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In recent years, policymakers have recognized the economic values associated with biodiversity; economists have found ways to incorporate values associated with biodiversity into economic thinking; and scientists have documented the variety of services that diverse ecosystems provide. Those present at the 2006 AIBS annual meeting had the opportunity to explore the diverse linkages among these fields.
Evolutionary biologists strive to understand the immense variation in animals' breeding systems. Shorebirds represent an ideal model system for this endeavor, because they exhibit diverse breeding systems that include monogamy, with the parents cooperating to rear the young; and polygamy by the male, the female, or both parents, with one parent taking full responsibility for incubating the eggs and rearing the young. Recent experimental manipulations, mathematical models, and phylogenetic analyses reveal that evolutionary pressures may diverge as they act on mated pairs of shorebirds, favoring one parent at a cost to the other. We argue that different reproductive payoffs for the male and the female have had fundamental implications for the evolution of diverse breeding systems.
Opinions about how disturbance affects stream biodiversity differ. Models that assume that communities are shaped by biotic interactions emphasize the positive effects of stream disturbance (such as possible colonization by species that would be outcompeted under stable environmental conditions), whereas models assuming that communities are shaped by physical habitat factors emphasize the negative effects (such as the exclusion of species lacking adaptations to stress). Empirical studies on macroinvertebrate assemblages show that at small spatial scales, disturbance caused by floods affects diversity negatively. However, the same mechanisms that disturb the biota—scour and fill of sediments—also maintain the heterogeneity of riverine habitats, which underpins the existence of rich communities in the long term and at larger spatial scales. Therefore, the effects of flood-mediated disturbance on biodiversity probably depend on the spatiotemporal scale of observation. The magnitude of the observed effects is modulated by the predictability and severity of floods and the availability of food resources.
I outline models that describe vertebrate and microbial competition for carrion resources and help explain the resultant morphologies observed in extant vertebrate scavengers. Odors from microbial decomposition signal the presence of a carcass to vertebrate scavengers. Therefore, microbes must consume carcasses rapidly or evolve toxic defenses to protect themselves and their resource from their vertebrate competitors. Similarly, macroscavengers must evolve traits that allow rapid detection of carcasses or develop chemical defenses against microbial toxins. My modeling suggests that the most efficient macroscavenger adaptations increase the probability of carcass detection, which explains why highly vagile species, such as vultures, are the most obligate of vertebrate scavengers. Empirical data from vultures and from a scavenging snake species suggest that evolutionary pressures favor detection maximizers relative to toxification minimizers in competitive interactions for carcasses. However, detoxification mechanisms allow safe consumption of carrion and may have influenced the development of the complex digestive enzymes and delivery systems now seen in minimally vagile scavenging snakes.
Islands in the seas of northwestern Mexico have the largest number of insular endemic species in North America. The islands have the greatest number of extinct mammalian taxa in Mexico, and many of the remaining taxa are rare, threatened, or endangered. Thus the Mexican government's plan to build 24 modern ports—the “Escalera Nautica” project—will place enormous pressure on island species, which are exceptionally vulnerable to human activities, including the introduction of alien species. The intensified port activities would most likely lead to an ecological disaster. Several mammal species inhabiting the islands are already close to the limit of their capacity to survive. For many endangered species, a small change in habitat can be the final push into extinction. In this article, we make some recommendations to try to prevent the extinction of species at risk.