Bees, Urbanization, Habitat Loss

Transcription

1 Bees, Urbanization, Habitat Loss

2 To exist on the Earth, humans depend upon life support services provided by the biological and geological processes that make up its ecosystems. The economic value of most of these services is not known, because we currently only estimate the monetary value of these services when they are threatened. One example is pollination. Our agricultural system depends extensively upon animal pollinators, both domesticated (honeybees, Osmia bees), and wild. It has been estimated that the pollination services of ecosystems amount to 20 to 40 billion dollars per year in the United States alone, perhaps half of that provided by bees.

3 As pollinators, bees are ubiquitous and essential components of terrestrial ecosystems. The pollination services of bees are essential for normal function, since the majority of angiosperm species rely on insect pollinators, and bees are some of the most important. Bees

4 Other important groups of pollinators include; Flies.this is an Eristalis sp. Birds and bats; an agave bat and a rufus throated hummingbird Moths and butterflies; A hummingbird hawkmoth Beetles; a soldier beetle

5 What, Exactly, is a Bee? A bee is, in essence, a glamorous wasp. Bees are a branch of a larger group, an insect order called the hymenoptera. The more evolutionarily advanced members of this group are usually called wasps, as a sort of generic term. One lineage of wasps switched from hunting insect prey for its offspring, to feeding its offspring nectar and honey, sometime during thea age of dinosaurs. They did pretty well for themselves, we call them bees.

6 It is important to remember that, as with all pollinators, pollination by bees is a mutualistic relationship that evolved from a fundamentally antagonistic interaction. The original pollinators were foraging for pollen, to eat or feed to their larvae, as herbivores. Plants evolved mechanisms to exploit these herbivores and make use of their ability to travel long distances. To this day, there is some conflict of interest in this interaction. It is in a plant s best evolutionary interest to provide a small nectar reward, both because nectar carries a cost, and also, because a well-nectared bee will not need to travel from flower to flower as frequently. Bees routinely rob flowers for nectar, as evidenced by this Xylocopa tabans robbing nectar. Likewise, many flowers, both entire species and individuals within species that normally provide nectar rewards, cheat pollinators by providing no nectar to visitors.

7 There are about 25,000-30,000 species of bees in the world, including approximately 3500 that inhabit the United States (Goulet and Huber, 1993). Bee taxa: Halictidae-sweat bees Andreneidae-mining bes Collettidae-plasterer bees Megachilidae-Leafcutters Anthophoridae-long tongued solitary and parasitic bees. Apidae-advanced corbiculate bees.

8 Honeybees, by the way, are not native to North America, They are members of an ancient oldworld genus that contains just four species, Apis florea, Apis dorsata, Apis cerana, and Apis mellifera, only the latter two are kept by humans. These are A. dorsata workers.

9 Not all bees are social, in fact, most are solitary. All bees visit flowers to collect nectar and pollen to provision their young. These young grow and develop in brood cells, in a nest, constructed by a female bee Bee anatomy, above. The relative sizes of these parts vary, but they are all variations on a theme.

10 The larvae are highly reduced, apodous and soft. In all apocritan (the group that includes ants, bees, wasps, and parasitic hymenoptera) larvae the midgut is not connected to the hindgut, an adaptation for avoiding fecal contamination of the host. At the last larval molt, the alimentary canal becomes complete, and the accumulated fecal material, or meconium, is voided just before pupation.

11 Ecologies Social Behavior Eusocial, Solitary, and various possibilities in between. Pollen Foragers and Cleptoparasites Diet Polylectic, feeding and gathering pollen from a variety of flowers. Oligolectic, specializing on a limited number of flowers, most likely close relatives. A bee can be relatively oligolectic when foraging for pollen, but forage for nectar from a wide variety of flowers. Phenology/Life History Univoltine, having one generation a year. Often, natural areas harbor a guild of bees that emerge in the spring or early summer, are univoltine and often oligolectic, and live for only a few weeks. Multivoltine, having several. Nest Sites Holes, Twigs, Sand, Packed Earth, Cavities, Tussocks of grass

12 What Do Bees Need? FLOWERS Bees require flowers, of the right general type and near their nest site, for the entire time they are active. Oligolectic species, require particular species of flowers. NEST SITES They also require nest sites, of the right substrate and other particulars such as sunlight and drainage. For instance, A. mellifera requires a tree hollow or nest box, and generally also requires a human helper to ward off various diseases.

13 Bees and Flowers Like many other creatures, such as hummingbirds, flies, moths, and flower beetles, adult bees use nectar as a food source. Unlike these other animals, however, bees also use a floral product, pollen, as a means of providing nutrition for their young. Thus, the entire bee life cycle is tied to the presence of flowers. Pollination, as with other animal pollinators, is an incidental byproduct of foraging for nectar and/or pollen. A bee s effectiveness as a pollinator depends greatly upon its own morphology and the morphology of the flower, specializations in its life history and behavior, its foraging patterns, and the extent to which other flowers in the environment compete for the bee s attention as a food source.

