newberryi Gray flowers over 2 years showed significant variation in seed production relative to pollinator and soil water availability. When pollinators were rare, there was a significant relationship between number of bees present and number of mature seeds produced, and supplemental hand cross-pollination (xenogamy) did improve seed set in Gentiana newberryi Gray. When pollinators were abundant, supplemental hand cross-pollination did not increase seed set. Self-fertilized seeds (autogamy) germinated at the same rate as cross-pollinated seeds. Seed production in unvisited flowers is probably limited anatomically and is not influenced by the type of fertilization. There was a significant relationship between soil moisture and flower size in G. newberryi , with larger flowers found in wetter areas.     

Comparisons in nesting biology of two sympatric carpenter bee species (Apidae: Xylocopini)

This work analyses the biology and nesting behaviour of Xylocopa ordinaria and Xylocopa frontalis, providing information for their conservation and management. The study was performed from August 2006 to December 2007 and considered 25 nests of X. ordinaria and 23 of X. frontalis. The X. frontalis nested between December and April, while X. ordinaria nested throughout the year. Nests of X. ordinaria dug in wider substrates had more tunnels, and the width of nest tunnels and the dimensions of brood cells were smaller than were observed for X. frontalis. Females spent most of their time in activities inside their nests, followed by nectar and pollen flights and nectar dehydration. Pollen resources used by these bees presented more than 40% similarity, and they were constant to flower resources while provisioning cells. Cissites maculata and a Diptera species were the natural enemies found.