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Bees are most abundant and diverse in certain warm temperate, xeric regions of the world, especially the Mediterranean basin, the Califomian region, and coniguous desertic areas. Other warm temperate xeric areas, like central Chile or the western part of southern Africa, have less rich faunas. Arid tropical regions, as well as tropical savannas, have poor bee faunas. For example, the southern margin of the Sahara and northern Australia are not rich in bees, in spite of the nearness of the former to the Mediterranean basin with past nondesert connections to the Mediterranean and the contiguity of the latter with the large warm temperate AustraUan fauna! area. Equatorial savannas like those of east Africa are rather poor in bees.Warm temperate, mesic areas, such as those of eastern North America, Europe, or the southern Brazilian to Argentina region of South America, also have rich faunas, although less so than do the Mediterranean basin and southwestern United States. Perhaps because of its small area, the climatically equivalent region in South Africa (largely in Natal) has a fauna that is best described as depauperate tropical, with certain temperate elements, but without great richness.The moist tropics vary considerably in abundance and diversity of bees. In the Americas, they are almost or quite as rich as are the warm temperate mesic areas, but in Africa the fauna is far poorer, although richer than that of the Oriental region. There is a single Paleotropical bee fauna, richest in Africa and progessively smaller as one goes eastward across soudiem Asia to New Guinea, the Solomon Islands, and northeastern Australia. The poverty of the Oriental faunal region is shown by the ntimber of genera and subgenera â€" 89 compared to 175 in sub-Saharan Africa and 315 in the Neotropics (including temperate areas).Thus unlike many groups which abound in tlie tropics, bees attain their greatest abundance in warm temperate areas. It is especially in such areas, principally xeric ones, tliat certain presumably archaic groups of bees have survived, and it is likely that various groups originated in such areas.

Can economic forces be harnessed for biodiversity conservation? The answer hinges on characterizing the value of nature, a tricky business from biophysical, socioeconomic, and ethical perspectives. Although the societal benefits of native ecosystems are clearly immense, they remain largely unquantified for all but a few services. Here, we estimate the value of tropical forest in supplying pollination services to agriculture. We focus on coffee because it is one of the world's most valuable export commodities and is grown in many of the world's most biodiverse regions. Using pollination experiments along replicated distance gradients, we found that forest-based pollinators increased coffee yields by 20% within Ϸ1 km of forest. Pollination also improved coffee quality near forest by reducing the frequency of ''peaberries'' (i.e., small misshapen seeds) by 27%. During 2000 -2003, pollination services from two forest fragments (46 and 111 hectares) translated into Ϸ$60,000 (U.S.) per year for one Costa Rican farm. This value is commensurate with expected revenues from competing land uses and far exceeds current conservation incentive payments. Conservation investments in human-dominated landscapes can therefore yield double benefits: for biodiversity and agriculture.bees ͉ ecosystem service ͉ landscape ͉ pollination

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Most writers on castes in eusocial Hymenoptera stress one or another principal explanation for the origin and evolution of a worker caste, i.e., a class of individuals of reduced productivity. The principal theories are as follows: (a) The worker caste has arisen by kin selection such that the reduced reproductivity of a worker is more than compensated in terms of fitness by the increased reproductivity of the associated queen. The worker, which has given up part of its reproductivity, and is therefore altruistic in the sense of Hamilton (1), helps its mother, the queen, produce more offspring, which are brothers and sisters of the worker. If the queen mates only once, sisters in haplodiploid insects like Hymenoptera are more closely related to one another than a mother is to her daughter. Therefore, more genes like those of the worker may be contributed to the next generation by an individual that joins her mother as a worker and helps to produce siblings than by one that leaves her mother, mates, and produces an equal number of offspring. Hamilton, in a series of important papers (1-3), has explained this concept in detail.(b) The worker caste has arisen by individual selection on mothers resulting in their control of the activities of their female offspring. The influence that even a solitary mother hymenopteron exercises on her immature progeny by feeding and protecting them continues, in eusocial species, past maturation of the daughters. The queen is somehow able to keep them in the nest and diminish their reproductivity, and in a sense is parasitic upon her daughters. Altruism is not nec-* Contribution number 1526 from the