14 Oligolecithic Bees Some bees have life histories which are very closely tied to the ecology of the flowers they visit. They only forage for pollen at a particular type of flower, and often restrict their foraging for nectar to this type of flower, or similar types of flowers, as well. These oligolecithic bees are ecological specialists. This does not mean that these same flowers do not also received other visitors. It is a matter of debate whether oligolecithic bees are particularly good pollinators, although available evidence suggests that, for many flowers, this might be the case. The long-horned bee, Melissodes agilis only visits sunflowers when Visiting for pollen. This does not mean that sunflowers do not have any other pollinators. It is only active in late summer, when sunflowers are in bloom.

15 Nests Nests are made out of a wide variety of materials, including; Cavities dug in sand or clay: protective resin may be coated to the walls of the nest Hollow twigs and shoots, re-used beetle tunnels, opportune holes such as keyholes and soda straws: usually a mud partition is added between cavities Free-hanging mud or wax structures. Tussocks of grass, tree cavities. Re-used or purloined nests of other species.

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17 Threats to Bees Habitat Loss Pesticides Urbanization

18 The native bee fauna of North America encompasses diverse ecological generalists, as well as species whose ecologies are relatively specialized. The latter are particularly susceptible to anthropogenic disturbance and habitat change, as evidenced by a major study of British and Dutch Bees by Biesmeijer et al. It is virtually certain that human economic activity and development have had major impacts on North American bees as well.

19 Threats to Bees Habitat Loss Though much has been made of colony collapse disorder in honeybees. In fact, the biggest losses of bees and other pollinators are associated with the widespread development of land for agriculture (a process for which honeybees have been a contributing factor). Bees with specialized ecologies have taken the hardest hit. Right-Andrena labiata, Colletes

20 Pesticides and Habitat Change Neonicotinoids are thought by many to be a contributing factor to colony collapse disorder in some places. Overuse of other pesticides has contributed to declines in native pollinators, and an over-reliance on honeybees. Introduction of Exotic Diseases Apis mellifera, itself an exotic in most places (but essential for agriculture) has suffered a great deal from introduced diseases, notably the mite Varolla destructor, and many viruses. North American Bumblebees have suffered tremendous losses due to an introduced protozonan, Nosema ceranae.

21 The Urbanized Landscape Extensive large-scale anthropogenic impact is the rule rather than the exception for terrestrial communities. Increasingly, the landscape is coming to be made up of a patchwork of different communities, which vary in their level of human disturbance, all of which have affected by human industry and development in some way.

22 Less than 5% of the earth is covered by urban areas, but half the world s population lives in them. For a variety of historical and economic reasons (i.e., urbanites like to visit natural areas for the experience), many conservation areas are imbedded within an urban matrix, a situation that has profound potential to impact their ecology.

23 Urban Sites With Native Vegetation Have More Bee Species Richness of Bee Species Present Absent Presence of Native Plant Species

24 Tallgrass Prairies The loss of the North American prairie is a particularly wellknown, and lamentable example of habitat destruction. Tallgrass prairie once covered 170 million acres. Today, only 1-4% is left (depends upon whose estimate you cite).

25 years ago, in a short period of perhaps a years, the combined stresses of drought, grazing, and fire caused the cool hardwood forests that dominated the interior of North America at the time to be replaced by a new ecosystem, the North American Prairie.

26 From that point on, prairies have covered much of the area between the Rocky Mountains and Mississippi River, and elsewhere as well. Complex interactions of fire, drought and grazing maintain prairies.

27 In a single human lifetime, since the European settlers, aided by John Deere s moldboard plow began to farm the prairies, this landscape has virtually dissapperared. Black soil, bottomland, mesic tallgrass prairies are great farmland, and nearly all of this subtype has been farmed, grazed, or otherwise permanently altered. Nearly all the remnants, such as the Flint Hills of Kansas, are west of the Mississippi. Right-Bison grazing in the Tallgrass Prairie preserve, Osage County OK.

28 The James Woodworth Prairie is a 5.5 acre remnant of Mesic, bottomland, tallgrass prairie. It has never been plowed or heavily grazed, nor has it ever given way to woody vegetation. As such, it is one of the last remaining habitats of its kind in Illinois.

29 Scientists began to study the prairie in 1926, when the land was privately owned by the Peacock family. In 1968, the last of the prairie was saved from development, largely due to the actions of a single individual Bernice Popelka. In April of 1968 the University of Illinois at Chicago (UIC) acquired title after securing grants from the Chicago Community Trust and LAWCON (Land and Water Conservation, a federal program). Right Top-JWP in 1926 Right Bottom-JWP in 1968

30 The Value of a Remnant Prairie The James Woodworth Prairie is a very small fragment, and requires a fair amount of management to keep it from transforming into a woodland dominated by invasive woody vegetation. This program involves weeding invasive plants, and regular burns. Vegetation surveys have been conducted in 1929, 1969, 1984, and It has retained much of its distinctive flora. It also retains populations of distinctive animal species, including the Prairie cicada, and the Prairie crayfish. The prairie is open from May till October, and receives regular visitors. The extent to which sites like this can act as refugia of sorts for prairie species, in the long term, is not known, nor are the ecosystem services a site like this can provide. In both cases, it is one patch in a broader network of conserved areas in Northern Illinois, Illinois, and Wisconsin.