Influence of Forest Fragmentation on Community Structure of Frogs and Lizards in Northeastern Costa Rica

Abstract:  To better understand responses of reptiles and amphibians to forest fragmentation in the lowland Neotropics, we examined community and population structure of frogs and lizards in the fragmented landscape surrounding La Selva Biological Station in the Sarapiquí region of northeastern Costa Rica. We used diurnal quadrats and nocturnal transects to sample frogs and lizards in nine forest fragments (1–7 ha each) and La Selva (1100 ha). Species richness in all fragments combined was 85% of that found in La Selva with comparable sampling effort. Richness varied from 10 to 24 species among forest fragments, compared with 36 species at La Selva. Lizard density was higher and frog density was lower in forest fragments than in La Selva. Community composition varied among sites and by fragment size class, and species occurrence was nested with respect to fragment area. Isolation and habitat variables did not significantly affect species richness, composition, or nestedness. We classified 34% of species as fragmentation sensitive because they were absent or occurred at low densities in fragments. Nevertheless, the relatively high diversity observed in the entire set of fragments indicates that preserving a network of small forest patches may be of considerable conservation value to the amphibians and reptiles of this region.     

Environmental Dependency of Inbreeding Depression: Implications for Conservation Biology

Inbreeding depression is environmentally dependent, such that a population may suffer from inbreeding depression in one environment but not another. We examined the phenotypic responses of 35 inbred ( F = 0.672) lineages of the red flour beetle Tribolium castaneum in two different climatic environments. We found a significant environmental effect on males but not females. More important, we found that the rank fitness order of lineages differs between environments; lineages of high fitness in one environment may have low fitness in another environment. This change in rank is evident in a significant genotype-by-environment interaction for inbreeding depression for both females and males. These results suggest that even if we know the average environmental effect of inbreeding depression in a population, for any particular lineage measurements of inbreeding depression in one environment may not predict the level of inbreeding depression in another environment. Conservation biologists need to be aware of the environmental dependency of inbreeding depression when planning wildlife refuges or captive propagation programs for small populations. Ideally, captive propagation programs should maintain separate lineages for release efforts. Refuge design programs should consider maintaining a range of habitat types.     

Ethnobotany of Woody Species in Second-Growth, Old-Growth, and Selectively Logged Forests of Northeastern Costa Rica

Abstract: We assessed quantitatively the woody species used for timber, medicine, and other products in 10 tropical wet-forest stands with different land-use histories in the Atlantic lowlands of northeastern Costa Rica. Species were classified into 20 use categories based on regional ethnobotanical studies. Three size classes of woody vegetation were sampled in nested, contiguous plots along transects: trees (≥5 cm diameter at breast height [dbh]), saplings (>1 m high, <5 cm dbh), and seedlings (>20 cm high, <1 m high). Our study included five second-growth stands, three old-growth stands, and two selectively logged stands. Of the 459 woody species surveyed, 70% of the species and 86% of the total number of individuals had at least one use. Overall, species richness was highest for medicinal species (167 species). Absolute and relative abundance of medicinal and timber trees was significantly higher in second-growth stands than in old-growth and selectively logged stands. For 8 of the 15 use categories examined statistically, stem density showed no significant differences across forest types for any stem size class. Young, tropical, second-growth forests and selectively logged forests have high utilitarian as well as conservation value and will likely become important sources of forest products. The success of secondary forest regeneration, however, depends critically upon conservation of genetically diverse source populations in forest fragments and protected old-growth stands.     

Conservation in Action: Past,Present, and Future of the National Park System of Costa Rica*

Costa Rica’s national parks stand as a model for the preservation of biodiversity in the tropics, with 622,000 ha, or 12.2%, of the country set aside in preserves. In 1970, efforts to establish the parks were met with indifference but a practical strategy for nature conservation and favorable opportunities led to success, including establishment of Poas Volcano, Cahuita, Santa Rosa and Tortuguero National Parks in 1970–1971. Since then we have concentrated on four main activities. (1) procuring funds and personnel; (2) obtaining national and international support; (3) developing conservation education programs; and (4) getting environmental legislation passed Today we continue to build the national park system. We are creating a system of national forests, encouraging commercial reforestation and management of private land, consolidating the national parks system, and continuing to raise funds. Because most tourism is based on the national parks, we are asking the tourism industry to do its fair share to support the parks and to encourage wise use and conservation. Many organizations use funds to maintain an international bureaucracy rather than supporting direct conservation in the field. We do not need more planning studies and documents to tell us what to do, but instead we need funds to make environmental conservation a reality at the grass-roots level. International environmental standards should be set by a United Nations environmental organization that is empowered to infringe on the sovereignty of individual states in environmental matters. Future concerns for the national parks of Costa Rica include the economic situation, conservation education, the need to demonstrate the monetary value of conservation, population growth, the need for citizen involvement and the need for effective environmental legislation.     

