Change in Fish Fauna as Indication of Aquatic Ecosystem Condition in Río Grande de Morelia–Lago de Cuitzeo Basin, Mexico

Chirostoma charari and C. compressum, and they are presumed extinct. Twelve (63%) of the remaining species had declines in distribution. Sixteen (80%) of the 20 localities sampled had lost species. The greatest declines occurred in Lago de Cuitzeo proper and in the lower portion of the Río Grande de Morelia watershed. Species losses from the lake were attributable to drying and hypereutrophication of the lake because of substantial reductions in the amount and quality of tributary inputs, whereas losses from the Río Grande de Morelia watershed were the result of pollution from agricultural, municipal, and industrial sources, especially in the region around the city of Morelia. Three localities in the upper portion of the Río Grande de Morelia watershed—Cointzio reservoir, La Mintzita spring, and Insurgente Morelos stream—contained most of the remaining fish species diversity in the basin and deserve additional protection. Fish faunal changes indicated major declines in the health of aquatic ecosystems in the Morelia–Cuitzeo basin.     

The cost of host egg damage caused by a brood parasite: experiments on great spotted cuckoos (Clamator glandarius) and magpies (Pica pica)

Adult great spotted cuckoos, Clamator glandarius, frequently damage one or more eggs of their magpie host, Pica pica, without removing or eating them. The presence of damaged host eggs could signal parasitism thereby increasing the probability that the parasitic egg is ejected. This hypothesis was tested by experimentally introducing a model cuckoo egg with or without damaged host eggs. Magpie responses to experimental parasitism did not differ significantly between treatments implying that damaged host eggs are not used by magpies to assess parasitism. We followed the fate of magpie eggs naturally damaged by the great spotted cuckoo or experimentally damaged by us. Host response was very similar for naturally or experimentally damaged host eggs, but varied significantly according to the type of egg damage, eggs being removed more frequently when pecked than crushed, while cracked eggs were never removed. However, the egg damage that most readily causes egg removal is albumen leakage. Received: 30 November 1998 / Received in revised form: 7 June 1999 / Accepted: 12 June 1999     

Effects of paternal care on reproductive success in the polygynous spotless starling Sturnus unicolor

For males of socially polygynous avian species like the spotless starling, there may exist a trade-off between investing in paternal care and controlling several nests. To determine how the intensity of paternal care affects reproductive success per brood sired or expressed as the total number of young raised in all nests controlled by the same male, it is necessary to manipulate paternal care. Testosterone (T) has been shown to depress the tendency for males to care for their young, and induces them to acquire more mates. The effects of paternal care on reproductive success were studied by treating certain male starlings with exogenous T and others with the antiandrogen cyproterone acetate (CA), and comparing the parental behavior of T- and CA-males throughout the breeding season with that of controls. CA-males fed their chicks more during the first week after hatching than T-males, with controls feeding at intermediate rates, both on a per nest basis and as total effort for all nests controlled by the same male. Paternal feeding rates during the first week of chick life had a significant positive effect on the number of fledged young. The hormone treatment significantly affected the number of chicks raised per nest, CA-males having a higher breeding success per nest than T-males, and controls showing intermediate levels of success. There was no significant effect of treatment on total reproductive success attained by males throughout the season. In the polygonous spotless starling, the intensity of paternal care of young affects reproductive success per nest positively but not on a seasonal basis. Received: 6 February 1999 / Received in revised form: 30 June 1999 / Accepted: 11 July 1999     

Effects of sex-associated competitive asymmetries on foraging group structure and despotic distribution in Andean condors

Phenotype-limited interference models assume competitive asymmetries among conspecifics and unequal sharing of resources. Their main prediction is a correlation between dominance status and patch quality: dominant individuals should preferentially exploit better-quality habitats. We tested assumptions and predictions of the phenotype-limited interference model in Andean condors (Vultur gryphus), a New World vulture with strong sexual size dimorphism (males are 30–40% heavier than females). We recorded searching birds in habitats differing in quality: mountains and plains. We also observed scavenging behaviour at 20 sheep carcasses, and videotaped 5 of them. Intraspecific hierarchy at carcasses was based on size: males dominated females and, within each sex, older birds dominated younger ones. Adult males and juvenile females occupied extreme positions in the feeding hierarchy. Aggression was directed at those individuals belonging to lower hierarchical levels. In high-quality areas (mountains), more condors arrived at carcasses. Juvenile females were more often observed searching in low-quality areas (plains), far from breeding areas and main roost sites. GLM analyses of individual behaviour showed that the hierarchy did not influence time of arrival, but low-ranking individuals spent more time at carcasses, especially if the number of condors at arrival was high. Additionally, low-ranking condors spent less time feeding at carcasses when individuals of higher hierarchical levels were present. On the other hand, the number of condors present had a positive effect on feeding rates of dominant individuals, probably because of a reduction in individual vigilance. These results support most of the assumptions and predictions of the phenotype-limited distribution model, although a spatial truncated distribution between phenotypes was not observed. Asymmetric feeding pay-off, unequal parental roles and sexual selection constraints could favour sexual divergence in body size in Andean condors. Received: 6 April 1998 / Accepted after revision: 11 July 1998     

Metabolic transformations of acquired lucibufagins by firefly “femmes fatales”

Summary. Female Photuris fireflies sequester defensive steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus. Lucibufagin analyses of Photuris females and Photinus ignitus males show that the lucibufagin mixtures of predator and prey differ in their composition. Analyses of whole body extracts showed that P. ignitus males contain a mixture of eight non-glycosylated lucibufagins, composed mostly of compounds with two oxygenated positions in the steroidal A-ring (C-3, C-5). After feeding on P. ignitus males, Photuris females contain six major lucibufagins. Three of these compounds are not present in the prey, including the novel lucibufagin glycoside 5β,11α-dihydroxy-12-oxo-3β-O-β-D-xylopyranosylbufalin, and two other lucibufagins with a trioxygenated A-ring (C-2, C-3, C-5). These results indicate that Photuris females transform the sequestered lucibufagins both by glycosylation and oxidation, which could affect the systemic transportability of these compounds due to an increase in their polarity. Received 18 February 1999; accepted 19 April 1999.     