Reef coral reproduction in the eastern Pacific: Costa Rica,Panama, and Galapagos Islands (Ecuador)

Reproductive ecology of two major reef-building corals in the eastern Pacific [Pocillopora damicornis (Linnaeus) andPocillopora elegans Dana] was investigated between 1984 and 1990 in Costa Rica, Panama (Gulf of Chiriqui and Gulf of Panama), and the Galapagos Islands (Ecuador) following the 1982–83 El Niño disturbance. Mature spermatocytes and oocytes were found in both species and were usually present in the same polyp in nearly equal ratios. Numerous zooxanthellae were observed in mature, unfertilized oocytes. Although spawning in field populations was not observed, it is likely that both pocilloporids are simultaneous hermaphroditic spawners, as evidenced by the disappearance of mature gametes after full moon. This is in contrast with most known pocilloporid corals that brood and release planula larvae. Corals were reproductively most active in the thermally stable environments of Costa Rica and the Gulf of Chiriqui (Panama) where 32 to 90% of all colonies contained gametes. In the moderately varying thermal conditions in the Galapagos Islands, 16 to 40% of colonies contained gametes, and in the pronounced seasonal upwelling environment of the Pearl Islands (Panama) only 6 to 18% of colonies contained gametes. Year-round reproduction occurred in Costa Rica and the Gulf of Chiriqui, whereas reproduction was confined to warm periods in the seasonally varying environments of the Galapagos Islands and the Gulf of Panama. Pocilloporid corals in Costa Rica and the Gulf of Chiriqui demonstrated lunar spawning activity, with mature gametes present a few days before and after full moon. Some limited spawning may have occurred also at new moon. While frequent gamete maturation has been demonstrated in this study, the relatively low rates of larval recruitment occurring on eastern Pacific coral reefs disturbed by the 1982–83 El Niño suggest that the recovery of important frame-building corals could be greatly prolonged.     

Mitochondrial DNA Variation in Black Rhinoceros (Diceros bicornis): Conservation Management Implications

Cell cultures have been established from 33 individual black rhinoceroses. These were from wild populations from various localities in southern Africa and include representatives from three geographical regions (southwestern, south-central, and eastern) corresponding to currently accepted conservation units, and include individuals previously attributed to one of the four subspecies, Diceros b. minor, D. b. bicornis, D. b. michaeli , and D. b. chobiensis (du Toit et al. 1987). Comparative mitochondrial DNA restriction maps were constructed using 16 restriction enzymes. These showed in each case two site differences between representative individuals from any two of the above geographical regions. Maps were monomorphic within geographical regions and, therefore, have the potential to provide diagnostic markers. The map from a single individual attributed to the D. b. chobiensis subspecies was identical to other individuals (attributed to D. b. minor ) in the south-central geographical region. The low amount of genetic diversity implied by these few differences renders it unlikely that problems with outbreeding depression will arise if, given the continuing decline in numbers of black rhinoceroses, it becomes necessary to supplement wild or captive populations with individuals from a different conservation unit in order to avoid inbreeding depression.     

Biological Integrity and the Goal of Environmental Legislation: Lessons for Conservation Biology

Abstract: Passage of environmental legislation often creates a state of euphoria among supporters such that implementation programs are not rigorously evaluated Endangered species and water resource legislation are two examples of sound environmental legislation with major weaknesses in their implementation. Regulations to implement the US. Clean Water Act, for example, emphasize water quality (physical and chemical properties of water) by calling for uniform standards for contaminants rather than the broader goal of improving the quality of water resources. As a result, improvements in the quality of water resource quality have been limited despite massive expenditures. Natural resource agencies' narrow emphasis on harvested and threatened and endangered species has similar consequences. Unless a comprehensive and rigorous definition of the goals of biodiversity legislation is developed and adhered to by regulatory agencies, efforts to implement biodiversity legislation could lead to similar problems. Protection of biodiversity should be considered a subset of the need to protect the biological integrity of natural resource systems and the ecological health of the biosphere. Programs to protect biodiversity should reflect that more holistic goal and include provisions for evaluating success at attaining stated goals and for making midcourse adjustments in programs when resources are not being adequately protected.     

Sex-Biased Harvesting and Population Dynamics in Ungulates: Implications for Conservation and Sustainable Use

The consumptive use of wildlife, in particular trophy hunting and game ranching of ungulates, has been advocated as a tool for conservation in Africa. We show that these methods of harvesting differ significantly from natural predation, with trophy hunting showing extreme selection for adult males and game ranching leading to disproportionate harvests of young males. Little information, either theoretical or empirical, exists concerning the effect of these harvesting regimes on the long-term population dynamics of ungulate populations. Despite that, the potential effects of sex-skewed harvests are numerous. In this paper, we investigate one potentially deleterious effect of sex-skewed harvests. Both theory and experimental data suggest that male ungulates are limited in their absolute ability to inseminate females. Using a Leslie-Matrix model and published data on impala, we show that the interaction between sperm limitation and harvests with highly male-biased sex ratios can lead to greatly reduced female fecundity (defined as the number of young born) and population collapse. These results are robust and suggest that present methods of harvesting may not be optimal, or viable, in the long term.     

Conservation Implications of Genetic Differentiation in Southern African Populations of Black Rhinoceros (Diceros bicornis)

We analyzed 30 protein-coding loci of four southern African black rhinoceros populations in order to calculate fixation indices and genetic distances for the different populations. We concluded that one of these populations is of the subspecies Diceros bicornis bicornis and the other three of Diceros bicornis minor. No evidence of inbreeding within populations was found. F- statistics revealed significant differentiation between populations. Small genetic distances found among the four populations reveal that they are conspecific, and no evidence was found to support the claim that the populations belong to discrete subspecies. Rather, an east-west cline in genetic characteristics appears to exist with G6pd and HB-2 alleles peculiar to western populations and Es-2 and GP-3 alleles peculiar to eastern populations.     

Developing Policy-Oriented Curricula for Conservation Biology: Professional and Leadership Education in the Public Interest

Abstract: Some conservation biologists question the ability of current university curricula to prepare students to meet the needs of the profession in solving real-life conservation problems or to integrate the goals of conservation biology with other societal goals. The gist of the criticism is that curricula tend to emphasize narrow, technical proficiency at the expense of more integrative, "policy-oriented" problem solving. Conservation biologists' work should be relevant to policy, and I argue that professional participation could become more effective through a broader educational curriculum. Such curricula should teach students three things: (1) an understanding of how the policy-making system works and how human value interactions constitute the core of professional work, (2) mastery of skills in critical thinking and development of an interdisciplinary, "procedural rationality" for analyzing problems and evaluating potential solutions, and (3) development of influence and responsibility within policy systems. Seminars, case studies, and field trips are among the tools that can develop these skills in students. Finally, the education committee of the Society for Conservation Biology has great potential to improve the quality and relevance of professional education.     

Remarkable Amphibian Biomass and Abundance in an Isolated Wetland: Implications for Wetland Conservation

Abstract:  Despite the continuing loss of wetland habitats and associated declines in amphibian populations, attempts to translate wetland losses into measurable losses to ecosystems have been lacking. We estimated the potential productivity from the amphibian community that would be compromised by the loss of a single isolated wetland that has been protected from most industrial, agricultural, and urban impacts for the past 54 years. We used a continuous drift fence at Ellenton Bay, a 10-ha freshwater wetland on the Savannah River Site, near Aiken, South Carolina (U.S.A.), to sample all amphibians for 1 year following a prolonged drought. Despite intensive agricultural use of the land surrounding Ellenton Bay prior to 1951, we documented 24 species and remarkably high numbers and biomass of juvenile amphibians (>360,000 individuals; >1,400 kg) produced during one breeding season. Anurans (17 species) were more abundant than salamanders (7 species), comprising 96.4% of individual captures. Most (95.9%) of the amphibian biomass came from 232095 individuals of a single species of anuran (southern leopard frog [Rana sphenocephala ]). Our results revealed the resilience of an amphibian community to natural stressors and historical habitat alteration and the potential magnitude of biomass and energy transfer from isolated wetlands to surrounding terrestrial habitat. We attributed the postdrought success of amphibians to a combination of adult longevity (often >5 years), a reduction in predator abundance, and an abundance of larval food resources. Likewise, the increase of forest cover around Ellenton Bay from <20% in 1951 to >60% in 2001 probably contributed to the long-term persistence of amphibians at this site. Our findings provide an optimistic counterpoint to the issue of the global decline of biological diversity by demonstrating that conservation efforts can mitigate historical habitat degradation.