Chemical egg defense in Photuris firefly “femmes fatales”

Summary. Female Photuris fireflies contain defensive chemicals of two types. They sequester steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus that they eat, and themselves produce the defensive betaine N-methylquinolinium 2-carboxylate. Chemical analyses of Photuris eggs showed that females that fed on Photinus males endow their eggs with both lucibufagin and the betaine, while those that did not feed on Photinus lay eggs that contain betaine, but virtually no lucibufagin. Photuris females collected in the field during the Photinus flight season laid eggs that invariably contained betaine, but lucibufagin only at times. Predation experiments showed that Photuris eggs are essentially unacceptable to larvae of a coccinellid beetle (Harmonia axyridis) and an ant (Leptothorax longispinosus), but moderately acceptable to an earwig (Forficula auricularia). When applied experimentally to palatable insect eggs, lucibufagin proved deterrent to these three predators, while the betaine proved deterrent to the ant and coccinellid larva only. Both types of defensive compound decreased egg predation in the field. By endowing their eggs with both exogenous and endogenous chemicals, Photuris females are essentially “maximizing their options”– when feeding on Photinus, their eggs are doubly protected, but they are not entirely defenseless when the females are unable to procure lucibufagin. Received 12 August 1999; accepted 27 August 1999     

Within-plant allocation of a chemical defense in Secale cereale. Is concentration the appropriate currency of allocation?

Summary. The among-leaves allocation of DIBOA, a hydroxamic acid associated with plant resistance, in the shoot of rye (Secale cereale) was evaluated over the vegetative development of the plant. The appropriateness of using the concentration of secondary metabolites, DIBOA in this case, as the parameter to evaluate defense allocation in plants is discussed. Both biological and statistical arguments are put forward to suggest that allocation of chemical defenses should refer to absolute content and not to concentration. Results showed that leaf age was significantly linked to leaf concentration of DIBOA, young leaves having higher concentrations. In contrast, leaf content of DIBOA, our proposed currency of allocation, was not significantly higher in younger leaves. Furthermore, a regression analysis showed that the DIBOA content of leaves was better explained by the leaf relative biomass (proportion of shoot biomass) than by leaf biomass itself. It is suggested that, rather than leaf age, leaf relative biomass is the major factor determining DIBOA allocation in rye shoots. It is proposed that studies addressing within-plant defense allocation should use chemical defense content as the currency, emphasizing the major factors driving this process and its underlying mechanisms. Likewise, it is proposed that studies aiming at characterizing optimal patterns of plant defense should use chemical defense concentration as the currency, and be accompanied by evaluations of the actual resistance against herbivores of the plant parts analyzed, together with the effect on plant fitness. Received 19 February 1999; accepted 28 April 1999.     

Measurements of selected PCBs in open urban ambient air of Madrid (Spain)

The focus of this study was to characterize the concentration levels of selected PCBs and compare them to compiled data in order to contribute to the international database. The sampling site is located in the outskirts of Madrid and can be considered an open urban area. 32 samples of air were taken from February 1998 to June 1998 by using a high volume air sampler. Glass fiber filters and polyurethane foam (PUF) were used to collect the paniculate and gas phase material, respectively. PUF plugs were Soxhlet extracted and filters were ultrasonically extracted by using pesticide-grade hexane and dichloromethane, respectively. The cleanup procedure was carried out on a florisil column with hexane and hexane/dichloromethane as elution solvents. GC/MS in a selected ion monitoring mode was used for quantification and 29 selected PCBs congeners were analyzed.     

Prevalence and perspectives of illegal trade in cacti and succulent plants in the collector community

Although illegal wildlife trade (IWT) represents a serious threat to biodiversity, research into the prevalence of illegal plant collection and trade remains scarce. Because cacti and succulents are heavily threatened by overcollection for often illegal, international ornamental trade, we surveyed 441 members of the cacti and succulent hobbyist collector community with a mixed quantitative and qualitative approach. We sought to understand collector perspectives on the Convention on the International Trade in Endangered Species of Wild Flora and Fauna (CITES) and on the threats IWT poses to cactus and succulent conservation. Most respondents (74% of 401 respondents) stated that illegal collection in cacti and succulents represents a “very serious problem” and that the problem of wild plant collection is increasing (72% of 319 respondents). Most forms of illegal collection and trade were seen as very unacceptable by respondents. Self-reported noncompliance with CITES rules was uncommon (11.2% of 418 respondents); it remains a persistent problem in parts of the cacti and succulent hobbyist community. People engaging in rule breaking, such as transporting plants without required CITES documents, generally did so knowingly. Although 60.6% of 381 respondents regarded CITES as a very important tool for conservation, sentiment toward CITES and its efficacy in helping species conservation was mixed. Collectors in our survey saw themselves as potentially playing important roles in cactus and succulent conservation, but this potential resource remains largely untapped. Our results suggest the need for enhanced consultation with stakeholders in CITES decision-making. For challenging subjects like IWT, developing evidence-based responses demands deep interdisciplinary engagement, including assessing the conservation impact of species listings on CITES appendices.     

The use of polymer compounds in the deposits from the combustion of briquettes in domestic heating as an identifier of fuel quality

Environmental Science and Pollution Research - The utilisation of waste wood from furniture production brings new problems connected with an incomplete thermochemical decomposition of additives...